Division of Endocrinology, CSIR-Central Drug Research Institute, Lucknow, India.
Biol Reprod. 2013 Oct 10;89(4):84. doi: 10.1095/biolreprod.112.106542. Print 2013 Oct.
Transforming growth factor-beta (TGF-B) plays an important role in embryo implantation; however, TGF-B requires liberation from its inactive latent forms (i.e., large latent TGF-B complex [LLC] and small latent TGF-B complex [SLC]) to its biologically active (i.e., monomer or dimer) forms in order to act on its receptors (TGF-BRs), which in turn activate SMAD2/3. Activation of TGF-B1 from its latent complexes in the uterus is not yet deciphered. We investigated uterine latent TGF-B1 complex and its biologically active form during implantation, decidualization, and delayed implantation. Our study, utilizing nonreducing SDS-PAGE followed by Western blotting and immunoblotting with TGF-B1, LTBP1, and latency-associated peptide, showed the presence of LLC and SLC in the uterine extracellular matrix and plasma membranous protein fraction during stages of the implantation period. A biologically active form of TGF-B1 (~17-kDa monomer) was highly elevated in the uterine plasma membranous compartment at the peri-implantation stage (implantation and nonimplantation sites). Administration of hydroxychloroquine (an inhibitor of pro-TGF-B processing) at the preimplantation stage was able to block the liberation of biologically active TGF-B1 from its latent complex at the postimplantation stage; as a consequence, the number of implantation sites was reduced at Day 5 (1000 h), as was the number of fetuses at Day 13. The inhibition of TGF-B1 showed reduced levels of phosphorylated SMAD3. Further, the delayed-implantation mouse model showed progesterone and estradiol coordination to release the active TGF-B1 form from its latent complex in the receptive endometrium. This study demonstrates the importance of liberation of biologically active TGF-B1 during the implantation period and its regulation by estradiol.
转化生长因子-β（TGF-β）在胚胎植入中发挥重要作用；然而，TGF-β需要从其无活性的潜伏形式（即大潜伏 TGF-β 复合物[LLC]和小潜伏 TGF-β 复合物[SLC]）中释放出来，才能转化为其生物活性形式（即单体或二聚体），从而作用于其受体（TGF-βR），进而激活 SMAD2/3。TGF-β1 从其在子宫中的潜伏复合物中激活尚未被破解。我们研究了植入、蜕膜化和延迟植入期间子宫潜伏 TGF-β1 复合物及其生物活性形式。我们的研究利用非还原 SDS-PAGE 后进行 Western blot 和 TGF-β1、LTBP1 和潜伏相关肽的免疫印迹，显示 LLC 和 SLC 存在于植入期的子宫细胞外基质和质膜蛋白部分。在植入期，子宫质膜隔室中 TGF-β1 的生物活性形式（~17-kDa 单体）高度升高。羟氯喹（一种前 TGF-β 加工抑制剂）在植入前阶段的给药能够阻止生物活性 TGF-β1 从其潜伏复合物在植入后阶段的释放；因此，第 5 天（1000 h）的植入部位数量减少，第 13 天的胎儿数量也减少。TGF-β1 的抑制作用显示磷酸化 SMAD3 的水平降低。此外，延迟植入的小鼠模型表明孕激素和雌二醇协调作用，从接受性子宫内膜中的潜伏复合物中释放出具有生物活性的 TGF-β1 形式。这项研究表明，在植入期间释放生物活性 TGF-β1 的重要性及其受雌二醇的调节。
