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Indeed, the beneficial effects of some stem cell therapies have been traced to immune-modulatory effects of the transplant, rather than the tissue-generating properties of the stem cells themselves. In addition to replacing lost tissue with cell therapies and in vivo reprogramming, many injurious and complex disease states evoke inflammatory responses that must also be suppressed (see the figure). INSIGHTS Nearly every human malady, be it injury, infection, chronic disease, or degenerative disease, damages tissues (1). Tissue overgrowth is a major concern of stem cell therapies because transferred cells can give rise to teratomas or other tumors. [Extracted from the article]

During the first month of life, the murine posterior-frontal suture (PF) of the cranial vault closes through endochondral ossification, while other sutures remain patent. These processes are tightly regulated by canonical Wnt signaling. Low levels of active canonical Wnt signaling enable endochondral ossification and therefore PF-suture closure, whereas constitutive activation of canonical Wnt causes PF-suture patency. We therefore sought to test this concept with a knockout mouse model. PF-sutures of Axin2−/− mice, which resemble a state of constantly activated canonical Wnt signaling, were investigated during the physiological time course of PF-suture closure and compared in detail with wild type littermates. Histological analysis revealed that the architecture in Axin2−/− PF-sutures was significantly altered in comparison to wild type. The distance between the endocranial layers was dramatically increased and suture closure was significantly delayed. Moreover, physiological endochondral ossification did not occur, rather an ectopic cartilage appeared between the endocranial and ectocranial bone layers at P7 which eventually involutes at P13. Quantitative PCR analysis showed the lack of Col10α1 upregulation in Axin2−/− PF-suture. Immunohistochemistry and gene expression analysis also revealed high levels of type II collagen as compared to type I collagen and absence of Mmp-9 in the cartilage of Axin2−/− PF-suture. Moreover, TUNEL staining showed a high percentage of apoptotic chondrocytes in Axin2−/− PF-sutures at P9 and P11 as compared to wild type. These data indicated that Axin2−/− PF-sutures lack physiological endochondral ossification, contain ectopic cartilage and display delayed suture closure. [ABSTRACT FROM AUTHOR]

Abstract: Recent evidence suggests that mechanical forces can significantly impact the biologic response to injury. Integrated mechanical and chemical signaling networks have been discovered that enable physical cues to regulate disease processes such as pathologic scar formation. Distinct molecular mechanisms control how tensional forces influence wound healing and fibrosis. Conceptual frameworks to understand cutaneous repair have expanded beyond traditional cell-cytokine models to include dynamic interactions driven by mechanical force and the extracellular matrix. Strategies to manipulate these biomechanical signaling networks have tremendous therapeutic potential to reduce scar formation and promote skin regeneration. [Copyright &y& Elsevier]

Abstract: Premature closure of cranial sutures, which serve as growth centers for the skull vault, result in craniosynostosis. In the mouse posterior frontal (PF) suture closes by endochondral ossification, whereas sagittal (SAG) remain patent life time, although both are neural crest tissue derived. We therefore, investigated why cranial sutures of same tissue origin adopt a different fate. We demonstrated that closure of the PF suture is tightly regulated by canonical Wnt signaling, whereas patency of the SAG suture is achieved by constantly activated canonical Wnt signaling. Importantly, the fate of PF and SAG sutures can be reversed by manipulating Wnt signaling. Continuous activation of canonical Wnt signaling in the PF suture inhibits endochondral ossification and therefore, suture closure, In contrast, inhibition of canonical Wnt signaling in the SAG suture, upon treatment with Wnt antagonists results in endochondral ossification and suture closure. Thus, inhibition of canonical Wnt signaling in the SAG suture phenocopies craniosynostosis. Moreover, mice haploinsufficient for Twist1, a target gene of canonical Wnt signaling which inhibits chondrogenesis, have sagittal craniosynostosis. We propose that regulation of canonical Wnt signaling is of crucial importance during the physiological patterning of PF and SAG sutures. Importantly, dysregulation of this pathway may lead to craniosynostosis. [ABSTRACT FROM AUTHOR]

Abstract: Endogenous electric fields play an important role in embryogenesis, regeneration, and wound repair and previous studies have shown that many populations of cells, leukocytes, fibroblasts, epithelial cells, and endothelial cells, exhibit directed migration in response to electric fields. As regenerative therapies continue to explore ways to control mesenchymal progenitor cells to recreate desirable tissues, it is increasingly necessary to characterize the vast nature of biological responses imposed by physical phenomena. Murine adipose-derived stromal cells (mASCs) migrated toward the cathode in direct current (DC) fields of physiologic strength and show a dose dependence of migration rate to stronger fields. Electric fields also caused mASCs to orient perpendicularly to the field vector and elicited a transient increase in cytosolic calcium. Additionally, their galvanotactic response appears to share classic chemotactic signaling pathways that are involved in the migration of other cell types. Galvanotaxis is one predominant result of electric fields on mASCs and it may be exploited to engineer adult stem cell concentrations and locations within implanted grafts or toward sites of wound repair. [Copyright &y& Elsevier]

Abstract: The ability of Adipose-derived Stem Cells (ASCs) to differentiate into various tissues in vitro and in vivo, a function known as “stem cell plasticity”, makes them an appealing cell source for tissue engineering. Our laboratory is particularly focused on the potential role of adipose tissue as a readily available postnatal source of osteoprogenitor. Fibroblast growth factors (FGF) and their receptors (FGFR) are important regulators of osteogenesis. The goal of this study was to elucidate how changes in temporal expression patterns of individual components of the fibroblast growth factor (FGF) signaling axis correlate with osteogenic differentiation of mASCs. Our results indicate that FGF ligand genes, such as Fgf-2, -4, -8, and -18, displayed a differential and dynamic profile during mouse ASC (mASC) osteogenesis. Fgf-2 transcript was down-regulated, while Fgf-18 transcript level was strongly up-regulated. Interestingly, a drift in the ratio of different FGF-2 protein forms, with translation favoring the HMWFGF-2 forms, occurred during osteogenic differentiation, whereas, the expression of LMWFGF-2 form was down-regulated. This finding shares similarity with a previous study suggesting that preferential expression of the HMWFGF-2 forms is associated with a more osteogenic differentiated state of calvarial osteoblast. Moreover, a differential expression of Fgf Receptor 1 and 2 resembling that previously found in in vivo osteogenic study was observed. Thus, mASCs undergoing osteogenesis recapitulate the in vivo osteogenic differentiation expression pattern of FGF ligands and receptors of calvarial mesenchymal cells during their own osteogenic differentiation. Indeed, this observation further validates ASCs as a suitable resource for skeletal tissue engineering. [Copyright &y& Elsevier]

