A reevaluation of the mechanism of testicular descent: reasons for failed descent or ascent

Clinically Differentiated Abnormalities of the Architecture and Expression of Myosin Isoforms of the Human Cremaster Muscle in Cryptorchidism and Retractile Testis

AIM

To describe architecture and expression of myosin isoforms of the human cremaster muscle (CM) and to individuate changes in clinically differentiated abnormalities of testicular descent: cryptorchidism or undescended testis (UDT) and retractile testis (RT).

BACKGROUND

The CM is a nonsomitic striated muscle differentiating from mesenchyme of the gubernaculum testis. Morphofunctional and molecular peculiarities linked to its unique embryological origin are not yet completely defined. Its role in abnormalities of testicular descent is being investigated.

SUBJECTS AND METHODS

Biopsy samples were obtained from corrective surgery in cases of cryptorchidism, retractile testis, inguinal hernia, or hydrocele. Muscle specimens were processed for morphology, histochemistry, and immunohistology.

RESULTS AND CONCLUSIONS

The CM differs from the skeletal muscles both for morphological and molecular characteristics. The presence of fascicles with different characterization and its myosinic pattern suggested that the CM could be included in the specialized muscle groups, such as the extrinsic ocular muscles (EOMs) and laryngeal and masticatory muscles. The embryological origin from the nonsomitic mesoderm is, also for the CM, the basis of distinct molecular pathways. In UDT, the histological alterations of CM are suggestive of denervation; the genitofemoral nerve and its molecular messengers directed to this muscle are likely defective. Compared with the other samples, RT has a distinct myosinic pattern; therefore, it has been considered a well-defined entity with respect to the other testicular descent abnormalities.

Etiology of Inguinal Hernias: A Comprehensive Review

Background

The etiology of inguinal hernias remains uncertain even though the lifetime risk of developing an inguinal hernia is 27% for men and 3% for women. The aim was to summarize the evidence on hernia etiology, with focus on differences between lateral and medial hernias.

Results

Lateral and medial hernias seem to have common as well as different etiologies. A patent processus vaginalis and increased cumulative mechanical exposure are risk factors for lateral hernias. Patients with medial hernias seem to have a more profoundly altered connective tissue architecture and homeostasis compared with patients with lateral hernias. However, connective tissue alteration may play a role in development of both subtypes. Inguinal hernias have a hereditary component with a complex inheritance pattern, and inguinal hernia susceptible genes have been identified that also are involved in connective tissue homeostasis.

Conclusion

The etiology of lateral and medial hernias are at least partly different, but the final explanations are still lacking on certain areas. Further investigations of inguinal hernia genes may explain the altered connective tissue observed in patients with inguinal hernias. The precise mechanisms why processus vaginalis fails to obliterate in certain patients should also be clarified. Not all patients with a patent processus vaginalis develop a lateral hernia, but increased intraabdominal pressure appears to be a contributing factor.

Muesothelial cyst of the spermatic cord as a cause of acquired cryptorchidism

Mesothelial cysts of the spermatic cord (MCSC) are a rare entity. A 2-year-old cryptorchid boy with an inguinal mass was found to have a MCSC which was confused with undescended testis. The testis was readily placed into the hemiscrotum after excision of the cyst. MCSC may present as undescended testis and may be an unusual cause of acquired cryptorchidism. It should be excised and the inguinal canal should be explored for the existence of an undescended testis.

Morphology and innervation of the human cremaster muscle in relation to its function

The electromyographic properties of the cremaster muscle (CM) are quite different from other skeletal muscles. It shows excessive spontaneous discharges, and the motor unit shape and firing frequency of the CM muscle differ from that of limb muscles. In this study, CM of six adult cadavers and six orchiectomy specimens were used to reveal the detailed histology of the muscle and provide an anatomophysiological explanation for these unusual electromyographic properties. Routine histochemical stains revealed the CM was composed of several distinct bundles of smooth and striated muscle fibers within connective tissue. The smooth muscle fibers that were more profuse than previously known and were not arranged in layers, but widely dispersed between striated muscle fibers. Bielschowsky silver staining technique, anti-neurofilament and anti-synaptophysin immunostaining showed the presence of multiple motor end-plates observed as a series of small dots or lines running along the striated muscle fibers and several nerve endings on a single muscle fiber. Myosin immunostaining confirmed the CM is a slow-twitch muscle, and alpha-actin smooth muscle immunostaining confirmed the presence of a large number of smooth muscle fibers. There were also small multipolar neurons forming nerve plexuses between smooth muscle fibers. Anti-GFAP immunostaining confirmed the presence of glial cells similar to astrocytes. In conclusion, the findings of this detailed anatomical study showed the CM, widely known as a striated muscle, contains a large number of smooth muscle fibers, and the spontaneous electromyographic discharges are due to the presence of multiple motor end-plates and dense innervation.

