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Background Adipose tissue-derived mesenchymal stem cells (AT-MSCs) are one of the most potent adult stem cells, capable of differentiating into bone, cartilage, adipose, muscle, and others. An innovative autologous AT-MSC-derived cell-based product (BonoFill-II) for bone tissue regeneration was developed to be suited as a bone graft for segmental bone defects. Methods BonoFill-II was transplanted into 8 sheep with 3.2-cm full cortex segmental defect formed in the tibia. Bone regeneration was followed by X-ray radiographs for 12 weeks. At experiment termination, the healed tibia bones were analyzed by computed tomography, histology, and mechanical tests. Results Our results indicate that one dose of BonoFill-II injectable formula led to an extensive bone growth within the transplantation site and to a complete closure of the critical gap in the sheep’s tibia in a relatively short time (8–12 weeks), with no inflammation and no other signs of graft rejection. This new and innovative product opens new prospects for the treatment of long bone defects. Conclusions Injection of BonoFill-II (an innovative autologous cell therapy product for bone tissue regeneration) into a critical size segmental defect model (3.2 cm), generated in the sheep tibia, achieved full bridging of the gap in an extremely short period (8–12 weeks).

Mesenchymal stromal cells (MSC) are widely investigated for treating ARDS in Covid-19. Nonetheless, these efforts are overshadowed by studies predating the pandemic that mostly failed to show MSC efficacy in ARDS and recent disappointments with repurposed MSC products. Relying on years of MSC-related experience, Bonus BioGroup developed MesenCure: An enhanced allogeneic MSC therapy for Covid-19, professionalized by a unique combination of culture conditions and optimized in ARDS-relevant models. MesenCure is currently evaluated in a Phase II study in severe Covid-19 patients and administered (IV) in three doses (1.5M cells/kg, d1, d3, d5). A Phase I/II study on ten severe patients demonstrated a significant improvement in ARDS-related parameters following MesenCure treatment. Patients were discharged within one day (median) following treatment, requiring no respiratory support. Speedy recovery from local inflammation was observed in these patients, demonstrated by a rapid reduction in diffuse lung pneumonia, from 55% of the lung area to 15% within 5-6 days from the first dose (p MesenCure efficacy may be attributable to the cells' de novo expression of the gene encoding for the IL-6 receptor, making them more responsive to inflammation than non-professionalized naïve MSC (NA-MSC); as well as >8-fold upregulation of the EDIL3 gene, encoding for an endogenous inhibitor of immune infiltration. A corresponding immunosuppressive effect of MesenCure MSCs was demonstrated in vitro, showing their ability to suppress T cells activation twice more effectively than NA-MSC. In this study, MesenCure inhibited the proliferation of primary CD4 T cells in a concentration-depended manner following non-specific activation. Over 98% inhibition was achieved in co-culture of 1:10 MSC-to-PBMC with an IC 50 of 6k MSC/200k PBMCs (r 2=1.00) compared to 12k NA-MSC/200k PBMCs (r 2=0.95). Comparable results were also obtained for CD8 T cells. Similarly, MesenCure inhibited ROS production by primary neutrophils remarkably fast and by up to 80% within less than 40 minutes following their activation (IC 50 = 19k MSC/200k neutrophils, r 2=1.00). In addition to local immunosuppressive outcomes, a significant increase in blood leukocytes was observed in patients treated with MesenCure (p The seemingly exclusively localized anti-inflammatory effects seen in severe patients treated with MesenCure were also observed in animal (murine) studies. An in vivo study in an acute lung injury model demonstrated a dose-dependent localized reduction in leukocyte counts in the lung fluids of animals treated with MesenCure (IV) using two dose levels. Relative to untreated animals, MesenCure reduced lung leukocyte counts by 35%-43% in animals treated with the low dose and by 62%-67% following high-dose MesenCure treatment (p MesenCure is administered at a much lower dose compared to other MSC products administered at up to 10M cells/kg. Considering the increase in blood leukocytes measured in patients treated with low-dose MesenCure and comparable preclinical findings, our data suggest that low-dose MesenCure could elicit a potent local anti-inflammatory effect without suppressing, and even enhancing, peripheral immunity that is needed to fight the virus. Further research is inevitably required into the mechanism behind this phenomenon. However, our results indicate MesenCure's potential in relieving local inflammation while giving the patient a fighting chance against viremia. Figure 1 Figure 1. Disclosures Bronshtein: Bonus BioGroup: Current Employment. Ben David: Bonus BioGroup: Current Employment. Novak: Bonus BioGroup: Current Employment. Kivity: Bonus BioGroup: Current Employment. Meretzki: Bonus BioGroup: Current Employment. Rozen: Bonus BioGroup: Consultancy.

