Metabolically activated energetic materials mediate cell anabolism for bone regeneration
While cellular energy metabolism regulates tissue regeneration, it remains as a challenge with its limited understanding of activation by engineered scaffolds to regenerate tissue or organ for therapeutic purpose. This study presents a biosynthesized poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [abbreviated as P(3HB-co-4HB)] and its major degradation product, 3-hydroxybutyrate (3HB), functioning as an endogenous bioenergetic molecule to facilitate bone regeneration and promote cellular anabolism via generations of adenosine triphosphate (ATP) and citrate that enhance the progression of human bone marrow mesenchymal stem cells (hBMSCs) towards osteoblastogenesis. Our studies demonstrate that 3HB not only significantly enhances in vitro ATP generation to elevate mitochondrial membrane potential (??m) and capillary-like tube formation, but also increases the content of intermediate metabolite, namely, citrate, in tricarboxylic acid (TCA) cycle, and ultimately promotes the formation of citrate-containing apatite during osteogenesis of hBMSCs. Furthermore, 3HB administration increases the bone mass in rats with ovariectomy (OVX)-induced osteoporosis. Results also show that the P(3HB-co-4HB) scaffold significantly enhances long-term induced bone repair in a rat model with critical-sized calvarial defects, compared to the commercialized available poly-L-lactic acid (PLLA) scaffold. Collectively, these findings uncover a previously undefined role of 3HB in promoting osteogenic differentiation of hBMSCs and highlight that the P(3HB-co-4HB) scaffold functions as a metabolically activated energetic material for bone regeneration. Overall design: Human bone marrow mesenchymal stem cells (hBMSCs) were seeded onto culture plates and allocated into three groups, namely vehicle group (control), 3HB group, and LA group. In the control group, hBMSCs were treated with OM supplemented with DPBS (10 µl) only, while in the 3HB and LA groups, hBMSCs were respectively treated with OM supplemented with 1.0 mM of 3HB or LA. After 14 days of induction, cells from different groups were harvested and total RNA was extracted using a TRIzol total RNA extraction kit (TIANGEN, China). The RNA sequencing and analysis were performed.