The multifunctional adhesion molecule CD44 is a major cell-surface receptor for hyaluronic acid (HUA). Recent data suggest that it may also bind the ubiquitous bone-matrix protein, osteopontin (OPN). Because OPN has been shown to be a potentially important protein in bone remodelling, we investigated the hypothesis that OPN interactions with the CD44 receptor on bone cells participate in the regulation of the healing of fractures. We examined the spatial and temporal patterns of expression of OPN and CD44 in healing fractures of rat femora by in situ hybridisation and immunohistochemistry. We also localised HUA in the fracture callus using biotinylated HUA-binding protein. OPN was expressed in remodelling areas of the hard callus and was found in osteocytes, osteoclasts and osteoprogenitor cells, but not in cuboidal osteoblasts which were otherwise shown to express osteocalcin. The OPN signal in osteocytes was not uniformly distributed, but was restricted to specific regions near sites where OPN mRNA-positive osteoclasts were attached to bone surfaces. In the remodelling callus, intense immunostaining for CD44 was detected in osteocyte lacunae, along canaliculi, and on the basolateral plasma membrane of osteoclasts, but not in the cuboidal osteoblasts. HUA staining was detected in fibrous tissues but little was observed in areas of hard callus where bone remodelling was progressing. Our findings suggest that OPN, rather than HUA, is the major ligand for CD44 on bone cells in the remodelling phase of healing of fractures. They also raise the possibility that such interactions may be involved in the communication of osteocytes with each other and with osteoclasts on bone surfaces. The interactions between CD44 and OPN may have important clinical implications in the repair of skeletal tissues

Cyclooxygenase-2 (COX-2) activity is necessary for fracture healing to proceed normally. In most cell types, COX-2 is inductively expressed and acts in a coordinated pathway to produce prostaglandins, which affect many physiological processes including inflammation. In the fracture callus, however, COX-2 expression and the molecular and cellular processes affected by COX-2 activity remain poorly understood. Using LC-MS/MS and xMAP, we measured fracture callus prostaglandin and inflammatory cytokine levels. We found that inflammatory cytokines rapidly peaked after fracture before declining to normal levels by day 4 after fracture. However, callus prostaglandin levels did not peak until 4 days after fracture before returning to normal levels by day 10. We used immunohistochemistry to detected COX-2 expression in callus cells and found that COX-2 was expressed in callus chondrocytes and osteoclasts during endochondral ossification, including those osteoclasts at the callus chondro-osseous junction. Targeted deletion of the COX-2 gene (Ptgs2) in osteoclasts or in chondrocytes was found to delay fracture healing. Using cell-based experiments, we found that COX-2 expression could be induced in osteoclasts by osteopontin treatment, suggesting an integrin-dependent induction of COX-2 expression in osteoclasts. This was confirmed in vivo using mice lacking osteopontin or integrin ß3. Immunohistochemistry also showed abundant osteopontin expression at the callus chondro-osseous junction. The results indicate that COX-2 expression in osteoclasts is controlled by integrin-dependent signalling, that COX-2 expression in osteoclasts and chondrocytes is necessary for fracture healing to proceed normally, and that COX-2 expression in chondro-osseous junction osteoclasts may be induced by osteopontin-dependent signalling by chondrocytes

Critical size bone defects deriving from large bone loss are an unmet clinical challenge1. To account for disadvantages with clinical treatments, researchers focus on designing biological substitutes, which mimic endogenous healing through osteogenic differentiation promotion. Some studies have however suggested that this notion fails to consider the full complexity of native bone with respect to the interplay between osteoclast and osteoblasts, thus leading to the regeneration of less functional tissue2. The objective of this research is to assess the ability of our laboratory's previously developed 6-Bromoindirubin-3’-Oxime (BIO) incorporated guanosine diphosphate crosslinked chitosan scaffold in promoting multilineage differentiation of myoblastic C2C12 cells and monocytes into osteoblasts and osteoclasts1, 3, 4. BIO addition has been previously demonstrated to promote osteogenic differentiation in cell cultures5, but implementation of a co-culture model here is expected to encourage crosstalk thus further supporting differentiation, as well as the secretion of regulatory molecules and cytokines2. Biocompatibility testing of both cell types is performed using AlamarBlue for metabolic activity, and nucleic acid staining for distribution. Osteoblastic differentiation is assessed through quantification of ALP and osteopontin secretion, as well as osteocalcin and mineralization staining. Differentiation into osteoclasts is verified using SEM and TEM, qPCR, and TRAP staining. Cellular viability of C2C12 cells and monocytes was maintained when cultured separately in scaffolds with and without BIO for 21 days. Both scaffold variations showed a characteristic increase in ALP secretion from day 1 to 7, indicating early differentiation but BIO-incorporated sponges yielded higher values compared to controls. SEM and TEM imaging confirmed initial aggregation and fusion of monocytes on the scaffold's surface, but BIO addition appeared to result in smoother cell surfaces indicating a change in morphology. Late-stage differentiation assessment and co-culture work in the scaffold are ongoing, but initial results show promise in the material's ability to support multilineage differentiation. Acknowledgements: The authors would like to acknowledge the financial support of the Collaborative Health Research Program (CHRP) through CIHR and NSERC, as well as Canada Research Chair – Tier 1 in Regenerative Medicine and Nanomedicine, and the FRQ-S

