Gremlin-1 suppression increases BMP-2-induced osteogenesis of human mesenchymal stem cells

Previous research focusing on rodent cells and animal models has demonstrated that gremlin-1 antagonizes bone morphogenetic proteins (BMPs) in order to suppress osteogenesis. However, the impact of gremlin-1 on osteogenesis in human bone marrow-derived mesenchymal stem cells (MSCs) remains unknown. The aim of the present study was to test the effects of gremlin-1 on viability and in vitro BMP-2-induced osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (MSCs). Gremlin-1-specific small interfering RNA (siRNA) inhibited gremlin-1 mRNA and protein expression in human MSCs. The mRNA expression levels of osteoblastic genes were analyzed using reverse transcription-quantitative polymerase chain reaction, and calcification and enzymatic alkaline phosphatase (ALP) activity assessed the BMP-2-induced osteogenic differentiation of human MSCs. The results indicated that gremlin-1 suppression significantly increased human MSC metabolism and DNA content. The expression levels of osteoblastic genes were also significantly increased by gremlin-1 inhibition. In the gremlin-1-inhibited group, enzymatic ALP activity was significantly increased. In addition, due to BMP-2-inducing osteoblasts, gremlin-1 inhibition increased calcium deposits. The present study indicated that gremlin-1 inhibited the cell viability and osteogenic differentiation of human MSCs and that the suppression of gremlin-1 expression suppressed can increase the cell viability and osteogenic differentiation of human MSCs induced by BMP-2.