Fernandez-Celis, A. | bioRxiv Science

bioRxiv2025

Aortic Valve Remodeling in Chronic Kidney Disease: A Mineralocorticoid Receptor-Driven Mechanism Involving NGAL and TLR4 Pathways

INTRODUCTIONAortic stenosis (AS) is the most prevalent valve heart disease. Renal failure increases the risk of AS and many circulating factors released during chronic kidney disease (CKD) participate to AS pathophysiology. We assessed in this study the role of increased aldosterone levels occurring in CKD as well as MR signaling and its interplay with Neutrophil Gelatinase-Associated Lipocalin (NGAL) in aortic valve interstitial cells (VICs) pathophysiology. METHODSWe conducted in vivo studies using a CKD rat model, including both wild-type (WT) and NGAL knockout (KO-NGAL) animals, for subsequent ex vivo analysis of aortic valves. In parallel, primary rat VICs were used in vitro to assess osteogenic, fibrotic, and inflammatory responses to aldosterone, as well as to identify the key signaling pathways involved. qPCR, Western blot, and ELISA were employed to characterize these pathways. RESULTSOur findings demonstrate that MR signaling plays a central role in AS progression during CKD, as well as in VIC differentiation, inflammation, fibrosis, and calcification, mediated via the TLR4-MyD88 innate immunity pathway in aldosterone-induced responses. Furthermore, NGAL was shown to act downstream of MR to activate TLR4, promoting additional remodeling and calcification in aortic valves and VICs. These results were further validated in human samples from CKD patients. CONCLUSIONOverall, this study identifies a novel signaling pathway in AS pathophysiology in the CKD rat model and in vitro systems, highlighting for the first time the interplay between MR, NGAL, and TLR4 in driving the pathological processes underlying AS in CKD. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=169 HEIGHT=200 SRC="FIGDIR/small/675970v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@c91353org.highwire.dtl.DTLVardef@113b9d4org.highwire.dtl.DTLVardef@d4437org.highwire.dtl.DTLVardef@f9a617_HPS_FORMAT_FIGEXP M_FIG https://BioRender.com/j7vufds C_FIG

pathology↗

bioRxiv2023

PROX1 inhibits PDGF-B expression to prevent myxomatous degeneration of heart valves

BackgroundCardiac valve disease (CVD) is observed in 2.5% of the general population and 10% of the elderly people. Effective pharmacological treatments are currently not available, and patients with severe CVD require surgery. PROX1 and FOXC2 are transcription factors that are required for the development of lymphatic and venous valves. We found that PROX1 and FOXC2 are expressed in a subset of valvular endothelial cells (VECs) that are located on the downstream (fibrosa) side of cardiac valves. Whether PROX1 and FOXC2 regulate cardiac valve development and disease is not known. MethodsWe used histology, electron microscopy and echocardiography to investigate the structure and functioning of heart valves from Prox1{Delta}VEC mice in which Prox1 was conditionally deleted from VECs. Isolated valve endothelial cells and valve interstitial cells were used to identify the molecular mechanisms in vitro, which were tested in vivo by RNAScope, additional mouse models and pharmacological approaches. The significance of our findings was tested by evaluation of human samples of mitral valve prolapse (MVP) and aortic valve insufficiency. ResultsHistological analysis revealed that the aortic and mitral valves of Prox1{Delta}VEC mice become progressively thick and myxomatous. Echocardiography revealed that the aortic valves of Prox1{Delta}VEC mice are stenotic. FOXC2 was downregulated and platelet-derived growth factor-B (PDGF-B) was upregulated in the VECs of Prox1{Delta}VEC mice. Conditional knockdown of FOXC2 and conditional overexpression of PDGF-B in VECs recapitulated the phenotype of Prox1{Delta}VEC mice. PDGF-B was also increased in mice lacking FOXC2 and in human MVP and insufficient aortic valve samples. Pharmacological inhibition of PDGF-B signaling with imatinib partially ameliorated the valve defects of Prox1{Delta}VEC mice. ConclusionPROX1 antagonizes PDGF-B signaling partially via FOXC2 to maintain the extracellular matrix composition and prevent myxomatous degeneration of cardiac valves. Novelty and SignificanceWhat Is Known? O_LIThe transcription factors PROX1 and FOXC2 are critical regulators of lymphatic and venous valve development. C_LIO_LIPROX1 and FOXC2 are expressed in the downstream valvular endothelial cells of heart valves. C_LI What Is New? O_LIDeletion of Prox1 from the valvular endothelial cells of mice results in enlarged and myxomatous aortic and mitral valves. Aortic valves of the mutant (Prox1{Delta}VEC) mice were stenotic. C_LIO_LIFOXC2 is partially responsible for the phenotype of Prox1{Delta}VEC mice. C_LIO_LIPROX1 and FOXC2 inhibit the expression of the cytokine PDGF-B in heart valves. C_LIO_LIHyperactivation of PDGF-B signaling results in aortic and mitral valve thickening. C_LIO_LIInhibition of PDGF-B signaling ameliorates aortic valve stenosis in Prox1{Delta}VEC mice. C_LIO_LIPDGFB is overexpressed and PROX1 is downregulated in human mitral valve prolapse (MVP) samples. C_LI Our findings suggest that PROX1 is an inhibitor of myxomatous valve disease that afflicts ~10% of the elderly population. We have also identified PDGF-B as a potential target for treating myxomatous valve disease.

developmental biology↗