Does proximal genitofemoral nerve division induce testicular maldescent or ascent in the rat?

The curious case of testicular descent: factors controlling testicular descent with a note on cryptorchidism

Background

The testicular descent is a uniquely complex process depending upon multiple factors like growth and reorganisation of the specific gonadal ligaments, hormones, etc., which interplay with each other. Though an unambiguous event, it is still laced with incredulity since the data interpretation were intermingled between different species creating more ambiguity in certain aspects of this process. In order to understand the aetiopathology of cryptorchidism the extensive study of the factors controlling the descent is necessitous.

Main body

Though testes originate in the abdomen, they migrate to an extra abdominal site the scrotum, which makes it vulnerable to pathological conditions associated with the descent. The hormones that play vital role in the first phase of descent are insulin-like hormone 3 (INSL3), Anti-müllerian hormone as well as testosterone, whereas androgens, genitofemoral nerve and its neurotransmitter calcitonin gene-related peptide (CGRP) influence the second phase. Despite the vast research regarding the complex nexus of events involving the descent there are disparities among the cross species studies. However all these discrepancies make testicular descent yet again fascinating and perplexing. Our aim is to provide a comprehensive review including recent advances which provides thorough coverage of anatomical and hormonal factors in the descent as well as cryptorchidism.

Conclusion

Though our understanding on testicular descent has evolved over the decades there still has obscurity surrounding it and the studies on the factors responsible for descent are becoming more intense with the time. Our knowledge on many factors such as INSL3 and CGRP is more established now; however, on the other hand the role of androgens still remains speculative. As the knowledge and understanding of the biological process of testicular descent increases it will pave ways to new treatment plans to treat cryptorchidism more effectively.

Perspectives in Pediatric Pathology, Chapter 14. Natural History of Undescended Testes

Cryptorchidism is one of the most frequent problems encountered in pediatric urology. Its causes, associated lesions, and prognosis in terms of fertility have been a source of interest and discrepancies for pediatric pathologists and urological surgeons.

Reasons for delayed orchiopexies in a korean tertiary care hospital

PURPOSE

Since the 1990s, it has been well known that orchiopexies should be performed by no later than 2 years of age. Nevertheless, studies from other countries report a substantial number of delayed orchiopexies. On the basis of an analysis of a tertiary care hospital database, we aimed to investigate the incidence of delayed orchiopexies performed in patients after 5 years of age and to understand the causes of such delays and the possible consequences.

MATERIALS AND METHODS

We retrospectively analyzed the surgical database of Seoul National University Hospital between 2004 and 2012 and detected patients who underwent orchiopexy later than 5 years of age. Reasons for delayed orchiopexies were studied and the possible consequences of delayed orchiopexies were assessed with respect to surgical difficulty and testicular volume.

RESULTS

We found 160 cases of delayed orchiopexies, which accounted for about 15% of all orchiopexies performed. Two major reasons for delay were related to the parents of the child: parental delay and parental request for the treatment of persistent retractile testis. Acquired cryptorchidism was found in 21 cases (13.1%), mainly associated with hypospadias. Surgical difficulty, especially owing to a short testicular cord, was encountered in 48 cases (30.2%), and a comparison with age-matched normative values showed substantially smaller testicular volume.

CONCLUSIONS

Despite well-established guidelines for the optimal age of surgery, 15% of orchiopexies were not performed at a proper time. Improved propagation of an optimal age limit is necessary to reduce the rate of delayed orchiopexies considering increases in surgical difficulty and potential testicular growth retardation.

Intrascrotal extratesticular neurofibroma as a possible cause of failed descent in ipsilateral testis

Intrascrotal extratesticular neurofibromas (IEN) often originate from genitofemoral nerve (GFN) and present as a paratesticular mass. Synchronous presence of IEN and undescended testis has not been reported previously. A 12-year-old boy with neurocutaneous syndrome and congenital giant melanocytic nevi along with IEN and ipsilateral undescended testis is presented, to discuss the underlying pathophysiology of failed testicular descent in the presence of IEN.

Acquired undescended testes in boys with hypospadias

PURPOSE

We determined the incidence of acquired undescended testes in boys with hypospadias.

MATERIALS AND METHODS

We retrospectively reviewed the records of 566 boys with hypospadias who were referred to our outpatient clinic between January 2000 and September 2009. Acquired undescended testes were defined as testes that were documented at the bottom of the scrotum at least once after birth by the pediatric urologist at our institution but were subsequently documented to have moved from a satisfactory scrotal position by the same pediatric urologist or an equally experienced pediatric urologist. However, this definition did not include undescended testes after inguinoscrotal surgery. We excluded boys with gender development disorders with testicular dysgenesis, those who underwent bilateral inguinoscrotal surgery and those without congenital cryptorchidism who were followed less than 3 months.

RESULTS

Of the 566 boys with hypospadias 100 met study exclusion criteria. Of the 466 boys included in analysis 29 (6.2%) had congenital cryptorchidism and 15 (3.2%) had acquired undescended testes. Urethroplasty was performed in 413 boys, including 91 with distal, 132 with mid and 181 with proximal hypospadias. The incidence of congenital cryptorchidism and acquired undescended testes in boys with proximal hypospadias was significantly higher than that in boys with other types of hypospadias (p = 0.03 and 0.001, respectively).

CONCLUSIONS

Boys with proximal hypospadias are at a higher risk for acquired undescended testes than those with other mild types of hypospadias. Thus, testicular location should be monitored regularly until after puberty.

