Co-culture of TGF-beta1 gene transfected fibroblast decreases nitric oxide (NO) production and mineralization of osteoblast.

초록

Bone undergoes continuous remodeling through the coordinated processes of bone formation and bone resorption. Osteoblasts form the structural components of bone and produce regulatory factors that influence both bone formation and bone resorption. Regulatory factors that are mediated the physiological activities of osteoblasts include PTH, vitamin D3, insulin growth factor, TGF-b1, nitric oxide (NO). TGF-b1 and NO have been considered as the important signaling molecules in bone cells and the roles of TGF-b1 and NO in wound healing have been intensively studied. However, the effects of TGF-b1 on the production of NO and the osteogenesis of rat osteoblasts are clearly not understood. To investigate the effects of the TGF-b1 on osteoblast metabolisms and the NO production of osteoblasts by cytokine, we co-cultured TGF-b1 gene transfected NIH3T3 fibroblasts and rat osteoblasts. We also uesed TGF-b1 conditioned media that were derived from NIH3T3 fibroblasts transfected with TGF-b1 gene. The results were as follows. (1) TGF-b1 conditioned media increased the proliferation of osteoblasts. (2) TGF-b1 conditioned media decreased the alkaline phosphatase expression and the mineralizaton of osteoblasts. (3) TGF-b1 decreased NO production by iNOS of osteoblasts. (4) TGF-b1 significantly increased the intracellular Ca2+ activities in osteoblasts. (5) NO increased the intracellular Ca2+ activities in osteoblasts. However, higher concentration of NO decreased the intracellular Ca2+ activities. (6) The clearance of intracellular Ca2+ by Na+-Ca2+ exchanger was depressed with NO treatments. These results show that TGF-b1 increase the proliferation and further suggest that the decrease in NO production may be responsible for the proliferation of osteoblasts.