Hamster: a unique model for studying implantation

描述（由申请方提供）：在所有研究的种属中，卵巢孕酮对着床至关重要。然而，在这个过程中胚胎雌激素的需求仍然是一个悬而未决的问题，除了在小鼠和大鼠中，胚胎不具备雌激素合成的机制。着床可以发生在包括仓鼠在内的几个物种中，如果提供孕酮，在没有卵巢雌激素的情况下，也可能发生在人类中。然而，我们最近的研究表明：（1）雌激素，而不是孕激素，调节子宫表达肝素结合EGF样生长因子基因（Hegfl）在卵巢切除仓鼠，和（2）Hegfl表达发生在子宫腔上皮细胞周围的胚泡在植入时，在循环雌激素的情况下，在孕激素引发的垂体切除妊娠仓鼠。这些结果表明，仓鼠囊胚可能是雌激素的替代来源，其局部作用以诱导子宫中Hegfl基因表达。事实上，我们的初步实验表明，细胞色素P450芳香化酶蛋白在仓鼠桑椹胚和囊胚的存在。此外，仓鼠桑椹胚暴露于培养物中的类固醇细胞色素P450芳香酶抑制剂显著抑制囊胚的形成。这些观察结果与我们在植入前仓鼠胚胎和子宫中雌激素受体α表达的初步结果一起，使我们假设该物种不依赖于卵巢雌激素，但需要胚胎雌激素来启动胚胎和子宫的植入所需的变化。然而，无论是合成或胚胎雌激素在囊胚形成，子宫容受性和植入仓鼠的作用还没有得到解决。因此，我们在仓鼠中研究的具体目标是：（1）仓鼠植入前胚胎是否产生雌激素？(2)桑椹胚-囊胚转化需要胚胎雌激素吗？(3)胚胎雌激素是否是建立着床子宫容受性所必需的？(4)在缺乏胚胎雌激素的情况下，全身雌激素是否诱导子宫容受性和着床？我们将使用多种方法，包括RT-PCR，原位杂交，免疫组织化学，免疫荧光，Western印迹，胚胎培养和移植等来实现我们的目标。随着对胚胎发育和子宫着床容受性机制的更好理解，将更有效地管理有关妇女生育和不育的问题。

DESCRIPTION (provided by applicant): Ovarian progesterone is essential for implantation in all species studied. However, the requirement of embryonic estrogen in this process is still an unsettled issue, except in mice and rats in which embryos do not possess the machinery for estrogen synthesis. Implantation can occur in several species including hamsters and perhaps in humans in the absence of ovarian estrogen if progesterone is provided. However, our recent study shows that: (1) estrogen, but not progesterone, regulates the uterine expression of heparin binding EGF-like growth factor gene (Hegfl) in ovariectomized hamsters, and (2) Hegfl expression occurs in the uterine luminal epithelium surrounding the blastocyst at the time of implantation in the absence of circulating estrogen in progesterone-primed hypophysectomized pregnant hamsters. These results suggest that hamster blastocysts could be an alternative source of estrogen that acts locally to induce Hegfl gene expression in the uterus. Indeed, our preliminary experiments suggest the presence of cytochrome P450 aromatase protein in hamster morulae and blastocysts. Furthermore, the exposure of hamster morulae to a steroidal cytochrome P450 aromatase inhibitor in culture significantly inhibits the formation of blastocysts. These observations together with our preliminary results of estrogen receptor-alpha expression in preimplantation hamster embryos and uterus at the time of implantation led us to postulate that this species does not depend on ovarian estrogen, but requires embryonic estrogen to initiate embryonic and uterine changes required for implantation. However, neither the synthesis nor the role of embryonic estrogen in blastocyst formation, uterine receptivity and implantation in hamsters has been resolved. Thus, our specific aims to study in hamsters: (1) Do hamster preimplantation embryos produce estrogen? (2) Is embryonic estrogen required for morula-blastocyst transformation? (3) Is embryonic estrogen required for the establishment of uterine receptivity for implantation? (4) Does systemic estrogen induce uterine receptivity and implantation in the absence of embryonic estrogen? We will use multiple approaches including RT-PCR, in situ hybridization, immunohistochemistry, immunofluorescence, Western blotting, embryo culture and transfer and others to accomplish our goals. With better understanding of the mechanisms of embryo development and uterine receptivity for implantation, issues concerning fertility and infertility in women will be more effectively managed.