Prospect of bone morphogenetic protein 13 in liver diseases.

Bone morphogenetic proteins (BMPs) belong to TGF-β superfamily and are a group of important cytokines involved in cell differentiation, proliferation and embryonic development. Multiple BMPs play important roles in several functions of vertebrates. Signaling pathway of BMPs is known to be mediated by Smad proteins, which include 8 members while Smad1, Smad5 and Smad8 are involved in BMPs signal transduction while Smad2 and Smad3 are mediated TGF-β signal transduction. Although several BMPs such as BMP4 and BMP9 have been documented in the liver, BMP13 has not been examined in the liver. BMP13 also known as growth differentiation factor (GDF)-6 or cartilage-derived morphogenetic protein (CDMP)-2 is one of the BMPs family members. Function of BMP13 has been investigated in bone and tendon repair. It can stimulate tendon-like cell proliferation. However, our recent findings revealed that there was expression of BMP13 in the liver and its expression was modulated during metabolic disorders. The current article is to understand biological function of BMP13 especially in the liver.