Morphometric studies of small follicles in ovaries of women at different ages

TLDR

The study classified small ovarian follicles into four morphological groups (B, B/C, C, D) based on granulosa cell characteristics and used morphometric measurements of granulosa cell number and follicle, oocyte, and germinal vesicle diameters to distinguish dormant from growth‑phase follicles. During the dormant phase follicles transition from Type B to C, growth phase begins between large Type C and D, and with increasing age the total follicle count and each type decline, with Type B decreasing and Types B/C, C, D increasing, and these changes correlate inversely with overall follicle population, suggesting intra‑ovarian regulation of early follicular growth. Summary.

Abstract

Summary. Small follicles in human ovaries were divided into 4 groups based on the morphological characteristics of the granulosa cells that surround the oocyte: B (flattened cells), B/C (mixture of flattened and cuboidal cells), C (one layer of cuboidal cells) and D (more than one layer of cells without epithelioid cells in the theca interna). On the basis of morphometric studies, including the number of granulosa cells in the largest cross-section, diameters of follicle, oocyte and germinal vesicle, folliculogenesis was categorized as in a dormant or growth phase. During the dormant phase, a transformation of follicles from Type B to Type C progressively took place. The growth phase started at an intermediary stage between large Type C and D follicles. The total ovarian follicular population and the numbers of each follicle type decreased significantly as age increased. The percentages of Type B follicles significantly decreased with increasing age whereas the percentages of Types B/C, C and D increased. In addition, there was a positive correlation between the percentages of Type B and a negative correlation between the percentages of Types B/C, C and D and the total ovarian follicular population. This last observation suggests the existence of an intra-ovarian regulation of the first steps of follicular growth.