Nottola S A, Macchiarelli G, Familiari G, Stallone T, Sathananthan A H, Motta P M
Department of Anatomy, Faculty of Medicine, University of Rome La Sapienza, Italy.
Ital J Anat Embryol. 1998;103(4 Suppl 1):85-101.
A large cumulus mass usually covers the human ovulated oocyte, and voluminous clusters of cumulus cells are still seen after fertilization around the egg. Cumulus cells surround oocytes and fertilized eggs also during in vitro fertilization (IVF) procedures. This study describes, by transmission and scanning electron microscopy, the morphology and the microtopography of the cells forming the human cumulus mass surrounding IVF samples (insemined but not fertilized oocytes and fertilized eggs). Particularly emphasized is their morphodynamic role in sperm-egg interactions. A comparison with the behavior in vivo of cumulus-enclosed oocyte/fertilized eggs has been also performed. All patients have given their informed consent to participate in this protocol. An inner layer (corona radiata cells) and an outer layer (proper cumulus cells) can be microtopographically recognized in the cumulus mass. Numerous cumulus-corona cells, particularly after fertilization, showed ultrastructural characteristics typical for steroid synthetic cells, thus undergoing a sort of "luteinization" parallel to that occurring in the sister granulosa cells of the postovulatory follicle. This steroid synthetic activity, particularly enhanced in vitro but present also in vivo, may be finalized to the release of small amount of steroids (estrogens and progesterone) in the oocyte/fertilized egg milieu. Various proteins, secreted by other cell subpopulations--as revealed in other studies by our research group--, may even enrich this milieu. Lymphocytes and macrophages were often found in the cumulus mass. They may modulate the steroid secretion of the neighboring cumulus cells by production of cytokines, mimicking what occurs in the ovarian follicle and, later, in the corpus luteum. Spermatozoa, both normal (acrosome-intact or--reacted) and abnormal, were frequently seen in the cumulus mass, free in the intercellular spaces or close to the cumulus cells, that can induce sperm capacitation and acrosome reaction. Leukocytes and cumuluscorona cells appeared both capable of actively phagocytizing supernumerary and/or abnormal sperms. Such spermiophagic response is present in a lesser extent around oocytes and eggs fertilized in vivo. In vitro, instead, cumulus spermiophagy leads to the elimination of a large part of the excess spermatozoa that have reached the oocyte, thus restoring in an extracorporeal medium the spermiophagic activity physiologically exerted by leukocytes and epithelial cells in the female and male genital tracts. In conclusion, the cumulus mass surrounding oocytes and fertilized eggs appears as a highly dynamic system, in which various subpopulations of cells cooperate in order to provide a suitable and healthy microenvironment for fertilization and early embryo development.
一个大的卵丘团通常覆盖着人类排卵后的卵母细胞，并且在受精后卵周围仍可见大量的卵丘细胞簇。在体外受精（IVF）过程中，卵丘细胞也围绕着卵母细胞和受精卵。本研究通过透射电子显微镜和扫描电子显微镜描述了围绕IVF样本（已受精但未受精卵母细胞和受精卵）形成人类卵丘团的细胞的形态和微观结构。特别强调了它们在精卵相互作用中的形态动力学作用。还与卵丘包裹的卵母细胞/受精卵在体内的行为进行了比较。所有患者均已签署知情同意书以参与本方案。在卵丘团中可以在微观结构上识别出内层（放射冠细胞）和外层（固有卵丘细胞）。许多卵丘 - 放射冠细胞，特别是在受精后，表现出类固醇合成细胞典型的超微结构特征，因此经历了一种与排卵后卵泡的姐妹颗粒细胞中发生的“黄素化”平行的过程。这种类固醇合成活性，特别是在体外增强但在体内也存在，可能是为了在卵母细胞/受精卵环境中释放少量类固醇（雌激素和孕酮）。正如我们研究小组在其他研究中所揭示的，其他细胞亚群分泌的各种蛋白质甚至可能使这种环境更加丰富。淋巴细胞和巨噬细胞经常在卵丘团中被发现。它们可能通过产生细胞因子来调节相邻卵丘细胞的类固醇分泌，类似于在卵巢卵泡以及随后在黄体中发生的情况。正常（顶体完整或已反应）和异常的精子经常在卵丘团中被看到，游离于细胞间隙或靠近卵丘细胞，这可以诱导精子获能和顶体反应。白细胞和卵丘 - 放射冠细胞似乎都能够主动吞噬多余的和/或异常的精子。这种吞噬精子的反应在体内受精的卵母细胞和受精卵周围程度较小。相反，在体外，卵丘吞噬精子导致到达卵母细胞的大部分多余精子被清除，从而在体外培养基中恢复了白细胞和上皮细胞在雌性和雄性生殖道中生理上发挥的吞噬精子活性。总之，围绕卵母细胞和受精卵的卵丘团似乎是一个高度动态的系统，其中各种细胞亚群协同作用，为受精和早期胚胎发育提供一个合适且健康的微环境。
