Immunohistochemical demonstration of myoid cells in the testis and its excurrent ducts in the domestic fowl

(1) Immunohistochemical methods and three antibodies (against actin, desmin and smooth muscle actin) were used to demonstrate the myoid cells in the domestic fowl testis and its excurrent ducts. (2) A positive reaction to actin, smooth muscle actin and desmin was found in the myoid cells of peritubular tissue of the testis and in rete testis, ductuli efferentes and ductus epididymidis. (3) In the testis myoid-reactive cells form a single layer. In the rete testis, ductuli efferentes and the ductus epididymidis reactive myoid cells form a main component of the stroma. (4) Positive reaction to actin, smooth muscle actin and desmin was also observed in the myoid cells of the tunica albuginea and in the wall of blood vessels in the testis and epididymis, indicating a contractile function for the testicular capsule.     

Seasonal Changes in the Immunolocalization of Cytoskeletal Proteins and Laminin in the Testis of the Black‐Backed Jackal (Canis mesomelas)

Manipulation of the reproductive activity of jackals is dependent on a thorough understanding of the reproductive biology of this species. This study describes seasonal morphological changes in the adult testis of the black‐backed jackal in relation to the immunoexpression of the basement membrane marker, laminin and the cytoskeletal proteins, cytokeratin, smooth muscle actin and vimentin. Laminin was immunolocalized in basement membranes surrounding seminiferous tubules, as well as in basement membranes associated with Leydig, peritubular myoid and vascular smooth muscle cells. Scalloped basement membranes enclosed seminiferous tubules in regressing testes. The seminiferous epithelium and interstitial tissue in all animals studied were cytokeratin immunonegative. Smooth muscle actin was demonstrated in vascular smooth muscle cells, as well as in peritubular myoid cells encircling seminiferous tubules. Vimentin immunoreactivity was exhibited in the cytoplasm of Sertoli cells, Leydig cells, vascular endothelial cells, vascular smooth muscle cells and fibrocytes. Vimentin immunostaining in Sertoli, Leydig and peritubular myoid cells varied depending on the functional state of the testis. The results of the study have shown that dramatic seasonal histological changes occur in the testes of the jackal. In addition, the use of immunohistochemistry accentuates these morphological changes.     

Immunolocalization of Intermediate Filaments and Laminin in the Oviduct of the Immature and Mature Japanese Quail (Coturnix coturnix japonica)

This study describes the distribution of vimentin, desmin, smooth muscle actin (SMA) and laminin in the oviduct of the immature and mature Japanese quail. The cytoskeletal proteins vimentin, desmin and SMA have been shown to be involved in cellular support, differentiation, migration and contractility. Laminin is a major component of basement membranes. Luminal epithelia in the infundibular and magnal regions of immature and mature birds exhibited strong vimentin immunoreactivity. Luminal epithelial cells exhibiting strong vimentin immunoreactivity were present in the isthmus and shell gland regions of only mature quails. Infundibular glandular grooves displayed strong vimentin immunostaining. In contrast, the glandular epithelia of the magnum, isthmus and shell gland were vimentin immunonegative. Fibroblasts and vascular endothelial cells in the lamina propria of the oviductal regions studied exhibited strong vimentin immunostaining. Smooth muscle cells forming the tunica muscularis and vascular tunica media displayed strong desmin and SMA immunostaining. Strong laminin immunostaining was demonstrated in the basement membranes associated with smooth muscle cells, as well as in the basement membranes underlying the luminal and glandular epithelia. In conclusion, this study has shown that the immunolocalization of desmin, SMA and laminin in the oviduct of the Japanese quail is similar to that in the domestic fowl. However, differences in the immunoexpression of vimentin in the LE of the two avian species were shown to exist. In addition, the study has shown that the immunolocalization of vimentin in the Japanese quail varies depending on the oviductal region, as well as the developmental stage of the oviduct.     

