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Tendon tissue engineering with a biomaterial scaffold that mimics the tendon extracellular matrix (ECM) and is biomechanically suitable, and when combined with readily available autologous cells, may provide successful regeneration of defects in tendon. Current repair strategies using suitable autografts and freeze-dried allografts lead to a slow repair process that is sub-optimal and fails to restore function, particularly in difficult clinical situations such as zone II flexor tendon injuries of the hand. We have investigated the effect of GDF-5 on cell proliferation and gene expression by primary rat adipose-derived stem cells (ADSCs) that were cultured on a poly(DL-lactide-co-glycolide) PLAGA fiber scaffold and compared to a PLAGA 2D film scaffold. The electrospun scaffold mimics the collagen fiber bundles present in native tendon tissue, and supports the adhesion and proliferation of multipotent ADSCs. Gene expression of scleraxis, the neotendon marker, was upregulated seven- to eightfold at 1 week with GDF-5 treatment when cultured on a 3D electrospun scaffold, and was significantly higher at 2 weeks compared to 2D films with or without GDF-5 treatment. Expression of the genes that encode the major tendon ECM protein, collagen type I, was increased by fourfold starting at 1 week on treatment with 100 ng mL(-1) GDF-5, and at all time points the expression was significantly higher compared to 2D films irrespective of GDF-5 treatment. Thus stimulation with GDF-5 can modulate primary ADSCs on a PLAGA fiber scaffold to produce a soft, collagenous musculoskeletal tissue that fulfills the need for tendon regeneration.

Scleraxis (Scx) is a basic helix-loop-helix transcription factor expressed in tendon and ligament progenitor cells and the differentiated cells within these connective tissues in the axial and appendicular skeleton. Unexpectedly, we found expression of the Scx transgenic reporter mouse, Scx-GFP, in interdental cells, sensory hair cells, and cochlear supporting cells at embryonic day 18.5 (E18.5). We evaluated Scx-null mice to gain insight into the function of Scx in the inner ear. Paradoxical hearing loss was detected in Scx-nulls, with ~50% of the mutants presenting elevated auditory thresholds. However, Scx-null mice have no obvious, gross alterations in cochlear morphology or cellular patterning. Moreover, we show that the elevated auditory thresholds correlate with middle ear infection. Laser interferometric measurement of sound-induced malleal movements in the infected Scx-nulls demonstrates increased impedance of the middle ear that accounts for the hearing loss observed. The vertebrate middle ear transmits vibrations of the tympanic membrane to the cochlea. The tensor tympani and stapedius muscles insert into the malleus and stapes via distinct tendons and mediate the middle ear muscle reflex that in part protects the inner ear from noise-induced damage. Nothing, however, is known about the development and function of these tendons. Scx is expressed in tendon progenitors at E14.5 and differentiated tenocytes of the stapedius and tensor tympani tendons at E16.5–18.5. Scx-nulls have dramatically shorter stapedius and tensor tympani tendons with altered extracellular matrix consistent with abnormal differentiation in which condensed tendon progenitors are inefficiently incorporated into the elongating tendons. Scx-GFP is the first transgenic reporter that identifies middle ear tendon lineages from the time of their formation through complete tendon maturation. Scx-null is the first genetically defined mouse model for abnormal middle ear tendon differentiation. Scx mouse models will facilitate studies of tendon and muscle formation and function in the middle ear.

Background: Rotator cuffs heal through a scar tissue interface after repair that makes them prone to failure. Scleraxis (Scx) is a basic helix-loop-helix transcription factor that is thought to direct tendon development during embryogenesis. The purpose of this study was to determine if the application of mesenchymal stem cells (MSCs) transduced with adenoviral-mediated scleraxis (Ad-Scx) could improve regeneration of the tendon-bone insertion site in a rat rotator cuff repair model. Hypothesis: Bone marrow–derived cells transduced with Scx would improve the structure of the healing tendon-bone interface and result in increased tendon attachment strength. Study Design: Controlled laboratory study. Methods: Sixty Lewis rats underwent unilateral detachment and repair of the supraspinatus tendon. Thirty animals received MSCs in a fibrin glue carrier, and 30 received Ad-Scx-transduced MSCs. Animals were sacrificed at 2 weeks and 4 weeks and evaluated for the presence of fibrocartilage and collagen fiber organization at the insertion. Biomechanical testing was performed to determine the structural and material properties of the repaired tissue. Statistical analysis was performed with a Wilcoxon rank sum test with significance set at P = .05. Results: There were no differences between the Scx and MSC groups in terms of histologic appearance at 2 weeks. However, the Scx group had higher ultimate stress-to-failure (2.6 ± 0.9 vs 1.7 ± 0.3 MPa; P = .03) and stiffness (8.4 ± 2.9 vs 5.0 ± 1.9 N/mm; P = .01) compared with the MSC group. At 4 weeks, the Scx group had more fibrocartilage (728.7 ± 50.4 vs 342.6 ± 217.0 mm2; P = .04), higher ultimate load to failure (26.7 ± 4.6 vs 20.8 ± 4.4 N; P = .01), higher ultimate stress to failure (4.7 ± 1.3 vs 3.5 ± 1.0 MPa; P < .04), and higher stiffness values (15.3 ± 3.4 vs 9.3 ± 2.2 N/mm; P < .001) as compared with the MSC group. Conclusion: Mesenchymal stem cells genetically modified with Scx can augment rotator cuff healing at early time points. Clinical Relevance: Biologic augmentation of acutely injured rotator cuffs with Scx-transduced MSCs may improve rotator cuff tendon healing and reduce the incidence of re-tears. However, further studies are needed to determine if this remains safe and effective in larger models.

The capability to engineer microenvironmental cues to direct a stem cell population toward multiple fates, simultaneously, in spatially defined regions is important for understanding the maintenance and repair of multi-tissue units. We have previously developed an inkjet-based bioprinter to create patterns of solid-phase growth factors (GFs) immobilized to an extracellular matrix (ECM) substrate, and applied this approach to drive muscle-derived stem cells toward osteoblasts ‘on–pattern’ and myocytes ‘off–pattern’ simultaneously. Here this technology is extended to spatially control osteoblast, tenocyte and myocyte differentiation simultaneously. Utilizing immunofluorescence staining to identify tendon-promoting GFs, fibroblast growth factor-2 (FGF-2) was shown to upregulate the tendon marker Scleraxis (Scx) in C3H10T1/2 mesenchymal fibroblasts, C2C12 myoblasts and primary muscle-derived stem cells, while downregulating the myofibroblast marker α-smooth muscle actin (α-SMA). Quantitative PCR studies indicated that FGF-2 may direct stem cells towards a tendon fate via the Ets family members of transcription factors such as pea3 and erm. Neighboring patterns of FGF-2 and bone morphogenetic protein-2 (BMP-2) printed onto a single fibrin-coated coverslip upregulated Scx and the osteoblast marker ALP, respectively, while non-printed regions showed spontaneous myotube differentiation. This work illustrates spatial control of multi-phenotype differentiation and may have potential in the regeneration of multi-tissue units.

Because periodontal ligament (PDL) cells are reported to contain progenitor or stem cell populations, they are considered a beneficial cell source for clinical periodontal regeneration. Both bone morphogenetic protein 4 (BMP4) and human telomerase reverse transcriptase (hTERT) have essential roles in the modulation of stem cell properties. In this study we report for the first time that the combined ectopic expression of BMP4 and hTERT significantly enhanced the multipotent differentiation efficiency and capacity of human PDL fibroblasts (PFs), as shown by osteogenic, adipogenic and neurogenic differentiation in vitro, and cementum/PDL-like tissue regeneration in vivo. These findings may be attributed, at least in part, to the original upregulation of important stem cell markers, such as scleraxis, Stro-1 and CD146, and the extremely lowered threshold for BMP concentration to activate BMP signaling by enhanced basal phosphorylation levels of Smad 1/5/8. In addition, the significantly reduced expression levels of CD146 and CD90 with the presence of Noggin confirms the direct effect of BMP4 on the stem cell-like phenotype of genetically modified PF cells (BT-PFs). Furthermore, BT-PFs exhibited a high neural differentiation capacity (>75%). After transplantation into NOD/SCID mice, genetically modified-PFs generated cementum/PDL-like structures on the surface of the carrier. The multipotency of these modified cells potentially provides an attractive source of stem cells for therapeutic purposes and regenerative medicine.