Introduction and Objective. Osteonecrosis of the femoral head (ONFH) is an evolving and disabling condition that often leads to subchondral collapse in late stages. It is the underlying diagnosis for approximately 3%–12% of total hip arthroplasties (THAs) and the most frequent aetiology for young patients undergoing THA. To date, the pathophysiological mechanisms underlying ONFH remain poorly understood. In this study, we investigated whether ONFH without an obvious etiological factor is related to impaired osteoblast activities, as compared to age-matched patients with primary OA. Materials and Methods. We cultured osteoblasts isolated from trabecular bone explants taken from the femoral head of patients with ONFH and from intertrochanteric region of patients with ONFH or with OA and compared their in vitro mineralisation capacity and secretion of paracrine factors. Results. Compared to patients with OA, osteoblasts obtained from the intertrochanteric region of patients with ONFH showed reduced mineralisation capacity, which further decreased in osteoblasts from the femoral head of the same patient. Lower mineralisation of osteoblasts from patients with ONFH correlated with lower mRNA levels of genes encoding osteocalcin and bone sialoprotein and higher osteopontin expression. Osteoblasts from the intertrochanteric region of patients with ONFH secreted lower osteoprtegerin levels than those from patients with OA, resulting in a higher receptor activator of NF-κB ligand (RANKL)-to-osteoprotegerin (OPG) ratio. Notably, the RANKL-to-OPG ratio, as well as the secretion of the proresorptive factors interleukin-6 and prostaglandin E. 2. , was higher in osteoblasts from the femoral head of patients with ONFH than in those from the intertrochanteric region. Conclusions. ONFH is associated with a reduced mineralisation capacity of osteoblasts and increased secretion of proresorptive factors

Bone remodelling is mediated through the synchronism of bone resorption (catabolism) by osteoclasts and bone formation (anabolism) by osteoblasts. Imbalances in the bone remodelling cycle represent an underling cause of metabolic bone diseases such as osteoporosis, where bone resorption exceeds formation (1). Current therapeutic strategies to repair osteoporotic bone fractures focus solely in targeting anabolism or supressing catabolism (2). However, these therapeutics do not reverse the structural damage present at the defect site, ultimately leading to impaired fracture healing, making the repair of osteoporotic fractures particularly challenging in orthopaedics. Herein, we focus on investigating a combined versatile pro-anabolic and anti-catabolic effect of Magnesium (Mg. 2+. ) to modulate bone cell behaviour (3), to develop an engineered biomimetic bio-instructive biomaterial scaffold structurally designed to enhance bone formation while impeding pathological osteoclast resorption activities to facilitate better bone healing and promote repair. Pre-osteoblasts MC3T3-E1 (OBs) and osteoclasts progenitors RAW 264.7 (OCs) cell lines were cultured in growth media exposed to increasing concentrations of MgCl. 2. (0, 0.5, 1, 10, 25 and 50mM) and the optimal concentration to concurrently promote the differentiation of OBs and inhibit the differentiation or funtion of RANKL-induced OCs was assessed. We next used Fluorescence Lifetime Imaging Microscopy to investigate changes in the metabolic pathways during OBs and OCs differentiation when exposed to increasing MgCl. 2. concentrations. We developed a range of magnesium-incorporated collagen scaffolds to permit the spatiotemporal release of Mg. 2+. within the established therapeutic window, and to investigate the behaviour of bone cells in a 3D environment. In our results, we reported an increase in the expression of the bone formation markers osteocalcin and osteopontin for OBs exposed to 10mM MgCl. 2. , and a significant downregulation of the osteoclast-specific markers TRAP and cathepsin K in RANKL-induced OCs differentiation when exposed to 25mM MgCl. 2. Moreover, 25mM MgCl. 2. induced changes in the energy metabolism of OCs from a predominantly oxidative phosphorylation towards a more glycolytic pathway suggesting a regulatory effect of Mg. 2+. in the underlying mechanisms of osteoclasts formation and function. The developed porous collagen-magnesium scaffolds significantly reduced the expression of early osteoclastogenic markers RANK and NFkB, and an elevated expression of the osteogenic markers Runx2 and Col1A1 was reported after 7 days. Our research to date has provided evidences to demonstrate the potential of Mg. 2+. to concurrently enhance osteogenesis while inhibiting osteoclastogenesis in vitro, potentially introducing new targets for developing therapies to repair osteoporotic bone fractures

