Physiological role of implantation-associated factor Mac25 and the molecular mechanisms of implantation

Mac25(胰岛素样生长因子结合蛋白相关蛋白1)在大鼠着床前后的子宫中高表达。我们测定了妊娠早期子宫内膜细胞中Mac25基因的表达，并观察了重组Mac25基因对子宫内膜细胞增殖和前列环素(PGI_2)产生能力的影响。在着床前后，靠近着床处平滑肌的子宫内膜间质细胞中检测到高水平的Mac25mRNA，而胚胎周围的蜕膜区中没有表达Mac25mRNA。在延迟着床妊娠模型中也发现了子宫中Mac25的差异表达，但在蜕膜化模型中，随着蜕膜组织的形成，其表达水平下降。重组Mac25在体外可抑制子宫内膜间质细胞的增殖，并使其停滞于细胞周期的G1期。此外，Mac25还能显著刺激子宫肌层细胞PGI2合成和环氧合酶-2mRNA的表达，这两种分子都是成功着床所必需的。我们构建了编码Mac25的重组腺病毒载体(Ad-Mac)，并将其导入培养的早孕大鼠子宫细胞，以了解Mac25在子宫中的生物学活性。在72小时内，Ad-Mac感染使培养上清液中Mac25蛋白的表达增加。Mac25过表达促进环氧合酶-2和前列腺素E_2合成mRNAs的表达。这些数据表明，Mac25是一种着床相关蛋白，它调节着床围着床期大鼠子宫细胞的增殖和PGI2的产生。

Mac25 (insulin-like growth factor binding protein-related protein 1) is highly expressed in the rat uterus around the time of implantation. We determined the peri-implantation localization of Mac25 mRNA and assessed the effects of recombinant Mac25 on the proliferative and prostacyclin (PGI_2)-producing abilities of cultured endometrial cells early in pregnancy. Mac25 mRNA was detected at high levels in endometrial stromal cells close to the smooth muscle of inter-implantation sites around the time of implantation but absent from decidual zones surrounding the embryo. Differential uterine Mac25 expression was also recognized in the delayed implanting pregnant model, but the level of mRNA decreased as decidual tissues formed in the decidualization model. Recombinant Mac25 inhibited the proliferation of endometrial stromal cells in vitro and arrested them in the G1 phase of the cell cycle. Furthermore, Mac25 significantly stimulated PGI_2 synthesis and cyclooxygenase-2 mRNA expression in myometrial cells, both of which are essential molecules for successful implantation. We constructed a recombinant adenovirus vector encoding Mac25 (Ad-mac) and transfected it to cultured uterine cells derived from early pregnant rats to know bioactivities of Mac25 in the uterus. Ad-mac infection caused increases in Mac25 protein detected in culture media within 72h. Overexpression of Mac25 enhanced expressions for cyclooxygenase-2 and prostaglandin E_2 syntheses mRNAs. These data suggest that Mac25 is an implantation-associated protein and that it modulates the proliferation of rat uterine cells and their production of PGI_2 during the peri-implantation period.