Distribution and morphometry of fiber types in cremaster muscles of boys with inguinal hernia or undescended testis

Transcriptome analysis of the dihydrotestosterone-exposed fetal rat gubernaculum identifies common androgen and insulin-like 3 targets

Androgens and insulin-like 3 (INSL3) are required for development of the fetal gubernaculum and testicular descent. Previous studies suggested that the INSL3-exposed fetal gubernacular transcriptome is enriched for genes involved in neural pathways. In the present study, we profiled the transcriptome of fetal gubernaculum explants exposed to dihydrotestosterone (DHT) and compared this response to that with INSL3. We exposed fetal (Embryonic Day 17) rat gubernacula to DHT for 24 h (10 and 30 nM) or 6 h (1 and 10 nM) in organ culture and analyzed gene expression relative to that of vehicle-treated controls using Affymetrix arrays. Results were annotated using functional, pathway, and promoter analyses and independently validated for selected transcripts using quantitative RT-PCR (qRT-PCR). Transcripts were differentially expressed after 24 h but not 6 h. Most highly overrepresented functional categories included those related to gene expression, skeletal and muscular development and function, and Wnt signaling. Promoter response elements enriched in the DHT-specific transcriptome included consensus sequences for c-ETS1, ELK1, CREB, CRE-BP1/c-June, NRF2, and USF. We observed that 55% of DHT probe sets were also differentially expressed after INSL3 exposure and that the direction of change was the same in 96%. The qRT-PCR results confirmed that DHT increased expression of the INSL3-responsive genes Crlf1 and Chrdl2 but reduced expression of Wnt4. We also validated reduced Tgfb2 and Cxcl12 and increased Slit3 expression following DHT exposure. These data suggest a robust overlap in the DHT- and INSL3-regulated transcriptome that may be mediated in part by CREB signaling and a common Wnt pathway response for both hormones in the fetal gubernaculum.

Reduced expression of androgen receptor and myosin heavy chain mRNA in cremaster muscle of boys with nonsyndromic cryptorchidism

PURPOSE

To better define the developmental mechanisms of nonsyndromic cryptorchidism, we measured the expression of hormone receptor and muscle type specific mRNAs in target tissues of boys with and those without nonsyndromic cryptorchidism.

MATERIALS AND METHODS

Prospectively collected cremaster muscle and/or hernia sac tissues from boys with congenital (79) or acquired (66) nonsyndromic cryptorchidism and hernia/hydrocele (controls, 84) were analyzed for hormone receptor (RXFP2, AR, ESR1, ESR2) and myosin heavy chain specific (MYH1, MYH2, MYH7) mRNA expression using real-time reverse transcriptase polymerase chain reaction. Log transformed mRNA, phenotype and feeding history data were statistically analyzed using Pearson's correlation, ANOVA and 2-sample t tests.

RESULTS

AR mRNA expression was higher in cremaster muscle than in sac tissue, and significantly lower in congenital and acquired nonsyndromic cryptorchidism cases vs controls (p <0.01). Type 1 (slow/cardiac) MYH7 mRNA expression was also significantly reduced in both nonsyndromic cryptorchidism groups (p ≤ 0.002), while a reduction in type 2 (fast) MYH2 expression was more modest and significant only for the congenital cryptorchidism group (p <0.05). Cremasteric MYH7 and AR levels were strongly correlated (r(2) = 0.751, p <0.001). MYH7 and ESR1 mRNA levels were higher and lower, respectively, in boys with nonsyndromic cryptorchidism who were fed soy formula. Expression of other genes was not measurable.

CONCLUSIONS

Our data suggest that boys with congenital and acquired nonsyndromic cryptorchidism differentially express AR and slow twitch specific MYH7 mRNA in the cremaster muscle, and that MYH7 expression is correlated with AR levels and soy formula use. These differences in gene expression may reflect aberrant hormonal signaling and/or innervation during development with the potential for secondary functional effects and failed testicular descent.

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.

Contractility of rat gubernacula affected by calcitonin gene-related peptide and beta-agonist

PURPOSE

The effects of calcitonin gene-related peptide (CGRP), isoprenaline, and guanethidine on the neonatal rat gubernaculum were investigated in organ culture with the aim of seeing whether beta -agonists or beta -antagonists are involved in gubernacular development during testicular descent.

METHODS

A total of 200 gubernacula were studied. The gubernacula (n = 20 for each experiment) from male rat pups were incubated in aerated culture medium with isoprenaline (1 and 10 micromol/L) with/without CGRP (714 nmol/L) or guanethidine (1 and 10 micromol/L) with/without CGRP (714 nmol/L). Cultures were observed for 5 days by video camera to see spontaneous rhythmic contractions, which are known to correlate with normal gubernacular migration in the rodent.

RESULTS

Of gubernacula cultured without CGRP, 60% showed contractions by day 5, and the groups of isoprenaline and 10 micromol/L guanethidine showed similar rates, but only 15% of the 1 micromol/L guanethidine group showed contractility (P < .005). In contrast, of the gubernacula cultured with CGRP, each group showed high contractility from day 2 of the culture, and there was no difference between each group and the CGRP-alone group.

CONCLUSIONS

Although the beta -blocker showed a weak inhibitory effect on de novo gubernacular contractility, CGRP had a stronger effect on contractility, overriding any possible effects of the beta -neuron pathway. The contractility of the rat gubernaculum during testicular descent is primarily mediated by the genitofemoral sensory nerve fibers via release of CGRP, but beta -adrenergic nerves also may be involved.

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.