Scleraxis is a transcription factor that appears to play a key role in both the development of extracellular matrix-rich tissues such as tendons, and in the synthesis of matrix itself by regulating matrix gene expression. Our understanding of how scleraxis works, how its activity and expression are regulated, and the specific role it plays in disease is largely incomplete. However, enough data have accumulated to date to identify scleraxis as a critical factor in tendon formation, and ongoing studies in our laboratory have implicated scleraxis as a previously unappreciated driver of cardiac fibrosis due to its role in regulating type I collagen formation. Scleraxis may in fact behave as a master regulator of fibrillar collagen formation in multiple tissues, and the development of therapies aimed at reducing ­scleraxis function may provide a novel means to control tissue fibrosis in multiple pathologies.

Introduction We reported previously that important cellular characteristics such as the cell activity and the expression and synthesis of collagen I can be strongly enhanced by stimulation of tenocytes with BMP-7 [Klatte-Schulz et al. 2014]. Since tendon healing after surgical reconstructions still represents a challenging topic, due to complications such as retears or non-healing of the tendon tissue, the augmentation of the healing using growth factors like BMP-7 may be a possible treatment option. What remains unknown is how BMP-7 signals in tenocytes, which was analysed in the present study. Methods Tenocytes of 6 male donors (63–69 years) isolated from biopsies of supraspinatus tendon tears were seeded in cell culture dishes, cultured for 3–5 days and stimulated with 200 or 1000 ng/ml rhBMP-7. Protein lysate samples were collected after 15, 30, 60 and 120 min and the phosphorylation of Smad1/5/8 was analysed using Western Blotting technique. RNA was isolated after 1, 2, 4 and 8 h from the cells. The gene expression of BMP-Receptors (BMPR-Ia, BMPR-Ib, BMPRII), Activin receptors (ActR-I, ActR-IIa, ActR-IIb), Smad 1, 4, 5, 8 and the BMP target gene ID1, as well as scleraxis, osteocalcin and collagen II was analysed by Real-Time PCR. Statistics: Mann-Whitney-U Test, p ≤ 0.05, Bonferroni Holm Correction Results The relative phosphorylation level of Smad1/5/8 was significantly increased 30 and 60 min after stimulation with BMP-7 compared to unstimulated control cells (Figure 1). The expression of BMPR-Ib was increased the most compared to both other type I receptors 4 and 8 h after stimulation. In the type II receptor group, BMPR-II showed the highest increase after 2 to 8 h, while ActR-IIb was down-regulated after 2 h and 4 h. The expression of Smad1 and 4 was slightly increased and Smad5 showed no increase of expression. Smad8 expression was strongly up-regulated 4 h and 8 h after stimulation (Figure 2). The expression of ID1 was increased already at 1 h and 2 h and strongly enhanced 8 h after stimulation. Scleraxis expression showed a strong increase at 1, 2 and 4 h and a massive increase at 8 h after stimulation. No change in the osteocalcin and collagen II expression was found after BMP-7 stimulation. Discussion The study showed that the type I receptor BMPR-Ib and the type II receptor BMPR-II seem to be the most regulated receptors on their mRNA level after tenocyte stimulation with BMP-7. Additionally, the receptor-regulated Smad8 seems to represent the essential signalling molecule in tenocytes after BMP-7 stimulation. An important role of Smad8 in tenogenic differentiation was reported previously. [Hoffmann et al ., 2006] The strong increase of the tendon related gene scleraxis in the cells may underline the positive effect of BMP-7 treatment for rotator cuff repair. References Klatte-Schulz, et al . J Orthop Res . 2014;32(1):129–37 Hoffmann, et al . J Clin Invest . 2006;116(4):940–52

Introduction Rotator cuff healing after injury and/or repair is often compromised by excessive fibrosis both at the lesion site and in the surrounding tendon, particularly in patients with diabetes. Diabetic and hyperglycaemic patients have a higher incidence of tendinopathy than healthy populations. Proposed explanations, including a direct effect of glucose on tenocytes, are speculative. Metformin, a safe and widely-prescribed anti-hyperglycaemic agent, has direct effects on heart, nasal and kidney fibroblasts, preventing differentiation into myofibroblasts and reducing fibrosis. 1,2 Its effects on tendon are unknown. This study thus aimed to determine the molecular changes that occur in tendon explants with or without metformin in both a normoglycaemic and a hyperglycaemic environment. Methods Ovine infraspinatus tendon explants were cultured for 5 or 17 days in normal (5.5 mM) or high (25 mM) glucose in isotonic media (+10% FBS). After 8 days in the 17-day cultures, cells had grown out from the explants onto the plastic, so both outgrowth cells and explants were continued separately in varied glucose media. In a second experiment, explants were similarly cultured for 15 days with the addition of 0.5 mM or 1 mM metformin. Total RNA was isolated from tendon and cells and realtime RT-PCR performed using primers for matrix proteins, enzymes involved in matrix metabolism and other cellular factors. Results Stress depriving tendon in culture significantly affected 14 of 16 matrix protein genes and all 13 matrix-modifying enzymes tested compared to ex vivo tendon. COL2A1 , COMP , DCN , ELN , FMOD , VCAN and LOXL4 expression decreased; the other 19 changed genes increased. Higher glucose concentrations in the media significantly increased tendon explant expression of 8 of 16 matrix protein genes ( COL1A1 , COL3A1 , COL5A1 , COMP , DCN , ELN , FBN1 and LUM ), five of 13 enzymes ( ADAMTS4 , ADAMTS5 , MMP13 , LOXL3 and LOXL4 ) and CTGF . Increased glucose had no significant effect on any gene expression by outgrowth cells, however these cells had significantly elevated expression of smooth muscle actin ( ACTA2 ; p Under normoglycaemic conditions, metformin halved tendon explant CTGF (p = 0.016) and COL1A1 (p = 0.017) expression. Increased MMP13 expression was partially abrogated by metformin (p TGFB (p , scleraxis ( SCX; p ≤ 0.007) and VCAN (p ≤ 0.003) were restored to ex vivo levels by metformin. In hyperglycaemic media, increased CTGF expression was prevented (p = 0.039). Discussion Hyperglycaemic conditions significantly affected tenocyte matrix metabolism only when the cells were within their extracellular matrix (ECM) microenvironment. This suggests that the effects of excess glucose on tenocytes, though substantial, are indirect and via modifications to the ECM, perhaps by the action of advanced glycation endproducts. Fibrosis has not been widely recognised in association with tendon injury, however, a recent study reports induction of genes associated with epithelial (epitenon) to mesenchymal transition following acute Achilles tenotomy and repair in rats. 3 Peripheral fibrosis of the epitenon and joint capsule are common in conditions such as frozen shoulder. This evidence, and the appearance of myofibroblasts from tendon stress-deprived in culture, suggests that targeting these cells and associated excessive fibrosis with metformin may be a potential therapy for limiting tendinopathy and enhancing tendon repair after injury. The changes seen in these tendon explants by the addition of metformin would be expected to result in a reversal of collagen accumulation in tendon. The prevention of versican loss may also decrease interfasicular adhesion. Ongoing studies will determine whether metformin has beneficial effects in reducing tendon lesion fibrosis, and normalising tenocyte phenotype, in an animal model. References 1 Bai J, et al . PLoS One. 2013;8:e72120 2 Park IH, et al . Otolaryngol Head Neck Surg. 2014;150:148–153 3 Sugg KB, et al . J Orthop Res. 2014;32:944–951

