Paracrine regulation of Leydig cells by the seminiferous tubules

Testes of adult control and unilateral cryptorchid rats were fixed by vascular perfusion. The cell profile area of peritubular Leydig cells surrounding tubules in different stages of spermatogenesis, and the cell profile area of perivascular Leydig cells were determined. The size of peritubular Leydig cells was dependent on which type of tubulus the cells were surrounding. Some peritubular Leydig cells, especially those surrounding stages VII–VIII (88.1 ± 7.1 μm², mean ± SD, n = 6 rats), were larger than perivascular Leydig cells (69.3 ± 5.9 μm²). The size of Leydig cells surrounding stages IX–XIV was similar to that of perivascular cells. In the abdominal testes no spermatogenic cycle was present and the sizes of peritubular and perivascular Leydig cells were equal (63.0 ± 5.1, vs 66.7 ± 7.3 μm², mean ± SD, n = 5 rats). It is suggested that the tubules and the spermatogenic cycle locally modulate Leydig cell activity and that Leydig cell malfunction in abdominal testes may be due to a decreased stimulatory influence from the damaged tubules.     

Local differences in Leydig cell morphology in the adult rat testis: evidence for a local control of Leydig cells by adjacent seminiferous tubules

In order to test the hypothesis that Leydig cell function in the adult rat testis is influenced by the surrounding tubules, Leydig cell morphology was compared in different types of interstitial areas. Triangular interstitial areas surrounded by 3 cross-sectioned tubules in nearly the same stage of spermatogenesis were chosen for quantitative light microscopy. It was found that the volume density of Leydig cells in such areas was about 30%, except when the surrounding tubules were in stages IX-X or XI-XII, when it was only about 20%. This variation in total Leydig cell mass seemed to be due to a variation in Leydig cell size and not in Leydig cell number. The largest Leydig cell profile area, 118 pL 6 μm² (mean pL SE n = 6 rats), was observed when the surrounding tubules were in stages VII-VIII, i.e. just prior to sperm release. The smallest Leydig cells were seen when the surrounding tubules were in stages IX-X and XI-XII (68 pL 3 and 66 pL 4 μm²). The present results indicate that there may be a Leydig cell cycle in the adult rat testis, which is regulated by the adjacent tubules.     

Development of stage-specific paracrine regulation of Leydig cells by the seminiferous tubules

The size of peritubular Leydig cells surrounding tubules in different stages of the spermatogenic cycle was determined in 43- and 47-day-old male rats. A stage-dependent variation in the size of peritubular Leydig cells was not present in 43-day-old rats, but by 47 days those Leydig cells closely adjacent to tubules at stages VII-VIII were larger than others. At 43 days of age spermatogenesis had developed up to step 18 spermatids in late stage VI tubules. At 47 days of age the first mature sperm had just been released from the seminiferous epithelium, and consequently the first wave of the spermatogenic cycle was completed. Tubules at stages VII-VIII therefore acquire the ability to influence surrounding Leydig cells when they contain step 19 spermatids. It remains to be shown whether this maturation step is due to inherent maturation of the Sertoli cells or if step 19 spermatids specifically modulate Sertoli cell function.     

Effect of unilateral cryptorchidism on the intertubular tissue of the adult rat testis: evidence for intracellular changes within the Leydig cells