Factors controlling testis descent

Descent of the testis from an intra-abdominal site in foetal life to an extracorporeal location after birth is a mandatory developmental process to ensure that the mature testis promotes normal spermatogenesis. The two phases of transabdominal and inguinoscrotal descent occur approximately during the first and last thirds of gestation respectively. Key anatomical events to release the testis from its urogenital ridge location and to guide the free gonad into the scrotum are the degeneration of the cranio-suspensory ligament and a thickening of the gubernaculum. Androgens play a role in both these processes, particularly with respect to enabling the testis to traverse the inguinal canal in the final phase of descent. Experiments in animals suggest that androgens mediate this effect via the release of calcitonin gene-related peptide by the genitofemoral nerve, but direct evidence for such a mechanism is lacking in humans. The transabdominal phase of descent is under the control of insulin-like 3 (INSL3), a product of the Leydig cells. Definitive evidence of its role in rodent testis descent is illustrated by the phenotype of bilateral cryptorchidism in Insl3-/- null mice. Circulating levels of INSL3 are higher in boys at puberty, are undetectable in girls and are lower in boys with undescended testes. A minority also have a mutation either in the INSL3 gene or affecting its receptor gene, relaxin/insulin-like family peptide receptor 2 (LGRF8). Other factors that may play a role in testis descent include the anti-Mullerian hormone and members of the HOX gene family. Evidence that the prevalence of undescended testis may be increasing provides a phenotypic readout for the effects of postulated chemicals in the environment interfering in some way with the action of factors that control testis descent. Epidemiological studies point to profound geographical variations in prevalence in countries such as Denmark and Finland. Associations have been found with levels of chemicals labelled as endocrine disruptors being higher in breast milk samples from mothers with cryptorchid boys when compared with controls. The adverse effects of these compounds (e.g. bisphenol A) can be replicated in the offspring of dams exposed during pregnancy. A sensitive marker of an anti-androgen effect of a compound is a reduction in the anogenital distance, an anthropometric measurement that is significantly greater in males compared with females. The observation of an association between the anogenital distance in infant boys and the level of pesticides in the urine of their mothers in late gestation indicates that this has the potential to be a useful surrogate marker of the effects of environmental chemicals on testis descent in human population studies. The rightful place for the testis at birth is in the scrotum in order to provide the temperature differential essential for normal spermatogenesis. Appropriate screening programmes and early surgical intervention are the prerequisites to ensure optimal fertility in adulthood and a considerably lessened risk of testis cancer.

Evaluation of genitofemoral nerve motor conduction in inguinoscrotal pathologies

AIM

Inguinoscrotal pathologies are commonly seen in childhood. The genitofemoral nerve (GFN) is responsible for sensitive innervations of scrotal region and the motor innervations of cremasteric muscle. GFN also innervates the afferent and efferent pathways of cremasteric reflex. A prospective study was performed to evaluate the possible relation between inguinoscrotal pathologies and GFN motor functions.

METHODS

Patients with inguinal hernia, hydrocele, undescended or retractile testicles, aged between 2-12 years were enrolled in the study. Bilateral latency and duration of GFN motor conductions (GFNMC) were obtained electrophysiologically by surface electrodes. GFNMC recordings of non-pathological sides were assessed as control group. Latency and duration of each group were compared with control group (Mann-Whitney U test). P values lower than .05 were considered significant.

RESULTS

Seventy-three electrophysiologic evaluations were investigated in inguinal hernia (n:18), hydrocele (n:9), undescended testicle (n:14), retractile testicle (n:12) and control (n:20) groups. There was no age difference between groups and controls. Latency was significantly prolonged in inguinal hernia group when compared with control group (P = .028). Although the latencies were shortened in undescended testicle group, no significant difference detected (P > .05).

CONCLUSION

Prolonged latencies in inguinal hernia may be a result of nerve trap caused by hernia sac. GFN motor functions showed no causative role in other inguinoscrotal pathologies. It can be also suggested that clinical features of other inguinoscrotal pathologies were not affected by GFN motor functions. Electrophysiological studies in younger age groups with large number of patients are needed to support our suggestions.

Cryptorchidism in LhrKO animals and the effect of testosterone-replacement therapy

BACKGROUND

The objective of the current study was to characterize the morphological and genetic basis of cryptorchidism.

METHODS AND RESULTS

We investigated cryptorchidism in LH receptor (Lhr) knockout (LhrKO) mice and how testosterone-replacement therapy (TRT) worked to correct the phenotype. The results revealed that while gubernacular development was indistinguishable between Lhr-null and wild-type animals until 7 days of age, it was subsequently severely impaired in null animals. This was due to a reduction in mesenchymal cell division, differentiation into cremaster muscle cells and their delayed maturation. While transcript levels of Hoxa10, Hoxa11, Desrt and Dll1 were indistinguishable, the levels of Notch1, Numb and Lgr8 in the gubernaculum and Insl3 in the testes were lower in Lhr-null than in wild-type siblings. The TRT, which completed testicular descent into the scrotum, corrected the morphological changes and the expression of Lgr8, Numb and Notch, but not Insl3, to wild-type levels. Transection of the genitofemoral nerve did not prevent the TRT effect.

CONCLUSION

In summary, cryptorchidism in Lhr-null animals was caused by defects in the gubernacular development due to testosterone deficiency. TRT reversed all the morphological and gene expression changes except Insl3, suggesting that testosterone, not INSL3, secreted by Leydig cells, facilitates the completion of testicular descent.