Cryptorchidism in common eutherian mammals

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 insulinlike 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 Insl3K/K 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 con...

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“…1) (12). The human testis is descended generally at birth, in common with the rabbit, pig and horse.…”

Section: Introductionmentioning

confidence: 99%

Factors controlling testis descent

Hughes¹,

Acerini²

2008

European Journal of Endocrinology

142

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“…It is generally agreed that testicular descent in mammals occurs in two distinct steps with different anatomy and hormonal regulation (Hutson, 1985;Amann and Veeramachaneni, 2007;Foresta et al, 2008;Hughes and Acerini, 2008;Feng et al, 2009). In the first, or transabdominal phase, the genitoinguinal ligament, also known as the ''gubernaculum,'' undergoes enlargement or the ''swelling reaction.''…”

mentioning

confidence: 99%

Development of the Gubernaculum During Testicular Descent in the Rat

Nation

Buraundi

Farmer

et al. 2011

The Anatomical Record

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Gubernacular elongation during inguinoscrotal testicular descent and cremaster muscle development remains poorly described in mammals. The role of the genitofemoral nerve (GFN) remains elusive. We performed detailed histological analysis of testicular descent in normal rats to provide a comprehensive anatomical description for molecular studies. Fetuses and neonatal male offspring (5-10 per group) from time-mated Sprague-Dawley dams (embryonic days 15, 16, and 19; postnatal days 0, 2, and 8) were prepared for histology. Immunohistochemistry was performed for nerves (Class III tubulin, Tuj1) and muscle (desmin). At embryonic days 15 and 16, the gubernaculum and breast bud are adjacent and both supplied by the GFN. By embryonic day 19, the breast bud has regressed and the gubernacular swelling reaction is completed. Postnatally, the gubernacular core regresses, except for a cranial proliferative zone. The cremaster is continuous with internal oblique and transversus abdominis. By postnatal day 2 (P2), the gubernaculum has everted, locating the proliferative zone caudally and the residual mesenchymal core externally. Eversion creates the processus vaginalis, with the everted gubernaculum loose in subcutaneous tissue but still remote from the scrotum. By P8, the gubernaculum has nearly reached the scrotum with fibrous connections attaching the gubernaculum to the scrotal skin. A direct link between GFN, gubernaculum, and breast bud suggests that the latter may be involved in gubernacular development. Second, the cremaster muscle is continuous with abdominal wall muscles, but most of its growth occurs in the distal gubernacular tip. Finally, gubernacular eversion at birth brings the cranial proliferative zone to the external distal tip, enabling gubernacular elongation similar to a limb bud. Anat Rec, 294:1249Rec, 294: -1260Rec, 294: , 2011. V V C 2011 Wiley-Liss, Inc.

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“…En relación al saco cremastérico, Wensing (1986) describió esta estructura en la rata como un saco bilaminar, formado por dos capas de musculatura cremastérica que provienen de la prolongación de los mús-culos oblicuo interno y transverso del abdomen. En animales de compañía, animales de abasto y en el hombre es muy reducido (Amann & Veeramachaneni, 2007), en cambio en el conejo es de gran desarrollo, ya que rodea al testículo en toda su superficie (Smok). La túnica albugínea es visible sólo microscópicamente, está formada por tejido conjuntivo denso y fibras musculares lisas.…”

Section: Introductionunclassified

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Túnicas Testiculares Durante la Fase de Reposo y Actividad Sexual del Conejo Macho (Oryctolagus cuniculus)

et al. 2010

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SMOK, S.; FLORES, E.; CATTANEO, G.; ADARO, L. & ROJAS, M.Túnicas testiculares durante la fase de reposo y actividad sexual del conejo macho (Oryctolagus cuniculus). Int. J. Morphol., 28(2):595-599, 2010. RESUMEN:La domesticación del conejo (Oryctolagus cuniculus), ha permitido el paso de una reproducción de tipo anual a una de tipo no estacional, observándose pariciones durante todo el año. Sin embargo, existen parámetros reproductivos que nos indican que aún existe cierta estacionalidad, por ejemplo, la ubicación testicular, correspondiendo el conejo a un estacional de días largos. El presente estudio analiza la morfología de testículos y epidídimos, comparando la bioestructura de las cubiertas testiculares del conejo macho (Oryctolagus cuniculus), durante los meses de Enero y Septiembre. Para esto, se utilizaron seis conejos machos, tres correspondientes al mes de Enero, y tres al mes de Septiembre. Los ejemplares se encontraban clínicamente sanos y sexualmente maduros, de peso promedio 2,5 kg. Se obtuvieron los testículos junto a sus respectivos sacos escrotales, los que se procesaron mediante técnica histológica corriente y tricrómico. Se consignó el Indice espermatogénico (IE) e índice celular interticial (ICI) según Grocock & Clarke. Durante el mes de Enero, se evidenció una clara disminución de los parámetros reproductivos testiculares, con un IE =3, y un ICI=4. Por el contrario, durante el mes de Septiembre, se observó un IE=5 y ICI=5. La túnica albugínea mostró diferencias de espesor en ambos períodos. Sin embargo, se encontró un gran desarrollo de la musculatura cremastérica en ambas etapas, por lo que se concluye que ésta última no sufre atrofia durante el mes de Enero, atribuible posiblemente, a la criptorquidia facultativa que posee esta especie.PALABRAS CLAVE: Túnica Albugínea; Saco cremastérico; Estacionalidad; Testículo. INTRODUCCIÓNNo obstante la domesticación que ha sufrido el conejo (Oryctolagus cuniculus), y al cambio de su estatus de reproductor estacional a continuo, continúa siendo un criptórquido facultativo, una estrategia reproductiva relacionada con cambios en la ubicación testicular.Murray (2006) describe el escroto del conejo como dos hemiescrotos que alojan los testículos, y se encuentran craneal al pene. Las cubiertas testiculares fueron descritas por Smok (2009), las cuales de superficial a profundidad se componen por: 1) dartos; 2) fascia espermática externa, constituida por varias capas de tejido conjuntivo denso; 3) saco cremastérico, que corresponde a una capa formada por fibras musculares de tipo estriado, muy amplia en comparación con el resto de los componentes observados; 4) fascia espermática interna, la cual es imperceptible; 5) lámina parietal de la túnica vaginal; 6) lámina visceral de la túnica vaginal, ambas separadas por la cavidad vaginal y, 7) túnica albugínea. Finalmente se ubican los testículos, los cuales presentan una posición horizontal al cuerpo.En este trabajo, nos enfocaremos principalmente en las variaciones estacionales dentro del saco cremastérico y la ...

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Cryptorchidism in common eutherian mammals

Cited by 156 publications

References 88 publications

Factors controlling testis descent

Factors controlling testis descent

Development of the Gubernaculum During Testicular Descent in the Rat

Túnicas Testiculares Durante la Fase de Reposo y Actividad Sexual del Conejo Macho (Oryctolagus cuniculus)

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