During mammalian skin development, wounds heal with regeneration rather than scar. Genomic microarray analysis of fetal (scarless) and postnatal (scarring) cutaneous wounds was performed to identify genes with differential expression and possible proregenerative function. Differentially expressed genes between the scarless and scarring wound transcriptomes were identified with significance analysis of microarrays. At early time points, the fraction of genes with increased expression was greater in the fetal wounds. Conversely, as time after injury increased, the fraction of genes with increased expression in postnatal wounds increased from 0% at 1 hour to 67% at 24 hours. The fetal 1- and 12-hour wound transcriptomes identified genes important in DNA transcription and repair, cell cycle regulation, protein homeostasis, and intracellular signaling. The predominant expression patterns of these genes from 1 to 24 hours predominantly revealed rapid up-regulation, followed by declining expression at 24 hours. Fewer genes with differential expression between the fetal scarless and postnatal scarring wound transcriptomes were identified at 24 hours, most of which had greater expression in the postnatal wound. Our data suggest that multiple gene products may be necessary for the coordination of skin regeneration during wound repair in the fetus. [ABSTRACT FROM AUTHOR]

The authors examine the process of hypertrophic scar formation, the results of current treatments, and areas of research likely to lead to significant advances in the field. [ABSTRACT FROM AUTHOR]

The article assesses the rate of return of the California Institute for Regenerative Medicine (CIRM), which was created by California's Proposition 71. Here, the authors review key components of the health and financial benefits Californians may have expected from the additional research funding and develop a framework for evaluating the success of California's initiative at meeting those goals.

Keloids are abnormal fibrous growths of the dermis that develop only in response to wounding and represent a form of benign skin tumor. Previous studies have shown increased protein levels of TGF-13 in keloid tissue, suggesting a strong association with keloid formation leading us to examine mechanisms for why it is more highly expressed in keloids. Here, we use serum stimulation as an in vitro model to mimic a component of the wound microenvironment and examine differential gene expression in keloid human fibroblasts (KFs) vs. normal human fibroblasts (NFs). Transcription of TGF-β2 was rapid and peaked between 1 and 6 h after serum stimulation in KFs vs. NFs. We confirmed increased TGF-β activity in the conditioned medium from KFs, but not NFs. Inhibition of second messenger signaling pathways demonstrated that only the p38 MAPK inhibitor SB-203580 could block upregulation of TGF-β2 following serum stimulation in KFs. Immunoblotting demonstrated that p38 MAPK was phosphorylated within 15 min and was maintained at a high level in KFs but not in NFs. The transcription factors activating transcription factor-2 and Elk-1 are activated by p38 MAPK, and also showed rapid and prolonged phosphorylation kinetics in KFs but not in NFs. In conclusion, increased TGF-β2 transcription in response to serum stimulation in KFs appears to be mediated by the p38 MAPK pathway. This suggests the mechanism of keloid pathogenesis may be due in part to an inherent difference in how the fibroblasts respond to wounding. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical factors modulate the morphogenesis and regeneration of mesenchymally derived tissues via processes mediated by the extracellular matrix (ECM). In distraction osteogenesis, large volumes of new bone are created through discrete applications of tensile displacement across an osteotomy gap. Although many studies have characterized the matrix, cellular and molecular biology of distraction osteogenesis, little is known about relationships between these biological phenomena and the local physical cues generated by distraction. Accordingly, the goal of this study was to characterize the local physical environment created within the osteotomy gap during long bone distraction osteogenesis. Using a computational approach, we quantified spatial and temporal profiles of three previously identified mechanical stimuli for tissue differentiation–pressure, tensile strain and fluid flow–as well as another candidate stimulus–tissue dilatation (volumetric strain). Whereas pressure and fluid velocity throughout the regenerate decayed to less than 31% of initial values within 20 min following distraction, tissue dilatation increased with time, reaching steady state values as high as 43% strain. This dilatation created large reductions and large gradients in cell and ECM densities. When combined with previous findings regarding the effects of strain and of cell and ECM densities on cell migration, proliferation and differentiation, these results indicate two mechanisms by which tissue dilatation may be a key stimulus for bone regeneration: (1) stretching of cells and (2) altering cell and ECM densities. These results are used to suggest experiments that can provide a more mechanistic understanding of the role of tissue dilatation in bone regeneration. [Copyright &y& Elsevier]

The zebrafish (Danio rerio) is an alluring model system currently used to study early embryonic development, organogenesis and gene functional analysis. However, few studies have been devoted to post-embryonic development. We have explored the possibility of using this organism to analyze how cranial suture patterning occurs. This study reports on the establishment of the zebrafish skull vault anatomy, calvarial osteogenesis, and cranial suture morphology. Our results demonstrate that the anatomy of the zebrafish cranial vault and cranial sutures is very similar to that of mammalian organisms. Indeed, the zebrafish represents a versatile and valuable model system for the study of the biogenesis of cranial sutures. Copyright © 2005 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Abstract: Cranial suture development involves a complex interaction of genes and tissues derived from neural crest cells (NCC) and paraxial mesoderm. In mice, the posterior frontal (PF) suture closes during the first month of life while other sutures remain patent throughout the life of the animal. Given the unique NCC origin of PF suture complex (analogous to metopic suture in humans), we performed quantitative real-time PCR and immunohistochemistry to study the expression pattern of the NCC determinant gene Sox9 and select markers of extracellular matrix. Our results indicated a unique up-regulated expression of Sox9, a regulator of chondrogenesis, during initiation of PF suture closure, along with the expression of specific cartilage markers (Type II Collagen and Type X Collagen), as well as cartilage tissue formation in the PF suture. This process was followed by expression of bone markers (Type I Collagen and Osteocalcin), suggesting endochondral ossification. Moreover, we studied the effect of haploinsufficiency of the NCC determinant gene Sox9 in the NCC derived PF suture complex. A decrease in dosage of Sox9 by haploinsufficiency in NCC-derived tissues resulted in delayed PF suture closure. These results demonstrate a unique development of the PF suture complex and the role of Sox9 as an important contributor to timely and proper closure of the PF suture through endochondral ossification. [Copyright &y& Elsevier]