Although much is known about the effects of uniaxial mechanical loading on fibrocartilage development, the stress fields to which fibrocartilaginous regions are subjected to during development are mutiaxial. That fibrocartilage develops at tendon-to-bone attachments and in compressive regions of tendons is well established. However, the three-dimensional (3D) nature of the stresses needed for the development of fibrocartilage is not known. Here, we developed and applied an in vitro system to determine whether fibrocartilage can develop under a state of periodic hydrostatic tension in which only a single principal component of stress is compressive. This question is vital to efforts to mechanically guide morphogenesis and matrix expression in engineered tissue replacements. Mesenchymal stromal cells in a 3D culture were exposed to compressive and tensile stresses as a result of an external tensile hydrostatic stress field. The stress field was characterized through mechanical modeling. Tensile cyclic stresses promoted spindle-shaped cells, upregulation of scleraxis and type one collagen, and cell alignment with the direction of tension. Cells experiencing a single compressive stress component exhibited rounded cell morphology and random cell orientation. No difference in mRNA expression of the genes Sox9 and aggrecan was observed when comparing tensile and compressive regions unless the medium was supplemented with the chondrogenic factor transforming growth factor beta3. In that case, Sox9 was upregulated under static loading conditions and aggrecan was upregulated under cyclic loading conditions. In conclusion, the fibrous component of fibrocartilage could be generated using only mechanical cues, but generation of the cartilaginous component of fibrocartilage required biologic factors in addition to mechanical cues. These studies support the hypothesis that the 3D stress environment influences cell activity and gene expression in fibrocartilage development.

Rotator cuffs heal with an interposed layer of scar tissue that makes repairs prone to failure. Cell-based biologic therapies have the potential to augment this healing process. Scleraxis (Scx) is a transcription factor that is involved in tendon development during embryogenesis, and may help drive stem cells toward tenocyte differentiation in adults. QUESTIONS/HYPOTHESIS: (1) Overexpression of Scx with adenoviral-mediated gene transfer in stem cells will drive pluripotent stem cells toward tenoblastogenic lineages in vitro; (2) the application of these genetically modified cells will result in improved histologic and biomechanical healing of rotator cuff repairs.For the first hypothesis, we will determine whether stem cells derived from various sources can differentiate into tenocytes when genetically modified with Scx in vitro. We will assess morphologic features of cells with light microscopy, and gene expression analyses to confirm phenotypes consistent with tenocyte differentiation. For the second hypothesis, we will determine whether these genetically modified cells augment rotator cuff repairs in a rat model based on histology and biomechanical outcomes.Development of this technology may substantially advance our ability to repair large to massive rotator cuff tears while limiting the rates of anatomic failure.

Adipose-derived mesenchymal stem cells (ADMSCs) are a unique population of stem cells with therapeutic potential in the treatment of connective tissue injuries. Growth differentiation factor-5 (GDF)-5 is known to play a role in tendon repair and maintenance. The aim of this study was to investigate the effects of GDF-5 on proliferation and tendonogenic gene expression of rat ADMSCs.ADMSCs were treated in culture with different concentrations of GDF-5 (0-1000 ng/mL) for 12 days. Biochemical, temporal, and concentration kinetic studies were done. Extracellular matrix (ECM) synthesis, tendonogenic differentiation, and matrix remodeling gene and protein expression were analyzed.GDF-5 led to increased ADMSC proliferation in a dose- and time-dependent manner. ADMSCs demonstrated enhanced ECM (collagen type I, decorin, and aggrecan) and tendonogenic marker (scleraxis, tenomodulin, and tenascin-C) gene expression with 100 ng/mL of GDF-5 (p0.05). ECM and tendon-specific markers showed time-dependent increases at various time points (p0.05), although decorin decreased at day 9 (p0.05). GDF-5 did alter expression of matrix remodeling genes, with no specific trends observed. Western blot analysis confirmed dose- and time-dependent increases in protein expression of tenomodulin, tenascin-C, Smad-8, and matrix metalloproteinase-13.In vitro GDF-5 treatment can induce cellular events leading to the tendonogenic differentiation of ADMSCs. The use of combined GDF-5 and ADMSCs tissue-engineered therapies may have a role in the future of tendon repair.

Human embryonic stem cells (hESC) and their differentiated progenies are an attractive cell source for transplantation therapy and tissue engineering. Nevertheless, the utility of these cells for tendon tissue engineering has not yet been adequately explored. This study incorporated hESC-derived mesenchymal stem cells (hESC-MSCs) within a knitted silk-collagen sponge scaffold, and assessed the efficacy of this tissue-engineered construct in promoting tendon regeneration. When subjected to mechanical stimulation in vitro, hESC-MSCs exhibited tenocyte-like morphology and positively expressed tendon-related gene markers (e.g. Collagen type I & III, Epha4 and Scleraxis), as well as other mechano-sensory structures and molecules (cilia, integrins and myosin). In ectopic transplantation, the tissue-engineered tendon under in vivo mechanical stimulus displayed more regularly aligned cells and larger collagen fibers. This in turn resulted in enhanced tendon regeneration in situ, as evidenced by better histological scores and superior mechanical performance characteristics. Furthermore, cell labeling and extracellular matrix expression assays demonstrated that the transplanted hESC-MSCs not only contributed directly to tendon regeneration, but also exerted an environment-modifying effect on the implantation site in situ. Hence, tissue-engineered tendon can be successfully fabricated through seeding of hESC-MSCs within a knitted silk-collagen sponge scaffold followed by mechanical stimulation.

Anterior cruciate ligament (ACL)-derived cells have a character different from medial collateral ligament (MCL)-derived cells. However, the critical difference between ACL and MCL is still unclear in their healing potential and cellular response. The objective of this study was to investigate the mesenchymal differentiation property of each ligament-derived cell. Both ligament-derived cells differentiated into adipogenic, osteogenic, and chondrogenic lineages. In chondrogenesis, ACL-derived cells had the higher chondrogenic property than MCL-derived cells. The chondrogenic marker genes, Sox9 and alpha1(II) collagen (Col2a1), were induced faster in ACL-derived pellets than in MCL-derived pellets. Sox9 expression preceded the increase of Col2a1 in both pellet-cultured cells. However, the expression level of Sox9 and a ligament/tendon transcription factor Scleraxis did not parallel the increase of Col2a1 expression along with chondrogenic induction. The present study demonstrates that the balance between Sox9 and Scleraxis have an important role in the chondrogenic differentiation of ligament-derived cells.

Recent evidences have suggested that humoral factors released from the appropriate co-cultured cells influenced the expansion and differentiation of mesenchymal stem cells (MSCs). However, little is known about the proliferation and differentiation of MSCs subjected to co-culture condition with tenocytes. In this study, we aimed to establish a co-culture system of MSCs and tenocytes and investigate the proliferation and tendon/ligament related gene expression of MSCs. MTT assay was used to detect the expansion of MSCs. Semi-quantitative RT-PCR was performed to investigate the expression of proliferation associated c-fos gene and tendon/ligament related genes, including type I collagen (Col I), type III collagen (Col III), tenascin C and scleraxis. Significant increase in MSCs expansion was observed after 3 days of co-culture with tenocytes. The c-fos gene expression was found distinctly higher than for control group on day 4 and day 7 of co-culture. The mRNA expression of four tendon/ligament related genes was significantly up-regulated after 14 days of co-culture with tenocytes. Thus, our research indicates that indirect co-culture with tenocytes promotes the proliferation and mRNA expression of tendon/ligament related genes in MSCs, which suggests a directed differentiation of MSCs into tendon/ligament.

