The immature human ovary shows loss of abnormal follicles and increasing follicle developmental competence through childhood and adolescence

R A Anderson,E E Telfer,D F Albertini,W H B Wallace,M Mclaughlin

doi:10.1093/humrep/det388

R A Anderson, E E Telfer + Show 3 more

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https://doi.org/10.1093/humrep/det388

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Abstract

STUDY QUESTIONDo the ovarian follicles of children and adolescents differ in their morphology and in vitro growth potential from those of adults?SUMMARY ANSWERPre-pubertal ovaries contained a high proportion of morphologically abnormal non-growing follicles, and follicles showed reduced capacity for in vitro growth.WHAT IS KNOWN ALREADYThe pre-pubertal ovary is known to contain follicles at the early growing stages. How this changes over childhood and through puberty is unknown, and there are no previous data on the in vitro growth potential of follicles from pre-pubertal and pubertal girls.STUDY DESIGN, SIZE, DURATIONOvarian biopsies from five pre-pubertal and seven pubertal girls and 19 adult women were analysed histologically, cultured in vitro for 6 days, with growing follicles then isolated and cultured for a further 6 days.PARTICIPANTS/MATERIALS, SETTING, METHODSOvarian biopsies were obtained from girls undergoing ovarian tissue cryopreservation for fertility preservation, and compared with biopsies from adult women. Follicle stage and morphology were classified. After 6 days in culture, follicle growth initiation was assessed. The growth of isolated secondary follicles was assessed over a further 6 days, including analysis of oocyte growth.MAIN RESULTS AND THE ROLE OF CHANCEPre-pubertal ovaries contained a high proportion of abnormal non-growing follicles (19.4 versus 4.85% in pubertal ovaries; 4004 follicles analysed; P = 0.02) characterized by indistinct germinal vesicle membrane and absent nucleolus. Follicles with this abnormal morphology were not seen in the adult ovary. During 6 days culture, follicle growth initiation was observed at all ages; in pre-pubertal samples there was very little development to secondary stages, while pubertal samples showed similar growth activation to that seen in adult tissue (pubertal group: P = 0.02 versus pre-pubertal, ns versus adult). Isolated secondary follicles were cultured for a further 6 days. Those from pre-pubertal ovary showed limited growth (P < 0.05 versus both pubertal and adult follicles) and no change in oocyte diameter over that period. Follicles from pubertal ovaries showed increased growth; this was still reduced compared with follicles from adult women (P < 0.05) but oocyte growth was proportionate to follicle size.LIMITATIONS, REASONS FOR CAUTIONThese data derive from only a small number of ovarian biopsies, although large numbers of follicles were analysed. It is unclear whether the differences between groups are related to puberty, or just age.WIDER IMPLICATIONS OF THE FINDINGSThese findings show that follicles from girls of all ages can be induced to grow in vitro, which has important implications for some patients who are at high risk of malignant contamination of their ovarian tissue. The reduced growth of isolated follicles indicates that there are true intrafollicular differences in addition to potential differences in their local environment, and that there are maturational processes occurring in the ovary through childhood and adolescence, which involve the loss of abnormal follicles, and increasing follicle developmental competence.Study funding/competing interest(s)Funded by MRC grants G0901839 and G1100357. No competing interests.

Highlights

Human primordial follicle formation is completed in fetal life and is rapidly followed by the initiation of follicle growth, such that all stages of pre-antral follicles and antral follicles other than pre-ovulatory stages have been reported before puberty (Lintern-Moore et al, 1974; Peters et al, 1978)
Using whole mount confocal microscopy, it was apparent that the great majority of follicles in uncultured tissue were confined to a region subtending the tunica albuginea, recognizable because of the lower cell density and absence of nerve fibres (Fig. 1B)
While a small number of secondary follicles were observed in tissue from the pubertal group, none were found in the pre-pubertal group (Fig. 1C)

Summary

Introduction

Human primordial follicle formation is completed in fetal life (with primordial follicles present from 17 weeks of gestation) and is rapidly followed by the initiation of follicle growth, such that all stages of pre-antral follicles and antral follicles other than pre-ovulatory stages have been reported before puberty (Lintern-Moore et al, 1974; Peters et al, 1978). The rise in gonadotrophin secretion during puberty results in the progression of all stages of follicle growth and the onset of ovulation, but there are few data relating to developmental changes in the ovary between follicle formation and post-pubertal, adult function. This reflects the limited availability of samples for histological analysis, and the absence until recently of any serum marker of early follicle growth. Competent oocytes have been obtained from antral follicles in young girls (Revel et al, 2009) but no previous studies have explored directly the in vitro growth potential of follicles from children and adolescents

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