The Analysis Of Age Effects In Lymphocytes From Chinese Men

The effects of aging in humans appear to be a combination of influence of genetically programmed phenomena and exogenous environmental factors. The age effects primarily take place at the cellular level (senescence) then exhibit at the level of the organism after long time accumulation. There are many factors, which drive genetic aberrations in human cell aging (accumulation of mutations, telomere shortening, deregulation of mitotic checkpoints, etc.). In age related genetic aberrations, the two most obvious events are age effects on chromosome malsegregation and aneuploid cells.In our study, we used cytokinesis-block method to analyze age effects on aspects of chromosome malsegregation and aneuploid cells in lymphocytes from Chinese men.i) For the first time, we analyzed the age effects on chromosome malsegregation in lymphocytes from Chinese men. In this study, peripheral blood lymphocytes were collected from 14 old (60-70 yr) and 10 young (22-26 yr) healthy Chinese men. To detect malsegregation of sex chromosomes, multi-color fluorescence in situ hybridization (FISH) was performed on binucleated lymphocytes, cytokinesis-blocked by cytochalasin B at the first mitosis after phytohaemagglutinin stimulation. Compared to that was in young men, a significantly increase in frequencies of loss of chromosome X (9.2±3.2‰vs. 1.1±0.9‰, P<0.001) and Y (2.5±1.9% vs. 0.2±0.3‰, P<0.001) were found in old men. Similarly, nondisjunction of chromosome X (16.5±3.4‰vs. 3.5±1.1‰, P<0.001) and Y (7.2±2.6‰vs. 2.4±1.3‰, P<0.001) occurred more frequently in old men than in young men. Regardless of donor's age, nondisjunction is more prevalent than loss for both chromosome X and Y. The frequencies of observed simultaneous malsegregations were relatively higher than the expected, suggesting an association between malsegregations. These results indicate that in Chinese men, malsegregation of the sex chromosomes increases with age in an associated fashion,and nondisjunction accounts for the majority of spontaneous chromosome malsegregation.ii) We discussed the fates of different aneuploid lymphocytes in old and young Chinese men. By comparing the in vivo lymphocytes population to daughter nuclei of lymphocytes when malsegregation had occurred, cells lacking X chromosome appear to be more easily to die than other aneuploid lymphocytes in men (expected 25.7‰vs. no Chr X- observed population of 44h culture). Besides, by analyzing binucleated (mitotic) cells and mononucleated (non-mitotic) cells, aneuploid cells with different karyotype showed discrepancies in their mitotic capacity. In old men, cells lacking Y chromosome (Chr Y-) displayed the most robust mitotic capacity among aneuploid cells (P<0.001,χ~2-test), while in young men, cells with Y chromosome disomy (Chr Y+) displayed weakest ability to enter mitosis among aneuploid cells (P<0.001,χ~2-test). In conclusion, these results suggest lacking or gain chromosome would affect cell fates differently, and chromosomes have different importance to cells between old and young men.