Stimulation of proliferation and differentiation of dog dental pulp cells in serum-free culture medium by insulin-like growth factor

Insulin, insulin-like growth factors (IGF) I and II are considered to play an important part in the growth and differentiation of dental pulp cells. The present study examined the effects of these factors on pulp cells in serum-free culture conditions. The DNA content and alkaline phosphatase (ALPase) activity of dog pulp cells increased when they were cultured in a serum-free medium supplemented with transferrin, yolk lipoprotein and basic fibrobrast growth factor (TYF medium). The pulp cells produced type I collagen but not type III, suggesting that they might proliferate and differentiate into odontoblast-like cells in a serum-free culture. Both IGF-I and IGF-II enhanced the ALPase activity of pulp cells cultured in TYF medium to an equivalent level, but a higher concentration of IGF-II was necessary to produce a similar effect on DNA synthesis to that of IGF-I. Insulin dose-dependently enhanced DNA synthesis and increased ALPase activity, but its effects were weaker than those of the IGFs. These findings suggest that IGF-I might have a primary role in the growth and differentiation of pulp cells.