Development of more effective diagnostic and therapeutic solutions is vital to tackling the growing challenge of bone diseases and disorders in aging societies. Spatially offset Raman spectroscopy (SORS) enables the chemical specificity of conventional Raman spectroscopy to be combined with sub-surface probing. SORS has successfully been applied to transcutaneous investigations of underlying bone and shows great potential to become an in vivo tool for non-invasive diagnosis of various bone conditions. The volume within the complex hierarchical bone tissue probed by SORS depends on the specimen's optical properties. Understanding the actual sampling depth is important to correctly assign detected chemical changes to specific areas in the bone. This study explores the hypothesis that the effective Raman signal recovery from certain depths requires different spatial offsets depending on the bone mineralisation. SORS depth investigations were conducted on three bones with significantly different mineralisation levels. Thin slices (0.6 – 1.0 mm thickness) were cut from deer antler, horse metacarpal and whale tympanic bulla and stacked together (4 – 7 layers; 4.1 – 4.7 mm total thickness). A 0.38 mm thin slice of polytetrafluoroethylene (PTFE) served as reference sample and was inserted in between the layers of stacked bone slices. Raman spectra were acquired at 30 s using 830 nm excitation. A quantitative relation between the SORS offset and the primarily interrogated depth inside the bone was established. Maximum accessible depths at small offset strongly depend on the mineralisation level. Using large spatial offsets of 7 – 9 mm PTFE signal recovery depths of 4.4 – 4.6 mm through cortical bone can be realized with only minor dependence on the bone mineralisation. These findings highlight the potential of SORS for medical diagnostics by enabling the non-invasive detection of bone conditions characterised by chemical alterations several millimetres inside compact bone tissue (e.g. infections, tumours, etc.)

Mesenchymal stromal cells (MSCs) have been intensively researched in the orthopaedic field since they hold great promise for aiding the regeneration of musculoskeletal tissues. While there are a range of postulated surface markers to identify MSCs, currently there are no known cell markers that predict in vivo osteochondral potency. Runt-related transcription factor 2 (Runx2) is considered as an essential transcription factor in osteoblast differentiation [1] and has been shown to physically interact with retinoblastoma protein (pRb), which leads the loss of osteoblast proliferation and the activation of genes concerning terminal differentiation of osteoblasts [2]. The aim of this study was to use adenoviral-mediated gene overexpression/knockdown to investigate the interplay between Runx2 and pRb during in vitro osteogenic differentiation of human bone marrow (hBM)-MSCs. A first generation human adenovirus (hAd) serotype 5 dE/E3 carrying the gene of interest (Runx2 or shRNA-Runx2) were propagated and amplified in AD-293 cells, and purified over successive CsCl gradients. A second generation hAd serotype 5 carrying the gene of interest (Rb1) was generated. High efficiency single or double transduction of undifferentiated hBM-MSCs was achieved using lanthofection [3]. The transduced hBM-MSCs were then differentiated in osteogenic medium (OM) and osteogenic potency was assessed by quantification of alkaline phosphatase (ALP) activity (day 14) and Alizarin red staining (day 28). In addition, cell cultures were assessed for absorbance at OD 450nm, correlating to the refractive index of calcified areas, at days 0, 7, 14, 21 and 28 [4]. Quantitative RT-PCR was used to confirm expression of target genes following viral transduction. Basal medium was used as a control. Untransduced hBM-MSCs cultures grown in OM demonstrated peak calcium deposition at day 28, while the overexpression of either Runx2 or Rb1 accelerated peak calcium deposition to day 21. Consistent with this, Runx2 overexpression increased ALP activity of hBM-MSCs cultured in OM, while Rb1 overexpression enhanced ALP activity of hBM-MSCs cultured in both basal and osteogenic conditions. Co-expression of Runx2 and Rb1 did not further increase ALP activity compared to cells transduced with Runx2 or Rb1 alone. Alizarin red staining revealed that overexpression of either Runx2 or Rb1 increased mineral deposition in hBM-MSCs under basal conditions, although mineralisation was not enhanced above that of untransduced cells when cultured in OM. However, mineralisation was markedly enhanced above levels in untransduced cells when Runx2 and Rb1 were co-expressed in hBM-MSCs grown under both basal and osteogenic conditions. This study demonstrates an important stimulatory role of pRb in enhancing ALP activity of hBM-MSCs in the absence of osteogenic clues. However, pRb overexpression alone is insufficient to enhance mineralisation, requiring the co-expression of Runx2 in hBM-MSCs. The crucial nature of Runx2 for osteogenic differentiation of hBM-MSCs was demonstrated since knockdown of Runx2 prevented both mineral deposition and the increased ALP activity observed in untransduced cells grown in OM. Interestingly, overexpression of Rb1 could not compensate for the knockdown of Runx2 since Rb1 overexpression did not recover either mineral deposition or ALP activity in hBM-MSCs where Runx2 expression was inhibited

