Autosomal dominant polycystic kidney disease (ADPKD) is an inherited genetic disorder that results in progressive renal cyst formation and ultimate loss of renal function. Many cilia-related proteins, when functioning or expressed abnormally, result in polycystic kidney disease (PKD). Non-motile primary cilia, which have been proposed to be mechanosensory organelles in many cell types, have since been an intense research topic, especially in the PKD field. In particular, it has been shown that both structural and functional defects of primary cilia would result in PKD. To understand the etiology of PKD, we propose that mechanosensory cilia are structurally and/or functionally abnormal in the Pkd1 mouse model. In this proposal, I will use the conditional Pkd1 mouse model to study functional and structural cilia that have been shown to be associated with both hypertension and cystic kidney formation. In addition, I will study the roles of the Pkd1 gene in isolated arteries, endothelial cells, and will also study both the function and structure of primary cilia in vascular endothelia. In the first aim, the functions of the primary cilia in the Pkd1 mouse will be explored using arteries isolated from the conditional Pkd1 animal model. Aorta and femoral arteries will be isolated and studied as well ex vivo. In addition, blood pressure will be examined before and after induction of Pkd1 KO in vivo. In the second aim, the dynamics structure of the primary cilia will be examined in live endothelial cells. The sensitivity of ciliary bending by fluid flow will b measured in a Pkd1-inducible system. For this aim, I propose that ciliary structures play important roles in mechanosensing properties of endothelial cells and endothelial dysfunction in PKD. Failure to form appropriate structures would result in ciliary dysfunction. We will assess the physical structures of cilia in response to changes in fluid flow. Endothelial cells will be superfused, and ciliary structure, calcium and nitric oxide will be recorded as read-outs in normal and conditional Pkd1 endothelial cells. Together, we hope to provide crucial information toward understanding the functional and structural roles of mechanosensory ciliary organelles in Pkd1 blood vessels. Our study will provide new information on the etiology of hypertension in ADPKD patients. We are hopeful that the results of our study will bridge our understanding from the existing knowledge to future therapeutic treatment of hypertension in ADPKD.
Recent research revealed that polycystin-1 and -2 form a signaling complex and mediate mechanosensory function in the primary cilia of the kidney epithelia, vascular endothelia, osteochondrocytes, cholangiocytes and developing node. These findings encourage us to examine polycystin-1 function in a more physiologically relevant ex vivo setting by using conditional Pkd1 models to examine cilia function and structure more closely.
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