Human adipose-derived microvascular endothelial cells (HAMEC) and mesenchymal stem cells (MSC) have been shown to bear angiogenic and vasculogenic capabilities. We hypothesize that co-culturing HAMEC:MSC on a porous biodegradable scaffold in vitro, later implanted as a graft around femoral blood vessels in a rat, will result in its vascularization by host vessels, creating a functional vascular flap that can effectively treat a range of large full-thickness soft tissue defects. HAMEC were co-cultured with MSC on polymeric three-dimensional porous constructs. Grafts were then implanted around the femoral vessels of a rat. To ensure vessel sprouting from the main femoral vessels, grafts were pre-isolated from the surrounding tissue. Graft vascularization was monitored to confirm full vascularization before flap transfer. Flaps were then transferred to treat both abdominal wall and exposed bone and tendon of an ankle defects. Flaps were analysed to determine vascular properties in terms of maturity, functionality and survival of implanted cells. Findings show that pre-isolated grafts bearing the HAMEC:MSC combination promoted formation of highly vascularized flaps, which were better integrated in both defect models. The results of this study show the essentiality of a specific adipose-derived cell combination in successful graft vascularization and integration, two processes crucial for flap survival. Copyright © 2017 John Wiley & Sons, Ltd.

Objectives To identify the minocycline anti-inflammatory and antiapoptotic mechanisms through which it is believed to exert spinal cord protection during aortic occlusion in the rabbit model. Design An animal model of aortic occlusion-related spinal cord ischemia. Randomized study with a control group and pre-ischemia and post-ischemia escalating doses of minocycline to high-dose minocycline in the presence of either hyperglycemia, a pro-apoptotic maneuver, or wortmannin, a specific phosphatidylinositol 3-kinase antagonist. Setting Tertiary medical center and school of medicine laboratory. Participants Laboratory animals–rabbits. Interventions Balloon obstruction of infrarenal aorta introduced via femoral artery incision. Results Severe hindlimb paralysis (mean Tarlov score 0.36±0.81 out of 3) was observed in all the control group animals (9 of 11 with paraplegia and 2 of 11 with paraparesis) compared with 11 of 12 neurologically intact animals (mean Tarlov score 2.58±0.90 [p = 0.001 compared with control]) in the high-dose minocycline group. This protective effect was observed partially during a state of hyperglycemia and was completely abrogated by wortmannin. Minocycline administration resulted in higher neurologic scores (p = 0.003) and a shift to viable neurons and more apoptotic-stained nuclei resulting from reduced necrosis (p = 0.001). Conclusions In a rabbit model of infrarenal aortic occlusion, minocycline effectively reduced paraplegia by increasing the number of viable neurons in a dose-dependent manner. Its action was completely abrogated by inhibiting the phosphatidylinositol 3-kinase pathway and was inhibited partially by the pro-apoptotic hyperglycemia maneuver, indicating that the activation of cell salvage pathways and mitochondrial sites are possible targets of minocycline action in an ischemic spinal cord.

In complicated foot surgery with reconstruction of the hindfoot, a gap will sometimes be present between the bones that must be filled and stabilized. Bone grafting with structural bone graft is 1 alternative; however, it can collapse and must be stabilized with screws or a nail. A locking intramedullary nail can be used but could lead to nonunion owing to distraction. Newer nails include a compression device but that can result in shortening. We developed a technique that includes distraction of the fusion area with a spinal cage and then compression of the construct by inserting a compression screw through the cage. We present our experience with this technique.We reviewed the data from 7 patients who had undergone surgery using this technique. The technique included distraction of the fusion area and insertion of a titanium cylindrical spinal cage filled with autologous cancellous bone graft. A cannulated compression screw was then inserted through the cage, creating compression of the fusion area against the cage and achieving stabilization of the fusion area. Postoperatively, a non-weightbearing cast was applied for 3 months, followed by a full weightbearing cast until radiographic fusion was apparent. Complete radiographic union was observed in all 7 patients within 6 to 12 months postoperatively. At the latest follow-up visit, the mean American Orthopaedic Foot and Ankle Society scale score was 54 ± 16 (range 30 to 71) points. The use of a cylindrical titanium cage with a local bone graft and stabilization by distraction and compression provided a stable construct, avoided shortening, and led to good fusion. In addition, donor site complications and unpredictable strength loss and lysis of bone allograft were avoided.

