Early Life Exposure to the Mycotoxin Fumonisin B1 and Developmental Programming of the Ovary of the Offspring: The Possible Role of Autophagy in Fertility Recovery

Abstract

Mycotoxins are produced by more than one hundred fungi and produce secondary metabolites that contaminate various agricultural commodities, especially rice and corn. Their presence in the food chain is considered a serious problem worldwide. In recent years, a link between exposure to mycotoxins and impaired fertility has been suggested. Consequently, it has become vital to investigate the interactive effects of these mycotoxins on ovarian function. In this study, we investigated the intergenerational effects of mycotoxin fumonisin B1 (FB1) on ovarian structure and function. Virgin Wistar albino female rats were separated into control and FB1 treatment groups and examined from day 6 of pregnancy until delivery (20 and 50 mg/kg/day). The obtained females of the first (F1) and second generations (F2) were euthanized at 4 weeks of age, and ovary samples were collected. We found that the ovary weight index increased with the high dose of treatment (50 mg/kg/day) among both F1 and F2, similar to that observed in polycystic ovary syndrome. As expected, FB1 at a high dose (50 mg/kg) reduced the number of primordial follicles in F1 and F2, leading to an accelerated age-related decline in reproductive capacity. Moreover, it reduced the fertility rate among F1 females by affecting follicle growth and development, as the number of secondary and tertiary follicles was decreased. Histopathological changes were evidenced by the altered structures of most of the growing follicle oocytes, as revealed by a thinning irregular zona pellucida and pyknosis in granulosa cells. These findings are concomitant with steroidogenesis- and folliculogenesis-related gene expression, as evidenced by the decrease in CYP19 activity and estrogen receptor beta (ESR2) gene expression. Additionally, GDF-9 mRNA levels significantly decreased, and IGF-1 mRNA levels significantly increased. However, the results from the ovaries of the F2 treatment groups were different and unexpected. While there was no significant variation in CYP19 compared to the control, ESR2 significantly increased, leading to stereological and histopathological changes similar to those of the control, except for some altered follicles. The hallmark histological feature was the appearance of vacuolar structures within the oocyte and between granulosa cell layers. Interestingly, the autophagic marker LC3 significantly increased in F2 offspring, whereas this protein significantly decreased in F1 offspring. Therefore, we suggest that the promotion of autophagy among the ovaries of F2 offspring may be considered a recovery mechanism from the effect of prenatal FB1 exposure. Thus, autophagy corrected the effect of FB1 during the early life of F1 females, leading to F2 offspring with ovarian structure and function similar to those of the control. However, the offspring treated females may have early ovarian aging because their ovarian pool was affected.