HSP90AA1 Facilitates Vascular Calcification in Chronic Kidney Disease Involving Chaperone-Mediated Autophagy

Background: Chronic kidney disease (CKD) associated vascular calcification (VC) is a leading cause of cardiovascular mortality, partially driven by osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs). Chaperone-mediated autophagy (CMA) is a selective lysosomal degradation cellular process. However, the precise role and mechanism of CMA in CKD-associated vascular calcification remain unknown. Methods: We studied calcified arteries from CKD patients and rats fed on a high-phosphate diet using histological and ultrastructural methods. VSMCs' calcification was induced by a calcification medium containing high phosphate and calcium. CMA activity was measured by a KFERQ reporter and lysosomal staining. The expression of LAMP2a and HSP90AA1 was knocked down by siRNA, overexpressed by plasmid, and activated by QX77.1. Bioinformatic analysis, protein interaction studies, immunofluorescence and co-immunoprecipitation were performed to investigate the potential mechanism of CMA in VC. Results: The expression of LAMP2a was increased in human calcified radial artery tissues (n = 3, p < 0.05) and rats' calcified aortic tissues (n = 3, p < 0.01), accompanied by lysosomal abnormalities. The activity of CMA was increased during the osteogenic transdifferentiation of VSMCs, as indicated by increased expression of RUNX2 and reduced expression of SM22α (p < 0.05). LAMP2a knockdown attenuated VSMCs' calcification (p < 0.05), whereas pharmacological activation of CMA aggravated calcification in VSMCs (p < 0.01). Bioinformatic screening identified HSP90AA1 as a candidate involved in CMA in vascular calcification. Elevated HSP90AA1 expression was observed in human calcified radial artery tissues (n = 3, p < 0.01) and rat calcified aortic tissues (n = 3, p < 0.01), which promoted osteogenic transdifferentiation of VSMCs (p < 0.05). HSP90AA1 interacted with LAMP2a and positively regulated its expression (p < 0.01). Conclusions: These findings support an association between CMA activation and CKD vascular calcification. It suggests that HSP90AA1 facilitates vascular calcification in chronic kidney disease involving chaperone-mediated autophagy.