Calcitonin gene-related peptide stimulates mitosis in the tip of the rat gubernaculum in vitro and provides the chemotactic signals to control gubernacular migration during testicular descent

BACKGROUND/AIMS

We investigated whether calcitonin gene-related peptide (CGRP) released from sensory genitofemoral nerve branches could stimulate rodent gubernacular growth and provide chemotactic signals for directing inguinoscrotal gubernaculum migration in vitro.

MATERIALS AND METHODS

Neonatal rat gubernacula containing a developing cremaster sac (n = 60) were removed at days 0, 2, 4, 6, 8, and 10 (n = 10 per age; n = 5 per experimental group) and placed in organ culture for 24 hours with or without added CGRP (720 nmol/L). The gubernacula were stained for bromodeoxyuridine (BrdU) immunohistochemistry. Cells were counted (3 x 100 cells) in the mesenchymal tip of the gubernaculum to find the percentage of BrdU uptake. A further group of neonatal rat gubernacula (n = 21 per group) were placed in organ culture on an agar platform with 5 agarose beads soaked in either PBS or 10(-6) mol/L CGRP placed approximately 0.8 to 1 mm on each side of the tip of the cremaster sac. After 72 hours, the position of the gubernaculum was compared with its starting position and any deviation measured.

RESULTS

Exogenous CGRP caused a significant increase in BrdU uptake in the tip of the gubernaculum in 0-day-old rats compared with control cultures. Two-way analysis of variance in the cellular proliferation pattern between gubernacula cultured +/- CGRP between 0 and 10 days showed a significant difference (P < .001). The cultures containing CGRP-impregnated beads caused significant (P < .01) deviation of the tip of the gubernaculum toward the beads, whereas the controls demonstrated no net movement of the tip.

CONCLUSIONS

These studies demonstrate that mitosis in the tip of the rat gubernaculum is significantly increased in response to CGRP in vitro. Also, CGRP may provide chemotactic signals to control inguinoscrotal gubernacular migration in the rat.

Ascended testis in three brothers with Pelizaeus Merzbacher syndrome

Ascended testis is a rare clinical entity. The mechanism involved in testicular ascent is still not understood completely. Spasticity of cremaster muscle may cause secondary ascent of testis. The authors present 3 brothers with Pelizaeus Merzbacher syndrome, a rare, x-linked leukodystrophy in whom the testes bilaterally ascended from the normal scrotal position to an undescended position after onset of spasticity.

The unified theory of hernia formation

The perusal of surgical journals suggests that the etiology and the treatment of hernias are still based on the understanding of a simple mechanical defect, an idiopathic happenstance requiring a reliable hernia repair, preferably with a prosthetic mesh or device. The need for additional elucidation does not constitute an aim that is pervasive in the surgical community or with the corporate manufacturers of surgical implements. This may well be because surgeons are not trained scientists and laboratory workers. Fortunately, several disciplines are injecting a healthy dose of curiosity matched by ingenuity. Among these contributors, we can count anatomists, electron microscopists, biochemists, organic chemists, pathologists, geneticists, and molecular biologists, who have looked at collagen, enzymes, tobacco smoke, congenital diseases, and chromosomal defects. Every aspect of the researchers' work has identified and converged onto a final common organ: collagen. It is the pathological changes in collagen that set the stage for the development of a hernia. The multiple theories on mechanisms of hernia formation have, at last, melded into one single Unified Theory of hernia formation.

