Direct action through the sertoli cells is essential for androgen stimulation of spermatogenesis

Abstract

Androgens act to stimulate spermatogenesis through androgen receptors (ARs) on the Sertoli cells and peritubular myoid cells. Specific ablation of the AR in either cell type will cause a severe disruption of spermatogenesis. To determine whether androgens can stimulate spermatogenesis through direct action on the peritubular myoid cells alone or whether action on the Sertoli cells is essential, we crossed hypogonadal (hpg) mice that lack gonadotrophins and intratesticular androgen with mice lacking ARs either ubiquitously (ARKO) or specifically on the Sertoli cells (SCARKO). These hpg.ARKO and hpg.SCARKO mice were treated with testosterone (T) or dihydrotestosterone (DHT) for 7 d and testicular morphology and cell numbers assessed. Androgen treatment did not affect Sertoli cell numbers in any animal group. Both T and DHT increased numbers of spermatogonia and spermatocytes in hpg mice, but DHT has no effect on germ cell numbers in hpg.SCARKO and hpg.ARKO mice. T increased germ cell numbers in hpg.SCARKO and hpg.ARKO mice, but this was associated with stimulation of FSH release. Results show that androgen stimulation of spermatogenesis requires direct androgen action on the Sertoli cells.

Figure 1

Localization of AR expression. Immunohistochemistry was used to localize AR expression in adult testes from hpg (A), hpg.SCARKO (B), hpg.ARKO (C), and normal mice (D). In the hpg testis, ARs were clearly present in the PTMs (black arrows) and interstitial tissue with lighter staining apparent in the Sertoli cells (white arrows, cells identified by their nuclear shape and more prominent nucleolus). In hpg.SCARKO mice, there was clear staining for ARs in the PTMs (black arrows) and interstitial tissue, whereas no specific staining was seen in the hpg.ARKO mice. Apparent staining in the tubules is background staining. In normal mice, AR expression was apparent in Sertoli cells, PTMs, and interstitial tissue. Bar, 20 μm.

Figure 2

Effect of androgen on testis volume (A), tubule diameter (B), and seminal vesicle weight (C) in hpg, hpg.SCARKO, and hpg.ARKO mice. Adult mice were treated with T or DHT for 7 d. Results show the mean ± sem for three to six animals per group in A and B and nine to 36 animals per group in C. Within a particular animal type, groups with different letter superscripts were significantly (P < 0.05) different.

Figure 3

Semithin sections showing the effect of androgen on testicular morphology in hpg, hpg.SCARKO, and hpg.ARKO mice. In untreated animals, spermatogenesis was severely disrupted with only spermatogonia and some spermatocytes present. Treatment with T increased germ cell numbers in all mice, although the effect was most marked in the hpg. Treatment with DHT increased germ cell number only in the hpg. In the hpg.ARKO group, black arrows indicate the presence of microliths (13). Bar, 20 μm.

Figure 4

Effect of androgen on Sertoli cell number in hpg, hpg.SCARKO, and hpg.ARKO mice. Adult mice were treated with T or DHT for 7 d and cell numbers counted as described in Materials and Methods. Results show the mean ± sem for three to six animals per group. Within a particular animal type, there were no significant differences in Sertoli cell number.

Figure 5

Effect of androgen treatment on the number of total germ cells (A), spermatogonia (B), spermatocyte (C), and spermatids (D) in hpg, hpg.SCARKO, and hpg.ARKO mice. Adult mice were treated with T or DHT for 7 d and cell numbers counted as described in Materials and Methods. Results show the mean ± sem for three to six animals per group. Within a particular animal type, groups with different letter superscripts were significantly (P < 0.05) different. No statistical analysis was applied to spermatid numbers. ND, Not detected.

Figure 6

Serum levels of FSH in hpg, hpg.SCARKO, and hpg.ARKO males treated with T or DHT for 7 d. Results show values from individual animals in each group. The effect of testosterone was significant (P < 0.05) in all three groups.