Osteogenesis is key to fracture healing and osteointegration of implanted material. Modification of surfaces on a nanoscale has been shown to affect cell interaction with the material and can lead to preferential osteogenesis. We hypothesised that osteogenesis could be induced in a heterogeneous population of osteoprogenitor cells by circular nanopits on a material surface. Furthermore, we intended to assess any correlation between nanopit depth and osteoinductive potential. The desired topographies were embossed onto polycaprolactone (PCL) discs using pre-fabricated nickel shims. All pits had a diameter of 30μm and investigated pit depths were 80nm, 220nm and 333nm. Scanning electron microscopy confirmed successful embossing and planar controls were shown to be flat. A bone marrow aspirate was obtained from the femoral neck of a healthy adult undergoing a hip replacement. After establishing a culture, cells were seeded onto the PCL discs, suspended in basal media and incubated. Samples were fixed and stained after three and 28 days. Cells were stained for the adhesion molecule vinculin after three days. Lowest concentrations of vinculin were seen in the planar control group. Osteoprogenitor cells on the shallowest pits, 80nm, had larger and brighter adhesion complexes. After 28 days, osteocalcin and osteopontin expression were used as markers of cell differentiation into an osteoblastic phenotype. 220nm deep pits consistently produced cells with the highest concentrations of osteopontin (p = 0.017) with a similar trend of osteocalcin expression. Cells on all topographies had higher expression levels than the planar controls. We demonstrated stimulation of osteogenesis in a heterogeneous population of osteoprogenitor cells. This cell mix is similar to that present in fracture healing and after reaming for intramedullary devices or uncemented implants. All nanopit depths gave promising results with an optimum depth of 220nm after 28 days