Chemical sympathectomy by 6-OH dopamine during fetal life results in inguinal testis through altering cremasteric contractility in rats

BACKGROUND/PURPOSE

Androgens are proposed to influence testicular descent through modulating sympathetic tone. An experimental study was undertaken to evaluate the effects of prenatal chemical sympathectomy on testicular location associated with the alterations in contractile properties of cremaster muscles in rats.

METHODS

Time-mated pregnancies were started in 10 rats. Two groups, each receiving saline or 6-hydroxydopamine from day 15 to day 19 of intrauterine life were established. At 2 months of age, localization of testes were evaluated, cremaster muscles were removed, and contractile properties were studied. Twitch and tetanic contractions were recorded isometrically at 37 degrees C. Effects of verapamil, isoprenaline, and L-NNA were investigated. Results were compared through analysis of variance (ANOVA), and P values less than.05 were considered to be significant.

RESULTS

Both testes of all male offspring in the control group (n = 19) were in the scrotum. Six offspring among 17 subjected to 6-hydroxydopamine had undescended testes. Treatment with 6-hydroxydopamine had no effect on force-frequency relationship of cremaster muscle strips. Cremaster muscles of rats exposed to 6-hydroxydopamine had lower sensitivity to voltage-sensitive Ca++ channel blockade by verapamil (3 x 10(4) mol/L; P <.05). These muscles displayed greater contractile response to isoprenaline (10(-5) mol/L; P <.05) but not to nitric oxide synthase inhibition by N(omega)-nitro-L-arginine. Alterations in contractile properties of the muscles did not differ according to localization of testes among rats subjected to 6-hydroxydopamine.

CONCLUSIONS

Administration of 6-hydroxydopamine resulted in suprascrotally located testes. This localization has been associated with less exposure at sympathetic tonus. These findings support that sympathetic activity plays an important role in localization of testis.

Mechanisms involved in contractile differences among cremaster muscles according to localization of testis

BACKGROUND/PURPOSE

Evidence suggests differences in contractility in cremaster muscles (CM) associated with undescended testis caused by alterations of autonomic innervation. Contractile responses of CM to various pharmacologic agents were evaluated and compared according to the localization of testis.

METHODS

Samples of CM from boys with undescended testis or inguinal hernia were obtained. Twitch and tetanic contractions were recorded isometrically at 37 degrees C. Effects of verapamil, isoprenaline, calcitonin gene-related peptide (CGRP), substance P (SP) and N(omega)-nitro-L-arginine (L-NNA) were investigated. Results were compared through 2-way analysis of variance, and P values less than.05 were considered to be different.

RESULTS

Verapamil alone significantly (P <.05) decreased contraction amplitudes in CM from both sources; the decrease was more pronounced in CM from boys with inguinal hernia (P <.05). Although isoprenaline increased contraction amplitudes in CM associated with undescended testis (P <.05), CGRP and SP increased contraction amplitudes in CM associated with descended testis (P <.05). L-NNA increased contraction amplitudes in both groups (P <.05). The decrease of contraction amplitudes after verapamil displayed a similar pattern after isoprenaline, SP, and L-NNA. Verapamil-induced contractility decrease was more pronounced after CGRP in both groups (P <.05).

CONCLUSIONS

Sensitivity of CM to verapamil differs according to localization of testis. Isoprenaline enhances contractility by stimulating Na(+)-K(+)ATPase in undescended testis without altering voltage-sensitive channel sensitivity to verapamil. CGRP and SP increase contractility in inguinal hernia, and CGRP increases the sensitivity of voltage-sensitive Ca(2+) channels to verapamil in CM from both groups. Nitric Oxide (NO) exerts inhibitory action on CM contractility, and it is less pronounced in undescended testis. These differences may contribute to pathophysiology of undescended testis.

Cremasteric reflex and retraction of a testis

PURPOSE

A clinical study has been planned to define the clinical characteristics of cremasteric reflex (CR) for deciding on the possibility of a prolonged suprascrotal stay of a testis through this reflex.

METHODS

Five hundred boys from 3 days to 16 years of age were divided into 6 groups according to their ages and were evaluated for the presence of the CR. After evoking CR, the presence or absence of changes in testicular location and the most elevated position of the testis were recorded. Testicular position difference (TPD), the duration of the stay of testis in the most elevated position (DEP), and the interval for reevoking the CR (IRCR) were determined. The number of consecutive responses after repetitive evokings were recorded as reproducibility (R). Mean TPD, DEP, IRCR, and R values for both sides were calculated and compared among groups. The boys with a positive reflex were classified further according to their TPD, DEP, IRCR, and R values. Three groups were established according to the aforementioned criteria by dividing the values into 3 equal parts. The association of each of the parameters to other parameters were compared.

