Effects of OGP(10-14) and its derivative G38I on proliferation and differentiation of rat osteoblasts in vitro

Abstract

To investigate the effects of the carboxyl end of osteogenic growth peptide (OGP)-OGP((10-14)) and its derivative G38I on the proliferation and differentiation of osteoblasts (OBs). Osteoblasts were isolated from the calvariae of newborn SD rats and cultured to G3. OGP((10-14)) or G38I of the concentrations of 10(-15) to 10(-7) mol/L were added to culture medium for 48 hours respectively. The number of cells was counted and MTT analysis was used to examine the proliferation of the cells. The ultrastructure of cells was investigated by electron microscopy. The osteoblasts of G3 were divided into experimental groups, treated with OGP((10-14)) or G38I of the concentration of 10(-11) mol/L for 48 hours, and control group. The alkaline phosphatase activity in the culture medium was measured. The protein expression level of type-I collagen was evaluated by immunohistochemistry. The core binding factor 1 (Cbfa1) and type-I collagen mRNA level of osteoblasts were determined by RT-PCR. With a biphasic effect on, OGP((10-14)) and G38I stimulated the number enhancement of OBs dose-dependently at low concentration and inhibited it at high concentration. The numbers of OB were the highest (37 x 10(4)/ml +/- 7 x 10(4)/ml and 30 x 10(4)/ml +/- 5 x 10(4)/ml respectively) when treated by OGP((10-14)) or G38I of the concentration of 10(-11)mol/L. The rough endoplasm net was flourishing and the secreting vesicle was abounding in the experimental cells. There was calcium crystal in the control cells. The activity of alkaline phosphatase in the culture medium of the OGP (10(-14)) and G38I groups were higher than that in the control group (4.47 U/g and 3.82 U/g vs 2.21 U/g). The protein expression level of type-I collagen was higher and the mRNA levels of Cbfa1 and type-I collagen were higher in the OGP((10-14)) and G38I groups were increased in the experimental groups in comparison with the control group (P < 0.05, P < 0.01, and P < 0.05). They stimulated cell number enhancement dose dependently at low concentration and followed by inhibition at high concentration. Just as the native OGP, OGP((10-14)) and its derivative G38I stimulate the proliferation of osteoblasts, and improve their activity, up-regulate the Cbfa1 and type-I collagen mRNA expression levels and increase the collagen synthesis, thus promoting the differentiation and osteogenic effect of osteoblasts.