Summary Statement. A biomimetic tissue engineering strategy involving culture on bone scaffolds in perfusion bioreactors allows the construction of stable, viable, patient-specific bone-like substitutes from human induced pluripotent stem cells. Introduction. Tissue engineering of viable bone substitutes represents a promising therapeutic strategy to mitigate the burden of bone deficiencies. Human induced pluripotent stem cells (hiPSCs) have an excellent proliferation and differentiation capacity, and represent an unprecedented resource for engineering of autologous tissue grafts, as well as advanced tissue models for biological studies and drug discovery. A major challenge is to reproducibly expand, differentiate and organize hiPSCs into mature, stable tissue structures. Based on previous studies (1,2,3), we hypothesised that the culture conditions supporting bone tissue formation from adult human mesenchymal stem cells (hMSCs) and human embryonic stem cell (hESC)-derived mesenchymal progenitors could be translated to hiPSC-derived mesenchymal progenitors. Our objectives were to: 1. Derive and characterise mesenchymal progenitors from hiPSC lines. 2. Engineer bone substitutes from progenitor lines exhibiting osteogenic potential in an osteoconductive scaffold – perfusion bioreactor culture model. 3. Assess the molecular changes associated with the culture of hiPSC-progenitors in perfusion bioreactors, and evaluate the stability of engineered bone tissue substitutes in vivo. Methods. hESC and hiPSC lines (derived using retroviral vectors, Sendai virus and episomal vectors) were karyotyped, characterised for pluripotency and induced into the mesenchymal lineage. Mesenchymal progenitors were evaluated for growth potential, expression of surface markers and differentiation potential. Progenitors exhibiting osteogenic potential were cultured on decellularised bovine bone scaffolds in perfusion bioreactors for 5 weeks as previously (3). Global gene expression profiles were evaluated prior and after bioreactor culture. Bone development was investigated using biochemical and histological methods, and by micro-computed tomography (μCT) imaging over the duration of bioreactor culture and after 12-week subcutaneous implantation in immunodeficient mice. Results. Progenitors with high proliferation potential, expressing typical mesenchymal surface antigens were successfully derived from three hiPSC lines. Differences in mesenchymal surface antigens expression and global gene expression profiles of progenitors from different lines corresponded to their differentiation abilities toward the osteogenic, chondrogenic and adipogenic lineages. Bioreactor culture yielded constructs with significantly higher cellularity, AP activity and osteopontin release into the culture medium as compared to static culture. Dense bone matrix formation was evidenced by the positive staining of collagen, osteopontin, bone sialoprotein and osteocalcin. In comparison, static culture yielded constructs with uniformly distributed cells, however tissue formation was scarce. μCT revealed a significant increase in bone structural parameters, evidencing mineralization of the deposited bone tissue during the 5-week culture in bioreactors. Osteogenesis and bone tissue formation were comparable between hESCs, hiPSCs and hMSCs (3). Bioreactor cultivation resulted in repression of genes involved in proliferation and tumorigenesis, and upregulation of genes associated with osteogenesis and bone development. Engineered bone tissue displayed stable phenotype after 12-week implantation in vivo, with cells of human origin, ingrowing vasculature and osteoclasts, suggesting an initiation of tissue remodeling. Discussion/Conclusion. Our biomimetic strategy opens the possibility to construct an unlimited quantity of patient-specific bone grafts for personalised applications, and to generate qualified experimental models to study bone biology under normal and pathological conditions, as well as test new drugs using selected pools of hiPSC lines

Since the development of biomimetic and ceramic bone reconstructive in the early 1970, these specialised bioreactors intended for bone or cartilage regeneration have come a long way in trying to design an alternative procedure other than autogenous bone grafting. However, all known biomaterials still fall short of inducing substantial bone formation in vitro or in vivo, especially when treating large bony defects. As such there is a necessity to develop novel bone-reconstructive biomaterials that can more appropriately be utilised and can induce substantial more bone formation than current scaffolds. Using the rapid prototyping technique (Friedrich-Baur BioMed Center, Bayreuth, Germany) to develop new and improved hydroxyapatite/β-tricalcium phosphate devices, which can be predesigned to any outer shape with controlled pore structure and exhibit a unique intrinsic porosity <150µm due to the 3D-printing process to fit any skeletal bone loss site, the aim of our laboratories was to test the osteoinductive capacity of these new bioreactors in an in vitro culture system utilising adipose-derived stem cells (ADSCs). Immunofluorescent staining revealed that beside the standard surface protein expression patterns typical for ADSCs, the cells also produced osteoblast specific proteins, specifically osteocalcin, osteopontin and dentin matrix acidic phosphoprotein 1. ADSCs seeded on the surface of the biomimetic scaffolds showed constant proliferation, maintained viability and differentiation throughout the scaffold, including the small intrinsic pores. Subsequent, qRT-PCR also revealed that alkaline phosphatase and osteocalcin expression was significantly increased upon addition of osteogenic medium but even more so when human recombinant morphogenetic protein 2 (hBMP-2) was included. Immunofluorescent data of protein expression was consistent with qRT-PCR data. Taken into account with previous results by our laboratories in respect to adipose tissue as a viable inductive medium that can form substantial new bone formation in vivo the present results demonstrated that the investigated bioceramic devices possess the necessary capacity that could, together with adipose tissue, provide the next leap necessary to finally and decisively induce substantial or total new bone formation in clinical bone defects of humans

