Abstract: Objective To explore the morphological features and the division mode of rat cardiac fibroblasts cultured in vitro and to provide the cellular bases for further research of cardiac regeneration mechanism and myocardial damage therapy. Methods Primary neonatal rat CFs were cultured and double labeled by vimentin and H3P, vimentin and Tubulin respectively using immunofluorescence technique. Then mitosis CFs were searched with living cell station, scanning electron microscope and a fluorescence microscope. Results Primary cultured CFs were stick wall and extended pseudopodia within 0.5-1h, keeping a great growing state with varied shapes and were rich in binucleated cells. These cells became fecund after 3 - 4 days and it is easy to find a large number of cells which were swelled up and round into mitosis phase. A few CFs in mitosis still maintained flat,and amitosis was observed incidentally. The mitosis phase of CFs in round and swelled shape was lasted about 20-30min; while for those flat ones, it was about 40-50min.In the prophase of the mitosis, the nucleus was in regular shape, and H3P began to express; then the karyotheca broke and spindle was formed in prometaphase. At metaphase, chromosomes were found in the equatorial plane, in which H3P was expressed actively. In this phase, spindles were typically in the shape of spindle. The chromatids were separated then moved towards the cellular poles; and H3P split with their separation in the anaphase. In the telophase, two daughter nuclei were formed and between them, microtubules were distributed. At cytokinesis period, two daughter cells were generated and H3P dissolved. Conclusion CFs cultured in vitro have two different morphological features – flat, round and swelled, and two division modes- amitosis and mitosis. And it is believed that these two division modes could be complementary.

Key words: Division Mode of Cultured Rat Cardiac Fibroblast in vitro