Dentin matrix protein 1 (DMP1): a new bone matrix protein

摘要

Bone, dentin and cementum are composed of mineralized extracellular matrix. The matrix consists of coJlagenous (predominantly) and non-collagenoiis proteins. One of the non-collagenous proteins identified with the help of recombinant DNA techniques from rat incisors was termed dentin matrix protein 1 (DMP1). DMP1 was originally postulated to be dentin-specific, but later its expression was shown to be present in the other mineralization tissues. The cellular expression pattern of DMP1 was demonstrated to be different from that of the other known non-collagenous proteins. In the bone, DMP1 messenger RNA (mRNA) was predominantly expressed in osteocytes, but not in osteoblasts. Its protein was localized in the pericellular bone matrix of osteocytes, including their processes. The unique characteristic feature of DMP1 is that it contains an unusually large number of acidic domains. It could be postulated that DMP1, because of its high acidic nature, can bind to calcium, thereby regulating matrix mineralization. In fact, an in vitro nodule formation assay demonstrated that overexpression of DMP1 enhanced the mineralization of cultured osteoblastic cells. These findings suggest that DMP1 is an accelerating factor in the matrix mineralization. Mineralization is an essential process in the hard tissue formation. Although several non-collagenous proteins in the mineralized tissues have been identified, most were not capable of promoting the matrix mineralization. Therefore, DMP1 is an essential protein in the mineralization process and may have applications in hard tissue engineering.