Evidence is accumulating for the role of bone in the pathogenesis of osteoarthritis (OA). Previous studies have shown a generalised increase in bone mass and hypo-mineralisation in OA patients. However, the molecular and cellular mechanisms involved in the increased bone mass and matrix compositional profiles in OA, at distal skeletal sites to the articular cartilage, have not yet been well defined. This study examined whether gene expression of bone anabolic factors, trabecular bone architecture and matrix mineralisation are altered in human OA and non-OA hipbone. Intertrochanteric (IT) trabecular bone samples were obtained from 15 primary hip OA patients (mean age 65 [48–85] years) and 13 closely age- and gender-matched autopsy controls (mean age 63 [44–83] years). Semi-quantitative RT-PCR analysis revealed elevated mRNA expression levels of alkaline phosphatase (p < 0.002), osteocalcin (p < 0.0001), osteopontin (p < 0.05), collagen type-I α chains COL1A1 (p < 0.0001) and COL1A2 (p < 0.002), in OA bone compared to control, suggesting possible increases in osteoblastic biosynthetic activity and/or bone turnover at the IT region in OA. Interestingly, the ratio of COL1A1:COL1A2 mRNA was almost 2-fold greater in OA bone compared to control (p < 0.001), suggesting the potential presence of collagen type-I homotrimer at the distal site that may associate with hypomineralisation in OA individuals. Using a quantitative backscatter electron imaging technique, mineralisation profiles of IT trabecular bone indicated decreased mineralisation in the OA group compared to the control group (24.2 weight percent calcium [wt%Ca] versus 25.3 wt%Ca). Bone histomorphometric analysis found OA IT bone had increased surface density of bone and decreased trabecular separation compared to control bone. Taken together with a reported increase in diffuse microdamage in OA IT bone (Fazzalari et al. Bone 31:697–702, 2002), possibly due to hypomineralisation, these results are consistent with the altered bone material properties found in OA individuals. The finding of differential gene expression, altered mineralisation and architectural changes in OA bone, at a skeletal site distal to the active site of joint degeneration, supports the concept of systemic involvement of bone in the pathogenesis of OA

Summary Statement

Repetitive concavities threaded on the surface of bone implants have been already demonstrated to be effective on ectopic bone formation in vivo. The aim of this study was to investigate the effect of concavity on the mineralization process in vitro.

Introduction. Endochondral ossification (EO) is the process of bone development via a cartilage template. It involves multiple stages, including chondrogenesis, mineralisation and angiogenesis. Importantly, how cartilage mineralisation affects angiogenesis during EO is not fully understood. Here we aimed to develop a new in vitro co-culture model to recapitulate and study the interaction between mineralised cartilage generated from human mesenchymal stromal cells (hMSCs) and microvascular networks. Method. Chondrogenic hMSC pellets were generated by culture with transforming growth factor (TGF)-β3. For mineralised pellets, β-glycerophosphate (BGP) was added from day 7 and TGF-β3 was withdrawn on day 14. Conditioned medium (CM) from the pellets was used to evaluate the effect on human umbilical vein endothelial cells (HUVECs) in migration, proliferation and tube formation assays. To perform direct co-cultures, pellets were embedded in fibrin hydrogels containing vessel-forming cells (HUVECs, adipose stromal cells) for 10 days with BGP to induce mineralisation. The pellets and hydrogels were characterised by immunohistochemistry and confocal imaging. Result. The CM from d14 chondrogenic or mineralised pellets significantly stimulated HUVEC migration and proliferation, as well as in vitro vascular network formation. When CM from pellets subjected to prolonged mineralisation (d28) was used, these effects were strongly reduced. When chondrogenic and mineralised pellets were directly co-cultured with vessel-forming cells in fibrin hydrogels, the cartilage matrix (collagen type II/X stainings) and the mineral deposition (von Kossa staining) were well preserved. Confocal imaging analyses demonstrated the formation of microvascular networks with well-formed lumina. Importantly, more microvascular structures were formed in the proximity of chondrogenic pellets than mineralized pellets. Conclusion. The angiogenic properties of tissue engineered cartilage are significantly reduced upon prolonged mineralisation. We developed a 3D co-culture model to study the role of angiogenesis in endochondral bone formation, which can have applications in disease modelling studies

