Crosstalk Between Wnt/β-Catenin and Hedgehog Supports Gli1+ Lineage Osteogenesis in Cranial Sutures

Sutures such as fibrous joints in craniofacial bones provide a niche for Gli1+ mesenchymal stem cells (MSCs) in promoting calvarial bone development and growth. However, the underlying molecular mechanism behind the fate of the Wnt/β-catenin regulation of Gli1+ MSCs during calvarial bone formation remains unclear. Here, we showed that β-catenin was colocalized with Gli1+ lineage cells near the osteogenic front within a suture, and postnatal skull development was delayed via a conditional knockout of <i>Ctnnb1</i> in Gli1+ MSCs. Calcein-Alizarin Red dual staining revealed that Wnt/β-catenin signal inhibition impaired the rate of bone formation. Furthermore, immunofluorescent staining indicated that Wnt/β-catenin signaling was crucial in facilitating the proliferative capacity of Gli1+ MSCs and their commitment to the osteogenic lineage. Notably, activating hedgehog (Hh) signaling partially restored the suture morphology in <i>Ctnnb1</i> knockout mice. Collectively, our findings revealed the crosstalk between Wnt and Hh signaling modulates the fate of Gli1+ MSCs during calvarial bone formation.