CTGF/Hcs24, hypertrophic chondrocyte‐specific gene product, interacts with perlecan in regulating the proliferation and differentiation of chondrocytes

Abstract

Connective tissue growth factor/hypertrophic chondrocyte-specific gene product 24 (CTGF/Hcs24) plays important roles in the control of the proliferation and differentiation of chondrocytes in vitro. To clarify the mechanisms of regulation by CTGF/Hcs24 with respect to cartilage metabolism, we investigated the interaction between CTGF/Hcs24 and heparan sulfate proteoglycan perlecan. An immunofluorescence study showed that CTGF/Hcs24 was colocalized with heparan sulfate and perlecan in human chondrosarcoma-derived chondrocytic cell line HCS-2/8 in vitro. Northern blot analysis showed that perlecan, syndecan-1, -2, and -4 transcripts were detected in HCS-2/8 cells. Particularly, expression of the perlecan gene increased markedly in HCS-2/8 cells by recombinant CTGF/Hcs24 (rCTGF/Hcs24) treatment. We also found that CTGF/Hcs24 interacted with perlecan from HCS-2/8 cells in vitro. Furthermore, CTGF/Hcs24-stimulated gene expression of the aggrecan gene, as well as DNA/proteoglycan synthesis, was diminished when HCS-2/8 cells were pretreated with heparinase, indicating that the effects of CTGF/Hcs24 on chondrocytes occurred through the interaction between CTGF/Hcs24 and heparan sulfate on the cells. An in vivo study using mouse growth plate revealed that CTGF/Hcs24 produced by hypertrophic chondrocytes was localized from the proliferative to the hypertrophic zone, whereas perlecan was predominantly localized in the prehyphertrophic zone. Consistent with such findings in vivo, the binding of (125)I-rCTGF/Hcs24 to maturing chondrocytes was at higher levels than that to chondrocytes in hypertrophic stages. These findings suggest that CTGF/Hcs24 produced in the hypertrophic region may act on chondrocytes in the proliferative and maturative zone via some heparan sulfate proteoglycan, such as perlecan.

Recent advances in annular pathobiology provide insights into rim-lesion mediated intervertebral disc degeneration and potential new approaches to annular repair strategies

“…When substituted with HS, perlecan domain-1 promotes binding to laminin-1 and collagen IV and can also act as a low affinity co-receptor for FGF-1, 2, 7, 9 and 18 while domains III and V act as a receptor for FGF-7 [63][64][65]. The low density lipoprotein (LDL) repeats in perlecan domain II bind connective tissue growth factor (CTGF) [2,101], CTGF modulates bone morphogenetic protein (BMP) and transforming growth factor (TGF)-b signalling to co-ordinate morphogenesis, and chondrogenic and angiogenic events during skeletal development [2,101]. Perlecan also interacts with a number of matrix stabilising molecules including fibrillin-1, nidogen-1 and 2, fibulin-2, fibronectin, proline/argininerich and leucine-rich repeat protein/prolargin (PRELP), von Willebrand factor protein-A related protein (WARP) and types XIII and XVIII collagen; and cell attachment proteins such as laminin, fibronectin and thrombospondin [6,8,45,54,78,87,141] and thus also has important roles to play in matrix organisation and stabilisation.…”

Profibrogenic transforming growth factor-β/activin receptor–like kinase 5 signaling via connective tissue growth factor expression in hepatocytes

“…At least some effects are provided through integrins, heparin sulfatecontaining proteoglycans, and the low-density lipoprotein receptor-related protein. 42,46,52,[61][62][63] However, identifying a specific CTGF receptor and determining how intracellular signals initiated by CTGF are mediated and if hepatocyte function is controlled via CTGF are subjects of current research.…”

Role of CTGF/HCS24/ecogenin in skeletal growth control

“…The expression of CTGF/Hcs24 increased during the continuous culture after confluence of RGC cells and peaked in the hypertrophic phase (Nishida et al, 2002a). Thus, when CTGF/Hcs24 gene expression and protein production in cell culture are being compared among studies, it is important to know the growth phase of the culture; because expression and production of CTGF/Hcs24 by cultured cells is generally higher in the sparse, growing phase than in the confluent, quiescent phase (Shimo et al, 2001a).…”