Synergistic effects of dimethyloxalylglycine and butyrate incorporated into alpha-calcium sulfate on bone regeneration

Osteogenesis is closely related to angiogenesis, and the combined delivery of angiogenic and osteogenic factors has been suggested to enhance bone regeneration. Small molecules have been explored as alternatives to growth factors for tissue regeneration applications. In this study, we examined the effects of the combined application of angiogenic and osteogenic small molecules on bone regeneration using a prolyl hydroxylase, dimethyloxalylglycine (DMOG), and a histone deacetylase inhibitor, butyrate. In a critical size bone defect model in rats, DMOG and butyrate, which were incorporated into a calcium sulfate (alpha CS), resulted in synergistic enhancements in bone and blood vessel formation, eventually leading to bone healing, as confirmed by micro-CT and histological analyses. In MC4 pre-osteoblast cultures, DMOG and butyrate enhanced the pro-angiogenic responses and osteoblast differentiation, respectively, which were evaluated based on the levels of hypoxia inducible factor (HIF)-1 alpha protein and the expression of pro-angiogenic molecules (VEGF, home oxidase-1, glucose transporter-1) and by alkaline phosphatase (ALP) activity and the expression of osteoblast phenotype marker molecules (ALP, alpha 1(I)col, osteocalcin, and bone sialoprotein). DMOG combined with butyrate synergistically improved osteoblast differentiation and pro-angiogenic responses, the levels of which were drastically increased in the cultures on alpha CS disks. Furthermore, it was demonstrated that alpha CS increased the level of HIF-1 alpha and as a consequence VEGF expression, and supported osteoblast differentiation through the release of calcium ions from the KS. Altogether, the results of this study provide evidence that a combination treatment with the small molecules DMOG and butyrate can expedite the process of bone regeneration and that alpha CS can be an efficient delivery vehicle for the small molecules for bone regeneration. (C) 2014 Elsevier Ltd. All rights reserved.