RESULTS

Bilateral positive CR was encountered in 42.7% of newborns, 36.3% of the boys between 1 month and 1 year old, 38.1% of the boys between 2 years and 4 years old, 75.2% of the boys between 5 years and 8 years old, 70.3% of the boys between 9 years and 12 years old, and 72.1% of the boys between 13 and 16 years old. The highest percentage of the contralateral activations during ipsilateral evokings were encountered in boys who were between 5 and 8 years of age. The highest mean TPD and mean R, the longest mean DEP, and mean IRCR were encountered in boys between 5 and 8 years of age. Boys with the highest TPD did not have shortest IRCR and highest R values. Similarly, boys with the longest DEP or shortest IRCR and highest R values did not have the association of other parameters that would suggest a hypersensitivity.

CONCLUSIONS

The rate of presence and the characteristics of a positive CR vary largely. However, suprascrotal location of a testis for extended periods through the activation of this reflex does not seem to be likely. Instead of a hyperactive reflex, the clinical condition, so called the retractile testis, might have resulted through alterations within the cremaster muscle itself. J Pediatr Surg 36:863-867.

Cremaster muscle is not sexually dimorphic, but that from boys with undescended testis reflects alterations related to autonomic innervation

BACKGROUND/PURPOSE

The genitofemoral nerve and its motor neuron are known to be sexually dimorphic. An association has been suggested to exist between antiandrogen-induced undescended testis and the genitofemoral nerve. Therefore, the cremaster muscles (CM) from boys and girls with inguinal hernia and boys with undescended testis were compared to evaluate the failed descent through sexual dimorphism.

METHODS

Samples of CM were obtained from 10 boys and 10 girls with inguinal hernia and 10 boys with undescended testis. Sections were stained for ATPase reactions after acid and alkaline preincubations, and for the expression of myosine heavy chains. The percentages of type 1 and type 2 fibers, and mean diameters of fibers according to the types were determined for each group. Values were compared through Mann-Whitney U test, and P values less than .05 were considered to be significant.

RESULTS

CM have mainly been composed of type 1 fibers. Distributions of type 1 and 2 fibers have not shown a difference among groups. Mean diameters of both type 1 and type 2 fibers from girls (P < .05), and mean diameter of type 2 fibers from boys with undescended testis have been significantly smaller than those encountered in boys with inguinal hernia (P < .05).

CONCLUSIONS

Although the mean diameter of type 1 fibers from boys with undescended testis has been as large as those encountered in boys with inguinal hernia, mean diameter of type 2 fibers has been as small as those encountered in girls. Among various reasons to selectively diminish the size of type 2 fibers, lack of beta adrenergic effect appears to be the most satisfactory explanation. J Pediatr Surg 36:877-880.

Ultrastructural deficiency in autonomic innervation in cremasteric muscle of boys with undescended testis

BACKGROUND/PURPOSE

The cremaster muscles (CM) associated with undescended testis reveal neurogenic alterations that mainly affect type 2 fibers. The ultrastructure of CM has been evaluated to define if further evidence to explain the alterations could be identified.

METHODS

CM of 8 boys with inguinal hernia and 8 boys with undescended testis at similar ages were biopsied. Samples were processed for electron microscopic evaluations. Semithin and thin sections were examined under an electron microscope.

RESULTS

The CM associated with inguinal hernia showed normal ultrastructure. However, some alterations were encountered in CM associated with undescended testis. Unmyelinated fibers were diminished in number, and myelinated fibers were outnumbering the unmyelinated fibers. Marked disorientation of myofibers, redundant sarcolemma, empty sleeves of basal lamina, disarray of myofibrils, densely packed myofilaments, Z disk streaming, dilated sarcoplasmic reticulum, and dense-irregularly shaped mitochondria were repeatedly encountered. Satellite cells appeared inactive. Most of the fibers were contracted.