Fabrication of biogenic coatings with suitable mechanical properties is a key goal in orthopedics, to overcome the limitations of currently available coatings and improve the clinical results of coated implants compared to uncoated ones. In this paper, biological-like apatite coatings were deposited from a natural bone-apatite source by a pulsed electron deposition technique (PED). Bone apatite-like (BAL) films were deposited directly from bone targets, obtained by standard deproteinization of bovine tibial cortical shafts and compared to films deposited by sintered stoichiometric-hydroxyapatite targets (HA). Deposition was performed at room temperature by PED in the Ionized Jet Deposition (IJD) version. Half of the samples was annealed at 400°C for 1h (BAL_400 and HA_400). As-deposited and annealed coatings were characterized in terms of composition and crystallinity (XRD, FT-IR), microstructure and morphology (SEM-EDS, AFM) and mechanical properties (nanoindentation and micro-scratch). For the biological tests, human dental pulp stem cells (hDPSCs) were isolated from dental pulp from patients undergoing a routine tooth extraction, plated on the samples (2500 cells/cm2) and cultured for 3 weeks, when the expression of typical osteogenic markers Runx-2, osteopontin, Osx and Osteocalcin in hDPSCs was evaluated. Results showed that deposition by PED allows for a close transfer of the targets” composition. As-deposited coatings exhibited low cristallinity, that was significantly increased by post-deposition annealing, up to resembling that of biogenic apatite target. As a result of annealing, mechanical properties increased up to values comparable to those of commercial plasma-sprayed HA-coatings. In vitro biological tests indicated that BAL_400 promotes hDPSCs proliferation to a higher extent compared to non-annealed bone coating and HA-references. Furher, immunofluorescence and western blot analyses revealed that the typical osteogenic markers were expressed, indicating that BAL_400 alone can efficiently promote the osteogenic commitment of the cells, even in absence of an osteogenic medium. In conclusion, bone-like apatite coatings were deposited by PED, which closely resembled composition and structure of natural-apatite. Upon annealing at 400°C, the coatings exhibited satisfactory mechanical properties and were capable of providing a suitable microenvironment for hDPSCs adherence and proliferation and for them to reach osteogenic commitment. These results suggest that bone apatite-like thin films obtained by biogenic source may represent an innovative platform to boost bone regeneration in the orthopedic, maxillofacial and odontoiatric field

Background. Following endosteal uncemented orthopaedic device implantation, the initial implant/bone interface retains spaces and deficiencies further exacerbated by pressure necrosis and resultant bone resorption. This implant-bone space requires native bone infill through the process of de novo osteogenesis. New appositional bone formation on the implant surface is known as contact osteogenesis and is generated by osteogenic cells, including skeletal stem cells (SSCs), colonising the implant surface and depositing the extracellular bone matrix. Surface nanotopographies provide physical cues capable of triggering SSC differentiation into osteoblasts, thus inducing contact osteogenesis, translated clinically into enhanced osseointegration and attainment of secondary stability. The current study has investigated the in vitro and in vivo effects of unique nanotopographical pillar substrates on SSC phenotype and function. Methods. Adult human SSCs were immunoselected, enriched using STRO-1 antibody and cultured on control and test surfaces for 21 days in vitro. The test groups comprised Ti-coated substrates with planar or modified surfaces with nanopillar. Osteoinductive potential was analysed using qPCR and immunostaining to examine gene expression and protein synthesis. Results. Following in vitro (n=5) culture on nanopillars, the expression of osteogenic genes (ALP, Collagen 1, OPN and OCN) and of Osteopontin protein (a bone matrix protein), on Ti pillars were both significantly enhanced when compared to control or Ti planar surfaces. Conclusions. Discrete raised surface nanopillars modulate adult SSC populations in the absence of any chemical cues and enhance their osteogenic properties, an effect not observed on planar Ti constructs. Hence, these findings herald exciting opportunities to improve the implant surface design, implant osseointegration, and, ultimately, implant survival. Level of evidence. Original experimental study

It is well established that cell behaviour is responsive to the surrounding environment. Chemistry, material stiffness and topography allow control of cell adhesion, proliferation, growth and differentiation. Biomimicry is playing a role in the next generation of biomaterials, surface engineering on orthopaedic implants may promote improved skeletal integration. Human osteoblasts were cultured on engineered micro-topographical features with nanoscale depths, similar in scale to an osteoclast resorption pit. Three different micro-topographies were used (in addition to planar controls.) created on a hot moulded polymer. The cells were cultured in basal media on surfaces with 20, 30 and 40 micrometer circular pits, each with a depth of 400 nanometers. The cells were fixed at time points 3 days, 21 days and 28 days to allow assessment of cytoskeletal development, production of protein markers of bone production (osteopontin) and mineral deposition respectively. At each time point greater indicators of cell activity and bone production were evident on the 30 and 40 micrometer structures as compared with the 20 micrometer structures and the planar controls. These positive results include increased focal adhesions, stronger expression of intracellular and extracellular osteopontin and more mature nodules of calcium formation. This in vitro study demonstrates that micro and nanotopographies influence cell activity. Osteoblast response can be induced on the surface of a future generation of orthopaedic implants, lasting long after the effects chemical application have expired. Further research is required to assess the potential application to implant grade materials

