Connective tissue growth factor promotes chemotaxis of preosteoblasts through integrin α5 and Ras during tensile force-induced intramembranous osteogenesis

Abstract

In vertebrates, new bone formation via intramembranous osteogenesis is a critical biological event for development, remodeling, and fracture healing of bones. Chemotaxis of osteoblast lineage cells is an essential cellular process in new bone formation. Connective tissue growth factor (CTGF) is known to exert chemotactic properties on various cells; however, details of CTGF function in the chemotaxis of osteoblast lineage cells and underlying molecular biological mechanisms have not been clarified. The aim of the present study was to evaluate the chemotactic properties of CTGF and its underlying mechanisms during active bone formation through intramembranous osteogenesis. In our mouse tensile force-induced bone formation model, preosteoblasts were aggregated at the osteogenic front of calvarial bones. CTGF was expressed at the osteogenic front, and functional inhibition of CTGF using a neutralizing antibody suppressed the aggregation of preosteoblasts. In vitro experiments using μ-slide chemotaxis chambers showed that a gradient of CTGF induced chemotaxis of preosteoblastic MC3T3-E1 cells, while a neutralizing integrin α5 antibody and a Ras inhibitor inhibited the CTGF-induced chemotaxis of MC3T3-E1 cells. These findings suggest that the CTGF-integrin α5-Ras axis is an essential molecular mechanism to promote chemotaxis of preosteoblasts during new bone formation through intramembranous osteogenesis.

Prostate cancer cell‑derived spondin 2 boosts osteogenic factor levels in osteoblasts via the PI3K/AKT/mTOR pathway

“…In the present study, it was indicated that spondin 2 secreted by AR-positive PCa cells could promote the differentiation of osteoblast precursors to mature osteoblasts (showed by the increased expression of Runx2 and Osterix) through the PI3K/AKT/mTOR signaling pathway. As a well-known receptor of spondin 2, integrin α5β1 plays a significant role in bone formation (23), and the present study showed that spondin 2 receptor inhibitor ATN-161 could inhibit spondin 2-mediated PI3K, AKT and mTOR phosphorylation in osteoblast precursor MC3T3-E1 cells.…”

“…Spondin 2 is known to bind to integrin receptors (9). Integrins α5 and β1 are known to be expressed in osteoblasts on the bone surface (23). In order to determine whether spondin 2 activated the PI3K/AKT/mTOR pathway via integrin α5β1, an integrin α5β1 inhibitor (ATN-161) was used to determine its effects on spondin 2-mediated osteogenic factor production.…”

Identification of a Potential MiRNA–mRNA Regulatory Network for Osteoporosis by Using Bioinformatics Methods: A Retrospective Study Based on the Gene Expression Omnibus Database

“…Ras is a crucial regulator of normal bone growth and development ( 35 ). During intramembranous osteogenesis induced by tensile force, Ras was proven to promote chemotaxis of chemotaxis in preosteoblasts both in vivo and in vitro ( 36 ). Fisher et al.…”