If good things come from above, do bad things come from below?

Factors in the synovial fluid that maintain healthy articular cartilage, such as hyaluronic acid and lubricin, come from above. Is it possible that factors which lead to the destruction of cartilage come from below in the subchondral bone? The recent acquisition of tools to probe early events in osteoarthritis is shedding new light on possible contributions from this compartment on the initiation and progression of the disease. Tanamas and co-workers now provide evidence that bone marrow lesions in the subchondral bone are predictive, both of loss of cartilage and of formation of subchondral cysts. These data provoke questions about the nature and role of bone marrow lesions

Molecular Mechanisms of Stem Cells Pluripotency and Cell Fate Specification

International audienc

Microarray gene expression profiling of osteoarthritic bone suggests altered bone remodelling, WNT and transforming growth factor-β/bone morphogenic protein signalling

Osteoarthritis (OA) is characterized by alterations to subchondral bone as well as articular cartilage. Changes to bone in OA have also been identified at sites distal to the affected joint, which include increased bone volume fraction and reduced bone mineralization. Altered bone remodelling has been proposed to underlie these bone changes in OA. To investigate the molecular basis for these changes, we performed microarray gene expression profiling of bone obtained at autopsy from individuals with no evidence of joint disease (control) and from individuals undergoing joint replacement surgery for either degenerative hip OA, or fractured neck of femur (osteoporosis [OP]). The OP sample set was included because an inverse association, with respect to bone density, has been observed between OA and the low bone density disease OP. Compugen human 19K-oligo microarray slides were used to compare the gene expression profiles of OA, control and OP bone samples. Four sets of samples were analyzed, comprising 10 OA-control female, 10 OA-control male, 10 OA-OP female and 9 OP-control female sample pairs. Print tip Lowess normalization and Bayesian statistical analyses were carried out using linear models for microarray analysis, which identified 150 differentially expressed genes in OA bone with t scores above 4. Twenty-five of these genes were then confirmed to be differentially expressed (P < 0.01) by real-time PCR analysis. A substantial number of the top-ranking differentially expressed genes identified in OA bone are known to play roles in osteoblasts, osteocytes and osteoclasts. Many of these genes are targets of either the WNT (wingless MMTV integration) signalling pathway (TWIST1, IBSP, S100A4, MMP25, RUNX2 and CD14) or the transforming growth factor (TGF)-β/bone morphogenic protein (BMP) signalling pathway (ADAMTS4, ADM, MEPE, GADD45B, COL4A1 and FST). Other differentially expressed genes included WNT (WNT5B, NHERF1, CTNNB1 and PTEN) and TGF-β/BMP (TGFB1, SMAD3, BMP5 and INHBA) signalling pathway component or modulating genes. In addition a subset of genes involved in osteoclast function (GSN, PTK9, VCAM1, ITGB2, ANXA2, GRN, PDE4A and FOXP1) was identified as being differentially expressed in OA bone between females and males. Altered expression of these sets of genes suggests altered bone remodelling and may in part explain the sex disparity observed in OA

The Relationship between Sun Exposure, Dietary Vitamin D and Muscle Soreness in Collegiate Football Players