Delayed facture repair and bony non-unions pose a clinical challenge. Understandably, novel methods to enhance bone healing have been studied by researchers worldwide. Electrical stimulation (ES) has shown to be effective in enhancing bone healing, however the best wave form and mechanism by which it stimulates osteoblasts remains unknown. Interestingly, it is considered that osteoblast activity depends on specific waveforms applied. Therefore, the aim of this study was to evaluate whether particular waveforms have a differential effect on osteoblast activity. An osteoblast cell line was electrically stimulated with either capacitive coupling (CC) or a novel degenerate wave (DW) using a unique in vitro ES system. Following application of both waveforms, the extent of cytotoxicity, proliferation, differentiation and mineralisation of the osteoblasts were assessed using various assays. Differentiation and mineralisation were further analysed using quantitative real-time PCR (qRT PCR) and immunocytochemistry (ICC). DW stimulation significantly enhanced the differentiation of the osteoblasts compared to CC stimulation, with increased protein and gene expression of alkaline phosphatase and type 1 collagen at 28 hours (p < 0.01). DW significantly enhanced the mineralisation of the osteoblasts compared to CC with greater Alizarin Red S staining and gene expression of osteocalcin, osteonectin, osteopontin and bone sialoprotein at 28 hours (p < 0.05). Moreover, immunocytochemical assays showed higher osteocalcin expression after DW stimulation compared to CC at 28 hours. In conclusion. we have shown that ES waveforms enhanced osteoblast activity to different extent but importantly demonstrate for the first time that DW stimulation has a greater effect on differentiation and mineralisation of osteoblasts than CC stimulation. DW stimulation has potential to provide a secure, controlled and effective application for bone healing. These findings have significant implications in the clinical management of fracture repair and bone. non-unions

Objective. Human bone marrow stromal cells (HBMSCs) are multipotent and can form bone, cartilage or other tissues under different inductive conditions. The aim of this study was to investigate the effects of enamel matrix derivative (EMD) on the growth and osteogenic differentiation of HBMSCs. Methods. HBMSCs were cultured in monolayer with EMD (1, 10, 50,100, 250μg/ml) in aMEM supplemented with 2% FBS for 3 days. Cells cultured in aMEM supplemented with 2% FBS (basal medium) served as the control group. Double-stranded DNA was quantified by PicoGreen assay. Quantitative RT-PCR was performed to determine the expression levels of RUNX2, osteopontin (OPN) and osteocalcin (OCN), dentin matrix protein1 (DMP1) and dentin sialophosphoprotein (DSPP) at different time points (day 0, 5 and 10) when exposed to 10μg/ml EMD or basal medium. Alkaline phosphatase specific activity (ALPSA) was determined after 5 and 10 days culture. Mineral deposition (as calcium) was visualised using Alizarin Red staining. Results. All EMD groups showed increased dsDNA content after 3 days culture. However, EMD at 50μg/ml appeared optimal giving a 6.8 fold increase over the control group (p<0.01). Relative to day 0, RUNX2 expression was reduced in the presence of 10μg/ml EMD by 50% after 5 days culture (it was reduced by 30% in the control group), After 10 days culture, RUNX2 expression increased 1.5 fold in the presence of 10μg/ml EMD (increased 1.2 fold in the control group) OPN expression patterns were broadly similar to RUNX2. However, after 5 days culture OCN expression increased 4 fold (increased 7 fold in the control group) but by day 10, expression levels in the presence of EMD had fallen back to day 0 levels whereas levels in the control still showed a 6 fold increase compared to day 0. DMP1 and DSPP expression levels remained at very low levels over the full 10 days in culture. After 10 days culture, HBMSCs treated with 10μg/ml EMD showed significant increase of ALPSA compared with the control group. Mineral deposition was observed in both groups, but to a visibly greater extent in EMD treated groups. Conclusions. EMD stimulated HBMCs proliferation and osteogenic differentiation in vitro, suggesting that EMD may be a useful adjunct in inducing HBMSCs down an osteogenic lineage for use in bone tissue engineering applications. Acknowledgments. ORSAS, LDI Bursary, Xiros

