Role of the primary cilium in muscle tissue.
Muscles are contractile tissues commonly classified into skeletal, cardiac, and smooth muscle. Each type exhibits distinct structural and functional properties that rely on coordinated signaling pathways to maintain homeostasis and adapt to physiological demands. The primary cilium is a solitary, microtubule-based organelle that protrudes from the cell surface and functions as a sensory platform for mechanical and chemical cues. Growing evidence has implicated primary cilia in the regulation of muscle biology. In skeletal muscle, primary cilia are present in quiescent satellite cells, where they contribute to the regulation of activation, self-renewal, and hypertrophic responses through signaling pathways such as Hedgehog and Wnt. In cardiac tissue, primary cilia have been identified in cardiac fibroblasts and developmental cardiac cell populations, where they have been associated fibrogenic responses, cardiac remodeling, and developmental signaling pathways. Similarly, in smooth muscle cells, primary cilia participate in mechanosensory signaling and have been implicated in the regulation of proliferative and migratory responses, particularly in vascular pathology. Alterations in ciliary structure or signaling components have been associated with impaired muscle regeneration, increased adipogenesis, and maladaptive tissue remodeling. This review examines the current evidence regarding the role of primary cilium in skeletal, cardiac, and smooth muscle and discusses its potential relevance in muscle disease, providing an integrated overview of cilium-dependent signaling across muscle tissues.