Background: A growing body of research is raising concern regarding the prevalence of poor vitamin D status among athletes. Besides it’s well known association with low bone mineral density, an addition sign of vitamin D deficiency is muscular weakness and soreness, suggesting that deficiency in athletic populations may inhibit optimal physical performance and increase the risk of injury. It is difficult to achieve optimal vitamin D status through diet alone, so it is important to assess all sources of vitamin D, including dietary intake, supplementation, and amount and frequency of sun exposure to obtain a comprehensive profile of vitamin D risk. Currently, there are no studies that include such a complete profile of vitamin D risk in collegiate football players. Purpose: The purpose of this study is to investigate the associations between sun exposure and diet, as markers of vitamin D status, and training-induced muscle soreness in collegiate football players. More specifically, this study assesses if total sun exposure and dietary vitamin D intake are related to muscle soreness. Methods: Twenty-four male collegiate football players were recruited for this cross-sectional study in October 2015. Player body composition was measured using a multi-current bioelectrical impedance analyzer (BIA). Dietary intake, sun exposure, and muscle soreness data were collected via interview. The Sun Exposure Questionnaire and the Short Form McGill Pain Questionnaire (SF-MPQ) were used to assess weekly sun exposure and muscle soreness, respectively. Results: The mean vitamin D intake (10.8±9.5 mcg) was below the RDA for vitamin D (15 mcg), with only 7 participants (29.2%) meeting or exceeding the RDA. Dietary vitamin D intake was inversely associated with portion of muscle sore (rs = -0.393, p = 0.029). SF-MPQ total and affective scores were each inversely associated with weekly time outdoors (rs = -0.362, p = 0.041; rs = -0.449, p = 0.014, respectively). T-test analysis found that the mean SF-MPQ affective pain score was significantly lower for players with a time outdoors score above the mean (p = 0.04). Conclusion: There is a high prevalence of insufficient dietary vitamin D intake (70.8%) identified in a collegiate football team. Our findings suggest that higher dietary vitamin D intake and more time spent outdoors are associated with a lower proportion of muscular soreness and decreased perceived pain. Thus, achieving a satisfactory vitamin D status, through a combination of diet and sun exposure, may reduce vitamin D deficiency associated risks, including lowering muscle soreness, thereby serving to enhance athletic performance

Recombinant sclerostin antagonizes effects of ex vivo mechanical loading in trabecular bone and increases osteocyte lacunar size

Sclerostin has emerged as an important regulator of bone mass. We have shown that sclerostin can act by targeting late osteoblasts/osteocytes to inhibit bone mineralization and to upregulate osteocyte expression of catabolic factors, resulting in osteocytic osteolysis. Here we sought to examine the effect of exogenous sclerostin on osteocytes in trabecular bone mechanically loaded ex vivo. Bovine trabecular bone cores, with bone marrow removed, were inserted into individual chambers and subjected to daily episodes of dynamic loading. Cores were perfused with either osteogenic media alone or media containing human recombinant sclerostin (rhSCL) (50 ng/ml). Loaded control bone increased in apparent stiffness over time compared with unloaded bone, and this was abrogated in the presence of rhSCL. Loaded bone showed an increase in calcein uptake as a surrogate of mineral accretion, compared with unloaded bone, in which this was substantially inhibited by rhSCL treatment. Sclerostin treatment induced a significant increase in the ionized calcium concentration in the perfusate and the release of -CTX at several time points, an increased mean osteocyte lacunar size, indicative of osteocytic osteolysis, and the expression of catabolism-related genes. Human primary osteocyte-like cultures treated with rhSCL also released -CTX from their matrix. These results suggest that osteocytes contribute directly to bone mineral accretion, and to the mechanical properties of bone. Moreover, it appears that sclerostin, acting on osteocytes, can negate this effect by modulating the dimensions of the lacunocanalicular porosity and the composition of the periosteocyte matrix

Sclerostin Stimulates Osteocyte Support of Osteoclast Activity by a RANKL-Dependent Pathway

Sclerostin is a product of mature osteocytes embedded in mineralised bone and is a negative regulator of bone mass and osteoblast differentiation. While evidence suggests that sclerostin has an anti-anabolic role, the possibility also exists that sclerostin has catabolic activity. To test this we treated human primary pre-osteocyte cultures, cells we have found are exquisitely sensitive to sclerostin, or mouse osteocyte-like MLO-Y4 cells, with recombinant human sclerostin (rhSCL) and measured effects on pro-catabolic gene expression. Sclerostin dose-dependently up-regulated the expression of receptor activator of nuclear factor kappa B (RANKL) mRNA and down-regulated that of osteoprotegerin (OPG) mRNA, causing an increase in the RANKL∶OPG mRNA ratio. To examine the effects of rhSCL on resulting osteoclastic activity, MLO-Y4 cells plated onto a bone-like substrate were primed with rhSCL for 3 days and then either mouse splenocytes or human peripheral blood mononuclear cells (PBMC) were added. This resulted in cultures with elevated osteoclastic resorption (approximately 7-fold) compared to untreated co-cultures. The increased resorption was abolished by co-addition of recombinant OPG. In co-cultures of MLO-Y4 cells with PBMC, SCL also increased the number and size of the TRAP-positive multinucleated cells formed. Importantly, rhSCL had no effect on TRAP-positive cell formation from monocultures of either splenocytes or PBMC. Further, rhSCL did not induce apoptosis of MLO-Y4 cells, as determined by caspase activity assays, demonstrating that the osteoclastic response was not driven by dying osteocytes. Together, these results suggest that sclerostin may have a catabolic action through promotion of osteoclast formation and activity by osteocytes, in a RANKL-dependent manner

