Tumor Necrosis Factor α Knockout Increases The Fertility Of Mice

Ovary is one part of the female reproductive organs, the ovarian development of the animal is a complicate process, which from embryonic development to ovarian senescence. Furthermore, the ovary is a dynamic system which is continue to be repaired in the whole life period. The follicle is the functional unit of ovary, and follicles develop through the primordial, primary, secondary and mature stages. Follicle development in ovary is a series of complex processes governed by endocrine, autocrine and paracrine factors.One potential regulator of ovarian follicular development is tumor necrosis factorα(TNFα), which is a 17.3 kDa protein product of activated macrophages. The roles of TNFαare quite complex ranging from promoting cell survival to initiating cell death. The multiple activities of TNFαare mediated by specific cell surface receptors, the TNF receptorⅠ(TNFRⅠ) and TNF receptorⅡ(TNFRⅡ). Several reports have shown that the signal through TNFRⅠis necessary for many biological functions of TNFα. TNFαhas wide biologic activity, in addition, it also participate in the nosogenesis of some disease, such as angiocardiopathy and autoimmune disease. In the ovary of the mammal, several in vitro studies have indicated that TNFαplays an important role in follicular development, ovulation, steroidogenesis, luteinization, fertility and atresia, but the in vivo role of TNFαin ovary remains an enigma.The purpose of present study was using TNFαdeleted model for the first time to further elucidate the biological roles of this cytokine in the regulation of follicular development and female fertility, and studied the parameters of the fertility after deletion of the TNFαon molecular level and cellular level. This study may establish foundation for dentifying molecular mechanisms of TNFαin normal ovarian function.The results show:1. Vaginal opening was similar in TNFα-/- females when compared with WT females. At two months of age, cycle length was not significantly different between TNFαknockout and WT mice, but TNFα-/- mice spent more time in estrus and significantly less time in diestrus than did controls. Consequently, the number of cycles per mouse in a 21 day period was more in TNFα-/- mice than in controls. At six months of age, only 50% of TNFαnull mice exhibited estrous cycles, of those TNFαnull mice exhibiting estrous cycles, significantly more time in diestrus and relatively less time were spent in estrus. Thus, in aged animals, the number of cycles in a 21 day period was significantly reduced in TNFαnull mice compared to controls.2. On day of 21, TNFαknockout mice shed significantly more ova compared with WT controls of the same age. Furthermore, the greater number of ovulations by TNFаknockout mice was followed by higher serum levels of progesterone on day 21.3.The follicular detect experiment of the two types mice on postnatal 4,18,42,90 indicated that, the TNFα-/- ovaries contained more total follicles, more each stage follicles especially preantral and antral follicles than did wild type animals contemporaneity.4. The follicular proliferation and apoptosis detect experiment of the ovary of the two types of mice indicated that, on proteinum level, granulosa cells, theca cells and interstitial cells of TNFαknockout mice demonstrated higher levels of proliferation than WT ovaries did based on immunohistochemistry for CDK 4 on day 90, but TNFαknockout ovaries appeared to have lower levels of CASPASE 3 in oocytes than WT ovaries did. On molecular level, a significantly higher abundance of of Cdk 4 and Cyclin D2 transcripts was detected in TNFαdeficient ovaries compared with WT ovaries on PD 90, but a significantly lower expression of Bad and Bax (a proapoptotic factor) was detected in TNFαdeficient ovaries compared with WT ovaries.5. Fertility of TNFαnull mice was compared to that of controls by determining the number of pups per litter and the cumulative number of pups per female during a 12 month breeding period. The TNFα-/- females produced 30% more pups per litter than the wild type mice. Moreover, the TNFα-/- mice gave birth to 21% more pups than control mice did during a 12 month breeding period.6. At one year of age, the follicular reserve in TNFα-/- mice was more than that in WT mice.In a word, deletion of the TNFαcan improve overall reproductive capacity of the mice through affecting some factor related to the function of the ovary.