Bone repair strategies utilizing resorbable biomaterial implants aim to stimulate endogenous cells in order to gradually replace the implant with functional repair tissue. These biomaterials should therefore be biodegradable, osteoconductive, osteoinductive, and maintain their integrity until the newly formed host tissue can contribute proper function. In recent years there has been impressive clinical outcomes for this strategy when using osteoconductive hydrogel biomaterials in combination with osteoinductive growth factors such as human recombinant bone morphogenic protein (hrBMP-2). However, the success of hrBMP-2 treatments is not without risks if the factor is delivered too rapidly and at very high doses because of a suboptimal biomaterial. Therefore, the aim of this study was to evaluate the use of a PEGylated fibrinogen (PF) provisional matrix as a delivery system for low-dose hrBMP-2 treatment in a critical size maxillofacial bone defect model. PF is a semi-synthetic hydrogel material that can regulate the release of physiological doses of hrBMP-2 based on its controllable physical properties and biodegradation. hrBMP-2 release from the PF material and hrBMP-2 bioactivity were validated using in vitro assays and a subcutaneous implantation model in rats. Critical size calvarial defects in mice were treated orthotopically with PF containing 8 μg/ml hrBMP-2 to demonstrate the capacity of these bioactive implants to induce enhanced bone formation in as little as 6 weeks. Control defects treated with PF alone or left empty resulted in far less bone formation when compared to the PF/hrBMP-2 treated defects. These results demonstrate the feasibility of using a semi-synthetic biomaterial containing small doses of osteoinductive hrBMP-2 as an effective treatment for maxillofacial bone defects.

Aim Sinus augmentation procedures commonly employ osteoconductive scaffolding materials to stimulate and support bone formation. The aim of this study was to develop a simple screening methodology for the evaluation of the osteoconductive potential of various bone graft materials prior to clinical use. Materials and methods Materials tested were Bio-Oss, Bi-Ostetic, OraGraft, and ProOsteon. These Simple and composite bone substitutes were embedded with osteoprogenitor cells derived from either the human maxillary sinus schneiderian membrane (hMSSM) or from maxillary tuberosity bone marrow and then monitored both in vitro and in vivo. Results Cell adherence and proliferation was most pronounced in OraGraft, followed by ProOsteon. In vivo bone formation, within the bone graft, was also observed, with most marked results in OraGraft and ProOsteon grafts. Conclusions The proposed osteoconductivity testing method proved simple, informative, and reliable for the purpose of screening candidate biomaterials for sinus lifting or sinus augmentation.

Sustained and controlled delivery of growth factors, such as bone morphogenetic protein 2 (BMP-2), from polymer scaffolds has excellent potential for enhancing bone regeneration. The present study investigated the use of novel sintered polymer scaffolds prepared using temperature-sensitive PLGA/PEG particles. Growth factors can be incorporated into these scaffolds by mixing the reconstituted growth factor with the particles prior to sintering. The ability of the PLGA/PEG scaffolds to deliver BMP-2 in a controlled and sustained manner was assessed and the osteogenic potential of these scaffolds was determined in a mouse calvarial defect model. BMP-2 was released from the scaffolds in vitro over 3 weeks. On average, ca. 70% of the BMP-2 loaded into the scaffolds was released by the end of this time period. The released BMP-2 was shown to be active and to induce osteogenesis when used in a cell culture assay. A substantial increase in new bone volume of 55% was observed in a mouse calvarial defect model for BMP-2-loaded PLGA/PEG scaffolds compared to empty defect controls. An increase in new bone volume of 31% was observed for PLGA/PEG scaffolds without BMP-2, compared to empty defect controls. These results demonstrate the potential of novel PLGA/PEG scaffolds for sustained BMP-2 delivery for bone-regeneration applications. Copyright © 2012 John Wiley & Sons, Ltd.

