Sodium selenite improves folliculogenesis in radiation-induced ovarian failure: a mechanistic approach.

Radiotherapy is a major factor contributing to female infertility by inducing premature ovarian failure (POF). Therefore, the need for an effective radioprotective agent is evident. The present study investigated the mechanism of potential radioprotective effect of sodium selenite on radiation-induced ovarian failure and whether sodium selenite can stimulate in-vivo follicular development in experimental rats. Immature female Sprague-Dawely rats were either exposed to gamma-radiation (3.2 Gy, LD(20)), once and/or treated with sodium selenite (0.5 mg/kg), once daily for one week before irradiation. Follicular and oocyte development, apoptotic markers, proliferation marker as well as oxidative stress markers were assessed 24-h after irradiation. In addition, fertility assessment was performed after female rats became completely mature at two months of age. Sodium selenite significantly enhanced follicular development as compared to the irradiated group. Sodium selenite significantly reversed the oxidative stress effects of radiation that was evidenced by increasing in lipid peroxide level and decreasing in glutathione level, and glutathione peroxidase (GPx) activity. Assessment of apoptosis and cell proliferation markers revealed that caspase 3 and cytochrome c expressions markedly-increased, whereas, PCNA expression markedly-decreased in the irradiated group; in contrast, sodium selenite treatment prevented these alterations. Histopathological examination further confirmed the radioprotective efficacy of sodium selenite and its in-vivo effect on ovarian follicles' maturation. In conclusion, sodium selenite showed a radioprotective effect and improved folliculogenesis through increasing ovarian granulosa cells proliferation, estradiol and FSH secretion, and GPx activity, whilst decreasing lipid peroxidation and oxidative stress, leading to inhibition of the apoptosis pathway through decreasing the expressions of caspase 3 and cytochrome c

Immunohistochemical localization of caspase 3.

<p>(A & B) Expression of caspase 3 in ovaries and uterus of control groups shows a minimal degree. <b>(</b>C & D) Expression of caspase 3 in ovaries and uterus treated with sodium selenite (0.5 mg/kg) alone shows a minimal degree. (E & F) Expression of caspase 3 in ovaries and uterus exposed to <i>γ</i>-radiation (3.2 Gy) shows an extensive degree. (G & H) Expression of caspase 3 in ovaries and uterus treated with sodium selenite (0.5 mg/kg) for one week before being exposed to <i>γ</i>-radiation (3.2 Gy) was limited. (I & J): Ovarian and uterine negative controls omitting primary antibody. Scale bar, 10 <i>µ</i>m. (K): Quantification of ovarian caspase 3 staining represents the percent of immunopositive cells to the total area of the microscopic field (20×); averaged across 7 fields for each rat section. Each column represents the mean ± SD of at least three independent experiments. a or b: Statistically significant from control or irradiated group, respectively at P<0.05 using one-way ANOVA followed by Tukey–Kramer as a post-hoc test.</p

Representative photomicrographs of hematoxylin and eosin-stained ovarian tissue sections.

<p>Histological sections of control (A and B) and sodium selenite (C and D) treated ovaries exhibit similar organization, with different stages of growing follicles (blue arrows). Compared with controls, <i>γ</i>-irradiated ovaries (E and F) have few, if any, resting oocytes in the cortex with severe hemorrhage (black arrow). Many oocytes in small primary follicles are degenerating in irradiated ovaries. (G and H) Sections taken from ovaries of rats exposed to <i>γ</i>-irradiation and pre-treated with sodium selenite show the apparent normal structure of the ovary, with multiple types of ovarian follicles. Scale bar, 10 <i>µ</i>m. GF: Graffian follicle, S: Stroma.</p

Effect of sodium selenite injection (SS, 0.5 mg/kg, i.p.; once daily for 1 week) and/or whole body-irradiation on ovarian and uterine weights.

<p>Data expressed as Mean ± SD.</p><p>a or b: Significantly different from control or radiation group, respectively at P<0.05 using one-way ANOVA followed by Tukey–Kramer as a post-hoc test.</p

Representative photomicrographs of hematoxylin and eosin-stained uterine tissue sections.

<p>(A) Section taken from uterus of control rat and (B) Section taken from the uterus of sodium selenite treated rat show normal mucosal lining epithelium (blue arrow) with multiple glands (black arrow). (C) Section taken from the uterus of rats subjected to <i>γ</i>-radiation shows high degeneration of the mucosal epithelium with vacuole appearance (red arrow). (D) Section taken from the uterus of rats subjected to <i>γ</i>-radiation and pre-treated with sodium selenite shows regeneration of the glandular and luminal epithelium with intact structure. Scale bar, 10 <i>µ</i>m. le: luminal epithelium, ge: glandular epithelium, S: stroma.</p

Morphometric analysis of ovarian follicle populations.

<p>Numbers of (A) primordial, (B) preantral, (C) antral and (D) atretic ovarian follicles was expressed as a percentage of control in each follicle type. Follicle counts were performed on histological sections as described in Materials and Methods. Bars represent the mean ± SD of at least three independent experiments. a or b: Statistically significant from control or irradiated group, respectively at P<0.05. Data were analyzed by one-way ANOVA followed by Tukey–Kramer as a post-hoc test.</p

Circulating hormone levels.

<p>Changes in serum levels of FSH (A) and Estradiol (B), expressed as a percentage of control, after sodium selenite administration in <i>γ</i>-radiation subjected rats. Values are given as mean ± SD. a or b: Statistically significant from control or radiation group, respectively at P<0.05 using one-way ANOVA followed by Tukey–Kramer as a post-hoc test.</p

Reproductive performance of control, irradiated and selenite treated females.

<p>Fecundability was expressed as a percentage of pregnant females among mated females. Fecundity was expressed as the number of pups per mated females. Fecundity values represent the median; they were compared by Kruskal-Wallis’s test followed by Dunn’s multiple comparisons as a post-hoc test, and differences were considered significant when P<0.05. a or b: Significantly different from control or radiation group, respectively at P<0.05.</p

Effect of sodium selenite (SS, 0.5 mg/kg, i.p.; once daily for 1 week) on oxidative stress markers in rats subjected to a single dose whole-body irradiation (3.2 Gy).

<p>Data expressed as Mean ± SD.</p><p>a or b: Significantly different from control or radiation group, respectively at P<0.05, using one-way ANOVA followed by Tukey–Kramer as a post-hoc test. Abbreviations: GSH, reduced glutathione; GPx, glutathione peroxidase; MDA, malondialdehyde.</p

Immunohistochemical localization of cytochrome c.

<p>(A & B) Sections of ovaries and uterus of control rats show a minimal degree of cytochrome c expression. (C & D) Sections of ovaries and uterus treated with sodium selenite (0.5 mg/kg) alone show a minimal degree of cytochrome c expression. (E & F) Sections of ovaries and uterus exposed to <i>γ</i>-radiation (3.2 Gy) show extensive cytochrome c expression. (G & H) Sections of ovaries and uterus treated with sodium selenite (0.5 mg/kg) and exposed to <i>γ</i>-radiation (3.2 Gy) show limited cytochrome c expression. (I & J): Sections of ovarian and uterine negative controls omitting primary antibody. Scale bar, 10 <i>µ</i>m. (K): Quantification of ovarian cytochrome c staining represents the percent of immunopositive cells to the total area of the microscopic field (20×); averaged across 7 fields for each rat section. Each column represents the mean ± SD of at least three independent experiments. a or b: Statistically significant from control or irradiated group, respectively at P<0.05 using one-way ANOVA followed by Tukey–Kramer as a post-hoc test.</p