Pleiotrophin (Ptn) is a secreted, developmentally regulated growth factor associated with the extracellular matrix. During mammalian embryogenesis, Ptn has been suggested to play a role in the development of various embryonic structures including nervous system and skeleton. In the avian embryo, Ptn has been proposed to be involved in limb cartilage development, but embryonic Ptn expression has not been comprehensively studied. We isolated a cDNA fragment containing the full-length coding sequence of chick Ptn and studied the expression of Ptn in detail until embryonic day 10. We, furthermore, isolated a 6,385-bp phage clone containing the Ptn cDNA of 2,551 bp and additional 3,787 bp downstream of the published Ptn cDNA sequence classifying a yet Ptn-unrelated chEST clone as the 3′ untranslated region of Ptn. Our studies revealed novel expression domains in developing somites and during limb formation. We found prominent expression in the somitocoel cells of epithelial somites, and in a sclerotomal subcompartment, the syndetome, which gives rise to the axial tendons in the vertebral motion segment. In the limbs, Ptn was markedly expressed in tendon anlagen and in phalangeal joints. Our results introduce Ptn as a novel marker gene in avian somite and tendon development.

Effective strategies to guide cell alignment and the deposition of an oriented extracellular matrix are critical for the development of anisotropic engineered tissues suitable for the repair of ligament defects. Electrospinning is a promising means to create meshes that can align adherent cells, but the effect of fiber mesh architecture on differentiation has not been examined closely. Therefore, the goal of this study was to determine the effect of fiber diameter and the degree of fiber alignment on mesenchymal progenitor cell morphology, proliferation, and ligament gene expression. Specifically, a poly(ester urethane)urea elastomer was electrospun onto rigid supports under conditions designed to independently vary the mean fiber diameter (from 0.28 to 2.3 microm) and the degree of fiber alignment. Bone marrow stromal cells--seeded onto supported meshes--adhered to and proliferated on all surfaces. Cells assumed a more spindle-shaped morphology with increasing fiber diameter and degree of fiber alignment, and oriented parallel to fibers on aligned meshes. Expression of the ligament markers collagen 1alpha1, decorin, and tenomodulin appeared to be sensitive to fiber diameter and greatest on the smallest fibers. Concurrently, expression of the transcription factor scleraxis appeared to decrease with increasing fiber alignment. These results suggest that the formation of a ligament-like tissue on electrospun scaffolds is enhanced when the scaffolds consist of aligned submicron fibers.

SummaryDuring the assembly of the musculoskeletal system, bone ridges provide a stable anchoring point and stress dissipation for the attachment of muscles via tendons to the skeleton. In this study, we investigate the development of the deltoid tuberosity as a model for bone ridge formation. We show that the deltoid tuberosity develops through endochondral ossification in a two-phase process: initiation is regulated by a signal from the tendons, whereas the subsequent growth phase is muscle dependent. We then show that the transcription factor scleraxis (SCX) regulates Bmp4 in tendon cells at their insertion site. The inhibition of deltoid tuberosity formation and several other bone ridges in embryos in which Bmp4 expression was blocked specifically in Scx-expressing cells implicates BMP4 as a key mediator of tendon effects on bone ridge formation. This study establishes a mechanistic basis for tendon-skeleton regulatory interactions during musculoskeletal assembly and bone secondary patterning.

International audience; Gastrointestinal motility is ensured by the correct coordination of the enteric nervous system and the visceral smooth muscle cells (SMCs), and defective development of SMCs results in gut malformations and intestinal obstructions. In order to identify the molecular mechanisms that control the differentiation of the visceral mesenchyme into SMCs in the vertebrate stomach, we developed microarrays to analyze the gene expression profiles of undifferentiated and differentiated avian stomachs. We identify Scleraxis, a basic-helix-loop-helix transcription factor, as a new marker of stomach mesenchyme and find that expression of Scleraxis defines the presence of two tendons closely associated to the two visceral smooth muscles. Using targeted gene misexpression, we show that FGF signaling is sufficient to induce Scleraxis expression and to establish two tendon domains adjacent to the smooth muscle structures. We also demonstrate that the tendon organization is perturbed by altering Scleraxis expression or function. Moreover, using primary cells derived from stomach mesenchyme, we find that undifferentiated stomach mesenchyme can give rise to both SMCs and tendon cells. These data show that upon FGF activation, selected stomach mesenchymal cells are primed to express Scleraxis and to differentiate into tendon cells. Our findings identify a new anatomical and functional domain in the vertebrate stomach that we characterize as being two intermuscular tendons closely associated with the visceral SMC structures. We also demonstrate that the coordinated development of both tendon and smooth muscle domains is essential for the correct morphogenesis of the stomach.

Tendons are collagen-based fibrous tissues that connect and transmit forces from muscle to bone. These tissues, which are high in collagen type I content, have been studied extensively to understand collagen fibrillogenesis. Although the mechanisms have not been fully elucidated, our understanding has continued to progress. Here, we review two prevailing models of collagen fibrillogenesis and discuss the regulation of the process by candidate cellular and extracellular matrix molecules. Although numerous molecules have been implicated in the regulation of collagen fibrillogenesis, we focus on those that have been suggested to be particularly relevant to collagen type I fibril formation during tendon development, including members of the collagen and small leucine-rich proteoglycan families, as well as other molecules, including scleraxis, cartilage oligomeric matrix protein, and cytoskeletal proteins.Birth Defects Research (Part C) 84:228‐244, 2008. V C 2008 Wiley-Liss, Inc.

A mesenchymal stem cell (MSC)-seeded collagen gel under static or dynamic tension is a well-established model to study the potential of MSCs in regenerating a tendon- or ligament-like tissue. Using this model, upregulation of fibrillar collagen mRNA expression and protein production has been demonstrated in response to cyclic tensile mechanical stimulation. However, the mechanisms driving MSC tenogenesis (differentiation into tendon or ligament fibroblasts) have not been elucidated. This study investigated the mechanisms of tenogenesis of human bone marrow-derived MSCs in a dynamic, three-dimensional (3D) tissue-engineering model by investigating the effects of cyclic stretching on matrix production and gene expression of candidate tendon and ligament markers. The 3D MSC tenogenesis culture system upregulated scleraxis, but cyclic stretching was required to maintain expression of this putative tendon marker over time. Enhanced tendinous neo-tissue development demonstrated with extracellular matrix staining was largely due to changes in matrix deposition and remodeling activity under dynamic loading conditions, as evidenced by differential regulation of matrix metalloproteinases at a transcriptional level with minimal changes in collagen mRNA levels. Regulation of Wnt gene expression with cyclic stimulation suggested a similar role for Wnt4 versus Wnt5a in tenogenesis as in cartilage development. This first report of the potential involvement of matrix remodeling and Wnt signaling during tenogenesis of human MSCs in a dynamic, 3D tissue-engineering model provides insights into the mechanisms of tenogenesis in a mechanoactive environment and supports the therapeutic potential of adult stem cells.

