Effect of connective tissue growth factor (CCN2/CTGF) on proliferation and differentiation of mouse periodontal ligament-derived cells

In cell cultures of MPL, the mRNA expression of the CCN2/CTGF gene was stronger in sparse cultures than in confluent ones and was significantly enhanced by TGF-β. The addition of recombinant CCN2/CTGF (rCCN2) to MPL cultures stimulated DNA synthesis and cell growth in a dose-dependent manner. Moreover, rCCN2 addition also enhanced the mRNA expression of alkaline phosphatase (ALPase), type I collagen, and periostin, the latter of which is considered to be a specific marker of the periosteum and periodontium; whereas it showed little effect on the mRNA expression of typical osteoblastic markers, e.g., osteopontin and osteocalcin. Finally, rCCN2/CTGF also stimulated ALPase activity and collagen synthesis.These results taken together suggest important roles of CCN2/CTGF in the development and regeneration of periodontal tissue including the periodontal ligament.Connective tissue growth factor (CCN2/CTGF) is a cysteine-rich protein with a molecular weight of 36–38 kDa [1-3] and belongs to the CCN family, which stands for CTGF, CEF10/Cyr61, and Nov [4]. This family now consists of 6 distinct members [1-3], including additional members that had been named WISP1/ELM1, WISP2/COP-1, and WISP3. These proteins retain structural similarity to one another, characterized by an N-terminal secretory signal, followed by 4 modules, with the exception of COP-1, which lacks the C-terminal module [1-4]. As such, CCN proteins share 30–50% over all amino acid sequence homology and 40–60% nucleotide sequence homology with each other [1-4]. The members of this family exhibit functional diversity, being involved in such cellular processes as adhesion, migration, proliferation and differentiation, and in biological processes such as angiogenesis and chondrogenesis [1-3].CCN2/CTGF was discovered as a chemotactic and mitogenic factor for fibroblast-like cells in vitro and so was named accordingly [5]. It was also found in skin fibroblasts in vivo as a repairing growth factor [6]. Of note, transf