Adult male rats were made unilaterally cryptorchid for 1, 2 or 4 weeks, and the morphological response of the Leydig cells was then studied using morphometric assessment of total Leydig cell volume and number per testis in abdominal and scrotal testes. Serum hormone levels were measured and the steroidogenic properties of isolated Leydig cells were evaluated by in-vitro stimulation with hCG and interstitial fluid (IF) obtained from normal rat testes. Total Leydig cell volume and number per testis were not altered in abdominal vs scrotal testes, although the volume of the abdominal testis was 46, 29 and 21%, respectively, of the volume of the contralateral scrotal testis after 1, 2 and 4 weeks. This reduction was accompanied by significant (P less than 0.05) elevation of the serum levels of FSH and LH, although serum testosterone levels were unchanged from the normal range. Despite the lack of quantitative alterations in Leydig cell morphology, hCG- and IF-stimulated testosterone production was significantly (P less than 0.01) greater by abdominal Leydig cells when compared with scrotal Leydig cells derived from the same animals. Ultrastructural examination of Leydig cells in situ suggested an increase in volumetric density of mitochondria in abdominal Leydig cells. Together with the enhanced steroidogenic responses of these cells, these findings suggest that disruption of spermatogenesis in the cryptorchid testis is accompanied by intracellular activation of Leydig cells. Since these effects were not exhibited by Leydig cells from the scrotal testis it is concluded that local factors within the cryptorchid testis are responsible, at least in part, for regulation of Leydig cell activity.     

Multi-Vacuolated Leydig Cells in Human Adult Cryptorchid Testes

A histological study of 23 testicular biopsies or surgical specimens from adult cryptorchid testes revealed the presence of multi-vacuolated Leydig cells in 12 cases. These cells showed abundant lipid inclusions and scarce secondary lysosomes as well as liprofuchsin pigment granules. Some of these cells contained crystals of Reinke but others had only microcristalline inclusions. This Leydig cell alteration may be related either to heat or to congenital lesions.     

Regulation of interstitial cell function by seminiferous tubules in intact and cryptorchid rats

The effects of experimental cryptorchidism on seminiferous tubule secretions and interstitial cell testosterone production were studied in vitro. Spent media obtained from incubations of seminiferous tubules (SMST) from cryptorchid rats caused a significant increase in testosterone production when added to interstitial cells isolated from intact rats. The previously noticed inhibitory activity of the SMST from stages VIII–XI of the sperma-togenic epithelial cycle gradually disappeared after the induction of experimental cryptorchidism. SMST obtained from both sham-operated or cryptorchid rats stimulated basal testosterone production when added to interstitial cells from cryptrochid rats. SMST from rats had been cryptorchid for 7, 14 and 28 days stimulated testosterone production when added to interstitial cells prepared from intact animals. Seminiferous tubules from cryptorchid rats therefore appear to be the source of a heat stable, trypsin-resistant factor with an apparent molecular weight of between 5000 and 10 000 daltons which stimulates testosterone production when added to interstitial cells in vitro. Its activity could not be blocked by an LRH antagonist. This factor enhances both basal and LH-stimulated secretion of testosterone in contrast to the inhibitory activity which involves only a partial blockade of LH-dependent steroidogenesis.     

Early signs of Sertoli and Leydig cell dysfunction in the abdominal testes of immature unilaterally cryptorchid rats

Testicular descent was prevented unilaterally by cutting the gubernaculum testis of newborn rats. When 20 days old unilaterally cryptorchid rats were injected intraperitoneally with 2 μg bFSH per gram body weight and killed 6 h later when testicular testosterone (T) and oestradiol (E₂) concentrations were determined. The increase in E₂ was subnormal in abdominal testes. In 18-day-old unilaterally cryptorchid rats the efferent ducts were ligated bilaterally, and the rats were killed 48 h later. The weight increase, due to accumulation of seminiferous tubule fluid, was significantly greater in the abdominal testes. In contrast, the ABP content of the abdominal epididymis was subnormal in 20-day-old unilaterally cryptorchid rats. Unilateral orchidectomy was performed in 16-day-old unilaterally cryptorchid rats and at 20 days of age intratesticular T and E₂, and plasma FSH and LH concentrations were determined and compared to that in 20-day-old control unilaterally cryptorchid rats. Removal of an abdominal testis resulted in increased plasma FSH and intratesticular E₂, whereas plasma levels of LH and intratesticular levels of T were unaffected. Removal of a scrotal testis resulted in increased plasma FSH and LH coupled with increased intratesticular T and E₂. Rats with a single abdominal testis had higher plasma FSH and LH and intratesticular T, but similar intratesticular E₂, than rats with a single scrotal testis. It is concluded that Sertoli and Leydig cell function are influenced by cryptorchidism at a stage when the temperature difference, and the morphological differences between the testes are very discrete.     

