OSTEOBLASTIC CELLS FROM RAT LONG BONE II: ADHESION TO SUBSTRATA AND INTEGRIN EXPRESSION IN PRIMARY AND PROPAGATED CULTURES

✍ Scribed by MIRCO CASTOLDI; MARIO PISTONE; CRISTINA CARUSO; ALESSANDRA PUDDU; CRISTINA FILANTI; DANIELE PICCINI; CARLO TACCHETTI; PAOLA MANDUCA

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 729 KB
• Volume: 21
• Category: Article
• ISSN: 1065-6995
• DOI: 10.1006/cbir.1996.0110

✦ Synopsis

Propagation in vitro of rat tibial osteoblasts (ROB) is accompanied by increased expression of the early osteogenic marker alkaline phosphatase (AP) and maturation of the osteogenic phenotype. In order to establish the pattern of the integrin expressed in ROB during progression to the mature osteoblastic phenotype, we have used biosynthetic, immunoblotting and immunohistochemical assays. We immunoprecipitated from osteoblasts, expanded for 1.5-and 7.5doubling, 5 1, v 3, 3 1, 6 1 and 1 1 integrin heterodimers; furthermore 5, 2 and 4 chains were detected by immunoblots and indirect immunofluorescence. v, 1, 6 subunits in most cells, and 3 and 1 subunits in a minority, were found to be associated with adhesion plaques in osteoblasts of 1.5-, 4.5-and 7.5-doubling grown in the presence of FCS, while all other subunits stained diffusely all the cells. Adhesion to fibronectin (FN), laminin (LN), collagen type I (COL I) and III (COL III) by ROB at different doubling (1.5-11) was dependent on substratum concentration, and after 2.5 h at 55 n 60% of the cells adhered to all substrata. Arg-Gly-Asp-Ser (RGDS) containing peptides inhibited adhesion of cells differentially, according to substratum; no dependence on extent of progation in vitro was observed. In conclusion, ROB cultured in vitro for 1.5-to 11-doubling had an unchanged pattern of expression of integrin subunits, heterodimer association and cellular distribution. Adhesion specificity and affinity were also unchanged. These results suggest that the phenotypic maturation, detected as an increase in AP expression, is not accompanied by major changes in the potential for cell-matrix interactions, and does not correspond to changes in the type of integrin subunits expressed by osteoblasts.