Chondrocyte responses to neurovascular peptides, cytokines, and a 3D environment: focus on ADAMs

Chondrocyte exposure to inflammatory stimuli in several arthritic conditions, including osteoarthritis, results in the well-characterised induction of extracellular matrix (ECM) degrading proteinases, notably members of a disintegrin and metalloproteinase with thrombospondin domains (ADAMTS) and matrix metalloproteinase (MMP) families. Here we briefly review the less-studied a disintegrin and metalloproteinase (ADAM) family of proteinases in chondrocyte and cartilage biology. Following damage, cartilage is exposed to neurovascular peptides, and in this study we hypothesised that substance P and bradykinin, alongside inflammatory cytokines, may modulate chondrocyte steady state messenger RNA levels for the proteolytic ADAM family members as well as for key cytokines and neuropeptides. We compared chondrocytes cultured in both 2-dimensional (2D) and 3D environments and found that 3D culture generally resulted in repression of expression of the genes under investigation, with the exception of anti-inflammatory interleukin 10 (IL10) which was markedly up-regulated in a 3D environment. Substance P and bradykinin had little effect on ADAM family expression but further investigation revealed that a combination of bradykinin and cytokines led to enhanced expression of ADAM28 and a synergistic up-regulation of IL6, also observed under hypoxic conditions. Overall this data reveals wider chondrocyte responses to neurovascular peptides which may have an impact in an osteoarthritis context

Effects of Pre-Natal Vitamin D Supplementation with Partial Correction of Vitamin D Deficiency on Early Life Healthcare Utilisation: A Randomised Controlled Trial

Funded by Asthma UK grant number 09/ 36

Vitamin D during pregnancy: why observational studies suggest deficiency and interventional studies show no improvement in clinical outcomes? A narrative review

International audienc

rBMP Represses Wnt Signaling and Influences Skeletal Progenitor Cell Fate Specification During Bone Repair

Bone morphogenetic proteins (BMPs) participate in multiple stages of the fetal skeletogenic program from promoting cell condensation to regulating chondrogenesis and bone formation through endochondral ossification. Here, we show that these pleiotropic functions are recapitulated when recombinant BMPs are used to augment skeletal tissue repair. In addition to their well-documented ability to stimulate chondrogenesis in a skeletal injury, we show that recombinant BMPs (rBMPs) simultaneously suppress the differentiation of skeletal progenitor cells in the endosteum and bone marrow cavity to an osteoblast lineage. Both the prochondrogenic and antiosteogenic effects are achieved because rBMP inhibits endogenous β-catenin-dependent Wnt signaling. In the injured periosteum, this repression of Wnt activity results in sox9 upregulation; consequently, cells in the injured periosteum adopt a chondrogenic fate. In the injured endosteum, rBMP also inhibits Wnt signaling, which results in the runx2 and collagen type I downregulation; consequently, cells in this region fail to differentiate into osteoblasts. In muscle surrounding the skeletal injury site, rBMP treatment induces Smad phosphorylation followed by exuberant cell proliferation, an increase in alkaline phosphatase activity, and chondrogenic differentiation. Thus different populations of adult skeletal progenitor cells interpret the same rBMP stimulus in unique ways, and these responses mirror the pleiotropic effects of BMPs during fetal skeletogenesis. These mechanistic insights may be particularly useful for optimizing the reparative potential of rBMPs while simultaneously minimizing their adverse outcomes. © 2010 American Society for Bone and Mineral Research

Genetic variation in inflammatory and bone turnover pathways and risk of osteolytic responses to prosthetic materials

Wear particle-induced inflammatory bone loss (osteolysis) is the leading cause of total hip arthroplasty (THA) failure. Individual susceptibility to osteolysis is modulated by genetic variation. In this 2-stage case-control association study we examined whether variation within candidate genes in inflammatory and bone turnover signaling pathways associates with susceptibility to osteolysis and time to prosthesis failure. We examined two cohorts, comprising 758 (347 male) Caucasian subjects who had undergone THA with a metal on polyethylene bearing couple; 315 of whom had developed osteolysis. Key genes within inflammatory, bone resorption, and bone formation pathways were screened for common variants by pairwise-SNP tagging using a 2-stage association analysis approach. In the discovery cohort four SNPs within RANK, and one each within KREMEN2, OPG, SFRP1, and TIRAP (p < 0.05) were associated with osteolysis susceptibility. Two SNPs within LRP6, and one each within LRP5, NOD2, SOST, SQSTM1, TIRAP, and TRAM associated with time to implant failure (p < 0.05). Meta-analysis of the two cohorts identified four SNPs within RANK, and one each within KREMEN2, OPG, SFRP1, and TIRAP associated with osteolysis susceptibility (p < 0.05). Genetic variation within inflammatory signaling and bone turnover pathways may play a role in susceptibility to osteolysis