Background: Fibroblast survival in a three-dimensional collagen matrix is dependent in part upon the rigid anchorage of the matrix to tissue culture plastic. We hypothesized that focal adhesion kinase (FAK) and protein kinase B (Akt) would be activated and that the p53 level would be low in the rigidly anchored (attached) collagen matrix; loss of anchorage (detachment) was hypothesized to have the opposite effects.Materials and methods: Human foreskin fibroblasts were cultured in attached bovine collagen matrices for 48 h before detachment as free-floating matrices. At various time points postrelease, matrix lysates were blotted for the proteins of interest, and the terminal deoxynucleotidyltransferase-mediated dUTP nick-end label assay was performed on both whole matrices and cytospin preparations. Irradiated monolayer fibroblasts were used as positive controls for the amount of p53 protein.Results: Terminal deoxynucleotidyltransferase-mediated dUTP nick-end label positivity in attached versus detached matrices (at 24 h post detachment) was 0.7 ± 03 versus 5.3 ± 1.7% (P < 0.05, unpaired t test). FAK and Akt were phosphorylated (activated) in the attached matrix; there was a near complete of loss of both activated forms within 4 h of matrix detachment. Irradiated monolayer fibroblasts had increased levels of p53, mdm2, and p21. In contrast, the p53, mdm2, and p21 levels were just at the level of detection in the attached matrix, but were induced 5- to 10-fold within 2–4 h after matrix detachment.Conclusions: FAK and Akt are activated in the attached fibroblast-populated collagen matrix whereas the p53 level is relatively low; matrix detachment downregulates FAK and Akt activity and induces p53. The state of mechanical anchorage of the collagen matrix regulates the survival of embedded fibroblasts through a mechanism which may involve FAK. [Copyright &y& Elsevier]

The fibroblast-populated collagen matrix (FPCM) has been utilized as an in vitro model of wound healing for more than 2 decades. It offers a reasonable approximation of the healing wound during the phases of established granulation tissue and early scar. The gross and microscopic morphology of the FPCM and the healing wound are similar at analogous phases. The processes of proliferation, survival/apoptosis, protein synthesis, and contraction act in similar directions in these two models, and the response to exogenous agents also is consistent between them. If its limitations are respected, then the FPCM can be used as a model of the healing wound. (WOUND REP REG 2004;12:–) [ABSTRACT FROM AUTHOR]

It is widely believed that rapid growth of the human brain generates tensile strain in cranial sutures, and that this strain influences the rate of bone deposition at the sutural margins during development. We developed general theoretical techniques for estimating sutural bone deposition rate and strain magnitude during mammalian cranial development. A geometry-based analysis was developed to estimate sutural bone deposition rate. A quasi-static stress analysis was developed to estimate sutural strain magnitude. We applied these techniques to the special case of normal cranial development in humans. The results of the bone deposition rate analysis indicate that average human sutural bone deposition rate is on the order of 100 μm/day at 1 month of age and decreases in an approximately exponential fashion during the first 4 years of life. The results of the strain analysis indicate that sutural strain magnitude is highly dependent on the assumed stiffness of the sutures, with estimated strain at 1 month of age ranging from approximately 20 to 400 microstrain. Regardless of the assumed stiffness of the sutures, the results indicate that sutural strain magnitude is small and decreases in an approximately exponential fashion during the first 4 years of life. The finding that both sutural bone deposition rate and strain magnitude decrease with increasing age is consistent with quasi-static tensile strain in sutures influencing sutural osteoblast activity in a dose-dependent manner. However, the small magnitude of the predicted strains suggests that tissue level strains in sutures may be too small to directly influence osteoblast biology. In light of these results, we suggest other biomechanical mechanisms, such as a tension-induced angiogenic environment in the sutures or mechanotransduction in the underlying dura mater, through which tension across sutures may regulate the rate of bone deposition in sutures. [Copyright &y& Elsevier]

Describes a novel rat cDNA named keratinocyte proline-rich protein (KPRP) isolated by RNA differential display during skin development. Expression of KPRP in stratified squamous epithelium; Similarity of KPRP to a human hypothetical protein; Detection of KPRP; Localization of KPRP to keratinocytes in E19 skin.

Purpose. Fibroblast survival within an in vitro collagen matrix is dependent on matrix anchorage to a rigid substratum. The purpose of this study was to determine whether granulation tissue survival in vivo also is dependent on matrix anchorage. We hypothesized that splinting an excisional wound (i.e., anchoring the wound edges) would promote granulation tissue survival and that desplinting a splinted wound would produce granulation tissue apoptosis.Methods. Eighteen Wistar rats (3 months, 350 g) underwent excisional wounding (2 × 2 cm, dorsal skin) with immediate wound splinting (a metal template affixed with sutures) on day 0. On day 6, rats (n = 6 per group) underwent splint removal (desplinted), splint removal with circumferential incision of the wound edge (desplint/release), or no intervention (splinted); sacrifice of all animals was on day 7. Frozen sections of granulation tissue were stained with TUNEL or H&E; data were analyzed with ANOVA and the unpaired t test.Results. The cross-sectional and surface area of the desplinted and desplint/release granulation tissue both decreased compared to the splinted granulation tissue (&ast;P < 0.05). The nuclear density of the desplint/release granulation tissue was 25% less compared to the splinted granulation tissue (&ast;P < 0.05). The desplinted and desplint/release apoptotic rates were twice and >10× greater than the splinted apoptotic rate, respectively (&ast;P < 0.05).Conclusions. The rate of cell death in a splinted wound (an in vivo equivalent of an anchored FPCM) is minimal to nil, which is consistent with our hypothesis. Desplinting and releasing the wound edge of a previously splinted wound (the in vivo equivalent of a detached FPCM) results in granulation tissue regression and a large increase in apoptosis. Desplinting a wound alone results in changes somewhat intermediate to the splinted and desplint/release conditions. Loss of wound anchorage acutely promotes granulation tissue apoptosis. [Copyright &y& Elsevier]