Matrix-bound vesicles (MBVs) are embedded within osteoid and function as the site of initial mineral formation. However, they remain insufficiently characterised in terms of biogenesis, composition and function while their relationship with secreted culture medium EVs (sEVs) such as exosomes remains debated. We aimed to define the biogenesis and pro-mineralisation capacity of MBVs and sEVs to understand their potential in regenerative orthopaedics. sEVs and MBVs isolated from conditioned medium (differential ultracentrifugation) and ECM (collagenase digestion and differential ultracentrifugation) of mineralising MC3T3 pre-osteoblast and human bone marrow MSC cultures were characterised by nanoparticle tracking analysis, western blotting, nano-flow cytometry, super resolution microscopy (ONI) and TEM. Immunoprecipitated populations positive for alkaline phosphatase (ALP), a putative marker of mineralisation capacity, were also characterised. Collagen binding efficiency was evaluated using MemGlow staining. Results reported were comparative across both cell lines. Western blots indicated MBV fractions were positive for markers of endosomal biogenesis (CD9, CD81, ALIX, TSG101) and pro-mineralising proteins (ALP, Pit1, Annexin II, Annexin V), with Annexin V and CD9 present in immunoprecipitated ALP-positive fractions. MBVs were significantly larger than sEVs (p<0.05) and contained a higher amount of ALP (p<0.05) with a significant increase from day 7 to day 14 of cellular mineralisation (p<0.05). This mirrored the pattern of electron-dense vesicles seen via TEM. Super resolution single vesicle analysis revealed for the first-time co-expression of ALP with markers of endosomal biogenesis (CD9, CD63, CD81, ALIX) and Annexin II in both vesicle types, with higher co-expression percentage in MBVs than sEVs. MBVs also exhibited preferential collagen binding. Advanced imaging methods demonstrated that contrary to opinions in the field, MBVs appear to possess exosomal markers and may arise via endosomal biogenesis. However, it was evident that a higher proportion of MBVs possessed machinery to induce mineralisation and were enriched in mineral-dense material

Introduction. Fusion represents an effective treatment option in patients affected by end-stage arthritis. To minimise the risk of non-union following fusion, biological preparations such as bone marrow aspirate concentrate (BMAC) are commonly used intra-operatively. Mechanotransduction represents an emerging field of research whereby physical stimuli can be used to modulate the behaviour and differentiation of cells. Blast waves (a subtype of shock waves) are one such physical stimulus. The aim of this study was to investigate whether the osteogenic potential of BMAC can be enhanced using a blast wave, and thus improve its efficacy in fusion surgery. Methods. Human BMAC samples were obtained from three healthy patients and exposed to a single blast wave (peak overpressure= 50psi), before being placed in a suspension of mesenchymal stem cells, to represent the biological environment of the fusion site. Three test groups were used: MSC (the experimental control); MSC + BMAC; MSC + BMAC + blast wave. Calcium mineralisation assays were performed on the MSCs on Day 7 and 14 to assess for osteoblastic transformation. Results. Calcium mineralisation on Day 7 was significantly increased in the MSC + BMAC group compared to the MSC group (mean percentage change 42.12 vs 0.0, p=0.012). The MSC + BMAC + blast wave group also demonstrated significantly increased levels compared to the MSC + BMAC group (84.56 vs. 42.14, p = 0.039). The difference in calcium mineralisation between the MSC and MSC + BMAC + blast wave groups was strongly significant (0.00 vs. 84.56, p = 0.003). Conclusion. Exposure of BMAC to a single blast wave enhances its osteogenic potential. This represents a potential novel way to improve healing following fusion surgery and reduce the rates of non-union

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

Objectives. Osteophytes are products of active endochondral and intramembranous ossification, and therefore could theoretically provide significant efficacy as bone grafts. In this study, we compared the bone mineralisation effectiveness of osteophytes and cancellous bone, including their effects on secretion of growth factors and anabolic effects on osteoblasts. Methods. Osteophytes and cancellous bone obtained from human patients were transplanted onto the calvaria of severe combined immunodeficient mice, with Calcein administered intra-peritoneally for fluorescent labelling of bone mineralisation. Conditioned media were prepared using osteophytes and cancellous bone, and growth factor concentration and effects of each graft on proliferation, differentiation and migration of osteoblastic cells were assessed using enzyme-linked immunosorbent assays, MTS ((3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium)) assays, quantitative real-time polymerase chain reaction, and migration assays. Results. After six weeks, the area of mineralisation was significantly higher for the transplanted osteophytes than for the cancellous bone (43803 μm. 2. , . sd. 14660 versus 9421 μm. 2. , . sd. 5032, p = 0.0184, one-way analysis of variance). Compared with cancellous bone, the conditioned medium prepared using osteophytes contained a significantly higher amounts of transforming growth factor (TGF)-β1 (471 pg/ml versus 333 pg/ml, p = 0.0001, Wilcoxon rank sum test), bone morphogenetic protein (BMP)-2 (47.75 pg/ml versus 32 pg/ml, p = 0.0214, Wilcoxon rank sum test) and insulin-like growth factor (IGF)-1 (314.5 pg/ml versus 191 pg/ml, p = 0.0418, Wilcoxon rank sum test). The stronger effects of osteophytes towards osteoblasts in terms of a higher proliferation rate, upregulation of gene expression of differentiation markers such as alpha-1 type-1 collagen and alkaline phosphate, and higher migration, compared with cancellous bone, was confirmed. Conclusion. We provide evidence of favourable features of osteophytes for bone mineralisation through a direct effect on osteoblasts. The acceleration in metabolic activity of the osteophyte provides justification for future studies evaluating the clinical use of osteophytes as autologous bone grafts. Cite this article: K. Ishihara, K. Okazaki, T. Akiyama, Y. Akasaki, Y. Nakashima. Characterisation of osteophytes as an autologous bone graft source: An experimental study in vivo and in vitro. Bone Joint Res 2017;6:73–81. DOI: 10.1302/2046-3758.62.BJR-2016-0199.R1