Introduction. P-15 (GTPGPQGIAGQRGVV), a fifteen residue synthetic peptide, is a structural analogue of the cell binding domain of Type 1 collagen and creates a biomimetic environment for bone repair when immobilized on anorganic bovine mineral (ABM) scaffolds. ABM-P-15 scaffolds have been shown to enhance bone marrow stromal cell growth and differentiation. This study aimed at evaluating the osteogenic potential of human dental pulp stromal cells (HDPSCs) compared to human bone marrow stromal cells (HBMSCs) in monolayer and on 3D ABM-P-15 scaffolds in vitro and in vivo. Materials and Methods. HDPSCs and HBMSCs were cultured as monolayers in basal or osteogenic media for 3 weeks. Osteogenic differentiation was confirmed using alkaline phosphatase (ALP) staining and ALP specific activity (ALPSA). In addition, the presence and distribution of osteogenic markers including Type 1 collagen, bone sialoprotein (BSP), osteopontin (OPN) and osteocalcin (OCN) was determined by immunohistochemisty. Gene expression for COL1, RUNX2 and OCN was determined using RT-PCR after 1, 3 and 5 weeks in basal culture. For 3D culture, HDPSCs were seeded on ABM scaffolds ± P-15 (CeraPedics LLC) and cultured in basal media for 6 weeks. Cell viability and growth were visualized by confocal and scanning electron microscopy. Osteogenic differentiation was confirmed by ALP staining and ALPSA. For in vivo studies, HDPSCs were injected and sealed in diffusion chambers containing ABM-P-15 or ABM alone which were then implanted intraperitoneally in nude mice for 8 weeks. The retrieved samples were then processed for histology. Results. In monolayers, HDPSCs showed stronger ALP staining compared to HBMSCs in both culture conditions. Type I collagen, BSP and OPN were detected by immunohistochemistry for both HBMSCs and HDPSCs; however, OCN was not detected. RT-PCR indicated an up regulation of all osteogenic markers in both cell types at weeks 1 and 3. At week 5, there was a marked down regulation of COL1 and RUNX2 in HDPSCS compared to HBMSCs. Confocal microscopy and SEM showed ABM-P-15 promoted HDPSCs bridge formation between the scaffold particles. Histological staining and biochemical analysis confirmed that P-15 enhanced HDPSC ALP activity in vitro and fibrillar collagen formation in vivo compared to ABM alone. Discussion and Conclusion. HDPSCs have higher osteogenic capacity compared to HBMSCs. ABM-P-15 enhanced HDPSC ALPSA and collagen formation, suggesting that a combination of ABM-P15 with HDPSCs could be used as an autologous cell based therapy for bone tissue engineering. Acknowledgement: Supported by a University of Leeds studentships and Cerapedics Inc

