Molecular signals governing cremaster muscle development: clues for cryptorchidism

An overview on androgen-mediated actions in skeletal muscle and adipose tissue

Androgens are a class of steroid hormones primarily associated with male sexual development and physiology, but exert pleiotropic effects in either sex. They have a crucial role in various physiological processes, including the regulation of skeletal muscle and adipose tissue homeostasis. The effects of androgens are mainly mediated through the androgen receptor (AR), a ligand-activated nuclear receptor expressed in both tissues. In skeletal muscle, androgens via AR exert a multitude of effects, ranging from increased muscle mass and strength, to the regulation of muscle fiber type composition, contraction and metabolic functions. In adipose tissue, androgens influence several processes including proliferation, fat distribution, and metabolism but they display depot-specific and organism-specific effects which differ in certain context. This review further explores the potential mechanisms underlying androgen-AR signaling in skeletal muscle and adipose tissue. Understanding the roles of androgens and their receptor in skeletal muscle and adipose tissue is essential for elucidating their contributions to physiological processes, disease conditions, and potential therapeutic interventions.

Comparison of Laparoscopic Orchiopexy and Traditional Inguinal Incision Orchiopexy for Palpable Undescended Testes in Cryptorchidism

Background: Laparoscopic orchiopexy (LO) has become a standard procedure for the treatment of nonpalpable undescended testes (UDT). LO for palpable UDT is still controversial. The aim of this study is to explore the method and effect of LO procedure for palpable UDT in children suffering from cryptorchidism. Methods: A retrospective study was performed for LO and traditional inguinal incision orchiopexy (TIO) for palpable UDT. A total of 291 children were enrolled, and they were aged 9-96 months with either left- or right-side palpable inguinal canalicular testes. Patients with testes that were nonpalpable, ectopic, and retractable were excluded. One hundred seventy patients received LO and 121 patients received TIO. Patient age, operative time, and clinical outcomes were reviewed. Independent t-test and Fisher's exact test were performed by SPSS 25.0 software. Results: The mean operative time (30.77 ± 6.02 minutes versus 44.76 ± 6.70 minutes) and postoperative normal activity time (1.25 ± 0.43 days versus 2.48 ± 0.68 days) of LO were significantly shorter than those of TIO group (P < .05). Forty-seven of 49 cases (95.9%) aged <1 year successfully achieved LO. Conclusion: LO is an appropriate choice for palpable UDT, especially in younger children aged <2 years. The success rate of LO decreased with age.

An immunohistochemical analysis of the effects of androgen receptor knock out on gubernacular differentiation in the mouse

AIM

Cryptorchidism affects 2%-4% of newborn boys and causes infertility and cancer. While normal androgen function is required for successful inguinoscrotal descent, its exact role on gubernacular morphology remains unidentified. We aimed to decipher the effect of androgen blockade on the gubernaculum and surrounding structures.

METHODS

Genetically modified mice with androgen receptor knock out (ARKO) were sectioned at ages E17, D0, and D2 for immunohistochemical analysis and D4 for morphological analysis (with ethical approval; A644). Mutants and control littermates were labeled with Ki67, Desmin, and Pax7 to identify the degree of gubernaculuar eversion and the composition of the growth center in the gubernaculum, using light or confocal microscopy.

RESULTS

Androgen blockade prevented gubernacular eversion in all animals aged between E17 and D2 when compared to wild types. Furthermore, a growth center was visible, as indicated by a 'swirl' of immature fibroblasts, in D2 animals but was absent in ARKO mice. Moreover, the gubernacular cord was seen to increase in ARKO mice when compared to wild types and increased in size with age. There were no labeling differences in the antibodies tested for gubernacular differentiation.

CONCLUSION

Gubernacular eversion in rodents prior to inguinoscrotal migration was androgen dependent, as well as maintenance of gubernacular cord length. This study shows that androgen blockade causes cryptorchidism in mice by preventing gubernacular eversion and possibly by preventing shortening of the gubernacular cord. Altering the morphology of the gubernaculum in response to androgen clearly contributes to the clinical problem of cryptorchidism.

Genome-wide screening for smallest regions of overlaps in cryptorchidism

Cryptorchidism is a urogenital abnormality associated with increased rates of testicular neoplasia and impaired spermatogenesis. The field is facing expansion of genomics data; however, it lacks protocols for biomarker prioritization. Identification of smallest regions of overlap (SRO) presents an approach for candidate gene identification but has not yet been systematically conducted in cryptorchidism. The aim of this study was to conduct a genome-wide screening for SRO (GW-SRO) associated with cryptorchidism development. We updated the Cryptorchidism Gene Database to version 3, remapped genomic coordinates of loci from older assemblies to the GRCh38 and performed genome-wide screening for overlapping regions associated with cryptorchidism risk. A total of 73 chromosomal loci (68 involved in chromosomal mutations and five copy number variations) described in 37 studies associated with cryptorchidism risk in humans were used for SRO identification. Analysis resulted in 18 SRO, based on deletions, duplications, inversions, derivations and copy number variations. Screening for SRO was challenging owing to heterogeneous reporting of genomic locations. To our knowledge, this is the first GW-SRO study for cryptorchidism and it presents the basis for further narrowing of critical regions for cryptorchidism and planning functional experiments. The developed protocol could also be applied to other multifactorial diseases.

Neurotrophin signaling in a genitofemoral nerve target organ during testicular descent in mice

BACKGROUND/AIM

It has been proposed that androgens control inguinoscrotal testicular descent via release of calcitonin gene-related peptide (CGRP) from a masculinised genitofemoral nerve (GFN). As there are androgen receptors in the inguinoscrotal fat pad (IFP) during the window of androgen sensitivity (E14-17 in mouse embryos), we tested the hypothesis that neurotrophins in the IFP may masculinise the sensory fibers of the GFN supplying the gubernaculum and IFP prior to gubernacular migration.

METHODS

Androgen-receptor knockout (ARKO) and wild-type (WT) mouse embryos were collected at E17, with ethical approval (AEC 734). Sagittal sections of IFP, mammary area and bulbocavernosus (BC) muscle were processed for standard histology and fluorescent immunohistochemistry for ciliary neurotrophic factor (CNTF), ciliary neurotrophic factor receptor (CNTFR) and cell nuclei (DAPI).

RESULTS

In the ARKO mouse CNTFR immunoreactivity (CNTFR-IR) was increased in the IFP but decreased in BC. Perinuclear staining of CNTF-IR was seen in mouse sciatic nerve but only weakly in IFP. In the mammary area, also supplied by GFN, there were no differences in IR staining.

CONCLUSION

This study found CNTFR-IR in the IFP was negatively regulated by androgen, suggesting that CNTF signaling may be suppressed in GFN sensory nerves to enable CGRP expression for regulating gubernacular migration in the male, but not the female. The indirect action of androgen via the GFN required for testicular descent may be one of the sites of anomalies in the putative multifactorial cause of cryptorchidism.