BMP-1 is the major procollagen-C-peptidase activating, besides fibrillar collagen types I-III, several enzymes and growth factors involved in the generation of extracellular matrix. This study investigated the effect of adding and inhibiting BMP-1 directly post fracture. Standardised femoral fractures were stabilized by an intramedullary nail in 12 week-old female C57Bl/6J mice. We injected either 20 µL recombinant active BMP-1, activity buffer or the BMP-1 specific inhibitor “sizzled”. After 7, 14 and 28 days, mice were sacrificed. Femurs were dissected and paraffin slides were prepared. Callus composition was divided into soft tissue, mineralized and cartilaginous callus. Murine MC3T3 pre-osteoblastic cells were kept in culture adding BMP-1 and sizzled during osteoblastic differentiation. Putative cytotoxicity was determined using MTT-vitality assay. Cell calcification, collagen deposition, and BMP-2 and myostatin protein quantity were characterized. Adding BMP-1 displayed a weak positive effect on the outcome. After 7 days, more mineralised callus was present, meanwhile the cartilaginous callus was apparently remodelled at higher rate. In the case of BMP-1 inhibition, we observed more cartilaginous callus, which may indicate reduced stability. In cell culture, we could observe a high interference with mineralisation capabilities depending on the stage of osteoblastic development when adding BMP-1 or inhibiting it. Addition and inhibition impaired myostatin (anti-osteogen) and BMP-2 (pro-osteogen) expression. Interfering with BMP-1 homeostasis in this early stage of fracture repair seems to have rather negative effects. Inhibition apparently yields lower callus quality while the addition of BMP-1 does not significantly accelerate the healing outcome. Cell culture experiments show that BMP-1 application after 7 days of healing leads to higher collagen output but has no effect on mineralisation. This may suggest that BMP-1 application at a later time-point may lead to more pronounced beneficial effects on fracture repair

The implantation of endoprosthesis is a routine procedure in orthopaedics. Endoprosthesis are mainly manufactured from ceramics, polymers, metals or metal alloys. To ensure longevity of the implants they should be as biocompatible as possible and ideally have antibacterial properties, to avoid periprosthetic joint infections (PJI). Various antibacterial implant materials have been proposed, but have so far only been used sporadically in patients. PJI is one of the main risk factors for revision surgeries. The aim of the study was to identify novel implant coatings that both exhibit antibacterial properties whilst having optimal biocompatibility. Six different novel implant coatings and surface modifications (EBM TiAl6V4, strontium, TiCuN, TiNbN, gentamicin phosphate (GP), gentamicin phosphate+cationic polymer (GP+CP)) were compared to standard CoCrMo-alloy. The coatings were further characterized with regard to the surface roughness. E. coli and S. capitis were cultured on the modified surfaces to investigate the antibacterial properties. To quantify bacterial proliferation the optical density (OD) was measured and viability was determined using colony forming units (CFU). Murine bone marrow derived macrophages (BMMs) were cultured on the surfaces and differentiated into osteoblasts to quantify the mineralisation using the alizarin red assay. All novel coatings showed reduced bacterial proliferation and viability compared to standard CoCrMo-alloy. A significant reduction was observed for GP and GP+CP coated samples compared to CoCrMo (OD. GP,E.coli. = 0.18±0.4; OD. GP+CP,E.coli. = 0.13±0.3; p≤0.0002; N≥7-8). An increase in osteoblast-mediated mineralisation was observed on all surfaces tested compared to CoCrMo. Furthermore, GP and GP+CP coated samples showed a statistically significant increase (M. GP. = 0.21±0.1; M. GP+CP. = 0.25±0.2; p<0.0001; N≥3-6). The preliminary data indicates that the gentamicin containing surfaces have the most effective antibacterial property and the highest osseointegrative capacity. The use of antibiotic coatings on prostheses could reduce the risk of PJI while being applied on osseointegrative implant surfaces

