Preservation of the primordial follicle pool in Oo<i>Pten</i>^−/− ovaries by rapamycin treatment.

Abstract

<p>(<b>A</b>) Prevention of the primordial follicle over-activation in Oo<i>Pten</i>^−/− mice by treatment with rapamycin. Rapamycin (5 mg/kg body weight) was injected daily into Oo<i>Pten</i>^−/− mice from postnatal day (PD) 4 to PD 22, and the ovaries were collected at PD 23 for morphological analysis. Ovaries from rapamycin-treated Oo<i>Pten</i>^−/− mice appeared smaller (c) than the ovaries from vehicle-treated Oo<i>Pten</i>^−/− mice (a). Scale bar = 50 µm. Clusters of primordial follicles were seen in rapamycin-treated Oo<i>Pten</i>^−/− mice at PD 23 (d, arrows) whereas all primordial follicles were activated in vehicle-treated Oo<i>Pten</i>^−/− mice at PD 23 (b, arrows). Scale bar = 50 µm. (<b>B</b>) Average numbers of total and primordial follicles in Oo<i>Pten</i>^+/+, Oo<i>Pten</i>^−/− (vehicle-treated), and Oo<i>Pten</i>^−/− (rapamycin-treated) ovaries at PD 23. Proportions of primordial follicles ± SEM (relative to the total number of follicles) are also shown. The proportion of primordial follicles in rapamycin-treated Oo<i>Pten</i>^−/− ovaries was 20±4.1%, which was smaller than the proportion in the Oo<i>Pten</i>^+/+ ovaries (70±3.1%). Three mice were used for each experimental group. Rapa, rapamycin. (<b>C</b>) Comparison of the rpS6 and Akt phosphorylation levels in the ovaries of vehicle- and rapamycin-treated Oo<i>Pten</i>^−/− mice. Rapamycin (5 mg/kg body weight) was injected daily into Oo<i>Pten</i>^−/− mice from PD 4 to PD 22, the ovaries were collected at PD 23 and homogenized, and immunoblotting was performed as described in <i>Materials and Methods</i>. Rapamycin injection effectively suppressed the level of phosphorylated rpS6 (p-rpS6) without affecting the level of phosphorylated Akt (p-Akt) in the ovaries of Oo<i>Pten</i>^−/− mice. Levels of total rpS6, Akt, and β-actin were used as internal controls.</p