Cilia in cardiac differentiation

In a study of chick heart development, approximately 700 cilia were observed in random and serial sections from differentiating myoblasts, myocytes, fibroblasts and fibrocytes following glutaraldehyde-osmium fixation. Additional cilia were observed in hearts of embryonic and adult lizards, mice, and rabbits. The diplosomal "9+0" cilia, often observed completely enclosed in the cytoplasm, were revealed to be present in most nonmitotic cells but were never observed in mitotic cells (P=0.001). Because the number of cells increases greatly during early cardiogenesis and because most of the cells were revealed to possess a single abbreviated cilium each, the deposition of cilia presumably occurs. Therefore, we suggest that the blockage of mitosis usually associated with the initiation of cytodifferentiation can be correlated with the formation of cilia and maybe mediated by the transformation of the mitotic centrioles into ciliary basal bodies.