Bone is the second most frequently transplanted tissue in humans and efforts are focused on developing cell-scaffold constructs which can be employed for autologous implantation in place of allogenic transplants. The objective of the present study was to examine the efficacy of a gelatin-based hydrogel scaffold to support osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (MSCs) and its application in a cranial defect model. MSCs which were cultured on hydrogel under osteogenic conditions demonstrated typical osteogenic differentiation which included cluster formation with positive Alizarin Red S staining, sedimentation of calcium phosphate as defined by SEM and EDS spectroscopy and expression of mRNA osteogenic markers. Empty scaffolds or those containing either differentiated cells or naïve cells were implanted into cranial defects of athymic nude mice and the healing process was followed by μCT. Substantial bone formation (65%) was observed with osteogenic cell-scaffold constructs when compared to the naïve cell construct (25%) and the cell free scaffold (10%). Results demonstrated the potential of hydrogel scaffolds to serve as a supportive carrier for bone marrow-derived MSCs.

Bone repair is a major concern in reconstructive surgery. Transplants containing osteogenically committed mesenchymal stem cells (MSCs) provide an alternative source to the currently used autologous bone transplants which have limited supply and require additional surgery to the patient. A major drawback, however is the lack of a critical mass of cells needed for successful transplantation. The purpose of the present study was to test the effects of FGF2 and FGF9 on expansion and differentiation of MSCs in order to establish an optimal culture protocol resulting in sufficient committed osteogenic cells required for successful in vivo transplantation. Bone marrow-derived MSCs cultured in αMEM medium supplemented with osteogenic supplements for up to three passages (control medium), were additionally treated with FGF2 and FGF9 in various combinations. Cultures were evaluated for viability, calcium deposition and in vivo osteogenic capacity by testing subcutaneous transplants in nude mice. FGF2 had a positive effect on the proliferative capacity of cultured MSCs compared to FGF9 and control medium treated cultures. Cultures treated with FGF2 followed by FGF9 showed an increased amount of extracted Alizarin red indicating greater osteogenic differentiation. Moreover, the osteogenic capacity of cultured cells transplanted in immunodeficient mice revealed that cells that were subjected to treatment with FGF2 in the first two passages and subsequently to FGF9 in the last passage only, were more successful in forming new bone. It is concluded that the protocol using FGF2 prior to FGF9 is beneficial to cell expansion and commitment, resulting in higher in vivo bone formation for successful bone tissue engineering.

The design of mat-like scaffolds slow-releasing bone morphogenetic protein-2 (BMP-2) retaining bone regeneration functions has been a major challenge in tissue engineering. This study aimed to develop core-shell fiber scaffolds releasing BMP-2 to support bone regeneration. BMP-2 was incorporated in an aqueous core solution of poly(ethylene oxide), whereas the shell solution was made of polycaprolactone blended with poly(ethylene glycol). This blending induced pores in the shell, which pronouncedly affected the movement of proteins out of the fibers. BMP-2 release profiles were monitored. In vitro bioactivity of BMP-2 released from the scaffolds was assessed using human mesenchymal stem cells by measuring alkaline phosphatase activity. Bone regeneration capabilities were demonstrated by implanting the BMP-2-embedded scaffolds in rat cranial defect model followed by micro-computed tomography analysis. The degree of fiber's shell porosity, highly correlative with the slow- and fast-release patterns of BMP-2, were found to be dependent on the relative amount of poly(ethylene glycol) within the shell. In vitro assays of scaffolds manifesting the slow-release pattern have revealed significant (∼9-fold) increase in alkaline phosphatase activity, compared to fast BMP-2 releasing scaffolds. Likewise, in vivo studies have revealed significant bone regeneration in cranial defects of scaffold implants with recombinant human BMP-2 with slow-release pattern.

