Food restriction during pregnancy and female offspring fertility: adverse effects of reprogrammed reproductive lifespan

Abstract

Background: Food restriction during pregnancy can influence the health of the offspring during the adulthood. The aim of the present study was to examine the effect of maternal food restriction (MFR) on the reproductive performance in female rat offspring from the first (FR1) and second (FR2) generations.

Methods: Adult virgin Wistar female rats were given free access to tap water and were fed ad libitum on standard rodent chow, were mated with virgin adult males, and then were randomly divided into two groups: controls (that was fed ad libitum ) and food-restricted group (FR, that was given only 50% of ad libitum food throughout gestation). Their first (FR1) and the second (FR2) generation of offspring were fed ad libitum and sacrificed before puberty and at adulthood. Their ovaries were removed and their histology evaluated by estimating the number of follicles (total and at various stages of folliculogenesis), and the presence of multi-nuclei oocytes and multi-oocyte follicles.

Results: Total number of ovarian follicles was lower in FR1 females at week 4 in comparison with controls, while it was not different in FR2 females vs.

Controls: The number of the primordial follicle was lower in FR1 and FR2 females vs. controls at both week 4 and at week 8. When compared to the controls, the follicles containing multi-nuclei oocytes were more frequent in ovaries from FR1 and FR2 females at week 4, and higher and lower respectively in ovaries form FR1 and FR2 females at week 8.

Conclusion: MFR affects ovarian histology by inducing the development of abnormal follicles in the ovaries in first and second generation offspring. This finding could influence the ovarian function resulting in an early pubertal onset and an early decline in reproductive lifespan.

Keywords: Follicle; Food restriction; Oocyte; Ovary; Pregnancy.

Fig. 1

Effect of MFR on ovarian weight results in a significant reduction in 8-week-old FR2 females when compared to controls (P = 0.0003), and to FR1 females (P = 0.0011); no effect is observed in 4-week-old females

Fig. 2

Effect of MFR on the number of follicles per section of ovarian tissue. a Total number of follicles: MFR significantly affects the total number of follicles in ovaries from FR1 females at 4 weeks (P = 0.0006) and 8 weeks (P = 0.0485), and from FR2 females at 8 weeks (P = 0.0013). The total number of follicles from FR2 at week 4 is higher vs. FR females (P = 0.0020), whereas it is lower in FR2 females at week 8 compared to FR females (P = 0.0074). b Primordial follicles: significant effect of MFR on the number of primordial follicles in FR1 and FR2 females at week 4 when compared to control (P = 0.0014 and P < 0.0001, respectively) and in FR2 females at week 8 (P = 0.0002). The total number of primary follicles from FR2 at both week 4 and 8 is significantly lower when compared to FR1 females (P = 0.0020 and P = 0.003, respectively). c Primary follicles are significantly higher in number in ovaries of 4-week-old females in both FR1 and FR2 vs. controls (P = 0.034 and P = 0.003). At week 8, FR1 females have significantly higher number of primary follicles vs. control (P = 0.0072), whereas FR2 females have significantly lower number of primary follicles vs. FR1 (P = 0.0014). d Secondary follicles: FR1 females at week 4 have significantly lower number of secondary follicles vs. control (P = 0.0002) and vs. FR2 (P = 0.001), whereas at week 8 FR2 have significantly higher number of secondary follicles vs. FR1 females (P = 0.0002). e Antral follicles: MFR has the same effect as in secondary follicles, except for a significant increase in FR2 females vs. control at week 8 (P = 0.008). f MOFs: The number of MOFs is significantly higher in ovaries from FR and FR2 females vs. control at week 4 (P = 0.0044 and P = 0.006, respectively); it is also significantly higher in FR1 females at week 8 (P = 0.0013), and again significantly lower in ovaries from FR2 females vs. control (P = 0.0075). FR2 females at week 8 have significantly lower number of MOFs when compared to FR1 females (P < 0.0001). All results are given as mean ± SD; P < 0.05, *FR1 vs. controls (C) and FR2 vs. controls, * with error bars: FR1 vs. FR2

Fig. 3

Hematoxylin and eosin staining of paraffinized ovarian sections from FR1 and FR2 females showing the generation of MOFs. a Ovaries from FR1 and FR2 females are mainly characterized by many growing follicles that are adjacent to each other, indicating their fusion. b-d Follicles in the process of merging (arrowheads); we can see in (d) the displacement of the oocyte from one follicle into the second one. e Primordial follicle with two oocytes. f primordial follicle with three oocytes. g Primary follicle with two oocytes, (h) Primary follicle with three oocytes. i Secondary follicle with two oocytes. (J) Antral follicle with two oocytes; (k) Antral follicle with three oocytes; (l) Antral follicle merging with an early secondary follicle (arrowhead), the large arrow is showing the oocyte position of the antral follicle. Scale bar = 200 μm

Fig. 4

Hematoxylin and eosin staining of paraffinized ovarian sections from FR1 and FR2 females showing the generation of MNOFs. a Primordial follicle with two nuclei- oocyte. b Secondary follicle containing one oocyte with two proportional nuclei (c) Secondary follicle containing one merged oocyte with four disproportional nuclei. d Secondary follicle with two oocytes that are very close to each other, suggesting that they will probably fuse soon to form a heterokaryon. e Secondary follicle containing two semi-fused oocytes (arrowhead). f The same secondary follicle in (e) but at another level of section. Scale bar = 200 μm