An Immunohistochemical Study of the Oviduct in the Domestic Fowl (Gallus domesticus)

This study describes the distribution of vimentin, desmin, smooth muscle actin (SMA) and laminin in the oviduct of the laying domestic fowl. Vimentin immunostaining was localised in the luminal epithelium of the infundibulum, magnum, magnum–isthmus junction and isthmus. The luminal epithelium of the shell gland regions displayed weak vimentin immunostaining. Vimentin immunostaining was demonstrated in the glandular grooves of the tubular infundibular region. In contrast, gland cells in the magnum, isthmus and shell gland regions were vimentin immunonegative. Fibroblasts and vascular endothelial cells in the lamina propria of the oviductal regions studied exhibited vimentin immunostaining. Strong desmin and SMA immunostaining were present in the smooth muscle cells of the tunica muscularis and vascular tunica media. In this study, basement membranes underlying the luminal and glandular epithelia were immunopositive for laminin. In addition, basement membranes associated with smooth muscle cells exhibited laminin immunostaining. The results of the study indicate that the immunolocalisation of desmin, SMA and laminin in the oviduct of the domestic fowl is similar to that in the mammalian uterus. The immunolocalisation of vimentin in the domestic fowl varies depending on the oviductal region.     

Distribution of CD68‐, CD8‐, MHCI‐ and MHCII‐positive cells in the bull and ram testis and epididymis

The mammalian testis possesses a special immunological environment because of its properties of remarkable immune privilege and effective local innate immunity. The testicular immune privilege protects immunogenic germ cells from systemic immune attack, and local innate immunity is important in preventing testicular microbial infections. Thus, this study aimed to immunohistochemically demonstrate the distribution and localization of CD68‐, CD8‐, MHCI‐ and MHCII‐positive immune cells in the testes and epididymes. Negative immunoreactivity was detected in the seminiferous tubule epithelium and peritubular myoid cells of the testes upon staining in CD68, CD8 and MHC Class I. Positive CD68 immunoreaction was determined in the Sertoli cells and some Leydig cells. The detection of positive cells for CD8 clearly indicated the presence of lymphocytes. Furthermore, the staining with MHCI intensity was ascertained to vary from weak to moderate in the Sertoli and Leydig cells and connective tissue cells. MHCII‐positive immunoreactivity was determined in myoid cells and Leydig cells in the interstitial area. The epithelium of the epididymis showed positive staining for CD68 and CD8, but the stroma displayed a rather weak staining. In the ram epididymis, neither intraepithelial nor interstitial positive reaction was observed for MHCI. In the epididymis, the basal cells displayed a stronger staining for MHCII. In conclusion, these cells not only contribute to local immunity through their direct effects on the quality of fertility in males, but also contribute either directly or indirectly to immune privilege by minimizing the development of both autoimmune reactions and potentially harmful risks.     

INSL-3 protein expression in normal and cryptorchid testes of Ziwuling black goats

Ziwuling black goats are typically found in loess plateaus regions and the Ziwuling Nature Reserve. Cryptorchidism is a common disease in this inbred goat, and its pathogenesis has been linked with the expression of insulin-like factor 3 (INSL-3). Therefore, this study aimed to investigate anatomical alterations caused by cryptorchism and the expression and distribution of INSL-3 in normal and cryptorchid testicular tissues. The testicular tissues of 6-month-old Ziwuling black goats were collected for microscopic analyses using histochemical, immunohistochemical, immunofluorescence and biometrical methods, as well as Western blotting to compare the expression and distribution of INSL-3. A lower expression of INSL-3 was observed in cryptorchid compared with normal testicular tissues (p < .01). Cryptorchidism caused a significant reduction in layers of spermatogenic epithelium and tubule areas in Ziwuling black goat (p < .01). The interstitial to seminiferous tubule area ratio was larger in cryptorchid than in normal group. Periodic Acid-Schiff (PAS) staining revealed pronounced positive bands in the interstitial tissue, while positive Alcian blue (AB) staining was not clear, and AB-PAS staining revealed a positive red band in the basement membrane of cryptorchid group. Immunofluorescence revealed a strong signal of INSL-3 expression in Sertoli and peritubular myoid cells, and moderate signal in Leydig and spermatogenic cells in the normal group. However, in cryptorchid testicular tissues, the signal of INSL-3 expression was strong in primary spermatocytes, occasional in Sertoli cells, limited in Leydig cells and absent in peritubular myoid cells. Furthermore, immunohistochemistry showed that INSL-3 expression was higher in normal testes compared with cryptorchid testicular tissues (p < .05), especially in primary spermatocytes and Sertoli cells. Collectively, our results indicate that cryptorchidism is closely related to the disorder of acid glycoprotein metabolism and the reduction in release of INSL-3 from Leydig cells. Moreover, Sertoli and peritubular myoid cells are crucial for INSL signalling and could underpin further research on the mechanism of cryptorchidism in animal.     

