Transforming growth factor-β modulates proliferation and differentiation of mouse clonal osteoblastic MC3T3-E1 cells depending on their maturation stages

Abstract

The effect of transforming growth factor-β (TGF-β) on proliferation and differentiation of mouse clonal osteoblastic cells (MC3T3-E1) was examined in vitro in three different stages of their differentiation. Stage I (1–3 days after plating) was characterized by rapid cell growth, negligible alkaline phosphatase (ALP) activity and high proteoglycan synthesis, but low collagen production. In stage II (3–5 days after plating), proteoglycan synthesis sharply decreased and ALP activity and collagen synthesis began to increase. Stage III (7–9 days after plating) was characterized by maximal osteoblastic phenotypes. Treating MC3T3-E1 cells with 1 ng/ml of TGF-β greatly inhibited DNA synthesis in stage I but not in stage II. In contrast, TGF-β dose-dependently stimulated the synthesis of collagenase digestible proteins (CDP), noncollagenous proteins (NCP) and proteoglycan, especially in stage II. The minimum effective dose of TGF-β in this stage was as low as 0.04–0.2 ng/ml. In stages I and III, the MC3T3-E1 cells were rather insensitive to TGF-β in increasing three osteoblastic phenotypes. The increase in ALP activity in stages II and III was inhibited by 1 ng/ml of TGF-β. These results indicate that the response to TGF-β of mouse clonal osteoblastic MC3T3-E1 cells changes depending on their maturation stages.