Effect of cryptorchidism on testicular and Leydig cell androgen production in the mouse

Unilateral cryptorchidism was induced surgically in adult mice and the effects on testicular and Leydig cell steroidogenesis were studied after 7 weeks. There was a 60% reduction in weight of the cryptorchid testis and this was associated with a significant reduction in intratesticular androgen content, both under basal conditions and following an injection of hCG. Testicular androgen production in vitro was also significantly lower in the cryptorchid testis compared to the scrotal testis, again under both basal conditions (29 +/- 6% of control) and in the presence of hCG (46 +/- 9% of control). Scrotal testes from the unilaterally cryptorchid animals did not show any significant difference in steroidogenic capacity compared to testes from untreated control animals. The decrease in steroidogenic capacity of the cryptorchid testis was due, at least in part, to a reduction in activity for each Leydig cell. In four experiments, androgen production by Leydig cells isolated from cryptorchid testes was 48 +/- 9% of cells from scrotal testes in the presence of a saturating dose of hCG. Under basal conditions the effect was more variable between experiments with steroid secretion by Leydig cells from cryptorchid testes being 58 +/- 32% of that for cells from scrotal testes. Leydig cell steroidogenesis in the scrotal testes of unilaterally cryptorchid animals did not differ significantly from untreated controls. These results show that induced cryptorchidism in the mouse causes a significant reduction in Leydig cell activity. This is apparently different from the effects of this procedure on the rat and raises the possibility that intratesticular regulation differs between the two species.     

Exploration for testicular remnants: implications of residual seminiferous tubules and crossed testicular ectopia

PURPOSE: Testicular remnants identified during exploration for cryptorchidism contain vascularized fibrous nodules at the termination of the vas deferens, hemosiderin, calcification, a pampiniform plexus or occasionally residual seminiferous tubules that may contain germ cells. An absent testis lacks the features of testicular remnants. To our knowledge testicular remnants have not been described in a crossed ectopic location. We reviewed orchiectomy specimens obtained at exploration for a nonpalpable testis to characterize the features of testicular remnants, including the frequency of seminiferous tubules, germ cells and crossed ectopia, as well as to clarify the diagnostic criteria for testicular remnants. MATERIALS AND METHODS: From 1990 to mid 2000 medical records and histological slides from 101 boys with nonpalpable testes who had undergone inguinal exploration and orchiectomy were reviewed. RESULTS: Of the 71 testicular remnants identified 7 (9.8%) contained residual tubules, of which 4 (5.6%) contained germ cells. In 4 boys the testis was deemed absent but 3 did not undergo laparoscopic exploration. There were 2 ectopic remnants (2.8%) on the contralateral side-the pelvis or in the scrotum. Both crossed remnants demonstrated dissociation of the testis from the vas/epididymis which remained on the correct side associated with a pampiniform plexus. No müllerian remnants were encountered. CONCLUSIONS: Adequate exploration for nonpalpable testis requires laparoscopy with visualization of the contralateral pelvic region because an ectopic remnant may be dissociated from the vas/epididymis and vessels. Identification of a pampiniform plexus, vas and spermatic vessels may not be a reliable indicator of a testicular remnant. Continued removal of testicular remnants is warranted because at least 9.8% contain residual viable tubules.     

