Expression Of Cysteine Sulfinate Decarboxylase (CSD) In The Reproductive System Of Adult Mice And Regulation Of CSD By Estradiol And Progesterone In The Uterus

Taurine (2-aminoethanesulfonic acid) is a free intracellular p-amino acid. It is rich in mammal reproductive systems and plays important roles in reproductive organs. However, the synthesis of taurine in reproductive systems is not still described in detail. Cysteine sulfinate decarboxylase (CSD) is the rate-limiting biosynthetic enzyme of taurine. In the present study, we detected CSD expression in reproductive organs of adult male and female mice by RT-PCR, Western blot and immunohistochemistry, the change pattern of CSD in mouse uterus during the peri-implantation and regulation of CSD by estrogen and progesterone in uterus. The results are described as four parts as follows:1. The results have firstly proved that CSD is expressed at both mRNA and protein levels in the female reproductive system of mice and this study also suggests that the uterus, oviducts and ovary have the function to synthesize taurine via the CSD pathway. By immunohistochemistry, CSD was detected in almost all epithelial cells and few stromal cells in the uterus and the infundibular, ampullar and isthmic segments of oviduct. No cyclic change was observed in the epithelial cells of uterus while some smooth muscle cells and blood vessels of the myometrium are immunostained stronger in the estrous phase than in the other phases. In the ovary, strong immunostaining for CSD was observed in the granulosa layer and oocytes of follicles from the primary to preovulatory stages while the zona pellucida and the follicular antrum were not stained. CSD immunoreactivity progressively decreased from the oocytes and corpus luteam during follicular atresia and corpus luteum regression. These results show that CSD is expressed and involved in taurine production in female genital organs.2. CSD was found to dynamically distribute in mouse uterus during the peri-implantation period. On pregnant days 1 (D1 )and D2, the epithelial cells and few stromal cells were immnuostained for CSD, as similar as that during the estrous cycle. The stromal cells became positive for CSD from D3 till D6, whereas these cells in the implantation site become weakly stained since D7 and almost disappeared on D9. Surprisingly, CSD was expressed in the luminal and glandular epithelia in the inter-implantation site on D6 and uterotubal junction on D18, and few stromal cells were stained. This expression was as similar as that in the nonpregnant mice. Meanwhile, injection of selective transport inhibitor of taurine, p-alanine into a uterine horn on D4 of pregnancy significantly reduced the number of mouse embryos that implanted on D9. The temporal and spatial localization of CSD protein in the mouse uterus during peri-implantation and the inhibition of p-alanine on embryo implantation implicate the role of CSD and the regulation of taurine on embryo implantation and uterine receptiveness.3. The expression and regulation of CSD by estrodial (E₂) and progesterone (P4) in mouse uterus of ovariectomized mouse model were investigated. The results demonstrated that ovariectomy significantly decreased CSD immunostaining and expression level in mouse uterus by means of immunohistochemistry, semi-quantitative RT-PCR and Western blot. All hormone treatment increaseduterine CSD level at both mRNA and protein levels. In single injection of hormone treatment group, E2 is more effective than P4. Single injection of P4 and combination of P4 and E2 increased the immunostaining for CSD in stromal cells. In the inducing uterine receptivity for implantation, the ovariectomized uterus in experimental group injected with (P4)3+P4+E2 showed strong staining for CSD in the luminal and glandular epithelia and more stromal cells also became positive. Meanwhile, the expression pattern and uterine receptivity were almost as similar as that in the normal pregnant mice. While in the control group injected with (P4)3+P4, the uterine is not the receptive state for implantation. More stromal cells also show positive staining for CSD. CSD and ERa were shown to be mainly co-localized in the luminal and glandular epithelium. These results demonstrated that the complex uterine CSD responses to E2 and P4 may be directly or indirectly mediated by differential cell-specific expression of their receptors.4. The expression of CSD in reproductive system of male mice was studied. The results firstly show that CSD is expressed both at the mRNA and protein levels in the testis, epididymis and ductus deferens and increase from the testis to the epididymis and highest in the ductus deferens. Immunohistochemical results demonstrate that the main cell types containing CSD are Leydig cells of testis, epithelial cells and some stromal cells throughout the efferent ducts, epididymis and ductus deferens. However, no staining was observed in the seminiferous tubules, including Sertoli cells and germ cells in all spermatogenic stages and spermatozoa in the excurrent ducts.As described above, CSD is expressed in specific cell types in reproductive organs of male and female mice and the genital organs have the function to produce taurine via the CSD pathway. CSD is also distributed in the uterus in a temporal and spatial pattern during peri-implantation period and taurine plays roles in embryo implantation. CSD is up-regulated by estrogen and progesterone in the uterus of ovariectomized mice. However, quantification of the relation between CSD expression to taurine synthesis, expression and regulation of CSD by sex hormones as well as the exact functions of taurine in mammal reproductive system still need to be elucidated in future studies.