Intrinsic innervation of the ovary and its variations in the rat senescence process

Juan M Bravo-Benitez,Leticia Morales-Ledesma,Berenice Venegas,Alfonso Díaz,Roberto Domínguez,Carolina Morán,Yolanda Cruz,Rosa A Lucio

doi:10.1007/s10735-022-10069-7

Abstract

Ovarian functions decrease with perimenopause. The ovary has extrinsic innervation, but the neural influence on ovarian functions and dysfunction is not well-studied. The present study aimed to biochemically and morphometrically characterize the intrinsic neurons in ovaries from young adult, middle-aged, and senescent Long Evans CII-ZV rats (3, 12, and 15 months old, respectively). Ovaries were extracted from four rats of each age group (n = 12 total), cryopreserved, and processed for immunofluorescence studies with the primary NeuN/β-tubulin and NeuN/tyrosine hydroxylase (TH) antibodies. The soma area and number of intrinsic neurons in the ovarian stroma, surrounding follicles, corpus luteum, or cyst were evaluated. The intrinsic neurons were grouped in cluster-like shapes in ovarian structures. In senescent rats, the intrinsic neurons were mainly localized in the ovarian stroma and around the cysts. The number of neurons was lower in senescent rats than in young adult rats (p < 0.05), but the soma size was larger than in young adult rats. Immunoreactivity to TH indicated the presence of noradrenergic neurons in the ovary with the same characteristics as NeuN/β-tubulin, which indicates that they are part of the same neuronal group. Taken together, the findings indicate that the intrinsic neurons may be related to the loss of ovarian functions associated with aging.

Highlights

In mammals in the mid-life stage, an exponential decrease in the number of ovarian follicles correlates with the beginning of female subfertility, a process known as reproductive senescence
Intrinsic neurons were observed in the ovaries of all rats (Figs. 1, 2 and 3)
The ovaries from the 12 M group had atretic follicles and CL in regression, as well as ovarian cysts. The neurons in this stage were localized around the follicular cyst (Fig. 2), with a tendency to concentrate in the middle region of the ovary

Summary

Introduction

In mammals in the mid-life stage, an exponential decrease in the number of ovarian follicles correlates with the beginning of female subfertility, a process known as reproductive senescence. Once this event occurs, there is a decrease in viable oocytes. The decrease in follicles continues until 12 months old (middle-aged), the rats experience subfertile and infertile periods as they grow older (senescent) (Acuna et al 2009; Chavez-Genaro et al 2007). There are modifications in the ovarian configuration; mainly, cysts begin to appear when rats are 6 months old and, by the age of 14 months (senescent rat), large cysts increase in number and occupy most of the ovarian cortex (Acuna et al 2009)

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