The First Joan L and Julius H Jacobson Promising Investigator Awardee, Michael T Longaker MD, FACS In 2005, the research committee of the American College of Surgeons was tasked with selecting the recipient of a newly established award, "The Joan L and Julius H Jacobson Promising Investigator Award." According to the Jacobsons, the $30,000 award funded by Dr Jacobson should be given at least once every 2 years to a surgeon investigator at "the tipping point," who can demonstrate that his/her research shows the promise of leading to a significant contribution to the practice of surgery and patient safety. Every year, the research committee receives many excellent nominations and has the difficult task of selecting 1 awardee. In 2005, the awardee was a young promising investigator, Michael T Longaker, MD, FACS. Ten years later, Dr Longaker, a prominent researcher in the field of "scar formation," presents his journey in research and the impact of the Jacobson award on his career. Dr Longaker is now a national and international figure in the field of wound healing, tissue regeneration, and stem cell research. Kamal MF Itani, MD, FACS and Gail Besner, MD, FACS, on behalf of the Research Committee of the American College of Surgeons. [ABSTRACT FROM AUTHOR]

Assesses the maternal risk of mortality, morbidity and reproductive potential after fetal surgery. Examples of advances in fetal diagnosis and treatment that treat some fetal diseases; Characteristics of the patients; Magnitude of the fetal surgical procedure.

A series of studies has shown that application of platelet-derived growth factor (PDGF) to a wound enhances the process of wound repair, especially in animals with wound-healing defects. In the current study, we investigated the regulation of PDGF A and PDGF B and theft receptors during wound repair in mice. Both ligands and both types of receptor were expressed in normal and wounded skin, whereby PDGF A and PDGF B proteins were found at different sites in the healing wound. Surprisingly, no significant induction of these genes was observed after skin injury in normal mice, and expression levels were similar at all stages of the repair process. To determine a possible role of endogenous PDGF in normal wound healing, we subsequently analyzed the regulation of PDGF and PDGF receptors during wound healing in healing-impaired animals. Genetically diabetic db/db mice showed a significant reduction in PDGF A and A-type receptor expression in non- wounded and wounded back skin. Furthermore, expression of the B-type receptor was also reduced during the repair process. Systemic glucocorticoid treatment caused a severe defect in wound repair that was accompanied by reduced expression of PDGF A and B and of the B-type receptor in the early phase of wound healing. These results provide an explanation for the beneficial effect of exogenous PDGF in the treatment of wound-healing disorders. Furthermore, our data suggest that a certain expression level of PDGF and its receptors is essential for normal repair. [ABSTRACT FROM AUTHOR]

The balance between matrix deposition and tissue turnover is fundamental in wound healing. It is likely that the balance between proteolytic enzymes and their inhibitors contributes to this balance. Matrix metalloproteinases are clearly important in tissue turnover, but their roles in wound healing are poorly understood, To investigate this, fluid from healing wounds resulting from mastectomies was collected from 1 h to 10 d post-surgery, and was analyzed for tissue inhibitor of metalloproteinases-1 concentrations. In all cases, tissue inhibitor of metalloproteinases-1 levels were initially comparable to those in serum, but increased rapidly to significantly higher levels within two days, with a tenfold average increase for five patients. On the other hand, zymography revealed that gelatinase A (72 kDa) levels increased moderately, whereas gelatinase B levels (92 kDa) decreased an average of twofold within 4 d. In contrast, fluid from chronic wounds had significantly more gelatinolytic activity, including lower-molecular-weight proteinase species that may represent activated or superactivated gelatinase fragments, as suggested by immunoprecipitation with specific antibodies. Tissue inhibitor of metalloproteinases-1 levels were lower in chronic than in healing wounds. These data may indicate that excess proteolysis in chronic wounds retards successful healing, and results from an Imbalance of proteinase and inhibitors, as well as the presence of higher levels of activated metalloproteinases. [ABSTRACT FROM AUTHOR]

Understanding the cellular and molecular determinants of mammalian tissue regeneration and repair is crucial for developing effective therapies that restore tissue architecture and function. In this review, we focus on the cell types involved in scarless wound response and regeneration of spiny mice (Acomys). Comparative -omics approaches with scar-prone mammals have revealed species-specific peculiarities in cellular behavior during the divergent healing trajectories. We discuss the developing views on which cell types engage in restoring the architecture of spiny mouse tissues through a co-ordinated spatiotemporal response to injury. While yet at the beginning of understanding how cells interact in these fascinating animals to regenerate tissues, spiny mice hold great promise for scar prevention and anti-fibrotic treatments. [ABSTRACT FROM AUTHOR]

Simple Summary: When a medical implant or electrode is placed, the body often evokes an immune response in an attempt to remove it. As it fails to do so, this inflammatory response leads to a chronic fibrosis, wherein the material is walled off from the body with scar tissue. This phenomenon is known as foreign body response (FBR) and poses a significant burden, as it often impacts the implant's function and longevity. Single-cell RNA sequencing (scRNA-seq), a technique evaluating the genes transcribed at a single-cell level within a given sample, has been used to identify targets to reduce the extent of fibrosis caused by FBR. We performed a meta-analysis collecting all available FBR mouse scRNA-seq studies to identify gene signatures specific to FBR across different models and anatomic locations. Through our integrated analysis, we identified specific groups of fibroblasts and macrophages associated with FBR, characterizing their associated genes and signaling pathways. Fibroblasts enriched in FBR had increased pro-fibrotic signatures, while macrophages enriched in FBR had both increased pro-fibrotic and pro-inflammatory profiles. Collectively, our meta-analysis identifies common cell-specific gene signatures in FBR and provides potential therapeutic targets for patients requiring long-term implanted biomedical devices. Foreign body response (FBR) is a universal reaction to implanted biomaterial that can affect the function and longevity of the implant. A few studies have attempted to identify targets for treating FBR through the use of single-cell RNA sequencing (scRNA-seq), though the generalizability of these findings from an individual study may be limited. In our study, we perform a meta-analysis of scRNA-seq data from all available FBR mouse studies and integrate these data to identify gene signatures specific to FBR across different models and anatomic locations. We identify subclusters of fibroblasts and macrophages that emerge in response to foreign bodies and characterize their signaling pathways, gene ontology terms, and downstream mediators. The fibroblast subpopulations enriched in the setting of FBR demonstrated significant signaling interactions in the transforming growth factor-beta (TGF-β) signaling pathway, with known pro-fibrotic mediators identified as top expressed genes in these FBR-derived fibroblasts. In contrast, FBR-enriched macrophage subclusters highly expressed pro-fibrotic and pro-inflammatory mediators downstream of tumor necrosis factor (TNF) signaling. Cell–cell interactions were additionally interrogated using CellChat, with identification of key signaling interactions enriched between fibroblasts and macrophages in FBR. By combining multiple FBR datasets, our meta-analysis study identifies common cell-specific gene signatures enriched in foreign body reactions, providing potential therapeutic targets for patients requiring medical implants across a myriad of devices and indications. [ABSTRACT FROM AUTHOR]

