Although primary cilia have been shown to play crucial roles in the development of embryonic mouse heart, their presence and function in adult mouse heart remains controversial. In this study, the presence of primary cilia in adult mouse heart was investigated. The presence of primary cilia was initially demonstrated in the surface of cardiac cells of mouse hearts from both young and adult mice by immunostaining with acetylated α-tubulin, a ciliary structural marker. The presence of cardiac primary cilia in 1-, 3-, 6- and 12-month old mice was further confirmed by staining heart tissues with an antibody against pericentrin, a marker for the basal body or the centriole. Ciliary polycystin-2 is a calcium channel and mechanosensory molecule, was demonstrated for the first time to localize to primary cilia of cardiac cells in both early and late stages of mouse adulthood, thus proposing a role of primary cilia in adult mouse heart calcium signaling. Primary cilia presence in different heart chambers was further confirmed by immunostaining. Furthermore, the abundance and length of cardiac primary cilia during mouse adulthood in three different age groups (\u3c 3 month, 3-6 month, and \u3e6 month old mice)was studied and found out that cardiac cells with primary cilia in the first age group (\u3c 3 month) accounted for 37% of the total number of cells; however, the number of primary cilia in the 3-6 month and \u3e 6 month age groups accounted for 29% and 25%, respectively, suggesting that primary cilia abundance is age dependent
