Stem Cell Biology Department, ICMR - National Institute for Research in Reproductive Health, Jehangir Merwanji Street, Parel, Mumbai, 400 012, India.
J Ovarian Res. 2018 Sep 21;11(1):83. doi: 10.1186/s13048-018-0454-4.
Very small embryonic-like stem cells (VSELs) exist in adult organs, express pluripotent markers and have the ability to differentiate into three germ layers in vitro. Testicular, ovarian and hematopoietic stem/progenitor cells express receptors for follicle stimulating (FSH) and ovarian hormones and are activated by them to undergo proliferation/differentiation. VSELs exist in mouse uterus and are regulated by physiological dose of estradiol (E) & progesterone (P) during endometrial growth, differentiation and regeneration/remodeling. In the present study, effects of daily administration of E (2 μg/day), P (1 mg/Kg/day) or FSH (5 IU/day) for 7 days on the endometrium and stem/progenitor cells was studied in bilaterally ovariectomized mice.
E treatment resulted in hypertrophy whereas P resulted in hyperplasia and overcrowding of epithelial cells. FSH also directly stimulated the endometrial cells. Nuclear OCT-4A positive VSELs were visualized in ovariectomized (atrophied) endometrium and cytoplasmic OCT-4B positive epithelial, stromal and endothelial cells were observed after treatment. FSH treated uterine tissue showed presence of 4 alternately spliced FSHR isoforms by Western blotting. 3-5 μm VSELs with a surface phenotype of LIN-/CD45-/SCA-1+ were enumerated by flow cytometry and were found to express ER, PR, FSHR1 and FSHR3 by RT-PCR analysis. Differential effects of treatment were observed on pluripotent (Oct4A, Sox2, Nanog), progenitors (Oct-4, Sca-1), primordial germ cells (Stella, Fragilis) and proliferation (Pcna) specific transcripts by qRT-PCR analysis. FSH and P (rather than E) exerted profound, direct stimulatory effects on uterine VSELs. Asymmetric, symmetric divisions and clonal expansion of stem/progenitor cells was confirmed by co-expression of OCT-4 and NUMB.
Results confirm presence of VSELs and their regulation by circulatory hormones in mouse uterus. Stem cell activation was more prominent after P and FSH compared to E treatment. The results question whether epithelial cells proliferation is regulated by paracrine influence of stromal cells or due to direct action of hormones on stem cells. VSELs expressing nuclear OCT-4A are the most primitive and pluripotent stem cells, undergo asymmetric cell division to self-renew and differentiate into epithelial, stromal and endothelial cells with cytoplasmic OCT-4B. Role of follicle stimulating and steroid hormones on the stem cells needs to be studied in various uterine pathologies.
非常小的胚胎样干细胞（VSELs）存在于成人器官中，表达多能标志物，并具有在体外分化为三个胚层的能力。睾丸、卵巢和造血干细胞/祖细胞表达卵泡刺激素（FSH）和卵巢激素的受体，并被它们激活以进行增殖/分化。VSELs存在于小鼠子宫中，并在子宫内膜生长、分化和再生/重塑过程中受到生理剂量的雌二醇（E）和孕酮（P）的调节。在本研究中，研究了每天给予 E（2μg/天）、P（1mg/Kg/天）或 FSH（5IU/天）7 天对去卵巢小鼠子宫内膜和干细胞/祖细胞的影响。
E 处理导致肥大，而 P 导致上皮细胞增生和过度拥挤。FSH 也直接刺激子宫内膜细胞。在去卵巢（萎缩）子宫内膜中可以观察到核 OCT-4A 阳性的 VSELs，并且在用 FSH 处理后可以观察到细胞质 OCT-4B 阳性的上皮、基质和内皮细胞。Western blot 显示 FSH 处理的子宫组织存在 4 种交替剪接的 FSHR 异构体。通过流式细胞术计数到 3-5μm 的 VSELs，其表面表型为 LIN-/CD45-/SCA-1+，通过 RT-PCR 分析发现其表达 ER、PR、FSHR1 和 FSHR3。qRT-PCR 分析显示，治疗对多能（Oct4A、Sox2、Nanog）、祖细胞（Oct-4、Sca-1）、原始生殖细胞（Stella、Fragilis）和增殖（Pcna）特定转录物有不同的影响。FSH 和 P（而非 E）对子宫 VSELs 具有深远的直接刺激作用。通过共表达 OCT-4 和 NUMB 证实了干细胞/祖细胞的不对称、对称分裂和克隆扩张。
结果证实了 VSELs 的存在及其在小鼠子宫中受循环激素的调节。与 E 处理相比，P 和 FSH 处理后干细胞的激活更为明显。结果质疑上皮细胞的增殖是由基质细胞的旁分泌影响还是由激素对干细胞的直接作用来调节的。表达核 OCT-4A 的 VSELs 是最原始和多能的干细胞，通过不对称细胞分裂自我更新，并分化为细胞质 OCT-4B 的上皮、基质和内皮细胞。需要在各种子宫病变中研究卵泡刺激素和类固醇激素对干细胞的作用。