The article discusses scar formation and method of treatment which might have been caused by an injury, burns, lacerations or incisions. It states bone morphogenetic protein (BMP)) method involves myofibroblasts isolated from keloid patients induced to become adipocytes and effectively leads to scarless treatment. It states fibroblast plasticity includes cell-intrinsic and extrinsic factors and isolation techniques may be employed for scarless treatment.

Chronic non-healing wounds significantly strain modern healthcare systems, affecting 1–2% of the population in developed countries with costs ranging between $28.1 and $96.8 billion annually. Additionally, it has been established that chronic wounds resulting from comorbidities, such as peripheral vascular disease and diabetes mellitus, tend to be polymicrobial in nature. Treatment of polymicrobial chronic wounds with oral and IV antibiotics can result in antimicrobial resistance, leading to more difficult-to-treat wounds. Ideally, chronic ulcers would be topically treated with antibiotic combinations tailored to the microbiome of a patient's wound. We have previously shown that a topical collagen-rich hydrogel (cHG) can elute single antibiotics to inhibit bacterial growth in a manner that is nontoxic to mammalian cells. Here, we analyzed the microbiology of cultures taken from human patients diagnosed with diabetes mellitus suffering from chronic wounds present for more than 6 weeks. Additionally, we examined the safety of the elution of multiple antibiotics from collagen-rich hydrogel in mammalian cells in vivo. Finally, we aimed to create tailored combinations of antibiotics impregnated into cHG to successfully target and treat infections and eradicate biofilms cultured from human chronic diabetic wound tissue. We found that the majority of human chronic wounds in our study were polymicrobial in nature. The elution of multiple antibiotics from cHG was well-tolerated in mammalian cells, making it a potential topical treatment of the polymicrobial chronic wound. Finally, combinations of antibiotics tailored to each patient's microbiome eluted from a collagen-rich hydrogel successfully treated bacterial cultures isolated from patient samples via an in vitro assay. [ABSTRACT FROM AUTHOR]

Recent work has revealed that fibroblasts are remarkably heterogeneous cells, but the appropriate lens through which to study this variation (lineage, phenotype, and plasticity) and its relevance to human biology remain unclear. In this opinion article, we comment on recent breakthroughs in our understanding of fibroblast heterogeneity during skin wound healing, and on open questions that must be addressed to clinically translate these findings in order to minimize scarring in patients. We emphasize the need for experimental models of wound healing that better approximate human biology, as well as comparison of scarring and regenerative phenotypes to uncover master regulators of fibrosis. Fibroblast heterogeneity in wound healing has been described through the lenses of developmental lineage, molecular phenotype, and plasticity in response to wound cues. Fibroblast lineages differ in their embryonic expression of patterning genes such as the homeobox transcription factors Engrailed-1 and Prrx-1 ; lineage-positive fibroblasts are wound-responsive while lineage-negative fibroblasts are not. Fibroblasts are readily differentiated by molecular phenotype (surface markers, omics signature, etc.), but this approach is complicated by dynamic gene expression within the wound milieu. It is now known that fibroblasts demonstrate phenotypic plasticity in response to wound cues, but it remains to be seen if this plasticity is preserved in human wound healing. [ABSTRACT FROM AUTHOR]

Failure to properly form bone or integrate surgical implants can lead to morbidity and additional surgical interventions in a significant proportion of orthopedic surgeries. While the role of skeletal stem cells (SSCs) in bone formation and repair is well-established, very little is known about the factors that regulate the downstream Bone, Cartilage, Stromal, Progenitors (BCSPs). BCSPs, as transit amplifying progenitor cells, undergo multiple mitotic divisions to expand the pool of lineage committed progenitors allowing stem cells to preserve their self-renewal and stemness. Del1 is a protein widely expressed in the skeletal system, but its deletion led to minimal phenotype changes in the uninjured mouse. In this paper, we demonstrate that Del1 is a key regulator of BCSP expansion following injury. In Del1 knockout mice, there is a significant reduction in the number of BCSPs which leads to a smaller callus and decreased bone formation compared with wildtype (WT) littermates. Del1 serves to promote BCSP proliferation and prevent apoptosis in vivo and in vitro. Moreover, exogenous Del1 promotes proliferation of aged human BCSPs. Our results highlight the potential of Del1 as a therapeutic target for improving bone formation and implant success. Del1 injections may improve the success of orthopedic surgeries and fracture healing by enhancing the proliferation and survival of BCSPs, which are crucial for generating new bone tissue during the process of bone formation and repair. [ABSTRACT FROM AUTHOR]

