Biological Characteristics Of Luteal Cells Apoptosis During Cyclic Luteal Regression In Yak

In order to study the biological characteristics of luteal cells apoptosis during cyclic luteal regression in yak, different methods and experiments were carried out to observe the moporlogical changes of cyclic luteal cells, to investigate the apoptostic characteristics of of luteal cells in vitro, to detemine the effects of TNF-a on apoptosis of luteal cells in vitro, and to analyze the expression of c-myc and Bad of luteal cells. The following results were obtained.(1) Cyclic luteal tissue collected at different luteal stages were used to observe the microstacture and ultrastucture, also to investigate DNA in situ fluorescence labeling (DAPI)of luteal cells. It was found that apoptosis of luteal cells occurred in whole luteal phase, espcially in the period of estrus stage. Interestingly, the blood vessels retrogression was also visible in luteal tissue with the development of lutum.(2) Primary luteal cells of yak were obtained by the technichqe of enzyme digestion and cultured in vitro. The cells were induced to apoptosis by use of serum withdrawing method and then anlysed their characteristics. It was found that the apoptotic luteal cells were characterized by compact and shrinked nuclei with strong and intensive fluorescence in DAPI and PI assay and TUNEL positive in ISLE assay. Transmission electron microscope showed that the cells appeared the characteristics of compact and shrinked or distintegrated nuclei, condensed chromatin, and formation of apoptotic bodies. DNA electrophoresis showed representative ladderlike bands that were proved to be 180-200bp aliquots DNA fragments in apoptotic lutein cells.(3) It was detected that TNF-a of different concentration chould induce the apoptosis of luteal cells in vitro with a dose-dependent manner. The apoptotic peaks can be clearly seen in FCM assay.(4) Immunohistochemistry was used to detect the expression of c-myc and Bad of the cyclic corpus lutum in different stages. Immunostaining was seen in cytoplasm of lutein cells in whole luteal phase. Furthermore, the positive rate and immunostaining intensity increased gradually with thedevelopment of corpus luteum. The levels of expression were relativelystable. In estrous stage, c-myc protein was also found in the nuclei of limited number of luteal cells.It is coududed from the results mentioned above that apoptosis of luteal cells plays a major role in the regression of cyclic corpus Lutum in yak. Luteal cells can be cultured in vitro and be induced to apoptosis by use of serum withdrawing method. TNF-cr of different concentration can also induce the apoptosis of luteal cells in vitro with a dose-dependent manner. Gene expression of c-myc and Bad may be involved in the regulation of luteal cells apoptosis.