Purine metabolism enhances neovascularization of type H vessels in the induced membrane technique

The induced membrane technique (IMT) is a 2-stage surgical intervention for critical-sized bone defects (CSBD), yet the metabolic mechanisms driving neovascularization within the induced membrane remain unclear. Here, we combined a rat IMT model, metabolomic profiling, and endothelial assays to delineate the role of purine metabolism in neovascularization of type H vessels. Using a rat IMT model and metabolomic profiling, we identified purine metabolism as the most substantial pathway during the formation of induced membranes, with consistent trends of adenosine, inosine, hypoxanthine, and xanthosine found in both serum and induced membranes. Histological analysis revealed abundant CD31hiEMCNhi type H vessels, critical for osteogenesis, within the induced membrane. Inhibition of purine metabolism suppressed the CD31hiEMCNhi type H phenotype in human umbilical vein endothelial cells, whereas treatment with inosine, hypoxanthine, or xanthosine promoted endothelial activation and the type H phenotype. Notably, inosine and hypoxanthine displayed parallel changes across consistent systemic (serum) and local alterations (induced membranes), highlighting their potential as serum indicators of induced membrane formation. Collectively, these findings uncover a previously unrecognized metabolic mechanism driving neovascularization of type H vessels in induced membranes and suggest purine metabolites as promising indicators and therapeutic targets for improving IMT outcomes as well as CBSD treatment.