Actions of bovine plasma fibronectin on cultured human dental pulp cells

Fibronectin (FN) has been shown to play a crucial role in odontoblast differentiation, and it is involved in the repair of dentine and pulp. The responsiveness of human dental pulp (HDP) cells to bovine plasma FN was investigated.

After isolation and selection noncarious freshly extracted third molars in vitro, HDP cells were incubated for 72 hours one of four concentrations (10, 20, 40, 80 micrograms/ml) of bovine plasma FN with Dulbecco's modified eagle medium (DMEM) containing 1% fetal calf serum (FCS). We examined cell proliferation (using an MTT assay), DNA synthesis (using incorporation of [3H]-thymidine), the cell area, and alkaline phosphatase (ALPase) activity of the culture supernatant. The expression of FN, types I and III collagens, binding of lectins concanavalin(ConA), or wheat germ agglutinin (WGA) in vitro was examined by means of immunocytochemistry. The expression degree and the cell area were analyzed semi-quantitatively with an image processing and analysis system.

After 72 hours, HDP cells appeared contracted and smaller in the absence of FN when compared to cells incubated with FN. HDP cells were in spread state with all four concentrations of FN. FN (20, 40 micrograms/ml) stimulated cell proliferation, promoted incorporation of [3H]-thymidine, and increased the levels of ALPase activity in supernatant. The binding of ConA, the expression of type I collagen, and FN were significantly increased, while the binding of WGA, and the expression of type III collagen were significantly decreased in the FN (40, 80 micrograms/ml) groups when compared to the FN (10, 20 micrograms/ml) groups.

These findings suggest that HDP cells utilize FN for attachment and subsequent spreading. FN might have mitogenic activity and some role in the regulation of differentiation of pulp cells into odontoblasts.