Surface epithelium of the fetal guinea-pig ovary: a light and electron microscopic study

Ovarian cancer, Part I: Biology

The ovary is among the more complex organs of the body and its functions are achieved by numerous cell types. All of these cell types have some tendency to undergo malignant transformation, but the vast majority of ovarian cancers are believed to be the result of malignant transformation of the ovarian surface epithelium. The concept that most ovarian cancer arises from this modified peritoneal mesothelium is credited to Sir Spencer Wells in 1872. Ovarian cancer is the most frequently fatal gynecologic malignancy, and approximately 20,000 cases per year are diagnosed in the United States. Progress in understanding the biology of this disease, including factors involved in its etiology, progression, and tendency to change from a relatively chemotherapy-sensitive tumor to one with marked drug resistance, has been slow. In this review, the complex features of the normal ovarian surface epithelial cells are considered in relation to the etiology and progression of the disease. The hypothesis that incessant or repetitious ovulation contributes to the initiation of the disease is explored in detail based on experimental data, epidemiologic information, and the potential for antioncogene inactivation in this interesting cell type. Lastly, based on the experimental data available, potential mechanisms of resistance to platinum, the cornerstone of aggressive ovarian cancer therapy, are discussed, as are approaches to overcoming drug resistance. It is hoped that the reader will be left with the feeling that the pace of our understanding of the biology of ovarian cancer is increasing at such a rate that answers to the questions of etiology and why chemotherapy often fails will be known in the foreseeable future.

Expression of type I and III collagen during morphogenesis of fetal rat testis and ovary

The distribution of interstitial collagen type I and III was studied immunocytochemically and ultrastructurally in the fetal rat testis and ovary from the undifferentiated stage (day 12) until birth. The results suggest that there is a correlation between the differentiation, organization, and abundance of the mesenchyme and the differentiation of the testicular vs. ovarian cords. Type III collagen was already present in the undifferentiated gonadal mesenchyme, and it appeared at an early stage around the organizing gonadal cords. Type I collagen appeared later in a similar mesenchymal distribution as type III collagen. Fragmentation of the subepithelial basement membrane in the gonads starting morphogenesis was considered to indicate that the surface epithelium participates in the gonadal cord formation. The expression of type III collagen at first on the surface of the developing testicular cords and later around the ovarian cords suggests that the mesenchymal premyoid cells are actively involved in the male cord formation. Focal discontinuities were found in the basement membrane of the ovarian cords, which in part were separated from each other by a ramified and relatively sparse mesenchyme. A complex linkage between the cytoskeleton and the extracellular matrix is illustrated both in the cord forming Sertoli and granulosa cells, and in the adjacent mesenchymal cells. Depletion of the mesenchyme and the basement membrane around the germ cell-granulosa cell associations of the wide ovarian medullary cords may be causal for their subsequent degeneration.

Development of the ovarian surface and associated germ cells in the human fetus. A correlated study by scanning and transmission electron microscopy

The ovarian surface and associated germ cells have been studied in human fetuses from 12 weeks of age until near term, using light, TEM and SEM techniques. The surface epithelium and related cords proliferate extensively, especially at midterm. The cords of the ovarian cortex appear to be linked with ingrowths from the surface epithelium, and both structures have a common basal lamina. Germ cells are always interspersed among the somatic cells of the surface epithelium and associated cords. These results indicate that both the proliferating cords and surface epithelium may contribute to the formation of early follicles. Furthermore, the occurrence, of elements having some of the features of primitive steroidogenic cells in the regions of cord-surface epithelium continuity, suggests that both structures (surface epithelium and cords) contribute somatic cells, which in addition to becoming granulosa cells, might also contribute to the provision of primitive interstitial cells. Gonocytes tend to migrate through the developing ovarian tissue towards the surface where they become extruded into the peritoneal cavity. This phenomenon might contribute to the reduction in the number of germ cells at birth and parallels the atretic processes within the ovary.

The ultrastructure of follicle cells in fetal guinea-pig ovaries

The development of the follicle cells in fetal guinea-pig ovaries has been examined in the electron microscope. The findings were as follows: at days 34 and 38 there were broad intercellular clefts within the germinal cords. However, a continuous layer of thin cytoplasmic processes from the follicle cells separated the germinal cords from the stromal compartment. The germinal cords were everywhere limited by a basal lamina. During all the period examined coated vesicles, possibly emptying their contents into the region of the basal lamina, were observed in the follicle cells. At days 42, 46 and 50 the cellular membranes were closely apposed with an intercellular distance of about 200 A. Complexes of deeply interdigitating folds of the membrane of neighboring follicle cells were observed. The follicle cells forming part of the primordial follicles at days 54 and 58 were characterized by a disappearance of these folds and by the appearance of bundles of microfilaments in the cytoplasm. These were especially numerous at day 66. At days 34 and 38 gap junctions were observed between the follicle cells, but not between the follicle cells and the germinal cells. During the entire period examined junctions resembling desmosomes without filaments were observed between the follicle cells as well as between the follicle cells and the germinal cells. The ultrastructure of the follicle cells is considered in detail and the functional significance of the findings discussed.