Role of the Metabolism of 5'-Methylthioadenosine in the Proliferation and Differentiation of Osteoprogenitor Cells

-Effects of an Inhibitor of Methylthioadenosine Phosphorylase - on the Proliferation and Alkaline Phosphatase Activity of Fetal Rat Calvaria Cells-

Abstract

5'-Methylthioadenosine (MTA) is formed during the biosynthesis of polyamines. This nucleoside is cleaved to adenine and 5'-methylthioribose-l-phosphate in mammalian cells by methylthioadenosine phosphorylase (MTAPase). 5'-Difluoromethylthioadenosine (DFMTA), a synthetic analog of MTA is known to be an inhibitor of MTA Pase.
In this study, we examined the effects of DFMTA on the cell proliferation and alkaline phosphatase (ALPase) activity of enzyme-releasedr at calvaria cells (RCcells). RC cells were isolated by collagenase digestion of 21-day fetal rat calvariae and cultured in the medium containing 15% NU serum, which was used because its MTA Pase activity is very low. Under the culture conditions employed, the ALPase activity of RC cells was low in the exponential growth phase, but markedly increased when the cells reached confluency (day10). DFMTA strongly inhibited MTA Pase extracted from RC cells (Ki= 0.60μM). DFMTA at low concentrations (5, 10μM) decreased the ALPase activity of RC cells measured on day 7 and 14, without affecting cell proliferation. At higher concentrations (≥25μM), this analog suppressed both ALPase activity and cell proliferation. These results suggested that the metabolism of MTA is involved in regulating cell proliferation and differentiation.