Morphological Alteration of Murine MC3T3‐E1 Osteoblastic cells Induced by Inorganic Polyphosphate

Abstract

Inorganic polyphosphate [poly(P)] induces bone cell differentiation in vitro and in vivo; therefore, we examined morphological changes of MC3T3-E1 osteoblastic cells cultured in the presence of poly(P). MC3T3-E1 cells, which are immature murine bone cells, were cultured with or without poly(P) and then examined by light microscopy and electron microscopy. Ultrastructural observations revealed that MC3T3-E1 cells had morphological characteristics of osteoblasts. Cells cultured with poly(P) were strongly stained with an anti-collagen type I antibody, whereas cells cultured without poly(P) were not. Ultrastructural analysis of cells cultured with poly(P) revealed a well-developed Golgi apparatus, swollen and elongated rough endoplasmic reticulum, large mitochondria, and many coated pits. MC3T3-E1 cells were transformed from a resting phase into an active blastic phase when cultured in the presence of poly(P), which implies that poly(P) can effectively induce bone regeneration. MC3T3-E1 cells exhibiting osteoblastic characteristics in the resting stage can be transformed into the maturating or activating phase by culture with poly(P).