Effects of Bone Morphogenetic Protein Agonist Small Molecule, SB4, on Osteogenic Differentiation of Adipose-Derived...

Bone morphogenetic protein (BMP) signaling is crucial for osteogenic (OS) differentiation, bone growth, and repair. However, the clinical use of BMPs is limited due to their cost and challenges in delivery. SB4, a potent compound of benzoxazole, is a newly introduced small molecule shown to activate the BMP signaling pathway. In this study, we investigated the effects of SB4 on OS differentiation of adipose-derived mesenchymal stem cells (ADMSCs).

We first examined whether BMP signaling is active in osteoinduced ADMSCs. ADMSCs were treated with SB4 (5 and 10 μM) for 24 hr, and mRNA expression of BMP direct target genes (ID1 and ID3) was analyzed. ADMSCs were then cultured with or without SB4 (10 μM) for 7, 14, and 21 days, followed by Alizarin red staining and real-time polymerase chain reaction analysis of mRNA expression of OS markers RUNX2, BMP2, alkaline phosphatase (ALP), and Osteopontin. To investigate the most effective time period of SB4 in osteogenesis, SB4 was applied every 3.5 days during the 21-day differentiation period.

After 24 hr of treatment with SB4 (5 and 10 μM), increased mRNA expression of BMP direct target genes (ID1 and ID3) confirmed that SB4 acts as an active BMP agonist. SB4-treated ADMSCs showed enhanced bone matrix production and increased mRNA expression of RUNX2, BMP2, ALP, and Osteopontin. Increased mRNA expression of OS markers, bone matrix formation, and ALP activity during the first 7 days of SB4 treatment suggested the importance of SB4 at the early stage of differentiation.

These results indicate that SB4, with potential BMP-like activity, induces OS differentiation of ADMSCs, leading it to serve as a cost-effective BMP agonist for osteogenesis-related research as well as a potential therapeutic agent for bone repair and regeneration.