Simple Summary: Pancreatic cancer is a very deadly form of cancer with a low survival rate. One important characteristic of pancreatic cancer is the presence of a dense tissue called desmoplastic stroma, which creates an environment that promotes tumor growth. Within this environment, there are specialized cells called cancer-associated fibroblasts (CAFs) that play a crucial role. They are a diverse group of cells with different functions and surface markers. When activated, CAFs support the invasion, spread, and growth of cancer cells, as well as affect the immune system. Scientists have been studying how CAFs interact with cancer cells and immune cells to understand how they contribute to tumor growth and spread. However, there is still a lot we do not know about CAFs and their role in pancreatic cancer. Further research is needed to better understand CAFs and their impact on the development and progression of pancreatic cancer. Pancreatic cancer is one of the deadliest forms of cancer with one of the lowest 5-year survival rates of all cancer types. A defining characteristic of pancreatic cancer is the existence of dense desmoplastic stroma that, when exposed to stimuli such as cytokines, growth factors, and chemokines, generate a tumor-promoting environment. Cancer-associated fibroblasts (CAFs) are activated during the progression of pancreatic cancer and are a crucial component of the tumor microenvironment (TME). CAFs are primarily pro-tumorigenic in their activated state and function as promoters of cancer invasion, proliferation, metastasis, and immune modulation. Aided by many signaling pathways, cytokines, and chemokines in the tumor microenvironment, CAFs can originate from many cell types including resident fibroblasts, mesenchymal stem cells, pancreatic stellate cells, adipocytes, epithelial cells, endothelial cells, and other cell types. CAFs are a highly heterogeneous cell type expressing a variety of surface markers and performing a wide range of tumor promoting and inhibiting functions. Single-cell transcriptomic analyses have revealed a high degree of specialization among CAFs. Some examples of CAF subpopulations include myofibrotic CAFs (myCAFs), which exhibit a matrix-producing contractile phenotype; inflammatory CAFs (iCAF) that are classified by their immunomodulating, secretory phenotype; and antigen-presenting CAFs (apCAFs), which have antigen-presenting capabilities and express Major Histocompatibility Complex II (MHC II). Over the last several years, various attempts have been undertaken to describe the mechanisms of CAF–tumor cell interaction, as well as CAF–immune cell interaction, that contribute to tumor proliferation, invasion, and metastasis. Although our understanding of CAF biology in cancer has steadily increased, the extent of CAFs heterogeneity and their role in the pathobiology of pancreatic cancer remains elusive. In this regard, it becomes increasingly evident that further research on CAFs in pancreatic cancer is necessary. [ABSTRACT FROM AUTHOR]

Mandibular distraction osteogenesis (DO) is mediated by skeletal stem cells (SSCs) in mice, which enact bone regeneration via neural crest re-activation. As peripheral nerves are essential to progenitor function during development and in response to injury, we questioned if denervation impairs mandibular DO. C57Bl6 mice were divided into two groups: DO with a segmental defect in the inferior alveolar nerve (IAN) at the time of mandibular osteotomy ("DO Den") and DO with IAN intact ("DO Inn"). DO Den demonstrated significantly reduced histological and radiological osteogenesis relative to DO Inn. Denervation preceding DO results in reduced SSC amplification and osteogenic potential in mice. Single cell RNA sequencing analysis revealed that there was a predominance of innervated SSCs in clusters dominated by pathways related to bone formation. A rare human patient specimen was also analyzed and suggested that histological, radiological, and transcriptional alterations seen in mouse DO may be conserved in the setting of denervated human mandible distraction. Fibromodulin (FMOD) transcriptional and protein expression were reduced in denervated relative to innervated mouse and human mandible regenerate. Finally, when exogenous FMOD was added to DO-Den and DO-Inn SSCs undergoing in vitro osteogenic differentiation, the osteogenic potential of DO-Den SSCs was increased in comparison to control untreated DO-Den SSCs, modeling the superior osteogenic potential of DO-Inn SSCs. [ABSTRACT FROM AUTHOR]

Wound dehiscence, oftentimes a result of the poor tensile strength of early healing wounds, is a significant threat to the post‐operative patient, potentially causing life‐threatening complications. Vanadate, a protein tyrosine phosphatase inhibitor, has been shown to alter the organisation of deposited collagen in healing wounds and significantly improve the tensile strength of incisional wounds in rats. In this study, we sought to explore the effects of locally administered vanadate on tensile strength and collagen organisation in both the early and remodelling phases of excisional wound healing in a murine model. Wild‐type mice underwent stented excisional wounding on their dorsal skin and were divided equally into three treatment conditions: vanadate injection, saline injection control and an untreated control. Tensile strength testing, in vivo suction Cutometer analysis, gross wound measurements and histologic analysis were performed during healing, immediately upon wound closure, and after 4 weeks of remodelling. We found that vanadate treatment significantly increased the tensile strength of wounds and their stiffness relative to control wounds, both immediately upon healing and into the remodelling phase. Histologic analysis revealed that these biomechanical changes were likely the result of increased collagen deposition and an altered collagen organisation composed of thicker and distinctly organised collagen bundles. Given the risk that dehiscence poses to all operative patients, vanadate presents an interesting therapeutic avenue to improve the strength of post‐operative wounds and unstable chronic wounds to reduce the risk of dehiscence. [ABSTRACT FROM AUTHOR]

Background: Radiation-induced skin injury is a well-known risk factor for impaired wound healing. Over time, the deleterious effects of radiation on skin produce a fibrotic, hypovascular dermis poorly suited to wound healing. Despite increasing understanding of the underlying pathophysiology, therapeutic options remain elusive. Deferoxamine (DFO), an iron-chelating drug, has been shown in prior murine studies to ameliorate radiation-induced skin injury as well as improve wound healing outcomes in various pathologic conditions when administered transdermally. In this preclinical study, we evaluated the effects of deferoxamine on wound healing outcomes in chronically irradiated murine skin.Methods: Wild-type mice received 30 Gy of irradiation to their dorsal skin and were left to develop chronic fibrosis. Stented excisional wounds were created on their dorsal skin. Wound healing outcomes were compared across 4 experimental conditions: DFO patch treatment, vehicle-only patch treatment, untreated irradiated wound, and untreated nonirradiated wounds. Gross closure rate, wound perfusion, scar elasticity, histology, and nitric oxide assays were compared across the conditions.Results: Relative to vehicle and untreated irradiated wounds, DFO accelerated wound closure and reduced the frequency of healing failure in irradiated wounds. DFO augmented wound perfusion throughout healing and upregulated angiogenesis to levels observed in nonirradiated wounds. Histology revealed DFO increased wound thickness, collagen density, and improved collagen fiber organization to more closely resemble nonirradiated wounds, likely contributing to the observed improved scar elasticity. Lastly, DFO upregulated inducible nitric oxide synthase and increased nitric oxide production in early healing wounds.Conclusion: Deferoxamine treatment presents a potential therapeutic avenue through which to target impaired wound healing in patients following radiotherapy. [ABSTRACT FROM AUTHOR]

