Ultrastructural dynamics of the human endometrium from 14 to 22 weeks of gestation.

In order to elucidate the ultrastructural dynamics of endometrium differentiation, uterine samples of fetuses aged 14 to 22 weeks of gestation (WG) were analyzed. Samples were processed for light (LM), transmission (TEM) and field-emission scanning electron microscopy (FE-SEM). Initial stratification of the uterine wall occurred at 14 WG: endometrial, myometrial, and perimetrial primordia were identified. At this age, the endometrial epithelium was simple columnar to pseudostratified and consisted of microvillous cells. Blood capillaries developed mainly in the stroma and between the myometrium and perimetrium primordia. At 18-20 WG the endometrial epithelium became clearly pseudostratified, with active ciliogenesis and a predominance of microvillous cells. Primordia of tubular glands were present at 20 WG. Microvillous cells still predominated in the endometrial epithelium at 21-22 WG and showed morphological features of apoptosis. The endometrial stroma at this stage was organizing into a thick lamina propria provided with subepithelial capillary plexuses. However, the stroma was formed by still undifferentiated mesenchymal cells during the whole period of study. Our data showed that the epithelial differentiation and distribution in the uterus occur in the human fetus in a similar way as in the adult. The above events are likely the expression of an early developmental patterning and related to future reproductive processes, such as the regulation of gamete passage and blastocyst implantation. Because the structure of the adult uterus is determined by the degree of paramesonephric duct fusion, septum absorption, and differentiation of the uterine primordial layers, our study may contribute toward clarifying to normal urogenital development.

Oocyte-follicle cell interactions during ovarian follicle development, as seen by high resolution scanning and transmission electron microscopy in humans.

The aim of this article is to summarize and update, through an integrated analysis by transmission electron microscopy (TEM) and high resolution scanning electron microscopy (SEM) after osmium-dimethyl sulfoxide-osmium (ODO) maceration, the studies of our research group on the morphodynamics of oocyte-follicle cell associations during follicle development in humans. In resting oocytes, follicular cells project few and short cytoplasmic processes in the perioocytic space. They often form bulbous terminals very close to the oolemma where zonulae adherentes, maculae adherentes, and gap junctions are present. The oolemma mostly appears smooth with short and scanty microvilli. In early growing follicles, follicular cell projections appear as (a) long and tortuous microvilli or (b) large and short extensions. The oolemma shows numerous short microvilli. By TEM, long and thin follicular "intraooplasmic processes" have been seen to penetrate deeply into some oolemma invaginations. In macerated samples, they are observed by SEM to come very close to the nucleus and contact different oocyte organelles. These processes are more likely involved in early oocyte growth. In late growing follicles, oocyte-somatic cell interactions-now established through the interposition of the zona pellucida (ZP)-preserve the general features of early growth stage, with the exceptions of "intraooplasmic processes," which are no more present. In mature follicles subjected to a long ODO maceration, corona cells appear to contact the oocyte through an apical plume of numerous very long "curly hair-like microvilli." Corona cell microvilli, quite likely provide a sort of cytoplasmic skeleton for the ZP and they are possibly involved in (a) release of nutrients or removal catabolites to/from oocyte and vice versa and (b) transfer of substances to build up ZP. In conclusion, among oocyte and somatic cells a structural and functional association is revealed. This association, certainly highly dynamic in vivo, plays a key role in regulating the healthy folliculogenesis to assure a correct and timed oocyte maturation and ovulation.

Surface morphology of the zona pellucida surrounding human blastocysts obtained after in vitro fertilization.

Human zona pellucida (ZP) is maintained up to the blastocyst stage prior to hatching. In in vitro fertilized (IVF) embryos, it eventually acts as a morphodynamic interface between the cultured embryo and its microenvironment. Ultrastructural data on the ZP of IVF blastocysts are scarce in humans. We employed correlated phase contrast microscopy (PCM) and scanning electron microscopy (SEM) to study retrospectively the ultrastructural morphology of the ZP outer surface of 20 IVF human blastocysts from 16 Japanese patients (28-44 years of age, average 36.7+/-4.2) with a history of infertility. Blastocysts were derived from conventional in vitro fertilization (cIVF) (n = 10) and from intracytoplasmic sperm injection (ICSI) (n = 10). Both cIVF and ICSI groups included "clear blastocysts" (n = 5) and "dark blastocysts" (n = 5). By PCM, the clear blastocysts exhibited a regular, round-shaped contour and consisted of clear and voluminous cells. By SEM, they displayed a spongy ZP with numerous fenestrations formed by networked filaments. By PCM, dark blastocysts appeared irregularly shaped and often collapsed, and comprised dark cells and debris. By SEM, their ZP were smooth with remnants of compact fenestrations. In conclusion, viable blastocysts presented a normal ZP outer surface ultrastructure, whereas unhealthy blastocysts showed an altered ZP outer surface, comparable to that of immature/atretic oocytes. Such alterations could reflect sub-optimal culture conditions and/or could be related to blastocyst degenerative processes. The blastocyst ZP surface ultrastructure was unaffected by the fertilization technique (cIVF or ICSI). These data suggest that blastocyst survival in vitro is related to ZP ultrastructure maintenance.

Morphodynamics of the follicular-luteal complex during early ovarian development and reproductive life.

Female reproductive activity depends upon cyclic morphofunctional changes of the ovarian tissue during the female's fertile period, but the primum movens of an active gonadal rearrangement can be found from early phases of embryo development. To offer a basic account of the main steps of ovarian dynamics, we review the morphofunctional behavior of the follicular-luteal complex in an integrated study using light microscopy and transmission and scanning electron microscopy as well as through the use of numerous drawings. Particular emphasis is given to some reproductive aspects including (1) germ-somatic cell relationships and onset of folliculogenesis during early gonadal development; (2) follicular development and oocyte-follicle cell associations through adult folliculogenesis, finally leading to ovulation; (3) morphodynamics of corpus luteum formation, development, and regression, and (4) degenerative processes involving germ and somatic cells. The results reported, many of which originated in our laboratory, arise from some experiments on laboratory mammals but mostly from a large selection of human specimens. The data obtained are integrated and correlated with classic reports as well as with current views. Crucial biochemical, histophysiological, and clinical aspects are also emphasized.

Three-dimensional microanatomical dynamics of the ovary in postreproductive aged women.

OBJECTIVE: To evaluate the microanatomical dynamics of the ovary during postreproductive life. DESIGN: Retrospective, observational research study. SETTING: Institutional (university). PATIENT(S): Eleven (43- to 72-year-old) women in perimenopause, menopause, or postmenopause. INTERVENTION(S): Biopsies of ovaries obtained from patients undergoing gynecologic surgery or diagnostic procedures. MAIN OUTCOME MEASURE(S): Analysis of the 3-dimensional microanatomy of the ovary by transmission and high-resolution scanning electron microscopy. RESULT(S): The surface epithelium gets gradually flatter and is always present, even in advanced age. The surface appears smoother because of a smaller number of papillae and crypts as well as a decreased number and shortening of microvilli on surface epithelial cells. Signs of atrophy and fibrosis are evident. Primordial follicles are usually absent in postmenopause, whereas corpora atretica, hemorrhagica, and albicantia, scar tissue, and simple follicular cysts are common after menopause. Apoptotic and necrotic cells appear frequently within the surface epithelium. Major common features are a marked reduction in number and caliber of blood vessels with thickening of the vascular walls and changes in endothelial cells. CONCLUSION(S): Scanning electron microscopy studies are a useful complement to ordinary gynecologic diagnostic methods. Variations among patients of the same age range or functional status should be considered.