The Mechanisms And Effects Of γ-irradiation On The Thymus

Thymus, as a central immune organ where T lymphocytes differentiate and mature, plays an important role in the immune system. It is recently observed that the thymus maintains substantial output and plays a role in immune homeostasis throughout the lifetime of an individual.Thymus is highly sensitive to ionizing radiation. Radiation can evoke so multiple and complex cellular events that traditional methods by which we can only investigate one or two genes, can not meet the development of radiation molecular biology. The time-saving, high performance and high throughput features of gene chip technique enable it to be used widely in the radiobiology field in recent years.In our experiment we combined the routine pathological methods with cDNA microarray to investigate the change of gene expression profile at different time points after thymus was exposed to 6.0Gy y-radiation. We aimed to explore the molecular mechanisms of thymic radiation injury and provide some clues for its clinical treatment.Our results show that:1. After r-irradiation, pathological changes of thymic radiation injury could be divided into five main stages, that is, apoptosis and clearup stage, exhausting stage, regeneration stage, early recovery stage and late recovery stage.2. The maximal apoptotic rate of thymic lymphocytes occurred at 24 hour after γ-radiation. When the radiation doses were between 6~12Gy, a good dose-dependent manner was observed. When the doses were higher than 15Gy, there was no significant positive relationship to be observed between the doses and the apoptotic rates. It was indicated that some genes related to apoptosis, such as bax, bcl-2 and bcl-XL, played important roles in regulating γ-irradiation induced thymic lymphocytes apoptosis.3. The different subpopulations of thymic lymphocytes showed different sensitivity to the y-irradiation. The damage to the functional subpopulations of thymocytes led to persistent immunodeficiency and had potential effects for a long term.4. The differentially expressed genes of thymus induced by y-irradiation were involved in cell circle, immunity and stress, signal transduction pathway, regulation of transcription,...