Our previous research has demonstrated that minor adjustments to in vitro cellular aggregation parameters, i.e. alterations to aggregate size, can influence temporal and spatial mineral depositions within maturing bone cell nodules. What remains unclear, however, is how aggregate size might affect mineralisation within said nodules over long-term in vivo culture. In this study, we used an osteoblast cell line, MLO-A5, and a primary cell culture, mesenchymal stem cells (MSC), to compare small (approximately 80 µm) with large (approximately 220 µm) cellular aggregates for potential bone nodule development after 8 weeks of culturing in a mouse model (n = 4 each group). In total, 30 chambers were implanted into the intra-peritoneal cavity of 20 male, immunocompromised mice (MF1-Nu/Nu, 4 – 5 weeks old). Nine small or three large aggregates were used per chamber. Neoveil mesh was seeded directly with 2 × 10. 3. cells for monolayer control. At 8 weeks, the animals were euthanised and chambers fixed with formalin. Aggregate integrity and extracellular material growth were assessed via light microscopy and the potential mineralisation was assessed via micro-CT. Many large aggregates appeared to disintegrate, whilst the small aggregates maintained their form and produced additional extracellular material with increased sizes. Both MLO-A5 cells and MSC cells saw similar results. Interestingly, however, the MSCs were also seen to produce a significantly higher volume of dense material compared to the MLO-A5 cells from micro-CT analysis. Overall, a critical cell aggregate size appeared to exist balancing optimal tissue growth with oxygen diffusion, and cell source may influence differentiation pathway despite similar experimental parameters. The MSCs, for example, were likely producing bone via the endochondral ossification pathway, whilst the matured bone cells, MLO-A5 cells, were likely producing bone via the intramembranous ossification pathway

Age-related fragility fractures are highly correlated with the loss of bone integrity and deteriorated morphology of the osteocytes. Previous studies have reported low-magnitude high-frequency vibration(LMHFV) promotes osteoporotic diaphyseal fracture healing to a greater extent than in age-matched normal fracture healing, yet how osteoporotic fractured bone responds to the mechanical signal has not been explored. As osteocytes are prominent for mechanosensing and initiating bone repair, we hypothesized that LMHFV could enhance fracture healing in ovariectomized metaphyseal fracture through morphological changes and mineralisation in the osteocyte Lacuno-canalicular Network(LCN). As most osteoporotic fractures occur primarily at the metaphysis, an osteoporotic metaphyseal fracture model was established. A total of 72 six-month old female Sprague-Dawley rats (n=72) were obtained(animal ethical approval ref: 16–037-MIS). Half of the rats underwent bilateral ovariectomy(OVX) and kept for 3 months for osteoporosis induction. Metaphyseal fracture on left distal femur was created by osteotomy and fixed by a plate. Rats were then randomized to (1) OVX+LMHFV(20 mins/day and 5 days/week, 35Hz, 0.3g), (2) OVX control, (3) SHAM+LMHFV, (4) SHAM control. Assessments of morphological structural changes, functional markers of the LCN(Scanning Electron Microscopy, FITC-Imaris, immunohistochemistry), mineralization status(EDX, dynamic histomorphometry) and healing outcomes(X-ray, microCT, mechanical testing) were performed at week 1, 2 and 6 post-fracture. One‐way ANOVA with post-hoc test was performed. Statistical significance was set at p < 0.05. Our results showed LMHFV could significantly enhance the morphology of the LCN. There was a 65.3% increase in dendritic branch points(p=0.03) and 93% increase in canalicular length(p=0.019) in the OVX-LMHFV group at week 2 post-fracture. Besides, a similar trend was also observed in the SHAM+LMHFV group, with a 43.4% increase in branch points and 53% increase in canaliculi length at week 2. A significant increase of E11 and DMP1 was observed in the LMHFV groups, indicating the reconstruction of the LCN. The decreasing sclerostin and increasing FGF23 at week 1 represented the active bone formation phase while the gradual increase at week 6 signified the remodelling phase. Furthermore, Ca/P ratio, mineral apposition rate and bone formation rate were all significantly enhanced in the OVX+LMHFV group. The overall bone mineral density in BV was significantly raised in the OVX+LMHFV group at week 2(p=0.043) and SHAM+LMHFV at week 6(p=0.04). Quantitative analysis of microCT showed BV/TV was significantly increased at week 2 in OVX+LMHFV group(p=0.008) and week 6(p=0.001) in both vibration groups. In addition, biomechanical testing revealed that the OVX+LMHFV group had a significantly higher ultimate load(p=0.03) and stiffness(p=0.02) at week 2. To our best knowledge, this is the first report to illustrate LMHFV could enhance osteocytes' morphology, mineralisation status and healing outcome in a new osteoporotic metaphyseal fracture animal model. Our cumulative data supports that the mechanosensitivity of bone would not impair due to osteoporosis. The revitalized osteocyte LCN and upregulated osteocytic protein markers implied a better connectivity and transduction of signals between osteocytes, which may foster the osteoporotic fracture healing process through an enhanced mineralisation process. This could stimulate further mechanistic investigations with potential translation of LMHFV to our fragility fracture patients

