マスピンは潜在型TGF-β の蓄積を介して骨基質の成熟に関与している

Introduction: Maspin is a serine protease inhibitor that exhibits tumor suppressive and anti-angiogenic activities. This study was performed to elucidate a possible role for maspin in bone formation.
Materials and Methods: We performed immunohistochemical analysis of the expression of maspin during endochondral ossification. We evaluated the expression of maspin mRNA and protein in ROS 17/2.8 cells and primary rat osteoblastic cells by RT-PCR, immunocytochemistry and Western blot analysis. We also examined the accumulation of TGF-β in the extracellular matrix of cultured ROS 17/2.8 cells following transfection with vectors expressing either maspin or maspin antisense.
Results: We observed expression of maspin by active osteoblasts in vivo. Rat osteoblastic cells also expressed maspin mRNA and protein in vitro. Moreover, the accumulation of latent TGF-β in the extracellular matrix significantly decreased in cultures exposed to an anti-maspin antibody and when cells were transfected with a maspin antisense-expressing vector. In contrast, accumulation of latent TGF-β in the extracellular matrix increased following transfection of cells with a vector expressing maspin.
Conclusions: These findings suggest that maspin expressed in active osteoblasts plays an important physiological role during maturation of the bone matrix, and in particular during the process of accumulation of latent TGF-β in the extracellular matrix.