The skin is a complex organ involved in thermoregulation, gas exchange, protection against pathogens, and barrier function to maintain proper hydration. When dry, the ability for skin to execute these tasks becomes impaired. Dry skin affects almost everyone as we age, but it is also dependent on external factors, such as dry climate, colder temperatures, and repeated washing. In addition, increasing evidence has shown racial variability in the physiological properties of skin, which directly impacts water content of the stratum corneum and sensitivity to exogenously applied agents. A multitude of products have been developed to treat dry skin, and as a group, moisturizers have been designed to either impart or restore hydration in the stratum corneum. Given the large number of moisturizers presently available, depending on individual components, several different mechanisms may be employed to promote skin hydration. As there exists dramatic racial variability in skin properties, certain moisturizers may thus be more effective in some and less effective in others to treat the common condition of dry skin. [ABSTRACT FROM AUTHOR]

The skin is a complex organ involved in thermoregulation, gas exchange, protection against pathogens, and barrierfunction to maintain proper hydration. When dry, the ability for skin to execute these tasks becomes impaired. Dry skinaffects almost everyone as we age, but it is also dependent on external factors, such as dry climate, colder temperatures,and repeated washing. In addition, increasing evidence has shown racial variability in the physiological properties of skin,which directly impacts water content of the stratum corneum and sensitivity to exogenously applied agents. A multitudeof products have been developed to treat dry skin, and as a group, moisturizers have been designed to either impart orrestore hydration in the stratum corneum. Given the large number of moisturizers presently available, depending onindividual components, several different mechanisms may be employed to promote skin hydration. As there existsdramatic racial variability in skin properties, certain moisturizers may thus be more effective in some and less effectivein others to treat the common condition of dry skin. [ABSTRACT FROM AUTHOR]

Biological scaffolds such as hydrogels provide an ideal, physio-mimetic of native extracellular matrix (ECM) that can improve wound healing outcomes after cutaneous injury. While most studies have focused on the benefits of hydrogels in accelerating wound healing, there are minimal data directly comparing different hydrogel material compositions. In this study, we utilized a splinted excisional wound model that recapitulates human-like wound healing in mice and treated wounds with three different collagen hydrogel dressings. We assessed the feasibility of applying each dressing and performed histologic and histopathologic analysis on the explanted scar tissues to assess variations in collagen architecture and alignment, as well as the tissue response. Our data indicate that the material properties of hydrogel dressings can significantly influence healing time, cellular response, and resulting architecture of healed scars. Specifically, our pullulan-collagen hydrogel dressing accelerated wound closure and promoted healed tissue with less dense, more randomly aligned, and shorter collagen fibres. Further understanding of how hydrogel properties affect the healing and resulting scar architecture of wounds may lead to novel insights and further optimization of the material properties of wound dressings. [ABSTRACT FROM AUTHOR]

Human skin is a highly specialized mechanoresponsive interface separating our bodies from the external environment. It must constantly adapt to dynamic physical cues ranging from rapid expansion during embryonic and early postnatal development to ubiquitous external forces throughout life. Despite the suspected role of the physical environment in cutaneous processes, the fundamental molecular mechanisms responsible for how skin responds to force remain unclear. Intracellular pathways convert mechanical cues into biochemical responses (in a process known as mechanotransduction) via complex mechanoresponsive elements that often blur the distinction between physical and chemical signaling. For example, cellular focal adhesion components exhibit dual biochemical and scaffolding functions that are critically modulated by force. Moreover, the extracellular matrix itself is increasingly recognized to mechanically regulate the spatiotemporal distribution of soluble and matrix-bound ligands, underscoring the importance of bidirectional crosstalk between cells and their physical environment. It seems likely that a structural hierarchy exists to maintain both cells and matrix in mechanical homeostasis and that dysregulation of this architectural integrity may underlie or contribute to various skin disorders. An improved understanding of these interactions will facilitate the development of novel biophysical materials and mechanomodulatory approaches to augment wound repair and regeneration. [ABSTRACT FROM AUTHOR]

Background: As a culmination of efforts over the last years, our knowledge of the embryonic origins of the mammalian frontal and parietal cranial bones is unambiguous. Progenitor cells that subsequently give rise to frontal bone are of neural crest origin, while parietal bone progenitors arise from paraxial mesoderm. Given the unique qualities of neural crest cells and the clear delineation of the embryonic origins of the calvarial bones, we sought to determine whether mouse neural crest derived frontal bone differs in biology from mesoderm derived parietal bone. Methods: BrdU incorporation, immunoblotting and osteogenic differentiation assays were performed to investigate the proliferative rate and osteogenic potential of embryonic and postnatal osteoblasts derived from mouse frontal and parietal bones. Co-culture experiments and treatment with conditioned medium harvested from both types of osteoblasts were performed to investigate potential interactions between the two different tissue origin osteoblasts. Immunoblotting techniques were used to investigate the endogenous level of FGF-2 and the activation of three major FGF signaling pathways. Knockdown of FGF Receptor 1 (FgfR1) was employed to inactivate the FGF signaling. Results: Our results demonstrated that striking differences in cell proliferation and osteogenic differentiation between the frontal and parietal bone can be detected already at embryonic stages. The greater proliferation rate, as well as osteogenic capacity of frontal bone derived osteoblasts, were paralleled by an elevated level of FGF-2 protein synthesis. Moreover, an enhanced activation of FGF-signaling pathways was observed in frontal bone derived osteoblasts. Finally, the greater osteogenic potential of frontal derived osteoblasts was dramatically impaired by knocking down FgfR1. Conclusions: Osteoblasts from mouse neural crest derived frontal bone displayed a greater proliferative and osteogenic potential and endogenous enhanced activation of FGF signaling compared to osteoblasts from mesoderm derived parietal bone. FGF signaling plays a key role in determining biological differences between the two types of osteoblasts. [ABSTRACT FROM AUTHOR]

