Androgen receptor and calcitonin gene-related peptide in neurons of the genitofemoral nerve during testicular descent induced with human chorionic gonadotropin

BDNF is upregulated by androgen in the inguinal fat pad of immature mice and may regulate inguinoscrotal testicular descent

BACKGROUND

Androgens control rodent inguinoscrotal testicular descent during a "programming window" (E12-17). It is proposed that androgen masculinises the genitofemoral nerve, but the mechanism remains unknown. We investigate androgen receptor (AR)-containing target organs: inguinal fat pad (IFP) and mammary bud (MB), supplied by the genitofemoral nerve, hypothesizing that neurotrophic factors may retrogradely masculinise the GFN.

METHODS

The IFP, MB and bulbocavernosus (BC) muscle were collected at E12.5/E17.5 from androgen receptor knockout (ARKO) mice and wild-type (WT) littermates. Immunofluorescence and gene expression (RT-qPCR; n = 8/group) for Bdnf, active (TrkB) and inactive (truncated TrkB) receptors, Cntf and Cntf receptor were performed.

RESULTS

In the IFP at E12.5, ARKO TrkB mRNA expression was significantly downregulated compared to WT males (p < 0.0026). By E17.5, there was increased Bdnf expression (p < 0.0233). The MB had no differences at E12.5 and had regressed in WT males by E17.5. The BC had no differences at E12.5, but at E17.5 had significant upregulation of Bdnf expression in ARKO, compared to WT males. There were no differences in CNTF or CNTF receptor expression.

CONCLUSIONS

Androgen alters active TrkB and Bdnf expression in the IFP. IFP Bdnf signalling may regulate "masculinisation" of the GFN sensory nerves to indirectly control inguinoscrotal testicular descent.

IMPACT

Androgen mediates neurotrophin release in the inguinal fat pad in mice, which may facilitate normal testicular descent by masculinising the GFN by peripheral uptake of neurotrophin. This is the first study to examine the role of neurotrophins in testicular descent. This suggests novel steps in the mechanical process of normal testicular descent that may be abnormal in some children with undescended testes.

The area and attachment abnormalities of the gubernaculum in patients with undescended testes in comparison with those with retractile testes

PURPOSE

In order to evaluate the gubernaculum (GN) abnormalities quantitatively in patients with undescended testes (UDT), the area and attachment site of the gubernaculum were evaluated.

PATIENTS AND METHODS

Sixty-seven testes from 61 patients with an undescended testis treated in the past 11 years at our institution were examined. Using intraoperative photographs or DVDs, the area of the GN inside the processus vaginalis was measured, and the ratio to that of the testis was determined. When the GN was attached to the vas deferens, the GN distance from the testis was also measured, and the ratio to that of the transverse length of the testis (deviation index) was calculated. Reference values were obtained from 23 testes from 15 patients with mobile testes.

RESULTS

In cases with mobile testes, the GN attached to the bottom of the testis, and involved the lower pole of the epididymis. Even though the GN was attached to the bottom of the testis in 43 testes in the UDT patients (64 %), the GN was found to be elongated. The mean GN area ratio was 1.58 (1SD, 0.6) in the UDT cases, in comparison to 0.47 (0.2) in the cases with mobile testes. The GN was attached to the vas deferens in 24 testes (36 %). The deviation index was 1.34 (1.0), but the GN area ratio of these cases was 1.56 (0.7), which was similar to that of the GN attached to the bottom of the testis.

CONCLUSION

The present study revealed that an increase in the GN area ratio was the most common imaging abnormality in cases with UDT.

Androgen receptor (AR) physiological roles in male and female reproductive systems: lessons learned from AR-knockout mice lacking AR in selective cells

Androgens/androgen receptor (AR) signaling is involved primarily in the development of male-specific phenotypes during embryogenesis, spermatogenesis, sexual behavior, and fertility during adult life. However, this signaling has also been shown to play an important role in development of female reproductive organs and their functions, such as ovarian folliculogenesis, embryonic implantation, and uterine and breast development. The establishment of the testicular feminization (Tfm) mouse model exploiting the X-linked Tfm mutation in mice has been a good in vivo tool for studying the human complete androgen insensitivity syndrome, but this mouse may not be the perfect in vivo model. Mouse models with various cell-specific AR knockout (ARKO) might allow us to study AR roles in individual types of cells in these male and female reproductive systems, although discrepancies are found in results between labs, probably due to using various Cre mice and/or knocking out AR in different AR domains. Nevertheless, no doubt exists that the continuous development of these ARKO mouse models and careful studies will provide information useful for understanding AR roles in reproductive systems of humans and may help us to develop more effective and more specific therapeutic approaches for reproductive system-related diseases.

Androgen and estrogen receptor expression in the spinal segments of the genitofemoral nerve during testicular descent

AIM

During testicular descent (TD), the genitofemoral nerve (GFN) is masculinized by androgen. This study aimed to test whether androgen receptor (AR), estrogen receptor α (ERA), or estrogen receptor β (ERB) are expressed during TD in the GFN spinal segments and dorsal root ganglia (DRG) in normal and flutamide-treated rats.

METHODS

Time-mated Sprague-Dawley dams were injected with flutamide (75 mg/kg, subcutaneously (S/C) in sunflower oil) on embryonic (E) days 16 to 19. Embryonic and postnatal (P) male L1-2 spinal cord segments were collected (E16, E17, E19, P0, P2, and P4) in control and flutamide-treated groups (n = 5-10). Samples were fixed in 4% paraformaldehyde. Five-micrometer-thick sections were prepared immunohistochemically for AR, ERA, and ERB.

RESULTS

During TD, ERB was expressed in L1-2 DRG. Surprisingly, AR was not expressed in prenatal DRG, only after P2. There was no ERA expression. Flutamide had no effect on AR, ERB, or ERA expression in the L1-2 DRG during TD.

CONCLUSION

During the E window of androgen sensitivity, the GFN is not directly masculinized, with little AR expression and no change with flutamide over this period. Estrogen receptor β is expressed in the DRG during TD. However, its relevance is yet to be determined.