To determine whether spinal facet osteoblasts at the curve apex display a different phenotype to osteoblasts from outside the curve in patients with adolescent idiopathic scoliosis (AIS). Intrinsic differences in the phenotype of spinal facet bone tissue and in spinal osteoblasts have been implicated in the pathogenesis of AIS. However, no study has compared the phenotype of facet osteoblasts at the curve apex with the facet osteoblasts from outside the curve in patients with AIS. Facet bone tissue was collected from three sites, the concave and convex side at the curve apex and from outside the curve from three female patients with AIS (aged 13–16 years). Micro-CT analysis was used to determine the density and trabecular structure. Osteoblasts were then cultured from the sampled bone. Osteoblast phenotype was investigated by assessing cellular proliferation (MTS assay), cellular metabolism (alkaline phosphatase and Seahorse Analyser), bone nodule mineralisation (Alizarin red assay), and the mRNA expression of Wnt signalling genes (quantitative RT-PCR). Convex bone showed greater bone mineral density and trabecular thickness than did concave bone. The convex side of the curve apex exhibited a significantly higher proliferative and metabolic phenotype and a greater capacity to form mineralised bone nodules than did concave osteoblasts. mRNA expression of SKP2 was significantly greater in both concave and convex osteoblasts than in non-curve osteoblasts. The expression of SFRP1 was significantly downregulated in convex osteoblasts compared with either concave or non-curve. Intrinsic differences that affect osteoblast function are exhibited by spinal facet osteoblasts at the curve apex in patients with AIS

Integrin α2β1 is one of the major transmembrane receptors for fibrillary collagen. In native bone we could show that the absence of this protein led to a protective effect against age-related osteoporosis. The objective of this study was to elucidate the effects of integrin α2β1 deficiency on fracture repair and its underlying mechanisms. Standardised femoral fractures were stabilised by an intramedullary nail in 12 week old female C57Bl/6J mice (wild type and integrin α2. -/-. ). After 7, 14 and 28 days mice were sacrificed. Dissected femura were subjected to µCT and histological analyses. To evaluate the biomechanical properties, 28-day-healed femura were tested in a torsional testing device. Masson goldner staining, Alizarin blue, IHC and IF staining were performed on paraffin slices. Blood serum of the animals were measured by ELISA for BMP-2. Primary osteoblasts were analysed by in/on-cell western technology and qRT-PCR. Integrin α2β1 deficient animals showed earlier transition from cartilaginous callus to mineralized callus during fracture repair. The shift from chondrocytes over hypertrophic chondrocytes to bone-forming osteoblasts was accelerated. Collagen production was increased in mutant fracture callus. Serum levels of BMP-2 were increased in healing KO mice. Isolated integrin deficient osteoblast presented an earlier expression and production of active BMP-2 during the differentiation, which led to earlier mineralisation. Biomechanical testing showed no differences between wild-type and mutant bones. Knockout of integrin α2β1 leads to a beneficial outcome for fracture repair. Callus maturation is accelerated, leading to faster recovery, accompanied by an increased generation of extra-cellular matrix material. Biomechanical properties are not diminished by this accelerated healing. The underlying mechanism is driven by an earlier availability of BMP-2, one main effectors for bone development. Local inhibition of integrin α2β1 is therefore a promising target to accelerate fracture repair, especially in patients with retarded healing

Osteoporotic fracture has become a major problem in ageing population and often requires prolonged healing time. Low Intensity Pulsed Ultrasound (LIPUS) can significantly enhance fracture healing through alteration of osteocyte lacuno-canalicular network (LCN). DMP1 in osteocytes is responsible for maintaining LCN and mineralisation. This study aims to investigate osteocyte-specific DMP1's role in enhanced osteoporotic fracture healing in response to mechanical stimulation. Bilateral ovariectomy was performed in 6-month-old female SD rats to induce osteoporosis. Metaphyseal fracture was created at left distal femur using oscillating micro-saw. Rats were randomised to groups: (1) DMP1 KD, (2) DMP1 KD + LIPUS, (3) Control, or (4) Control + LIPUS, where KD stands for knockdown by injection of shRNA into marrow cavity 2 weeks before surgery. Assessments included weekly radiography, microCT and immunohistochemistry on DMP1, E11, FGF23 and sclerostin. DMP1 KD significantly impaired LIPUS-accelerated fracture healing when comparing KD + LIPUS group to Control + LIPUS group. The X-ray relative opacity showed less tissue growth at all timepoints (Week 1, 3 & 6; p=0.000, 0.001 and 0.003 respectively) and the bone volume fraction was decreased after DMP1 KD at Week 3 (p=0.006). DMP1 KD also significantly altered the expression levels of osteocyte-specific DMP1, E11, FGF23 and sclerostin during healing process. The lower relative opacity and bone volume fraction in DMP1 KD groups indicated that knockdown of DMP1 was associated with poorer fracture healing process compared to non-knockdown groups. The similar results between knockdown group with and without LIPUS showed that blockage of DMP1 would negate LIPUS-induced enhancement on fracture healing. Acknowledgment: General Research Fund (Ref: 14113018)