Abstract: In the skull vault, neural crest derived frontal bones have an increased healing capacity and higher expression levels of Fibroblast Growth Factor-ligands as compared to mesoderm-derived parietal bones. Thus, we asked whether Fibroblast Growth Factor-ligands are responsible for the superior healing potential of frontal bones. Parietal defects in juvenile and adult mice treated with Fibroblast Growth Factor-2, -9 and -18 showed increased bone regeneration, comparable to frontal defects. Immunohistochemistry revealed increased recruitment of osteoprogenitors and activation of FGF-signaling pathways in FGF-treated parietal defects. Conversely, calvarial defects in Fgf-9 + /− and Fgf-18 + /− mice showed impaired calvarial healing which could be rescued by exogenous Fibroblast Growth Factor-ligands. Moreover, by utilizing Wnt1Cre/R26R mice, the migration and contribution of dura mater and pericranium cells to calvarial healing could be demonstrated. Taken together our results demonstrated that different endogenous threshold levels of Fibroblast Growth Factor-ligands in frontal and parietal bones have a profound impact on calvarial regeneration. The present study thereby opens new avenues for translational medicine. [Copyright &y& Elsevier]

Bone heating requires a complex interaction of growth factors that establishes an environment for efficient bone regeneration. Among these, FGFs have been considered important for intrinsic bonehealing capacity. In this study, we analyzed the role of Fgf-9 in long bone repair. One-millimeter unicortical defects were created in tibias of Fgf-9+/-nd wild-type mice: Histomorphometry revealed that half-dose gene of Fgf-9 markedly reduced bone regeneration as compared with wild-type. Both immunohistochemistry and RT-PCR analysis revealed markedly decreased levels of proliferating cell nuclear antigen (PCNA), Runt-related transcription factor 2 (Runx2), osteocalcin, Vega-a. and platelet endothelial cell adhesion molecule 1 (PECAM-1) in Fgf-9+/- defects. μCT angiography indicated dramatic impairment of neovascularization in Fgf-9+/- mice as compared with controls. Treatment with FGF-9 protein promoted angiogenesis and successfully rescued the healing capacity of Fgf-9+/- mice. Importantly, although other pro-osteogenic factors [Fgf-2, Fgf-18, and bone morphogenic protein 2 (Bmp-2)) still were present in Fgf-9+/- mice, they could not compensate for the haploinsufficiency of the Fgf-9 gene. Therefore, endogenous Fgf-9 seems to play an important role in long bone repair. Taken together our data suggest a unique role for Fgf-9 in bone healing, presumably by initiating angiogenesis through Vegf-a. Moreover, this study further supports the embryonic phenotype previously observed in the developing limb, thus promoting the concept that healing processes in adult organisms may recapitulate embryonic skeletal development. [ABSTRACT FROM AUTHOR]

Abstract: Adipose-derived adult stem cells (ASCs), like their bone-marrow derived counterparts, possess the ability to differentiate down osteogenic, chondrogenic, adipogenic, and myogenic pathways. For bone differentiation of mouse ASCs (mASCs), retinoic-acid mediated upregulation of BMPR-IB has been found to be necessary. Interestingly, our previous work has also shown Fibroblast Growth Factor-2 (FGF-2) to strongly inhibit this osteogenic differentiation, even in the presence of retinoic acid. In this report, we investigated the molecular mechanisms underlying FGF-2 mediated osteogenic inhibition, demonstrating that addition of exogenous FGF-2 to mASCs antagonizes upregulation of BMPR-IB gene expression in response to retinoic acid. In addition, constitutive expression of BMPR-IB, but not BMPR-IA or BMPR-II, was found to counteract the inhibitory effects of FGF-2. Finally, p53−/− mASCs and human ASCs, both of which express high levels of endogenous BMPR-IB, underwent normal osteogenic differentiation even in the presence of FGF-2. Collectively, our data therefore indicate that FGF-2 antagonizes the response of mASCs to retinoic acid and also suggest that threshold levels of BMPR-IB may play a crucial role both in counteracting the inhibitory role of FGF-2 and in promoting osteogenic differentiation of ASCs in the absence of retinoic acid. Moreover, the present study also indicates that differences exist between mouse and human ASCs in relationship to FGF-2 activity in the osteogenic context. [Copyright &y& Elsevier]

Abstract: Wounds in fetal skin heal without scar, however the mechanism is unknown. We identified a novel group of E-cadherin positive cells in the blood of fetal and adult mice and named them “Dot cells”. The percentage of Dot cells in E16.5 fetal mice blood is more than twenty times higher compared to adult blood. Dot cells also express integrin β1, CD184, CD34, CD13low and Sca1low, but not CD45, CD44, and CD117. Dot cells have a tiny dot shape between 1 and 7 µm diameters with fast proliferation in vitro. Most of the Dot cells remain positive for E-cadherin and integrin β1 after one month in culture. Transplantation of Dot cells to adult mice heals skin wounds with less scar due to reduced smooth muscle actin and collagen expression in the repair tissue. Tracking GFP-positive Dot cells demonstrates that Dot cells migrate to wounds and differentiate into dermal cells, which also express strongly to FGF-2, and later lose their GFP expression. Our results indicate that Dot cells are a group of previously unidentified cells that have strong wound healing effect. The mechanism of scarless wound healing in fetal skin is due to the presence of a large number of Dot cells. [Copyright &y& Elsevier]

Abstract: Background: Keloids are pathologic scars afflicting a large segment of our population and for which there is no definitive therapy. The lack of an animal model for keloid formation has hampered study. We developed an in vitro organotypic skin model to simulate normal keloid biology, which may allow us to study keloid formation without an animal model. Methods: Normal (NFs) and keloid (KFs) human fibroblasts were cultured in a collagen matrix to create a 3-dimensional dermal structure. Normal human keratinocytes (NKs) were cultured as a second layer on top and exposed to an air–fluid interface to allow differentiation into a mature keratinocyte layer. The organotypic skin was maintained for 28 days in Dulbecco’s modified eagle medium with 10% fetal calf serum. Samples were collected, processed, sectioned, stained with hematoxylin and eosin, and then measured for qualitative analysis. α–smooth-muscle actin was also evaluated by immunoblotting. Results: KF/NK organotypic skin showed increased collagen deposition, based on significantly denser collagen staining, with increased dermal thickness compared with NF/NK organotypic skin. We saw increased contracture in the KF/NK construct, and this correlated with increased organization of α–smooth-muscle actin fibers in the dermal layer of KF/NK organotypic skin compared with NF/NK skin. Conclusions: We have shown that coculture of KFs with keloid keratinocytes leads to an increased collagen production and dermal contracture compared with NFs and NKs, consistent with known keloid behavior. Given the lack of an animal model, we believe that organotypic skin culture can serve as a surrogate to study keloid formation. [Copyright &y& Elsevier]