Structure-Function Relationships in the Wall of the Ovarian Follicle

Abstract

This paper reviews current knowledge of the light and electron microscopic structure of the three layers of the mammalian follicular wall-follicular epithelium (membrana granulosa), theca interna and theca externa-and discusses correlations between structure and function. The ultrastructure of follicular epithelial cells in growing follicles emphasizes their protein synthetic and secretory functions; features suggestive of a major steroidogenic function appear only at later stages. Regional differences in follicular epithelial cell function are probably important, although structurally these cells are relatively homogeneous. Structural diversity is more marked in the thecal layers : differentiation in the theca interna is towards fibrocytic and steroidogenic cell types, while that in the theca externa is towards fibrocytic and myoid types. Adherens and gap junctions are present between cells in all layers; however, tight (occludens) junctions have not been convincingly demonstrated between the cells in any of the three layers. Blood and lymph vessels are confined to the thecal layers. However, follicles possess no structural barrier comparable to that associated with the 'blood-testis barrier', and show a correspondingly greater permeability to large molecules than seminiferous tubules. Interactions between the layers of the follicular wall have not yet been intensively investigated, but are likely to play an important role in follicular function. To date, the best-documented interaction between layers is that described in the 'two-cell hypothesis' of oestrogen production. Some potentially useful directions for future research are proposed.

Immunocytochemical study of anti-Mullerian hormone in sheep ovarian follicles during fetal and post-natal development

“…Studies carried out in the rat show that during Graafian follicle growth, only granulosa cells in the cumulus proliferate (Hirshfield & Midgley, 1984), and can be considered as stem cells. When challenged by FSH, peripheral granulosa cells located near the basal lamina undergo terminal cytodifferentiation, characterized by acquisition of LH/hCG receptor, steroidogenic enzymes and lipid droplets (reviewed by O'Shea, 1981;Erickson et ai, 1985), whereas prolactin receptor development and reactivity to a monoclonal antibody raised to a mammary cell line (Erickson et ai, 1985) is restricted primarily to the cumulus and the innermost granulosa cells. There is evidence, reviewed by Erickson (1983), that supports the hypothesis that the position of the granulosa cell in the follicle determines in which way it will differentiate in response to FSH stimulation.…”

Morphometric analysis of the corpus luteum of 16‐day pregnant rats: The effect of preparative procedures on volume of luteal cell, interstitial, and vascular compartments

“…The capsule is derived from the theca externa of the follicle within which the CL forms. Since the theca contains contractile elements (O'Shea, 1981) it is likely that the capsule derived from it does also and can exert some pressure on the compartments within. The vascular compartment is a n interconnecting network of vessels but can be viewed collectively as a single large vessel with a potentially contractile, or at least elastic, and semipermeable wall.…”

Tumor Necrosis Factor-α Stimulates Proliferation of Rat Ovarian Theca-Interstitial Cells1

“…Theca-interstitial (T-I) cells control follicle growth and atresia, regulate ovarian steroidogenesis, and may provide mechanical support for ovarian follicles [1][2][3][4][5]. Normal follicular development requires accurate regulation of T-I function through extra-and intraovarian mechanisms.…”