Transforming growth factor-beta (TGF-beta) signaling is crucial for mandible development. During its development, the majority of the mandible is formed through intramembranous ossification whereas the proximal region of the mandible undergoes endochondral ossification. Our previous work has shown that TGF-beta signaling is required for the proliferation of cranial neural crest (CNC)-derived ectomesenchyme in the mandibular primordium where intramembranous ossification takes place. Here we show that conditional inactivation of Tgfbr2 in CNC cells results in accelerated osteoprogenitor differentiation and perturbed chondrogenesis in the proximal region of the mandible. Specifically, the appearance of chondrocytes in Tgfbr2(fl/fl);Wnt1-Cre mice is delayed and they are smaller in size in the condylar process and completely missing in the angular process. TGF-beta signaling controls Sox9 expression in the proximal region, because Sox9 expression is delayed in condylar processes and missing in angular process in Tgfbr2(fl/fl);Wnt1-Cre mice. Moreover, exogenous TGF-beta can induce Sox9 expression in the mandibular arch. In the angular processes of Tgfbr2(fl/fl);Wnt1-Cre mice, osteoblast differentiation is accelerated and Dlx5 expression is elevated. Significantly, deletion of Dlx5 in Tgfbr2(fl/fl);Wnt1-Cre mice results in the rescue of cartilage formation in the angular processes. Finally, TGF-beta signaling-mediated Scleraxis expression is required for tendonogenesis in the developing skeletal muscle. Thus, CNC-derived cells in the proximal region of mandible have a cell intrinsic requirement for TGF-beta signaling.

The periodontal ligament (PDL) that anchors the tooth root to the alveolar bone influences the lifespan of the tooth, and PDL lost through periodontitis is difficult to regenerate. The development of new PDL-regenerative therapies requires the isolation of PDL stem cells. However, their characteristics are unclear due to the absence of somatic PDL stem cell lines and because PDL is composed of heterogeneous cell populations. Recently, we succeeded in immortalizing human PDL fibroblasts that retained the properties of the primary cells. Therefore, we aimed to establish a human PDL-committed stem cell line and investigate the effects of basic fibroblast growth factor (bFGF) on the osteoblastic differentiation of the cells. Here, we report the development of cell line 1–17, a multipotent clonal human PDL cell line that expresses the embryonic stem cell-related pluripotency genes Oct3/4 and Nanog, as well as the PDL-related molecules periostin and scleraxis. Continuous treatment of cell line 1–17 with bFGF in osteoblastic induction medium inhibited its calcification, with down-regulated expression of FGF-Receptor 1 (FGF-R1), whereas later addition of bFGF potentiated its calcification. Furthermore, bFGF induced calcification of cell line 1–17 when it was co-cultured with osteoblastic cells. These results suggest that cell line 1–17 is a PDL-committed stem cell line and that bFGF exerts dualistic (i.e., promoting and inhibitory) effects on the osteoblastic differentiation of cell line 1–17 based on its differentiation stage.

The scleraxis (Scx) gene, encoding a bHLH transcription factor, is expressed in the progenitors and cells of all tendon tissues. To determine Scx function, we produced a mutant null allele. Scx-/- mice were viable, but showed severe tendon defects, which manifested in a drastically limited use of all paws and back muscles and a complete inability to move the tail. Interestingly, although the differentiation of all force-transmitting and intermuscular tendons was disrupted, other categories of tendons, the function of which is mainly to anchor muscles to the skeleton,were less affected and remained functional, enabling the viability of Scx-/- mutants. The force-transmitting tendons of the limbs and tail varied in the severity to which they were affected, ranging from dramatic failure of progenitor differentiation resulting in the loss of segments or complete tendons, to the formation of small and poorly organized tendons. Tendon progenitors appeared normal in Scx-/-embryos and a phenotype resulting from a failure in the condensation of tendon progenitors to give rise to distinct tendons was first detected at embryonic day (E)13.5. In the tendons that persisted in Scx-/-mutants, we found a reduced and less organized tendon matrix and disorganization at the cellular level that led to intermixing of tenocytes and endotenon cells. The phenotype of Scx-/- mutants emphasizes the diversity of tendon tissues and represents the first molecular insight into the important process of tendon differentiation.

International audience; The combinatorial action of separate cis-acting elements controls the cell-specific expression of type I collagen genes. In particular, we have shown that two short elements located between -3.2 and -2.3 kb and named TSE1 and TSE2 are needed for expression of the mouse COL1a1 gene in tendon fibroblasts. In this study, we analyzed the trans-acting factors binding to TSE1 and TSE2. Gel shift experiments showed that scleraxis (SCX), which is a basic helix-loop-helix transcription factor that is expressed selectively in tendon fibroblasts, binds TSE2, preferentially as a SCX/E47 heterodimer. In transfection experiments, overexpression of SCX and E47 strongly enhanced the activity of reporter constructs harboring either four copies of TSE2 cloned upstream of the COL1a1 minimal promoter or a 3.2-kb segment of the COL1a1 proximal promoter. Analysis of TSE1 showed that it contains a consensus binding site for NFATc transcription factors. This led us to show that the NFATc4 gene is expressed in tendons of developing mouse limbs and in TT-D6 cells, a cell line that has characteristics of tendon fibroblasts. In gel shift assays, TSE1 bound NFATc proteins present in nuclear extracts from TT-D6 cells. In transfection experiments, overexpression of NFATc transactivated a reporter construct harboring four copies of TSE1 cloned upstream of the COL1a1 minimal promoter. By contrast, inhibition of the nuclear translocation of NFATc proteins in TT-D6 cells strongly inhibited the expression of the COL1a1 gene. Taken together, these results suggest that SCX and NFATc4 cooperate to activate the COL1a1 gene specifically in tendon fibroblasts.

Defects in tendon patterning and differentiation are seldom assessed in mouse mutants due to the difficulty in visualizing connective tissue structures. To facilitate tendon analysis, we have generated mouse lines harboring two different transgene reporters, alkaline phosphatase (AP) and green fluorescent protein (GFP), each expressed using regulatory elements derived from the endogenous Scleraxis (Scx) locus. Scx encodes a transcription factor expressed in all developing tendons and ligaments as well as in their progenitors. Both the ScxGFP and ScxAP transgenes are expressed in patterns recapitulating almost entirely the endogenous developmental expression of Scx including very robust expression in the tendons and ligaments. These reporter lines will facilitate isolation of tendon cells and phenotypic analysis of these tissues in a variety of genetic backgrounds.

Purpose: Tendon healing is innately weak and transfer of growth factor gene therapy may activate multiple genes necessary or specific for tendon growth and regeneration. In this study we transferred bFGF or VEGF gene by AAV2 vectors to the healing tendon in a chicken flexor tendon model. We investigated how endogenous tendon healing related genes were activated after the delivery of AAV2-bFGF or AAV2-VEGF and the differences between epitenon and endotenon using a laser capture microdissection ((LCM).Methods: Eighteen digital flexor tendons from the big toes of 9 chickens were used. The tendons were completely transected and divided into three groups: AAV-bFGF injection, AAV-VEGF injection and no-injection control. After AAV injection, the tendons were surgically repaired. At 4 weeks after surgery, the tendons were harvested. The formalin-fixed, paraffin-embedded tendons were sectioned. LCM was used to dissect epitenon and endotenon separately. The tissue was subsequently analyzed for gene expression of collagen type I alpha 1 (COL1A1), collagen type III alpha 1 (COL3A1), proliferating cell nuclear antigen (PCNA), fibronectin 1 (FN1), scleraxis (SCX) and tenascin C (TNC) using RT-qPCR analysis.Results: In AAV-VEGF and AAV-bFGF injected tendons, we found significant increases in expression of FN1, PCNA, SCX, COL1A1 and COL3A1 genes (p < 0.05 or p

International audience

Tenomodulin (TeM) is a type II transmembrane glycoprotein containing a C-terminal anti-angiogenic domain and is predominantly expressed in tendons and ligaments. Here we report that TeM expression is closely associated with the appearance of tenocytes during chick development and is positively regulated by Scleraxis (Scx). At stage 23, when Scx expression in the syndetome has extended to the tail region, TeM was detectable in the anterior eight somites. At stage 25, TeM and Scx were both detectable in the regions adjacent to the myotome. Double positive domains for these genes were flanked by a dorsal TeM single positive and a ventral Scx single positive domain. At stage 28, the expression profile of TeM in the axial tendons displayed more distinct morphological features at different levels of the vertebrae. At stage 32 and later, Scx and TeM showed similar expression profiles in developing tendons. Retroviral expression of Scx resulted in the significant upregulation of TeM in cultured tenocytes, but not in chondrocytes. In addition, the misexpression of RCAS-cScx by electroporation into the hindlimb could not induce the generation of additional tendons, but did result in the upregulation of TeM expression in the tendons at stage 33 and later. These findings suggest that TeM is a late marker of tendon formation and that Scx positively regulates TeM expression in a tendon cell lineage-dependent manner.

