Spermatogenesis and sertoli cell activity in mice lacking sertoli cell receptors for follicle-stimulating hormone and androgen

Abstract

Spermatogenesis in the adult male depends on the action of FSH and androgen. Ablation of either hormone has deleterious effects on Sertoli cell function and the progression of germ cells through spermatogenesis. In this study we generated mice lacking both FSH receptors (FSHRKO) and androgen receptors on the Sertoli cell (SCARKO) to examine how FSH and androgen combine to regulate Sertoli cell function and spermatogenesis. Sertoli cell number in FSHRKO-SCARKO mice was reduced by about 50% but was not significantly different from FSHRKO mice. In contrast, total germ cell number in FSHRKO-SCARKO mice was reduced to 2% of control mice (and 20% of SCARKO mice) due to a failure to progress beyond early meiosis. Measurement of Sertoli cell-specific transcript levels showed that about a third were independent of hormonal action on the Sertoli cell, whereas others were predominantly androgen dependent or showed redundant control by FSH and androgen. Results show that FSH and androgen act through redundant, additive, and synergistic regulation of spermatogenesis and Sertoli cell activity. In addition, the Sertoli cell retains a significant capacity for activity, which is independent of direct hormonal regulation.

Fig 1

Gross and morphological appearance of testes from 8 week old mice. Semithin sections from testes of 8 week old Normal, FSHRKO, SCARKO and FSHRKO.SCARKO mice. The FSHRKO mice contained all stages of spermatogenesis although germ cell number was reduced. In SCARKO mice spermatogenesis progressed through meiosis but there was progressive loss of pachytene spermatocytes and few secondary spermatocytes or round spermatids were observed. In FSHRKO.SCARKO mice the tubules were of a smaller diameter with large numbers of Sertoli cells (black arrowheads) and smaller numbers of spermatogonia (red arrowheads). Spermatogonia entered meiosis but development stopped at early pachytene in most cells (yellow arrowhead). The bar represents 20μm.

Fig 2

Morphometric analysis Sertoli and germ cell numbers in 8 week old testes from control, FSHRKO, SCARKO and FSHRKO.SCARKO mice. Cell number were measured using the optical disector method. Results show the mean ± sem of 4 animals per group. Groups with different letter superscripts are significantly different. Where there was a significant interaction between the effects of the two gene knockouts this is indicated on the figure.

Fig 3

Morphometric analysis of germ cell types in 8 week old testes from control, FSHRKO, SCARKO and FSHRKO.SCARKO mice. Cell number were measured using the optical disector method. Results show the mean ± sem of 4 animals per group. Groups with different letter superscripts are significantly different.

Fig 4

Levels of Sertoli cell-specific mRNA transcripts in testes from 8 week old control, FSHRKO, SCARKO and FSHRKO.SCARKO mice. Transcripts levels were measured relative to an external standard by real-time PCR and corrected for Sertoli cell number as described in Methods. Results show the mean ± sem of 5 or 6 animals per group. Transcripts in A) showed no significant difference in expression per Sertoli cell between groups while transcripts in B) showed significant variation. In B) the groups with different letter superscripts are significantly different. Where there was a significant interaction between the effects of the two gene knockouts this is indicated on the figure.