Maxillary sinus membrane lifting is a common procedure aimed at increasing the volume of the maxillary sinus osseous floor prior to inserting dental implants. Clinical observations of bone formation in sinus lifting procedures without grafting bone substitutes were observed, but the biological nature of bone regeneration in sinus lifting procedures is unclear. This study tested whether this osteogenic activity relies on inherent osteogenic capacity residing in the sinus membrane by simulating the in vivo clinical condition of sinus lifting in an animal model. Maxillary sinus membrane cells were cultured in alpha-MEM medium containing osteogenic supplements (ascorbic acid, dexamethasone). Cultured cells revealed alkaline phosphatase activity and mRNA expression of osteogenic markers (alkaline phosphatase, bone sialoprotein, osteocalcin and osteonectin) verifying the osteogenic potential of the cells. Fresh tissue samples demonstrated positive alkaline phosphatase enzyme activity situated along the membrane-bone interface periosteum-like layer. To simulate the in vivo clinical conditions, the membranes were folded to form a pocket-like structure and were transplanted subcutaneously in immunodeficient mice for 8 weeks. New bone formation was observed in the transplants indicating the innate osteogenic potential within the maxillary Schneiderian sinus membrane and its possible contribution to bone regeneration in sinus lifting procedures.

Background Adipose-derived mesenchymal stem cells (MSCs) have been gaining fame mainly due to their vast clinical potential, simple isolation methods and minimal donor site morbidity. Adipose-derived MSCs and microvascular endothelial cells have been shown to bear angiogenic and vasculogenic capabilities. We hypothesized that co-culture of human adipose-derived MSCs with human adipose-derived microvascular endothelial cells (HAMECs) will serve as an effective cell pair to induce angiogenesis and vessel-like network formation in three-dimensional scaffolds in vitro. Methods HAMECs or human umbilical vein endothelial cells (HUVECs) were co-cultured on scaffolds with either MSCs or human neonatal dermal fibroblasts. Cells were immunofluorescently stained within the scaffolds at different time points post-seeding. Various analyses were performed to determine vessel length, complexity and degree of maturity. Results The HAMEC:MSC combination yielded the most organized and complex vascular elements within scaffolds, and in the shortest period of time, when compared to the other tested cell combinations. These differences were manifested by higher network complexity, more tube alignment and higher α-smooth muscle actin expression. Moreover, these generated microvessels further matured and developed during the 14-day incubation period within the three-dimensional microenvironment. Conclusions These data demonstrate optimal vascular network formation upon co-culture of microvascular endothelial cells and adipose-derived MSCs in vitro and constitute a significant step in appreciation of the potential of microvascular endothelial cells and MSCs in different tissue engineering applications that can also be advantageous in in vivo studies.

Tibialis anterior tendon tear is an uncommon injury. Nontraumatic or degenerative tears are usually seen in the avascular zone of the tendon. Treatment can be conservative or surgical. Conservative treatment is adequate for low-demand older patients. For active patients, surgical treatment can be challenging for the surgeon because after debridement of degenerative tissue, a gap may be formed that can make side-to-side suture impossible. The authors present allograft Achilles tendon insertion for reconstruction of chronic degenerative tears. Using Achilles tendon allograft has the advantage of bone-to-bone fixation, allowing rapid incorporation and earlier full weight bearing.

Bone tissue regeneration in load-bearing regions of the body requires high-strength porous scaffolds capable of supporting angiogenesis and osteogenesis. 70% porous Nitinol (NiTi) scaffolds with a regular 3-D architecture resembling trabecular bone were produced from Ni foams using an original reactive vapor infiltration technique. The "trabecular Nitinol" scaffolds possessed a high compressive strength of 79 MPa and high permeability of 6.9×10(-6) cm2. The scaffolds were further modified to produce a near Ni-free surface layer and evaluated in terms of Ni ion release and human mesenchymal stem cell (hMSC) proliferation (AlamarBlue), differentiation (alkaline phosphatase activity, ALP) and mineralization (Alizarin Red S staining). Scanning electron microscopy was employed to qualitatively corroborate the results. hMSCs were able to adhere and proliferate on both as-produced and surface-modified trabecular NiTi scaffolds, to acquire an osteoblastic phenotype and produce a mineralized extracellular matrix. Both ALP activity and mineralization were increased on porous scaffolds compared to control polystyrene plates. Experiments in a model coculture system of microvascular endothelial cells and hMSCs demonstrated the formation of prevascular structures in trabecular NiTi scaffolds. These data suggest that load-bearing trabecular Nitinol scaffolds could be effective in regenerating damaged or lost bone tissue.