OXA-48-like carbapenemases in the UK: an analysis of isolates and cases from 2007 to 2014

Objectives: OXA-48-like carbapenemases have spread worldwide since 2001. We analysed patient and microbiological data for UK isolates with these enzymes as confirmed by the national reference laboratory from November 2007 - December 2014.  Methods: MICs were determined using BSAC agar dilution. Isolates with reduced susceptibility or resistance to at least one carbapenem and high-level resistance to both piperacillin/tazobactam (MIC ≥ 64 mg/L) and temocillin (MICs ≥ 128 mg/L) were screened by PCR for blaOXA-48-like genes. The genomes of around half of the isolates were sequenced, with MLST types, resistance genes and plasmid replicon types inferred. Patient data provided by sending laboratories were reviewed.  Results: Isolates (n=741) with OXA-48-like carbapenemases were submitted from 111 UK laboratories, representing 536 patients. Almost all (99%; 736/741) were Enterobacteriaceae, predominantly Klebsiella pneumoniae (55%; 408), and most (80%; 595) were from inpatients. WGS of 351 non-duplicate isolates identified blaOXA-48 as the most common variant, found in two-thirds (235/351) of isolates, followed by blaOXA-181 (68), blaOXA-232 (32), blaOXA-244 (10), blaOXA-484 (5) and blaOXA-245 (1). Among K. pneumoniae (163/351), E.coli (114/351), and E. cloacae (42/351), 119 STs were identified. Mapping analyses revealed that 63% (222/351) of isolates harboured plasmids that shared >99% identity to one of four known plasmids; pOXA-48a (44%; 154/351), pOXA-232 (10%; 34/351), pOXA181 (9%; 30/351), and pKP3-A (1%; 4/351); the remaining 37% of isolates harboured blaOXA-48-like in unknown environments.  Conclusions: OXA-48-like carbapenemases are an increasing problem in the UK. This study highlights both the role of successful plasmids and polyclonal nature of their dissemination

Elevated expression of caspase-3 inhibitors, survivin and xIAP correlates with low levels of apoptosis in active rheumatoid synovium

Introduction: Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a tumour necrosis factor (TNF) family member capable of inducing apoptosis in many cell types. Methods: Using immunohistochemistry, terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling (TUNEL) and real-time PCR we investigated the expression of TRAIL, TRAIL receptors and several key molecules of the intracellular apoptotic pathway in human synovial tissues from various types of arthritis and normal controls. Synovial tissues from patients with active rheumatoid arthritis (RA), inactive RA, osteoarthritis (OA) or spondyloarthritis (SpA) and normal individuals were studied. Results Significantly higher levels of TRAIL, TRAIL R1, TRAIL R2 and TRAIL R4 were observed in synovial tissues from patients with active RA compared with normal controls (p < 0.05). TRAIL, TRAIL R1 and TRAIL R4 were expressed by many of the cells expressing CD68 (macrophages). Lower levels of TUNEL but higher levels of cleaved caspase-3 staining were detected in tissue from active RA compared with inactive RA patients (p < 0.05). Higher levels of survivin and x-linked inhibitor of apoptosis protein (xIAP) were expressed in active RA synovial tissues compared with inactive RA observed at both the protein and mRNA levels. Conclusions: This study indicates that the induction of apoptosis in active RA synovial tissues is inhibited despite stimulation of the intracellular pathway(s) that lead to apoptosis. This inhibition of apoptosis was observed downstream of caspase-3 and may involve the caspase-3 inhibitors, survivin and xIAP.Anak ASSK Dharmapatni, Malcolm D Smith, David M Findlay, Christopher A Holding, Andreas Evdokiou, Michael J Ahern, Helen Weedon, Paul Chen, Gavin Screaton, Xiao N Xu and David R Hayne