Summary. A promising approach to stimulate in vivo bone formation by using our newly developed magnesium-based bone substitutes, which can be an alternative to treat the patients with bone loss in addition to the anticatabolic drugs and growth factors. Introduction. Bone impairment arising from osteoporosis as well as other pathological diseases is a major health problem. Anti-catabolic drugs such as bisphosphonates and other biological agents such as bone morphogenetic proteins and insulin-like growth factor can theoretically apply to stimulate bone formation. However, the formation of more brittle bone and uncontrolled release rate are still a challenge nowadays. Hence, we propose to stimulate bone formation by using a newly developed magnesium-based bone substitute. Indeed, the presence of magnesium ions can stimulate bone growth and healing by enhancing osteoblastic activity. This study aims to investigate the mechanical, in vitro and in vivo properties of this novel bone substitute. Methods. The bone substitutes were prepared by incorporating 9% TMSPM-treated Mg granules (i.e. 45μm & 150μm) into biodegradable polymer, polycaprolactone (PCL). The TMSPM silane-coupling agent treatment was used to protect the Mg particles from rapid degradation. Compression test was performed to study the mechanical properties of the bone substitute by using the MTS machine. A 7-day stimulated body fluid (SBF) immersion test was conducted to test their bioactivity. The surface composition was checked by energy dispersive x-ray spectroscopy (EDX) after immersion. The cytocompatibility and osteogenic differentiation properties of the bone substitutes were studied by MTT, ALP assays and qRT-PCR with the use of MC3T3-E1 pre-osteoblasts. Finally, the in vivo response of the bone substitutes was evaluated by using rat model of 2 months. Micro-CT was used to monitor the volume change of bone formation. Pure PCL was used as the control. Results. At least 36% higher compressive modulus was found on the new bone substitutes as compared to pure PCL. Calcium and phosphate deposition were detected on the Mg bone substitutes but not on pure PCL after 7-day SBF immersion. Significantly higher cell viabilities and specific ALP activities were found on the new bone substitutes as compared to pure PCL. Additionally, significantly higher ALP, Type I collagen, osteopontin and Runx2 expressions were found on the Mg-based substitutes at different time points. Finally, more than 15% new bone was found on the Mg bone substitutes after 1 week of post-operation and 40% higher after 3 weeks. Discussion/Conclusion. The increased compressive moduli of the Mg-based bone substitutes suggested that the mechanical property of PCL could be enhanced by incorporating Mg granules and the values fall within the range of cancellous bone (50 – 800 MPa). Moreover, the detection of the calcium and phosphate on the bone substitutes showed that they might possess osteoinductivity. The in vitro study showed the enhanced cytocompatibility and osteogenic differentiation properties of the new bone substitutes, which was possibly due to the effect of Mg ions release. Our previous study showed that only a low level of Mg ions (i.e. 50ppm) is able to stimulate the growth and differentiation of osteoblasts. Hence, this suggested the importance of controlling the release of Mg ions. This also explained why more new bone formation was found on the new bone substitutes than pure PCL during animal implantation. Hence, all the data presented here suggested our new bone substitutes maybe a potential candidate to stimulate new bone formation

Aim

Osteoarthritis (OA) is caused by complex interactions between genetic and environmental factors. Epigenetic mechanisms control the expression of genes and are likely to regulate the OA transcriptome. We performed integrative genomic analyses to define methylation-gene expression relationships in osteoarthritic cartilage.

We have investigated whether cells derived from haemarthrosis caused by injury to the anterior cruciate ligament could differentiate into the osteoblast lineage in vitro. Haemarthroses associated with anterior cruciate ligament injuries were aspirated and cultured. After treatment with β-glycerophosphate, ascorbic acid and dexamethasone or 1,25 (OH)₂D₃, a significant increase in the activity of alkaline phosphatase was observed. Matrix mineralisation was demonstrated after 28 days and mRNA levels in osteoblast-related genes were enhanced.

Our results suggest that the haemarthrosis induced by injury to the anterior cruciate ligament contains osteoprogenitor cells and is a potential alternative source for cell-based treatment in such injury.

Objectives

We have observed clinical cases where bone is formed in the overlaying muscle covering surgically created bone defects treated with a hydroxyapatite/calcium sulphate biomaterial. Our objective was to investigate the osteoinductive potential of the biomaterial and to determine if growth factors secreted from local bone cells induce osteoblastic differentiation of muscle cells.

The haematoma occurring at the site of a fracture is known to play an important role in bone healing. We have recently shown the presence of progenitor cells in human fracture haematoma and demonstrated that they have the capacity for multilineage mesenchymal differentiation. There have been many studies which have shown that low-intensity pulsed ultrasound (LIPUS) stimulates the differentiation of a variety of cells, but none has investigated the effects of LIPUS on cells derived from human fracture tissue including human fracture haematoma-derived progenitor cells (HCs). In this in vitro study, we investigated the effects of LIPUS on the osteogenic activity of HCs. Alkaline phosphatase activity, osteocalcin secretion, the expression of osteoblast-related genes and the mineralisation of HCs were shown to be significantly higher when LIPUS had been applied but without a change in the proliferation of the HCs. These findings provide evidence in favour of the use of LIPUS in the treatment of fractures.

Objectives

The need for bone tissue supplementation exists in a wide range of clinical conditions involving surgical reconstruction in limbs, the spine and skull. The bone supplementation materials currently used include autografts, allografts and inorganic matrix components; but these pose potentially serious side-effects. In particular the availability of the autografts is usually limited and their harvesting causes surgical morbidity. Therefore for the purpose of supplementation of autologous bone graft, we have developed a method for autologous extracorporeal bone generation.