Adult human mesenchymal stromal cells (hMSCs) are an important source for tissue repair in regenerative medicine. Notably, targeted gene therapy in hMSCs to promote osteogenic differentiation may help in the development of novel therapeutic approaches for bone repair. We recently showed that α5 integrin (ITGA5) promotes osteoblast differentiation in bone marrow-derived hMSCs. Here, we determined whether lentiviral (LV)-mediated expression of ITGA5 in hMSCs derived from the bone-marrow stroma of healthy individuals may promote bone repair in vivo in two relevant critical-size bone defects in the mouse. In a first series of experiments, control or LV-ITGA5-transduced hMSCs were seeded on collagen-based gelatin sponge and transplanted in a cranial critical-size defect (5 mm) in Nude-Foxn1nu mice. Microcomputed tomography and quantitative histological analyses after 8 weeks showed no or little de novo bone formation in defects implanted with collagen sponge alone or with hMSCs, respectively. In contrast, implantation of collagen sponge with LV-ITGA5-transduced hMSCs showed greater bone formation compared with control hMSCs. We also tested the bone-repair potential of LV-mediated ITGA5 expression in hMSCs in a critical-size long-bone defect (2 mm) in femur in Nude-Foxn1nu mice. Bone remnants were stabilized with external fixation, and control or LV-ITGA5-transduced hMSCs mixed with coral/hydroxyapatite particles were transplanted into the critical-size long-bone defect. Histological analysis after 8 weeks showed that LV-ITGA5-transduced hMSCs implanted with particles induced 85% bone regeneration and repair. These results demonstrate that repair of critical-size mouse cranial and long-bone defects can be induced using LV-mediated ITGA5 gene expression in hMSCs, which provides a novel gene therapy for bone regeneration.

The activity of immune cells affects the balance between bone mineralization and resorption carried out by the opposing actions of osteoblasts and osteoclasts, respectively. This study was aimed at determining the possible interaction between inflammatory conditions and collagen type I degrading MMP (mainly MMP-2 and MMP-9) synthesis and secretion in rat osteoprogenitors.The study was performed using primary rat bone marrow-derived osteoprogenitors during their advanced osteogenesis. Biochemical, immunohistochemical, and molecular biology techniques were used to investigate the influence of pro-inflammatory cytokines on MMP-2 and MMP-9 synthesis and secretion in osteoprogenitors.Results indicated that both synthesis and secretion of MMPs (MMP-1, -2, -8, -9, and -13) were significantly induced after pro-inflammatory cytokine treatments, except MMP-2, whose levels remained unchanged. NF-κB (nuclear factor kappa-light chain enhancer of activated B cells) inhibition assays showed that induced MMP-9 secretion by inflammatory cytokines was mediated by activation of NF-κB via the classical pathway and that oxidants play a significant role in this signal transduction pathway. In contrast, no such effect was observed for synthesis of MMP-2.These results indicate the possibility that inflammatory processes may trigger osteoblasts to absorb bone by secreting elevated levels of MMPs capable of degrading collagen type I, especially MMP-9 which is upregulated due to increased NF-κB transcription activity.

Although growth factors naturally exert their morphogenetic influences within the context of the extracellular matrix microenvironment, the interactions among growth factors, their receptors, and other extracellular matrix components are typically ignored in clinical delivery of growth factors. We present an approach for engineering the cellular microenvironment to greatly accentuate the effects of vascular endothelial growth factor-A (VEGF-A) and platelet-derived growth factor-BB (PDGF-BB) for skin repair, and of bone morphogenetic protein-2 (BMP-2) and PDGF-BB for bone repair. A multifunctional recombinant fragment of fibronectin (FN) was engineered to comprise (i) a factor XIIIa substrate fibrin-binding sequence, (ii) the 9th to 10th type III FN repeat (FN III9-10) containing the major integrin-binding domain, and (iii) the 12th to 14th type III FN repeat (FN III12-14), which binds growth factors promiscuously, including VEGF-A165, PDGF-BB, and BMP-2. We show potent synergistic signaling and morphogenesis between α(5)β(1) integrin and the growth factor receptors, but only when FN III9-10 and FN III12-14 are proximally presented in the same polypeptide chain (FN III9-10/12-14). The multifunctional FN III9-10/12-14 greatly enhanced the regenerative effects of the growth factors in vivo in a diabetic mouse model of chronic wounds (primarily through an angiogenic mechanism) and in a rat model of critical-size bone defects (through a mesenchymal stem cell recruitment mechanism) at doses where the growth factors delivered within fibrin only had no significant effects.