CONCLUSIONS

The decrease in number of unmyelinated fibers appears to represent a decrease in autonomic nerve fibers. The alterations within muscle fibers may reflect a deficiency in autonomic innervation. Autonomic nervous system is highly responsive to circulating androgens. Factors decreasing the vulnerability of autonomic nervous system against androgenic effects may result in a CM with neurogenic alterations, thus inhibiting testicular descent. J Pediatr Surg 36:573-578.

Differences in the morphology of the processus vaginalis with sex and underlying disease condition

The structures of sacs from boys and girls with inguinal hernia, and from boys with undescended testis or hydrocele were evaluated and compared. Particular attention was directed to determine if a clue helpful in describing the mechanism of obliteration of processus vaginalis (PV) exists. Sacs from boys (n: 8) and girls (n: 11) with inguinal hernia, and sacs from boys with undescended testis (n: 11) and hydrocele (n: 10) were obtained and stained with hematoxylin-eosin, trichrome and elastic van Gieson. The histologic structures of each group of samples were determined and compared. Smooth muscle was presented as a layer within the sacs of girls and boys with inguinal hernia. However, smooth muscle bundles were sparsely presented in sacs associated with undescended testis and hydrocele. Myofibroblasts were commonly encountered in sacs associated with inguinal hernia. The smooth muscle was invariably presented in sacs that contained myofibroblasts. While sacs from boys only had smooth muscle, sacs from girls also had striated muscle. Since the muscle components of sacs vary, PV is sexually dimorphic. Persistence of PV seems to be associated with the presence of smooth muscle and myofibroblasts within the sac wall. Myofibroblasts may have originated from the smooth muscle, and reflect the attempts at obliteration of PV.

Excessive sac pressures: the pathogenesis and innocence of hydroceles in children

OBJECTIVE

To determine whether paediatric hydroceles result entirely from a small-calibre patent processus vaginalis, allowing free communication between the abdominal cavity and hydrocele sac, or whether there are other mechanisms.

PATIENTS AND METHODS

Twenty-five hydroceles were studied prospectively in 24 boys (aged 18-132 months). Consent for the intraoperative measurements was obtained before surgery. The hydrocele was repaired under general anaesthesia with endotracheal intubation, using a standard approach, taking care not to open the sac during mobilization. Intra-abdominal pressures during surgery were measured indirectly via a nasogastric tube after gastric decompression. The pressure in the sac was measured via a 20 G intravenous cannula inserted via a purse-string suture. The relative pressure was then calculated by subtracting the intra-abdominal from the sac pressure. The effects of age and laterality were evaluated.

RESULTS

The median (range) intra-abdominal, sac and relative pressures were 8 (2-18), 11 (3-30) and 4 (3-30) cmH2O, respectively. The sac pressure in the sac was greater than the intra-abdominal pressure in 17 of 25 (68%; P = 0.004) patients. Age or laterality had no significant influence on any of the pressures.

CONCLUSIONS

These results suggest that in a significant proportion of hydroceles in children the pressures are higher than the intra-abdominal pressure. Therefore, they cannot be explained simply as a freely communicating, narrow-calibre processus. In addition, the pressures may reach levels which are potentially damaging to the testis.

Myofibroblasts defined by electron microscopy suggest the dedifferentiation of smooth muscle within the sac walls associated with congenital inguinal hernia

OBJECTIVE

To ascertain the presence of myofibroblasts in sacs associated with inguinal hernia in children, through an ultrastructural evaluation using electron microscopy.

MATERIALS AND METHODS

Sacs were obtained from 10 boys and 10 girls (of similar age, approximately 45 months) with inguinal hernia and processed for electron microscopy. Thin sections were examined specifically for the presence of myofibroblasts.

RESULTS

The ultrastructural evaluation showed myofibroblasts with classical electron microscopic features within all of the sacs, regardless of the gender of origin.

CONCLUSION

The persistence of smooth muscle hinders the obliteration of the processus vaginalis; myofibroblasts are found in association with smooth muscle and thus such cells within the sac walls seem to originate from the smooth muscle, reflecting the dedifferentiation of smooth muscle. This dedifferentiated state may represent attempted apoptosis, which usually causes the disappearance of the smooth muscle and obliteration of the processus vaginalis after the descent of the testis into the scrotum.