3D spheroid culture is a bridge between standard 2D cell culture and in vivo research which mimics the physiological microenvironment in scaffold-free conditions. Here, this 3D technique is being investigated as a potential method for engineering bone tissue in vitro. However, spheroid culture can exhibit limitations, such as necrotic core formation due to the restricted access of oxygen and nutrients. It is therefore important to determine if spheroids without a sizeable necrotic core can be produced. This study aims to understand necrotic core formation and cell viability in 3D bone cell spheroids using different seeding densities and media formulations. Differentiated rat osteoblasts (dRObs) were seeded in three different seeding densities (1×10. 4. , 5×10. 4. , 1×10 cells) in 96 well U-bottom cell-repellent plates and in three different media i.e., Growth medium (GM), Mineralisation medium 1 (MM1) and MM2. Spheroids were analysed from day 1 to 28 (N=3, n=2). Cell count and viability was assessed by trypan blue method. One way ANOVA and post-hoc Tukey test was performed to compare cell viability among different media and seeding densities. Histological spheroid sections were stained with hematoxylin and eosin (H&E) to identify any visible necrotic core. Cell number increased from day 1 to 28 in all three seeding densities with a notable decrease in cell viability. 1×10. 4. cells proliferated faster than 5×10. 4. and 1×10. 5. cells and had proportionately similar cell death. The necrotic core area was relatively equivalent between all cell seeding densities. The larger the spheroid size, the larger is the size of the necrotic core. This study has demonstrated that 3D spheroids can be formed from dRobs at a variety of seeding densities with no marked difference in necrotic core formation. Future studies will focus on utilising the bone cell spheroids for engineering scalable scaffold-free bone tissue constructs

Abstract. OBJECTIVE. Knee varus malalignment increases medial knee compartment loading and is associated with knee osteoarthritis (OA) progression and severity. 1. Altered biomechanical loading and dysregulation of joint tissue biology drive OA progression, but mechanistic links between these factors are lacking. Subchondral bone structural changes are biomechanically driven, involve bone resorption, immune cell influx, angiogenesis, and sensory nerve invasion, and contribute to joint destruction and pain. 2. We have investigated mechanisms underlying this involving RANKL and alkaline phosphatase (ALP), which reflect bone resorption and mineralisation respectively. 3. and the axonal guidance factor Sema3A. Sema3A is osteotropic, expressed by mechanically sensitive osteocytes, and an inhibitor of sensory nerve, blood vessel and immune cell invasion. 4. Sema3A is also differentially expressed in human OA bone. 5. HYPOTHESIS: Medial knee compartment overloading in varus knee malalignment patients causes dysregulation of bone derived Sema3A signalling directly linking joint biomechanics to pathology and pain. METHODS. Synovial fluid obtained from 30 subjects with medial knee OA (KL grade II-IV) undergoing high tibial osteotomy surgery (HTO) was analysed by mesoscale discovery and ELISA analysis for inflammatory, neural and bone turnover markers. 11 of these patients had been previously analysed in a published patient-specific musculoskeletal model. 6. of gait estimating joint contact location, pressure, forces, and medial-lateral condyle load distribution in a published data set included in analyses. Data analysis was performed using Pearson's correlation matrices and principal component analyses. Principal Components (PCs) with eigenvalues greater than 1 were analysed. RESULTS. PC1 (32.94% of variation) and PC2 (25.79% of variation) from PCA analysis and correlation matrices separated patients according to correlated clusters of established inflammatory markers of OA pain and progression (IL6/IL8, r=0.754, p<0.001) and anti-inflammatory mediators (IL4/IL10, r=0.469, p=0.005). Bone turnover marker ALP was positively associated with KL grade (r=0.815, p=0.002) and negatively associated with IL10 (r=−0.402, p=0.018) and first peak knee loading pressures (r=−0.688, p=0.019). RANKL was positively associated with IL4 (r=0.489, p=0.003). Synovial fluid Sema3A concentrations showed separate clustering from all OA progression markers and was inversely correlated with TNF-α (r=−0.423, p=0.022) in HTO patients. Sema3A was significantly inversely correlated with total predicted force in the medial joint compartment (r=−0.621, p=0.041), mean (r=−0.63, p=0.038) and maximum (r=−0.613, p=0.045) calculated medial compartment joint pressures during the first phase and mean (r=−0.618, p=0.043) and maximum (r=−0.641, p=0.034) medial compartment joint pressures during midstance outputs of patient-specific musculoskeletal model. CONCLUSIONS. This study shows joint inflammatory status and mechanical overloading influence subchondral bone-remodelling. Synovial Sema3A concentrations are inversely correlated to patient-specific musculoskeletal model estimations of pathological medial overloading. This study reveals Sema3A as a biological mediator with capacity to induce OA pain and disease progression that is directly regulated by gait mechanical loading. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Bone fracture healing is regulated by a series of complex physicochemical and biochemical processes. One of these processes is bone mineralisation, which is vital for normal bone development, its biomechanical competence and fracture healing. Phosphatase, orphan 1 (PHOSPHO1), a bone-specific phosphatase, has been shown to be involved in the mineralisation of the extracellular matrix in bone. It can hydrolyse phosphoethanolamine and phosphocholine to generate inorganic phosphate, which is crucial for bone mineralisation. Phospho1−/− mice show hypomineralised bone and spontaneous fractures. All these data led to the hypothesis that PHOSPHO1 is essential for bone mineralisation and its structural integrity. However, no study to our knowledge has shown the effects of PHOSPHO1 on bone fracture healing. In this study, we examined how PHOSPHO1-deficiency might affect the healing and quality of the fractured bones in Phospho1−/− mice. We performed rodded immobilised fracture surgery on the right tibia of control wild type (WT) and Phospho1−/− mice (n=16 for each group) at eight weeks of age. Bone was left to heal for four weeks and then the mice were euthanised and their tibias were analysed using Faxitron X-ray analyses, microCT, histology and histomorphometry and three-point bending test. Our microCT and X-ray analyses revealed that the appearance of the callus and several static parameters of bone remodeling at the fracture sites were markedly different in WT and Phospho1−/− mice. We observed a significant increase of BS/BV, BS/TV and trabecular number and decrease in trabecular thickness and separation in Phospho1−/− callus in comparison to the WT callus. These observations were further confirmed by histomorphometry. The increased bone mass at the fracture sites of Phospho1−/− mice appears to be caused by increased bone formation as there is a significant increase of osteoblast number, while osteoclast numbers remained unchanged. There was a marked increase of osteoid volume over bone volume (OV/BV) in the Phospho−/− callus. Interestingly, the amount of osteoid was markedly higher at the fracture sites than that of normal trabecular bones. The three-point bending test showed that Phospho 1 −/− fractured bone had more of an elastic characteristics than the WT bone as they underwent more of a plastic deformity before the breakage point compare to the WT. Our work suggests that PHOSPHO1 plays an integral role during bone fracture repair. PHOSPHO1 can be an interesting target to improve the fracture healing process