Periodontal disease leads to destruction of the connective tissues responsible for restraining teeth within the jaw. To date, various conventional therapies for periodontal regeneration have shown limited and variable clinical outcomes. Recent studies have suggested that newly identified human periodontal ligament stem cells (PDLSCs) may offer an alternate and more reliable strategy for the treatment of periodontal disease using a cell-based tissue engineering approach. In the present study, we generated enriched preparations of PDLSCs derived from ovine periodontal ligament using immunomagnetic bead selection, based on expression of the mesenchymal stem cell-associated antigen CD106 (vascular cell adhesion molecule 1). These CD106+ ovine PDLSCs demonstrated the capacity to form adherent clonogenic clusters of fibroblast-like cells when plated at low densities in vitro. Ex vivo-expanded ovine PDLSCs exhibited a high proliferation rate in vitro and expressed a phenotype (CD44+, CD166+, CBFA-1+, collagen-I+, bone sialoprotein+) consistent with human-derived PDLSCs. Furthermore, cultured ovine PDLSCs expressed high transcript levels of the ligament/tendon-specific early transcription factor scleraxis. Importantly, ex vivo-expanded ovine PDLSCs demonstrated the capacity to regenerate both cementum-like mineral and periodontal ligament when transplanted into NOD/SCID mice. The results from the present study suggest that ovine PDLSCs may potentially be used as a novel cellular therapy to facilitate successful and more predictable regeneration of periodontal tissue using an ovine preclinical model of periodontal disease as a prelude to human clinical studies.

Xenopus laevis larvae can regenerate an exact replica of the missing part of a limb after amputation at an early limb bud stage. However, this regenerative capacity gradually decreases during metamorphosis, and a froglet is only able to regenerate hypomorphic cartilage, resulting in a spike-like structure (spike). It has been reported that the spike has tissue deformities, e.g., a muscleless structure. However, our previous study demonstrated that the muscleless feature of the spike can be improved. The existence of other kinds of tissue, such as tendon, has not been clarified. In this study, we focused on the tendon and dermis, and we isolated the scleraxis and dermo-1 genes, which are known to be marker genes for the tendon and dermis, respectively. The expressions of these genes were investigated in both the developmental and regenerating processes of a Xenopus limb. Although muscle was needed to maintain scleraxis expression, scleraxis transcription was detectable in the muscleless spike. Additionally, although grafting of matured skin, including dermal tissue, inhibited limb regeneration, the expression of dermo-1, a dermal marker gene, was detected from the early stage of the froglet blastema. These results indicate that tendon precursor cells and dermal cells exist in the regenerating froglet blastema. Our results support the idea that spike formation in postmetamorphic Xenopus limbs is epimorphic regeneration. Developmental Dynamics 235:1065–1073, 2006. © 2006 Wiley-Liss, Inc.

Keloids are a dermal fibrotic disease whose etiology remains totally unknown and for which there is no successful treatment. Here, we employed cDNA microarray analysis to examine gene expression in keloid lesions and control skin. We found that 32 genes among the 9000 tested were strongly up-regulated in keloid lesions, of which 21 were confirmed by Northern blotting. These included at least seven chondrocyte/osteoblast marker genes, and RT-PCR analysis revealed that transcription factors specific for these genes, SOX9 and CBFA1, were induced. Immunostaining and in situ hybridization further supported that these markers are expressed in keloid lesions. Intriguingly, scleraxis, a transcription factor known as a marker of tendons and ligaments, was also induced in keloid fibroblasts. We propose that reprogramming of gene expression or disordered differentiation from a dermal pattern to that of a chondrocytic/osteogenic lineage, probably closer to that of tendon/ligament lineage, may be involved in the etiology of keloids.

Sertoli cells are a postmitotic terminally differentiated cell population in the adult testis that form the seminiferous tubules and provide the microenvironment and structural support for developing germ cells. The transcription factors that regulate Sertoli cell differentiation remain to be elucidated. The basic helix-loop-helix transcription factors are involved in the differentiation of a variety of cell lineages during development and are expressed in pubertal Sertoli cells. A yeast-two-hybrid procedure was used to screen a Sertoli cell library from 20-d-old pubertal rats to identify dimerization partners with the ubiquitous E47 basic helix-loop-helix transcription factor. Scleraxis was identified as one of the interacting partners. Among the cell types of the testis, scleraxis expression was found to be specific to Sertoli cells. Analysis of the expression pattern of scleraxis mRNA in developing Sertoli cells revealed an increase in scleraxis message at the onset of puberty. Sertoli cells respond to FSH to promote expression of differentiated gene products such as transferrin that aid in proper development of the germ cells. Analysis of the hormonal regulation of scleraxis expression revealed a 4-fold increase in scleraxis mRNA in response to the presence of FSH or dibutryl cAMP in cultured Sertoli cells. An antisense oligonucleotide procedure and overexpression analysis were used to determine whether scleraxis regulates the expression of Sertoli cell differentiated gene products. An antisense oligonucleotide to scleraxis down-regulated transferrin promoter activity in Sertoli cells. A transient overexpression of scleraxis in Sertoli cells stimulated transferrin and androgen binding protein promoter activities and the expression of a number of differentiated genes. Observations suggest scleraxis functions in a number of adult tissues and is involved in the regulation and maintenance of Sertoli cell function and differentiation. This is one of the first adult and nontendon/chondrocyte-associated functions described for scleraxis.

The diverse cellular contributions to the skeletal elements of the vertebrate shoulder and pelvic girdles during embryonic development complicate the study of their patterning. Research in avian embryos has recently clarified part of the embryological basis of shoulder formation. Although dermomyotomal cells provide the progenitors of the scapular blade, local signals appear to have an essential guiding role in this process. These signals differ from those that are known to pattern the more distal appendicular skeleton. We have studied the impact of Tbx15, Gli3, Alx4 and related genes on formation of the skeletal elements of the mouse shoulder and pelvic girdles. We observed severe reduction of the scapula in double and triple mutants of these genes. Analyses of a range of complex genotypes revealed aspects of their genetic relationship, as well as functions that had been previously masked due to functional redundancy. Tbx15 and Gli3 appear to have synergistic functions in formation of the scapular blade. Scapular truncation in triple mutants of Tbx15, Alx4 and Cart1indicates essential functions for Alx4 and Cart1 in the anterior part of the scapula, as opposed to Gli3 function being linked to the posterior part. Especially in Alx4/Cart1 mutants, the expression of markers such as Pax1, Pax3 and Scleraxis is altered prior to stages when anatomical aberrations are visible in the shoulder region. This suggests a disorganization of the proximal limb bud and adjacent flank mesoderm, and is likely to reflect the disruption of a mechanism providing positional cues to guide progenitor cells to their destination in the pectoral girdle.

