Morphological alterations of primary cilia in renal tubules of a rat model of polycystic kidney disease

Polycystic kidney disease (PKD) is an inherited disorder characterized by progressive cyst formation in renal tubules, leading to renal failure. Primary cilia, projecting into the tubular lumen, act as mechanochemical sensors that detect urinary flow and extracellular signals such as Hedgehog, Wnt, and PDGF. Structural changes of cilia may therefore alter the mechanical forces they experience and their sensory function. This study aimed to characterize the morphology and ultrastructure of primary cilia in collecting duct cells of PCK rats, a model of autosomal recessive PKD.

Kidneys were collected from PCK rats and age-matched Sprague-Dawley controls. Samples were analyzed by hematoxylin-eosin staining and immunofluorescence, and primary cilia were visualized using confocal microscopy and serial block-face scanning electron microscopy. Ciliary length, curvature, and ultrastructural features were quantified. Statistical comparisons were performed using ANOVA with post hoc tests; P < 0.05 was considered significant.

Primary cilia in dilated collecting ducts of PCK rats were significantly longer and more curved than those in controls (P < 0.05). Ultrastructural examination confirmed alterations consistent with these morphological changes. Mechanical stress along a cilium depends on its length and curvature; therefore, mathematical analysis suggests that these structural differences may influence how cilia senses mechanical and chemical cues within the tubular environment.

In PCK rats, primary cilia exhibit abnormal elongation and curvature, suggesting that altered morphology may affect the mechanical forces they experience. These findings highlight that morphological remodeling of cilia, as interpreted through a mathematical approach, may contribute to impaired sensory function in PKD.