睾丸间质细胞的发生与调控

睾丸间质细胞分布于生精小管的疏松间质组织中,是产生雄性激素的主要场所。睾丸间质细胞的功能障碍是导致男性原发性性腺功能低下、隐睾、尿道下裂等疾病的重要原因,因此睾丸间质细胞对男性生殖具有重要意义。本文对近年来关于睾丸间质细胞的发生、发育及调节的研究进展予以综述。     

Cytoplasmic inclusion bodies in Leydig cells from the testes of postpubertal cryptorchid patients

During the course of electron microscopic studies on testes from cryptorchid patients, we have observed an inclusion body in the cytoplasm of Leydig cells. Such inclusion bodies were detected in Leydig cells of post-pubertal patients (16 to 30 years), but were not evident in the cells of pubertal and pre-pubertal patients (3 to 12 years), or in cells from the concralateral descended scrotal testes of cryptorchid patients or in cells from normal controls. These inclusion bodies are therefore believed to result from specific cytological changes which occur in cryptorchid testes during puberty.     

Carcinoma-in-situ cells in cultured human seminiferous tubules

For the first time, early germ-cell derived tumour cells were studied in an in-vitro system of cultured seminiferous tubules. The intratubular tumour cells not only survived in culture for 7 days but were also able to multiply. Dividing tumour cells were identified in semi-thin sections and electron micrographs by morphological criteria. Additionally, mitotic activity was demonstrated by [3H]thymidine histo-autoradiography. There are numerous reports on cell lines established from solid non-seminomas, but up to now no references to seminoma cell lines or cultures of intratubular tumour cells are available. The culture of seminiferous tubules offers a tool in making carcinoma-in-situ cells accessible for experimental work.     

Effect of prolonged cryptorchidism on germ cell apoptosis and testicular sperm count

Aim:To evaluate the long term effect of experimental cryptorchidism on germ cell apoptotic rate and testicular sperm content in adult rats.Methods:Bilateral cryptorchidism was created in 40 adult male Sprague-Dawley rats by surgically manipulating the testes into the abdominal cavity and closing the internal inguinal ring.The rats were sacrificed and the testes removed 6 hours and 2,4,7,21,28 and 56 days after cryptorchidism.Germ cell apoptosis was quantified by means of TUNEL assay and apoptosis was confirmed using transmission electron microscopy.Results:The rate of apoptosis peaked at 4 days of cryptorchidism and then progressively declined to a nadir at 14 days of cryptorchidism.At 56 days of cryptorchidism,the germinal epithelium was largely depleted by the apoptotic process and only a few mature sperm were seen within the testis.At this point,a few tubules were seen to be repopulating with primary spermatocytes and the level of germ cell apoptosis began to increase marginally.Testicular sperm count (TSC) began to decline rapidly at day 7 of cryptorchidism.Only a few mature sperm were found in the testes of rats following 56 days of cryptorchidism.Multinucleated giant cells (MGC) were most numerous within the seminiferous tubules at day 4.At day 7,35% of MGCs were TUNEL positive.At all subsequent time points,however,MGCs fail to stain positive for apoptosis.This resumption of increased apoptosis coincided with the appearance of a population of primary spermatocytes in some seminiferous tubules.Moreover,there was not a corresponding increase in the number of mature sperm after 56 days of cryptorchidism.Conclusion:The decline in germ cell apoptosis after 4 days of cryptorchidism can be attributed to be the result of an overall depletion of germ cells.It appears that after a prolonged cryptorchidism (56 days),there is a limited resumption of spermatogenesis presumably as a result of a decrease in the maturing germ cells undergoing programmed cell death.(Asian JAndrol2004 Mar;6:47-51)     

Effect of cryptorchidism on the morphology of testicular macrophages: Evidence for a Leydig cell-macrophage interaction in the rat testis

Macrophages and Leydig cells in the testes of adult rats which had been made bilaterally or unilaterally cryptorchid at birth were examined by morphometry for total mass, total number, volume density, and individual cell profile area. The total Leydig cell mass and the average size of Leydig cells, as well as the total mass and the average size of macrophages, were reduced in unilateral abdominal testes, but were unchanged in bilateral abdominal testes when compared to scrotal testes. Leydig cell and macrophage morphology were correlated suggesting a functional coupling between these cell types. The physiological significance of this cell interaction remains to be discovered.     