Sustained and controlled delivery of growth factors, such as bone morphogenetic protein 2 (BMP-2), from polymer scaffolds has excellent potential for enhancing bone regeneration. The present study investigated the use of novel sintered polymer scaffolds prepared using temperature-sensitive PLGA/PEG particles. Growth factors can be incorporated into these scaffolds by mixing the reconstituted growth factor with the particles prior to sintering. The ability of the PLGA/PEG scaffolds to deliver BMP-2 in a controlled and sustained manner was assessed and the osteogenic potential of these scaffolds was determined in a mouse calvarial defect model. BMP-2 was released from the scaffolds in vitro over 3 weeks. On average, ca. 70% of the BMP-2 loaded into the scaffolds was released by the end of this time period. The released BMP-2 was shown to be active and to induce osteogenesis when used in a cell culture assay. A substantial increase in new bone volume of 55% was observed in a mouse calvarial defect model for BMP-2-loaded PLGA/PEG scaffolds compared to empty defect controls. An increase in new bone volume of 31% was observed for PLGA/PEG scaffolds without BMP-2, compared to empty defect controls. These results demonstrate the potential of novel PLGA/PEG scaffolds for sustained BMP-2 delivery for bone-regeneration applications.

Biocompatible and osteoconductive cell-scaffold constructs comprise the first and most important step towards successful in vivo bone repair. This study reports on a new cell-scaffold construct composed of gelatin-based hydrogel and ceramic (CaCO(3)/beta-TCP) particles loaded with human MSCs producing a tissue-like construct applied as a transplant for in vivo bone formation. Bone marrow-derived human MSCs were cultured in osteogenic induction medium. 5 x 10(5) (P(2)) cells were loaded on a mixture of hydrogel microspheres and ceramic particles, cultured in a rotating dynamic culture for up to 3 weeks. Both hydrogel microspheres and ceramic particles coalesced together to form a tissue-like construct, shown by histology to contain elongated spindle-like cells forming the new tissue between the individual particles. Cell proliferation and cell viability were confirmed by Alamar blue assay and by staining with CFDA, respectively. FACS analysis conducted before loading the cells, and after formation of the construct, revealed that the profile of cell surface markers remained unchanged throughout the dynamic culture. The osteogenic potential of the cells composing the tissue-like construct was further validated by subcutaneous transplants in athymic nude mice. After 8 weeks a substantial amount of new bone formation was observed in the cell-construct transplants, whereas no bone formation was observed in transplants containing no cells. This new cell construct provides a system for in vivo bone transplants. It can be tailored for a specific size and shape as needed for various transplant sites and for all aspects of regenerative medicine and biomaterial science.

Background: Accurate placement of cannulated screws is essential to ensure secure fixation of femoral neck fractures. We compared computerized navigation and conventional fluoroscopy with regard to the accuracy of screw placement for the fixation of femoral neck fractures. Methods: We retrospectively compared two groups of twenty consecutive patients with a femoral neck fracture who underwent internal fixation with three cannulated screws. Computer-based navigation was used to guide screw placement in one group, and conventional fluoroscopy was used in the other group. Radiographic evaluation included the measurement of screw parallelism and spread, the calibrated distance from the lesser trochanter, and joint penetration. The follow-up period was two years. The rates of complications in both groups were evaluated. Results: The navigation-assisted group had better screw parallelism and greater spread of the screws. There was a tendency for fewer reoperations and significantly fewer overall complications in the patients in whom computerized navigation was used (p < 0.018). Conclusions: Computerized navigation improves the accuracy of cannulated screw placement in the internal fixation of femoral neck fractures. It may provide better mechanical stability and improved fracture outcome. Level of Evidence: Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.