## 4 Discussion  
The involvement of mechanosensitive ion channels in skeletogenesis and bone formation was well studied [33; 34; 35]. However, their role in vascular calcification and AAA has not been adequately explored. Furthermore, to our knowledge, the role of TRPV4, a Ca\({}^{2+}\)-permeable cation channel, in the progression of vascular calcification and AAA has not been studied. In the present study, the aortae of the TRPV4-KO mice were significantly  
Figure 6: Deletion of TRPV4 promotes aortic calcification in CaCl\({}_{2}\)-induced aorta injury. Representative Alizarin red stained images of cross sections of infrarenal aortas showing a remarkable calcification in the tunica media of TRPV4\(-\)KO aorta after CaCl\({}_{2}\) injury (scale bar: 100 \(\upmu\)m). WT: wild type, TRPV4\(-\)KO: Transient Receptor Channel Vanilloid 4\(-\)Knock out. dilated compared to the WT after CaCl\({}_{2}\)-induced aortic injury. Moreover, the histological analysis and morphometric measurements revealed that the tunicae adventitia and media areas increased, leading to aortic-wall thickening. Additionally, a remarkable calcification was observed in the medial layer of TRPV4-KO mice compared to the WT mice after CaCl\({}_{2}\)-induced aorta injury. Contrary to the present study results, in previous studies, the TRPV4 channel promoted bone formation and calcification [33; 34]. Recently, it has been widely accepted that vascular calcification occurs through the trans-differentiation of vascular smooth muscle cells (VSMCs) to osteoblast-like cells [36]. The underlying mechanism of this trans-differentiation is the activation of \(\beta\)-catenin in VSMCs, which in turn leads to the translocation of \(\beta\)-catenin to the nucleus, where it can ultimately lead to the transcription of different osteoblast genes, including osteoclast, alkaline phosphatase, and ostrex [20]. The inhibition of TRPV4 attenuated osteogenesis by reducing the expression of osteoblastic genes and Wnt3\(\alpha\)/\(\beta\)-catenin in bone marrow stem cells, which conflicts with our finding [37]. However, a recent study by the [PERSON] group demonstrated that TRPV4 inhibits \(\beta\)-catenin transcriptional activity through the interaction with \(\beta\)-catenin, the main regulator of osteoblast genes [37]. This might explain the remarkable calcification seen in the aortae of TRPV4-KO mice. Moreover, the function of TRPV4 can vary depending on the specific cell type in which it is expressed. TRPV4 plays a significant role in various physiological functions, such as detecting the osmolarity in kidneys, vascular sheer-stress changes, as well as osteoclast differentiation regulation. In previous studies, a TRPV4 deficiency resulted in altered vasodilation and fibrosis in the lungs and skin. It also participates in the regulation of oxidative metabolism in adipose tissue and inflammation [38]. It is highly expressed in articular chondrocytes, and its defective function is known to cause joint arthropathy and osteoarthritis [39]. In relation to cardiovascular health, deficiency of TRPV4 in endothelial cells in the carotid artery resulted in the vasodilation function, causing the dysregulation of vascular tone and blood pressure [40]. It has been shown to possess atheroprotective effects by promoting eNOS activation and inhibiting the adhesion of monocytes and endothelial cells. This channel function depends on Ca\({}^{2+}\) in a concentration-dependent fashion [41]. Thus, it can be hypothesized that TRPV4 works as a positive regulator for calcification in the bone and a negative regulator in the blood vessels. Infiltration of immune cells such as macrophages and T-cells within the adventitial layer is associated with vascular calcification and AAA [42; 43; 44]. They also contribute to the development of vascular calcification by releasing inflammatory cytokines and promoting the differentiation of smooth muscle cells into osteoblast-like cells [45].