Sertoli cell — Leydig cell interaction in the regulation of testicular function

Considerable evidence exists to indicate that the Leydig cells influence the seminiferous tubule by maintaining a high concentration of testosterone in the peritubular compartment of the testes. Recent studies using various types of agents to disrupt spermatogenesis, have shown that significant changes occur in the structure and function of the Leydig cells. In these situations, Leydig cells enlarge, show hyperresponsiveness to hCG stimulation in vitro and contain a reduced number of receptors for LH/hCG. Evidence is presented to support the hypothesis that the changes in Leydig cell structure and function are the result of local factors. The data provide support for the concept that the functioning of Leydig cells is modulated by the seminiferous tubules.     

大鼠睾丸间质细胞移植的实验研究

目的:观察大鼠同种异体睾丸间质细胞移植后的血清睾酮变化水平。方法:采用Percoll方法分离提取SD大鼠两侧睾丸间质细胞,异体移植后每月测定受体血清睾酮1次,连续3次。结果:睾丸间质细胞移植后,受体动物血清睾酮含量逐渐升高。移植术后3个月,血清睾酮水平明显上升,与出生后2个月内的动物比较,差异具有显著性。结论:异体睾丸间质细胞移植治疗男性原发性性腺功能低下症可能具有良好的应用前景。     

The Total Leydig Cell Volume of the Testis in some Common Mammals

Total-Leydig-Zell-Volumen des Hodens bei einigen Säugern
In einer quantitativen Studie wurde mittels der histometrischen Punktzählmethode bei sechs Säugern einschließlich des Menschen das Total-Leydig-Zell-Volumen bestimmt. Obgleich die Größe der Hoden von 1,3 ±0,1 ml bei der Ratte auf 19.8 ± 6.9 ml beim Büffel anstieg, blieb die Zusammensetzung leidlich konstant, wobei die Leydig-Zellen 9–16% des Hodenvolumens ausmachten. In absoluten Werten ergab sich, daß das Total-Leydig-Zell-Volumen progressiv mit dem Körpergewicht anstieg, und zwar von 0.11 ± 0.02 ml/Hoden bei der Ratte auf 2,44 ± 0.64 ml/Hoden beim Büffel; der Wert für den Menschen betrug 2.21 ± 0.40 ml/Hoden. Die Signifikanz dieser Resultate wird unter dem Gesichtspunkt der vergleichenden Physiologie der Reproduktion diskutiert.     

Multinucleate Leydig Cells in Normal Human Testes

The number of mononucleate and multinucleate Leydig cells per unit area of the testis was determined in normal adult men using the peroxidase-anti-peroxidase method for testosterone detection. The results of this study indicate that the number of multinucleate Leydig cells increases markedly with age, whereas the total Leydig cell population decreases.     

Microvasculature of the human testis in correlation to Leydig cells and seminiferous tubules

Summary. The microvasculature of the human testis is closely related to the Leydig cells and the seminiferous tubules. Semi-thin sections of testicular tissue serve as a basis for the computer-aided 3-D reconstruction of the microvasculature, the seminiferous tubules and the Leydig cells. After vascular perfusion with glutaraldehyde (5.5%) and paraformaldehyde (4%), it is possible by means of light and electron microscopy, to analyse the organization of the capillaries between the Leydig cells (inter-Leydig cell capillaries) as well as of those within the lamina propria (intramural capillaries). These arise from arterioles, deriving from branches of the segmental arteries. The capillaries ramify between the Leydig cells and run either semi-circumferentially around the seminiferous tubules (peritubular capillaries) or penetrate the lamina propria of the neighbouring tubules. This is the beginning of the intramural capillary which after leaving the tubular wall continues to a further capillary path. Consequently, the microvasculature of the human testis with regard to the seminiferous tubules is subdivided into afferent, intramural and efferent capillaries. Leydig cell clusters are present on both the arterial and the venous sides of the microvasculature.