The Effect Of Rapamycin On Adult Stem Cell Aging In Telomerase Knockout Mice

Telomere is formed from the complex of DNA repetative sequence and proteins and located at the end of linear chromosomes of eukaryotic cells and its structure is highly conserved. The discovery of telomerase explains the mechanism of maitaining DNA sequence while cell dividing, which laid a theoretical foundation for studying the relationship between telomeres and aging or cancer. Many studies show that telomere shortening is closely related to occurence and development of human aging and degenerative diseases. Telomerase knockout mouse is a classical animal model to study aging and degenerative diseases. Some early studies suggest that energy intake restriction can expand mice lifespan,and dalay occurrence of many disease, such as cancer, neurodegenerative diseases, diabetes and other age-related disease. Other studies indicate that Mammalian Target Of Rapamycin (mTOR) is increasingly expressed in old mice. The mTOR is a key protein to regulate growth, proliferation and survival,which can influence homeostasis maintainence of stem cells by regulate intracellular energy metabolism. Rapamycin can be combined with the cytoplasmic protein FKBP12to interfere the formation of mTORCl specifically and further interfere biological activity of mTORCl. In order to study the act of rapamycin on telomerase knockout mouse, we inject rapamycin of mTORC1inhibitor into the telomerase knockout mouse and discovered that the mouse lifespan of treatment group was shorter thanthat of the control group. Upon further analysis of hematopoietic stem cells and small intestinal crypts, we found that in the mouse of treatment group compared with that in control group, the number of hematopoietic stem cells slightly increased, the nunmber of intestinal stem cells increased, apoptosis of intestinal stem cells incerased and cell proliferaction of that decreased. We found monoclonal number in treatment group is less than that in control group through monoclonal analysis to hematopoietic stem cells, which indicate that the function of hematopoietic cell in treatment group is weaker than that in control group. It is reported that telomerase knock-out can up-regulate the regulation of P53on DNA injury recovery. We found there is no difference in life span between mouse of control group and that of threatment group in rapamycin treatement to telomerase and P53double knockout mice. We used Western Blot to examine expression of P70S6K wich is downstream of mTORC1in telomere knockout mouse in molecular level. The result indicate that the expression level of P70S6K is decreased in telomerase knock-out mouse..