Ibarrola, J. | bioRxiv Science

bioRxiv2026

Smooth muscle cell estrogen receptor alpha promotes arterial stiffness in the absence of estradiol

BackgroundClinical evidence supports a greater impact of arterial stiffening in cardiovascular mortality in women versus men. Arterial stiffness increases across the menopausal transition, implicating a role of the loss of estrogens in arterial stiffening, but mediating mechanisms remain unclear. MethodsThe role of estradiol and smooth muscle cell (SMC) estrogen receptor alpha (ER) in arterial stiffening, by aortic pulse wave velocity (PWV), was assessed in 3 models: (1) the loss of estradiol in young, female mice comparing sham surgery or bilateral ovariectomy (OVEX) {+/-} estradiol, (2) the impact of sham versus OVEX surgery in young, female SMC-ER-intact and SMC-ER-knockout (KO) littermates, and (3) arterial stiffening during natural aging by comparing young and aged, female and male SMC-ER-intact and SMC-ER-KO littermates. Mechanistic pathways were assessed using histological assessment of aortic fibrosis and elastin degradation, aortic MMP expression, and atomic force microscopy. ResultsOVEX increased PWV and aortic medial fibrosis, with no impact on elastin integrity, in young female mice. Arterial stiffening and fibrosis were prevented in OVEX mice that were supplemented with estradiol. OVEX-induced arterial stiffening in SMC-ER-intact female mice was prevented in SMC-ER-KO littermates. In this model, OVEX was also associated with increased aortic medial fibrosis without changes in elastin integrity. Aging from 3 to 18 months significantly increased PWV in female and male SMC-ER-intact mice. Aging-induced stiffening was fully prevented in female and partially prevented in male SMC-ER-KO mice. SMC-ER contributes to aging-associated arterial stiffening by sex-specific mechanisms, including elastin degradation in females and phenotypic changes in SMC stiffness and probability to form cellular adhesions in males. Circulating estradiol was significantly decreased in serum from aged compared with young female mice. ConclusionsThese findings support that SMC-ER contributes to arterial stiffening in female and male mice in situations where the vasculature is exposed to low levels of estradiol.

physiology↗

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↗