Millions of patients each year suffer from challenging non-healing bone defects secondary to trauma or disease (e.g. cancer, osteoporosis or osteomyelitis). Tissue engineering approach to non-healing bone defects has been investigated over the past few decades in a search for a novel solution for critical size bone defects. The success of the tissue engineering approach relies on three main pillars, the right type of cells; and appropriate scaffold; and a biologically relevant biochemical/ biophysical stimuli. When it comes to cells the mesodermal origin of mesenchymal stem cells and its well demonstrated multipotentiality makes it an ideal option to be used in musculoskeletal regeneration. For the presented set of experimental assays, fully characterised (passage 3 to 5)ovine adipose-derived mesenchymal stems cells (Ad-MSC) were cultured either in growth medium (GM) consisting of Dulbecco's Modification of Eagle's Medium (DMEM) supplemented with 10% (v/v) foetal bovine serum and 1% penicillin-streptomycin as a control or in osteogenic differentiation medium (DM), consisting of GM further supplemented with L- ascorbic acid (50 μg/ml), β-glycerophosphate (10 mM) and dexamethasone (100nM). Osteogenic differentiation was assessed biochemically by quantifying alkaline phosphatase (ALP) enzyme activity and alizarin red staining after 3, 7, 14 and 21 days in culture (where 1×105 cells/well were seeded in 24 well-plate, n=6/media type/ time point). Temporal patterns in osteogenic gene expression were quantified using real-time PCR for Runx-2, osteocalcin (OC), osteonectin (ON) and type 1 collagen (Col 1) at days 7, 15 and 21 (where 1×105 cells were seeded in T25 cell culture flasks for RNA extraction, n= 4 / gene/ media type/time point). The morphology of osteogenic cells was additionally evaluated by scanning electron microscopy (SEM) of cells seeded at low-density (1×102 cells) on glass coverslips for 2 weeks in GM or DM. The level of ALP activity of cells grown in osteogenic DM was significantly higher than the control growing in the standard growth medium (p ≤ 0.05) at days 3, 7 and 14. At 21 days there was a sharp drop in ALP values in the differentiating cells. Mineralisation, as evidenced by alizarin red staining, increased significantly by day 14 and then peaked at day 21. Quantitative real-time PCR confirmed early increases in Runx-2, Col 1 and osteonectin, peaking in the second week of culture, while osteocalcin peaked at 21 days of culture. Taken as a whole, these data indicate that ovine-MSCs exhibit a tightly defined pathway of initial proliferation and matrix maturation (up to 14 days), followed by terminal differentiation and mineralisation (days 14 to 21). SEM analysis confirmed the flattened, roughened appearance of these cells and abandoned extracellular matrix which resembled mature osteoblasts. Given the ready availability of adipose tissues, the use of Ad-MSCs as progenitors for bone tissue engineering applications is both feasible and reasonable. The data from this study indicate that Ad-MSCs follow a predictable pathway of differentiation that can be tracked using validated molecular and biochemical assays. Additional work is needed to confirm that these cells are osteogenic in vivo, and to identifying the best combination of scaffold materials and cell culture techniques (e.g. static versus dynamic) to accelerate or stimulate osteogenic differentiation for bone tissue engineering applications