Primary Cilia In Growth Plates Orchestrate Bone Development

The growth plate plays a crucial role in bone development and elongation, housing stem cells that contribute to bone formation. This study investigates the role of primary cilia, specialized organelles that regulate stem cell fate, in the development of bones. Control and CKO mice were used for comparison. Cellular, molecular, imaging, and histopathological analyses were conducted to evaluate differences between two groups. RNA sequencing was employed for transcriptomic profiling to explore the underlying molecular mechanisms. Cell activity was assessed using scratch-wound and EdU cell proliferation assays, while flow cytometry isolated SSCs. Time-lapse imaging was used to analyze mitotic behavior. Immunofluorescence verified primary cilia presence across all growth plate zones. Spatial transcriptomics and analysis of CKO mice identified that primary cilia mediate critical developmental signaling pathways within the growth plate. Disruption of primary cilia in growth plate impaired long bone development by activating the Wnt signaling pathway and disrupting the cellular stemness. This resulted in elevated Mmp13 secretion, abnormal mineralization, and structural defects, ultimately hindering bone elongation. Time-lapse imaging showed an increased frequency of abnormal mitosis and a reduced rate of asymmetric division in SSCs. Our findings indicated that primary cilia are critical for bone development, regulating stem cell fate through key signaling pathways. Loss of primary cilia leads to excessive Wnt signaling and disruption of SSC stemness, impairing bone elongation. This study highlights the essential role of primary cilia in bone development and suggests potential therapeutic targets for skeletal disorders.