Primary Cilium in Bone Growth and Mechanotransduction

Bone loss diseases, including osteoporosis affect millions of people worldwide. Understanding the underlying mechanisms behind bone homeostasis and adaptation is essential to uncovering new therapeutic targets for the prevention and treatment of bone loss diseases. Primary cilia have been implicated in the development and mechanosensation of various tissue types, including bone. The goal of the studies outlined in this thesis is to determine the mechanosensory role of primary cilia in bone cell function, bone growth, and adaptation. This goal was achieved by exploring two specific scenarios. In the first study, mice models with conditional knockouts of MKS5, a ciliary protein, in osteocytes were utilized to demonstrate that dysfunctional primary cilia in those cells result in impaired loading-induced bone formation. The hypothesis tested is that the existence of functioning primary cilia on osteocytes is crucial for proper bone adaptation following stress. The results of this study support the hypothesis, with the conditional knockout mice showing significantly lower loading-induced bone formation compared to controls. The second study highlighted the importance of the osteoblast primary cilia in bone growth by using mice models with osteoblast-specific deletion of the cilia. The hypothesis tested is that the presence of the primary cilia is crucial for proper bone growth. The results show that conditional knockout mice have lower body weights, decreased femur length, and a significantly lower rate of bone formation, confirming that the primary cilia play a great role in bone growth and development. This study has highlighted the role of primary cilia in bone health and this topic merits further investigation.