ROLE OF TRPV4 MECHANOSENSING IN DIFFERENTIATION OF VALVULAR INTERSTITIAL CELLS AND AORTIC ENDOTHELIAL CELLS

Abstract

Cardiovascular diseases, such as atherosclerosis and aortic valve stenosis, have continued to remain the leading cause of death for the past several decades. Although, due to the improvement in medical science, the mortality rates have decreased over time, the number of cases diagnosed in recent years has increased at a significant rate. While patients from higher socio-economic backgrounds can afford the treatment procedures, there has been a pressing need for preventative therapies to support the greater population, compelling us to study the fundamental process of the disease initiation and progression. Aortic valve stenosis (AVS), one of the most complicated disease conditions, leads to increased stiffness (rigidity) of the heart valve tissue, causing valvular interstitial cells (VICs) to differentiate into myofibroblasts. Endothelial-to-mesenchymal transition (Endo-MT) is a process where endothelial cells (ECs) differentiate into mesenchymal cells, which may lead to the endothelial dysfunctions which are involved in major cardiovascular diseases such as atherosclerosis. Matrix stiffness is recognized as a risk factor in both AVS and atherosclerosis development and progression. This study investigated the role of Transient Receptor Potential Vanilloid 4 (Trpv4), a mechanosensitive ion channel in VIC-myofibroblast activation and Endo-MT in response to both matrix stiffness and TGFβ, a major promoter of tissue fibrosis. We confirmed Trpv4 functionality in primary mouse VICs and aortic ECs (aECs) and found that its genetic and pharmacologic deletion/antagonism blocked VIC to myofibroblast and Endo-MT induced by matrix stiffness and TGFβ1, as indicated by changes in cell morphology, α-smooth muscle actin, and F-actin expression. Key findings revealed that residues 30-130 in Trpv4 were essential in stiffness-mediated VIC to myofibroblast differentiation and Endo-MT. Furthermore, Trpv4 was shown to regulate PI3K-AKT activity necessary for myofibroblast differentiation and cellular traction force generation. Moreover, we found that Trpv4 regulates the stiffness-mediated phosphorylation of MLC2, A major regulator which in turn regulates Endo-MT in aECs. These results highlight Trpv4's novel role in VIC- myofibroblast activation and mechanotransduction in regulating Endo-MT. Altogether our results suggest that Trpv4-based targeted therapeutic strategies may have the potential to prevent or suppress cardiovascular diseases.