Primary Cilia Orchestrate Cardiac Pathogenesis: A Central Nexus of Remodeling, Signaling, and Repair.

Roles of primary cilia and the signals they transmit in the development of myocardial fibrogenesis, cardiac hypertrophy, and atrial fibrillation. Left, Fibroblasts can differentiate into myofibroblasts in response to TGF-β1. TGF-β1 stimulation via both paracrine action in the heart and exogenous action on primary cultured fibroblasts activated the phosphorylation of SMAD3 and the transcription of the fibronectin and collagen type I and III genes. Middle, Vesicles derived from cilia are secreted at an accelerated rate under fluid shear stress. Blockage of ciliary protein, which is required for cELV generation with shRNA, led to blunted cELV secretion and left ventricular hypertrophy. Right, under pathological conditions such as atrial fibrillation (AF), fibroblasts exhibit increased proliferation and differentiation into α-smooth muscle Actin (αSMA)-expressing myofibroblasts. This disrupts ECM dynamics, ultimately leading to interstitial fibrosis within the atria. AF patients presented increased HDAC6 activity and reduced levels of acetylated α-tubulin in left atrial tissues. HDAC6 activity is activated by the interaction of aurora kinase A (AURKA), and neural precursor cells express developmentally downregulated protein 9 (NEDD9) via phosphorylation. LiCl prompts the reversion of αSMA-positive myofibroblasts into αSMA-negative fibroblasts.