Limited supplies of tendon tissue for use in reconstructive surgery require development of phenotypically stable tenocytes cultivated in vitro. Tenocytes in monolayer culture display an unstable phenotype and tend to dedifferentiate, but those in three-dimensional culture may remain phenotypically and functionally differentiated. In this study we established a three-dimensional high-density culture system for cultivation of human tenocytes for tissue engineering. Human tenocytes were expanded in monolayer culture before transfer to high-density culture. The synthesis of major extracellular matrix proteins and the ultrastructural morphology of the three-dimensional cultures were investigated for up to 2 weeks by electron microscopy, immunohistochemistry, immunoblotting and quantitative, real-time PCR. Differentiated tenocytes were able to survive over a period of 14 days in high-density culture. During the culture period tenocytes exhibited a typical tenocyte morphology embedded in an extensive extracellular matrix containing cross-striated collagen type I fibrils and proteoglycans. Moreover, expression of the tendon-specific marker scleraxis underlined the tenocytic identity of these cells. Taken together, we conclude that the three-dimensional high-density cultures may be useful as a new approach for obtaining differentiated tenocytes for autologous tenocyte transplantation to support tendon and ligament healing and to investigate the effect of tendon-affecting agents on tendon in vitro.

Members of the Twist subfamily of basic helix-loop-helix transcription factors are important for the specification of mesodermal derivatives during vertebrate embryogenesis. This subfamily includes both transcriptional activators such as scleraxis, Hand2, and Dermo-1 and repressors such as Twist and Hand1. Paraxis is a member of this subfamily, and it has been shown to regulate morphogenetic events during somitogenesis, including the transition of cells from mesenchyme to epithelium and maintaining anterior/posterior polarity. Mice deficient in paraxis exhibit a caudal truncation of the axial skeleton and fusion of the vertebrae. Considering the developmental importance of paraxis, it is important for future studies to understand the molecular basis of its activity. Here we demonstrate that paraxis can function as a transcriptional activator when it forms a heterodimer with E12. Paraxis is able to bind to a set of E-boxes that overlaps with the closely related scleraxis. Paraxis expression precedes that of scleraxis in the region of the somite fated to form the axial skeleton and tendons and is able to direct transcription from an E-box found in the scleraxis promoter. Further, in the absence of paraxis, Pax-1 is no longer expressed in the somites and presomitic mesoderm. These results suggest that paraxis may regulate early events during chondrogenesis by positively directing transcription of sclerotome-specific genes.

Abnormalities in valvuloseptal development significantly contribute to congenital heart defects, yet the underlying causes are complex and poorly understood. Early cardiac regulatory genes are differentially expressed during valvuloseptal development, consistent with novel functions during heart chamber formation in chicken and mouse embryos. Distinct valve cell lineages were identified in the leaflets, chordae tendineae, and myotendinous junctions with the papillary muscles based on restricted expression of extracellular matrix molecules. Specific cell types within these structures demonstrate characteristics of chondrogenesis and tendon development, identified by scleraxis, type II collagen, and tenascin expression. In chicken embryos, valve remodeling and maturation accompanies a decrease in mitotic index indicated by reduced bromodeoxyuridine incorporation. Analysis of Tie2-cre x ROSA26R mice demonstrates that mature valve structures, including the atrioventricular and outflow tract semilunar valve leaflets, chordae tendineae, and the fibrous continuity that connects the septal leaflets of mitral and tricuspid valves, arise from endothelial cells of the endocardial cushions. Together, these studies provide novel insights into the origins and cell lineage diversity of mature valve structures in the developing vertebrate heart.

Osteogenic protein-1 (OP-1, also called BMP-7), a member of the BMP family and the TGF-β superfamily, induces formation of new bone and cartilage, but also regulates a wide array of processes. In the present study, the expression of several characteristic biochemical markers of ligaments, such as Six1, Scleraxis, aggrecan, and type I collagen in primary cultures of adult rat medial collateral ligament (MCL) cells was determined. The effects of OP-1 on cell proliferation and on gene expression were subsequently examined. OP-1 stimulated cell proliferation, alkaline phosphatase (AP) activity, and the steady-state mRNA levels of the transcription factor Runx2/Cbfa1 in a dose- and time-dependent manner. The mRNA levels of type I collagen only increased slightly, but the activity of the cloned collagen promoter increased by 2-fold in transiently transfected MCL cells. OP-1 also stimulated aggrecan mRNA expression. The mRNA levels of Six1 and Scleraxis were not detectably altered by OP-1. In control cultures, the steady-state mRNA levels of ActR-I, BMPR-IA, BMPR-IB, and BMPR-II increased as a function of time in culture. The mRNA levels of BMP-1 and -4 increased significantly after 12 days, but those of BMP-2 and -6 did not change. The GDF-1, -3, -5, -6, and -8 mRNA levels in the control cultures also increased as a function of time. OP-1 treatment stimulated mRNA expression of BMPR-IA and BMPR-II, but had little effect on ActR-I and BMPR-IB mRNA expression. OP-1 lowered the BMP-1, -2, and -6 mRNA levels without changing the BMP-4 mRNA level. OP-1 treatment also reduced the mRNA levels of GDFs detected. In summary, the present study demonstrated that OP-1 stimulated cell proliferation and mRNA expression of several biochemical markers in this ligament cell culture model and established the spatial and temporal appearance of several members of the TGF-β superfamily. © 2003 Wiley-Liss, Inc.

Background 5-Aza-2′-deoxycytidine (dAZA), causes hindlimb phocomelia in CD-1 mice. Studies in our laboratory have examined the hypothesis that compound- induced changes in gene expression may uniquely affect hindlimb pattern formation. The present study tests the hypothesis that dAZA causes limb dysplasia by inducing cytotoxicity among rapidly proliferating cells in the limb bud mesenchyme. Methods Pregnant CD-1 mice were given a teratogenic dose of dAZA (i.p.) at different times on GD 10 and fetuses evaluated for skeletal development in both sets of limbs by standard methods. Using general histology and BrdU immunohistochemistry, limb mesenchymal cell death and cell proliferation were then assessed in embryos at various times post dosing, shortly after initial limb bud outgrowth. The effect of dAZA on early limb chondrogenesis was also studied using Northern analysis of scleraxis and Alcian blue staining of whole mount limb buds. Results Compound related hindlimb defects were not restricted to a specific set of skeletal elements but consisted of a range of temporally related limb anomalies. Modest defects of the radius were observed as well. These results are consistent with a general insult to the limb mesenchyme. Mesenchymal cell death and reduced cell proliferation were also observed in both sets of limbs. The timing and location of these effects indicate a role for cytotoxicity in the etiology of dAZA induced limb defects. These effects also agree with the greater teratogenicity of dAZA in the hindlimb because they were more pronounced in that limb. The expression of scleraxis, a marker of early chondrogenesis, was reduced 12 hr after dAZA exposure, a time coincident with maximal cell death, as was the subsequent emergence of Alcian blue stained long bone anlagen. Conclusions These findings support the hypothesis that cytotoxic changes in the limb bud mesenchyme during early limb outgrowth can induce the proximal limb truncations characteristic of phocomelia after dAZA administration. Teratology 65:180–190, 2002. © 2002 Wiley-Liss, Inc.

