Mechanical Regulation of Terminal Chondrocyte Differentiation via RGD-CAP/βig-h3 Induced by TGF-β

Abstract

RGD-CAP (beta ig-h3), initially cloned as a transforming growth factor (TGF)-beta inducible gene in human lung adenocarcinoma cells, was demonstrated to have a negative regulatory function in mineralization in hypertrophic chondrocytes, and the expression was shown to be associated with mechanical stimulation. We hypothesized that mechanical stimulation may regulate the terminal chondrocyte differentiation through the TGF-beta pathway by enhancing the RGD-CAP expression. To test this hypothesis, we investigated the effects of mechanical strain on the terminal differentiation and mineralization of growth-plate chondrocytes and assessed the mechanical regulation of TGF-ss and RGD-CAP expression. A cyclic mechanical strain of 12% elongation was applied to the cultured pre-hypertrophic chondrocytes isolated from the rib cartilage of 4-week-old male rats at 30 cycles/min (loading and relaxation on every alternate second). The terminal differentiation and mineralization of chondrocytes were assessed by alkaline phosphatase (ALP) activity assay and alizarin red staining. The gene expressions of TGF-ss and RGD-CAP, as well as chondrocytic terminal differentiation markers such as type X collagen and ALP, were examined with real-time RT-PCR. Cyclic mechanical strain decreased the ALP activity and intensity of alizarin red staining in pre-hypertrophic chondrocytes, as well as the gene expressions of type X collagen and ALP. TGF-ss and RGD-CAP were upregulated in the pre-hypertrophic chondrocytes subjected to mechanical strain, whereas the level of PTHrP receptor mRNA was not affected by the mechanical strain. The neutralizing antibody for TGF-ss suppressed the reduction of the mineralization of chondrocyte cultures with the downregulation of RGD-CAP. These results suggest that mechanical strain negatively regulates the terminal differentiation of chondrocytes through the signal pathway of TGF-ss with the induction of RGD-CAP.

Gene Expression Profiling of Soft and Firm Atlantic Salmon Fillet

“…3) while an opposite tendency was observed in genes encoding proteins of the extracellular matrix – ECM (collagens, microfibrillar-associated protein 2 and periostin) and proteins involved in deposition and turnover of the ECM (ADAM metallopeptidase and procollagen C-endopeptidase enhancer [27]) and differentiation of connective tissue (TGFβ induced protein ig-h3 [28], angiopoeitin like 3 and 7, FGF3 and noggin [29]). …”

Altered responsiveness to TGF-β results in reduced Papss2 expression and alterations in the biomechanical properties of mouse articular cartilage

“…A full list of all the regulated genes is given in Additional file 1. The list includes several genes known to be regulated by TGF-β, including proteoglycan 4/lubricin ( PRG4 ) [32], parathyroid hormone-like hormone ( PTHLH ) [33], TGF-β-induced protein IG-H3 ( TGFBI ) [34] and prostate transmembrane protein, androgen-induced 1 ( PMEPA1 ) [35], suggesting that the microarray was effective in identifying TGF-β-regulated genes. Surprisingly few genes encoding structural components of the ECM were identified; however, several matrix-modifying genes were upregulated, including 3'-phosphoadenosine 5'-phosphosulfate synthase 2 ( PAPSS2 ), procollagen lysine 2-oxoglutarate 5-dioxygenase 2 ( PLOD2 ), Β-1,3- N -acetylgalactosaminyltransferase 2 ( B3GALNT2 ), UDP-gal:βGlcNAcβ1,3-galactosyltransferase polypeptide 2 ( B3GALT2 ), glycosyltransferase 8 domain-containing 2 ( GLT8D2 ), dermatan sulfate epimerase ( DSE ) and arylsulfatase family, member I ( ARSI ).…”

Targeted Disruption of TGFBI in Mice Reveals Its Role in Regulating Bone Mass and Bone Size through Periosteal Bone Formation

“…Limited in vitro data show that TGFBI regulates the adhesion and migration of osteoblasts and precursors and influences their differentiation and mineralization [17,18,37,45]. It is also a mechanical strain-induced signaling molecule [46]. While these in vitro studies suggest that TGFBI may be an important molecule for mineral metabolism and bone development, its role in vivo in bone has not been studied.…”