Divergent Mechanisms of Cranial Suture Ossification in Normal Development and Pathologic Fusion.

Cranial sutures are dynamic growth sites that balance bone growth with mesenchymal patency to accommodate cranial expansion during development. While intramembranous ossification has traditionally been considered the default mechanism of suture fusion, accumulating evidence demonstrates that endochondral pathways might also play a significant role under both physiological and pathological conditions. In this review, we contrast normal developmental ossification processes with premature fusion in craniosynostosis, integrating histological, molecular, and imaging data. We highlight the context-dependent nature of cranial suture biology, influenced by embryonic origin, local signalling gradients, and genetic perturbations. Recognizing divergent ossification mechanisms reframes our understanding of both normal and premature suture fusion and has clinical implications for mechanism-specific therapeutic strategies. Finally, we outline areas for future investigation, including high-resolution profiling of human sutures across developmental stages, to establish a normative framework for cranial suture biology and inform mechanism-driven regenerative approaches.