Connective Tissue Growth Factor (CTGF/CCN2) is Essential for Secondary Palatogenesis

Abstract

Nonsyndromic cleft palate is a common craniofacial birth defect with an incidence of 1 in 700 live births. Connective tissue growth factor (CTGF/CCN2) has emerged as an essential player in normal craniofacial skeletal formation. Recent studies suggest that CTGF acts as a necessary downstream mediator of TGF-β-dependent mesenchymal stem cell proliferation in palatogenesis. Previous work in our laboratory identified numerous craniofacial defects such as failure of secondary palate formation in CTGF knockout (KO) mice. In this study, microCT and histological analyses showed that CTGF KO mice have a complete absence in midline convergence of mesenchymal tissue compared to wild-type (WT) mice. We isolated pre-osteoblasts from WT and CTGF KO mice for in vitro studies. CTGF KO cells exhibited decreased ability to adhere to extracellular matrices, reduced spreading, altered cytoskeletal organization, and reduced levels of total and activated Rac1 compared to WT cells. Proliferation of CTGF KO cells was also decreased and migration of CTGF KO cells was abnormal. Since these cellular functions are necessary for proper formation of the secondary palate during craniofacial development, we conclude that similar defects in the mesenchyme of the developing palate account for failure of the palatal shelves to form and fuse. Future studies aimed at elucidating the precise mechanism(s) responsible for secondary cleft palate in CTGF KO mice will enhance our understanding of its etiology, and lead to the development of novel therapeutic approaches for the clinical management of this birth defect. Grant Funding Source: NIAMS AR047432 (to SNP) and PA Dept. of Health (to AGL).