Wnt3a enhances bone morphogenetic protein 9-induced osteogenic differentiation of C3H10T1/2 cells

Background Bone morphogenetic protein 9 （BMP9） and Wnt/13-catenin signaling pathways are able to induce osteogenic differentiation of mesenchymal stem cells （MSCs）, but the role of Wnt/13-catenin signaling pathway in BMP9-induced osteogenic differentiation is not well understood. Thus, our experiment was undertaken to investigate the interaction between BMP9 and Wnt/13-catenin pathway in inducing osteogenic differentiation of MSCs. Methods C3H10T1/2 cells were infected with recombinant adenovirus expressing BMP9, Wnt3a, and BMPg＋Wnt3a. ALP, the early osteogenic marker, was detected by quantitative and staining assay. Later osteogenic marker, mineral calcium deposition, was determined by Alizarin Red S staining. The expression of osteopotin （OPN）, osteocalcin （OC）, and Runx2 was analyzed by Real time PCR and Western blotting. In vivo animal experiment was carried out to further confirm the role of Wnt3a in ectopic bone formation induced by BMP9. Results The results showed that Wnt3a enhanced the ALP activity induced by BMP9 and increased the expressions of OC and OPN, with increase of mineral calcium deposition in vitro and ectopic bone formation in vivo. Furthermore, we also found that Wnt3a increased the level of Runx2, an important nuclear transcription factor of BMP9. Conclusion Canonical Wnt/13-catenin signal pathway may play an important role in BMP9-induced osteogenic differentiation of MSCs, and Runx2 may be a linkage between the two signal pathways.

Addition of heparin binding sites strongly increases the bone forming capabilities of BMP9 in vivo

Bone Morphogenetic proteins(BMPs)like BMP2 and BMP7 have shown great potential in the treatment of severe bone defects.In recent in vitro studies,BMP9 revealed the highest osteogenic potential compared to other BMPs,possibly due to its unique signaling pathways that differs from other osteogenic BMPs.However,in vivo the bone forming capacity of BMP9-adsorbed scaffolds is not superior to BMP2 or BMP7.In silico analysis of the BMP9 protein sequence revealed that BMP9,in contrast to other osteogenic BMPs such as BMP2,completely lacks so-called heparin binding motifs that enable extracellular matrix(ECM)interactions which in general might be essential for the BMPs’osteogenic function.Therefore,we genetically engineered a new BMP9 variant by adding BMP2-derived heparin binding motifs to the N-terminal segment of BMP9′s mature part.The resulting protein(BMP9 HB)showed higher heparin binding affinity than BMP2,similar osteogenic activity in vitro and comparable binding affinities to BMPR-II and ALK1 compared to BMP9.However,remarkable differences were observed when BMP9 HB was adsorbed to collagen scaffolds and implanted subcutaneously in the dorsum of rats,showing a consistent and significant increase in bone volume and density compared to BMP2 and BMP9.Even at 10-fold lower BMP9 HB doses bone tissue formation was observed.This innovative approach of significantly enhancing the osteogenic properties of BMP9 simply by addition of ECM binding motifs,could constitute a valuable replacement to the commonly used BMPs.The possibility to use lower protein doses demonstrates BMP9 HB’s high translational potential.

The potential regulatory role of BMP9 in inflammatory responses

Inflammation is a protective response of the body to pathogens and injury.Hence,it is particularly important to explore the pathogenesis and key regulatory factors of inflammation.BMP9 is a unique member of the BMP family,which is widely known for its strong osteogenic potential and insensitivity to the inhibition of BMP3.Recently,several studies have reported an underlying pivotal link between BMP9 and inflammation.What is clear,though not well understood,is that BMP9 plays a role in inflammation in a carefully choreographed manner in different contexts.In this review,we have summarized current studies focusing on BMP9 and inflammation in various tissues and the latest advances in BMP9 expression,signal transduction,and crystal structure to better understand the relationship between BMP9 and inflammation.In addition,we also briefly summarized the inflammatory characteristics of some TGF-b superfamily members to provide better insights and ideas for the study of BMP9 and inflammation.