Introduction Overuse tendinopathy is one of the most common diseases in the orthopaedic region. Hyaluronic acid (HA) and Platelet-rich plasma (PRP) injection into or around the tendon seemed to be an option for difficult-to-treat tendinopathy according to recent research, however the mechanisms of these materials were not well known. The purpose of this study was to evaluate the tendon and chondrogenic markers after injecting HA and PRP for a murine overuse supraspinatus tendinopathy model. Material and Methods Tendinopathy models were made by 6-week forced decreased treadmill running according to Soslowsky’s methods [Soslowsky, 2006]. They were divided into 4 groups; Time 0 after running protocol (time 0), and 1 week after running protocol with 3 different treatments (No injection [rest], HA injection [HA] and PRP injection [PRP]). HA or PRP were injected once transcutaneously into subacrominal space just after the end of the running protocol. PRP were made by double spinning methods from allograft. Supraspinatus tendons were harvested under anaesthesia and mRNAs were extracted by Tissue Fibrous RNeasy kit (Qiagen). Tendon markers (decorin, Col1α1, Col3α1, tenascin-C, tenomodulin, scleraxis) and chondrogenic markers (byglican, aggrecan, Col 2 α1, SOX9) were detected by real time RT-PCR. Relative mRNAs compared to control rats (without running) were calculated. One-way ANOVA and post-hoc Tukey were used for statistical analysis. Results Tendon marker: scleraxis, tenomodulin, decorin, and Col3α1 were not significantly different among the 4 groups. Tenascin C in rest, HA and PRP were significantly decreased compared to time 0. Col1α1 was significantly increased in HA compared to time 0 [Table 1]. Chondrogenic markers: aggrecan, Col 2 α1 and SOX9 were not significantly different among the 4 groups. Biglycan in rest, HA and PRP were significantly decreased compared to time 0 [Table 2]. Discussion There were no significant differences between the treatment groups. Thus, we could not find any superiority of the HA and PRP injection, but only HA group showed significant increase of Col1α1. HA might be the best choice to create new type collagen in the early stage. Col 2 a1 and Sox9 were increased after 4 week running in a previous report [Archambault, 2007]. However we could not detect these chondrogenic changes. Cook et al. [2004] reported that degenerative changes were more severe in the proximal side near insertion. Possible reasons for this were the small number of samples or that the specimens we examined were only middle of tendon substance. Different times and different places of tendon might produce different results. References Archambault JM, et al . J Orthop Res. 2007;25:617–624 Cook LJ, et al . J Orthop Res. 2004;22:334–338 Soslowsky LJ, et al . J Shoulder Elbow Surg,1996;5:383–392

Introduction Mesenchymal stem cells (MSCs) have prospective applications in regenerative medicine and tissue engineering, demonstrating promising results (Mazzocca, 2010). In particular they represent an attractive possibility for tendon repair and regeneration (Butler, 2008). A number of studies have used MSCs to make tendon-like constructs in-vitro (Butler, 2010; Kapacee, 2010). Furthermore the principles of tissue engineering involve a complex interplay of factors (Kennard, 2011) and there is some question as to what extent these cells are subject to ageing. Consequently, any loss in functionality with age would have profound consequences for the maintenance of tissue viability and the quality of tissues. The capacity of MSCs to differentiate into various types of tissue seems to change with age (Ross, 2000). However no studies have been undertaken on age-related effects on differentiation potential into tendon. This study aims to evaluate the proteome of tendon constructs synthesised from young and old MSCs. Methods MSCs at passage 4 from young; n = 15 (22.2 years ± 2.3 SD) and old; n = 6 (64.8 years ± 6.6 SD) human donors were used to make tendon constructs as previously described (Kapacee, 2010). These were harvested after 28days. Tenogenic differentiation was assessed using histology, electron microscopy (EM) and quantitative real-time PCR. Following protein extraction from the constructs using 0.1% Rapigest™ and tryptic digestion, peptides were identified using liquid chromatography mass with a linear ion-trap Orbitrap mass spectrometer. Using Progenesis™ LC-MS the top 5 spectra were exported for database searching in PEAKS ® 7 against the Unihuman database. Proteins were identified with a false discovery rate of 1% and a minimum of 2 peptides per protein. The resulting peptide-spectrum matches were imported into Progenesis™ LC-MS for label-free relative quantification. Pathway analysis was undertaken using Ingenuity Pathway Analysis. Results A tenogenic phenotype was demonstrated by an increase in collagen 1 alpha 1, scleraxis and thrombospondin 4 gene expression in tendon constructs compared to undifferentiated MSCs. In addition collagen fibril formation was demonstrated using Masson’s Trichrome staining and brightfield microscopy or EM. There were no gross differences in histology between constructs from young and old MSCs. A total of 1401 proteins (young) and 1971 proteins (old) were identified, 207 with a greater than 2 fold change and false discovery adjusted p value Pathway networks including carbohydrate metabolism, glycolysis, gluconeogenesis, protein ubiquitination, and metabolism of proteins suggest an up regulation in energy metabolism and increased protein turnover in constructs derived from older donors. In addition upstream regulators identified included transforming growth factor B1 (TGFβ1), interleukin 1β (IL1β) and SMAD3. Discussion In tendon constructs derived from older MSCs there is evidence for increased energy metabolism, and matrix deposition and turnover. Interestingly SMAD3was identified as an upstream regulator; a critical regulator of tendon formation and protein expression especially matrix proteins. This together with an increase in a number of matrix proteins implies that constructs made from older MSCs may have the capacity to produce constructs with improved matrix. The increase in proteases may suggest increased turnover. Further work is required to determine what these protein changes mean to the mechanical competence of the constructs. References Butler et al . J Orthop Res 2008;26(1):1–9 Kapacee et al . Matrix Biol 2010;29:668–677 Kennard et al . Open Orthop J 2011;5(2):249–252 Mazzocca et al . Am J Sport Med 2010;38(7):1438–1447 Ross et al . Science 2000;289(5481):950–953

Introduction Tendon has a very slow self-healing capacity after injury 1 and tendon-derived stem cells (TDSCs) can be used in tendon regeneration and tendon wound healing. 2 In in-vivo situation and during inflammation, tendon could be subjected to oxidative stress. Studies show that oxidative stress can cause apoptosis in tendon fibroblast and contribute to tendon degeneration. 3 Also, oxidative stress can cause senescence in mesenchymal stem cells. 4 However, the effects of oxidative stress on tendon-derived stem cells are still unknown. The aim of this study is to investigate the effect of oxidative stress (hydrogen peroxide) on proliferation and differentiation of TDSCs. Methods Proliferation Assays TDSCs were cultured in expansion medium with 0, 0.1 and 0.5 mM hydrogen peroxide (H 2 O 2 ) with a density of 100 cells/ cm. 2 The total number of cells in each well was counted by haemocytometer every two days. Tenogenic differentiation in oxidative environment TDSCs were cultured in expansion medium until confluence and then the medium changed to tenogenic medium (expansion medium plus 25ng/ml cTGF and 25 mM Ascorbic acid) to induce tenogenic differentiation for 14 days with or without the presence of H 2 O 2 (0.1 or 0.5 mM). TDSCs cultured in expansion medium served as a control. Four tenogenic markers, Tenomodulin (Tnmd), Elastin (Eln), Scleraxis (Scx) and Collagen type one (Col1a1) were examined by real time PCR Alizarin red S staining To test if oxidative stress will drive TDSCs towards osteogenic differentiation in tenogenic niche. 2% Alizarin Red S solution was used to indicate the formation of calcium nodules in TDSCs cultured 21 days in tenogenic medium. Results and discussion The proliferation rate of TDSCs is significantly lower in 0.5 mM H 2 O 2 treatment while the difference is not statistically significant in 0.1 mM treatment compared with 0 mM group (Figure 1). Tenogenic differentiation The expression for Tnmd and Eln is significantly decreased (Figure 2) while no significant difference for the expression of Col1a1 and Scx (Data not shown). This implies that high oxidative stress may have adverse effect on TDSC differentiation. Alizarin Red S Staining Small amount of Calcium nodules formed in all the four groups and the absorbance for 0.5 mM H 2 O 2 treatment group is statistically significant compared with 0 mM H 2 O 2 group (data not shown). This implies that oxidative stress may drive TDSCs towards osteogenesis. Acknowledgement This research was made possible by resources donated by Lui Che Woo Foundation Limited. References 1 Brandl et al . J Exp Cell Res 2011;317:1541–1547 2 Ni et al . J Biomaterials 2013;(34):2024–2037 3 Sharama et al . J Musculoskelet Neuronal Interact 2006;6(2):181–190 4 Yuan et al . BBA 2003;1641:35–41