An immunohistochemical study of ovarian follicle histogenesis in the early post-hatch Japanese quail (Coturnix coturnix japonica)

The early post-hatch development of immunoreactivity to vimentin, desmin, smooth muscle actin (SMA) and laminin, in relation to follicle histogenesis, was described in this study. Ovigerous cords in day old quails contained pre-granulosa cells and oocytes. Pre-granulosa cells at the cortico-medullary junction were vimentin immunopositive. A laminin immunopositive basement membrane and desmin immunopositive mesenchymal cells lined the ovigerous cords. Ovigerous cords in 3-day-old quails contained developing primordial follicles, the vimentin immunopositive pre-granulosa cells of which were partially encircled by a basement membrane and desmin immunopositive mesenchymal cells. In 5- to 7-day-old quails, ovigerous cords formed an outer cortical region, while primordial follicles formed the inner cortical region. Early pre-vitellogenic follicles were present in 9- to 13-day-old quails. Underlying the granulosa cells of these follicles was a laminin immunopositive basement membrane and a layer of desmin immunopositive thecal cells. Early and late pre-vitellogenic follicles dominated the ovary in 15- to 17-day-old quails. The thecal layer in these follicles was desmin immunopositive, but SMA immunonegative. The results of the study have shown that the process of primordial follicle development in the Japanese quail is similar to that reported in mammals. The study suggests that in the quail pre-granulosa cells originate predominantly from the medulla. The study has shown that, in the Japanese quail, thecal cells are derived from desmin immunopositive mesenchymal cells lining the ovigerous cords.     

Changes in interstitial cells during development of buffalo testis

Interstitial cells were identified and counted in the testis of Murrah buffalo calves and bulls at the age of 1, 3, 6, 9, 12, 15, 18, 21, 24, 30, 36, 42, 48 and 72 months and older. Six types of cells were identified in the testicular interstitium of 1-month-old calves. These were mesenchymal cells, fetal type Leydig cells, fibroblasts, myoid cells, pericytes and endothelial cells. Adult Leydig cells were visible in 3-month-old calves, but mesenchymal cells were not seen from 18 months onwards. The percentage of mesenchymal cells reached a maximum in 1 month, fetal type Leydig cells in 3 months, adult Leydig cells in 72 months and beyond, fibroblasts in 36 months, myoid cells in 18 months, pericytes in 21 months and endothelial cells after 15 months. Changing percentages of various interstitial cells revealed that myoid cells may have differentiated into fibroblasts and mesenchymal cells, which then differentiated into adult Leydig cells.     

An immunohistochemical study of the distribution of intermediate filaments in the ovary of the emu (Dromaius novaehollandiae)

The immunohistochemical localization of the intermediate filaments desmin, vimentin and smooth muscle actin (SMA) in the ovary of the emu was described in the present study. The cortical region of the ovary contained developing and atretic primordial, pre-vitellogenic and vitellogenic follicles. Vimentin immunostaining was demonstrated in the granulosa cell layer of primordial, pre-vitellogenic and vitellogenic developing and atretic follicles. An interesting finding of the present study was the localization of SMA in fibroblasts located in the theca externa of late vitellogenic follicles. The presence of SMA in these fibroblasts suggests that they possess characteristics of smooth muscle cells.     

Position and histological structure of the testes in the brown hare (Lepus europaeus) during seasonal regression and recrudescence

The position and histological structure of the testes of 33 brown hares (Lepus europaeus) were studied from July to December. From July to September, the testes were located in the scrotum; in October and November, in some animals, the testes were positioned more or less in the inguinal canal towards the abdominal cavity, and in December none of the investigated animals had testes located in the scrotum. Testes were weighed and a quantitative analysis of tissue components was performed: the diameter of the seminiferous tubules, the depth of the seminiferous epithelium, the thickness of the tunica albuginea, the thickness of the peritubular tissue and the relative proportion of seminiferous tubules were determined. The tunica albuginea and peritubular tissue were thickest in September, October and at the beginning of November. In the same months the testis weight was low, and the diameter of the seminiferous tubules, the depth of the seminiferous epithelium and the relative proportion of seminiferous tubules in the testis tissue were significantly lower than in other months. We did not find any correlation between testicular regression or testis weight reduction and the change in the position of the testes. During recrudescence of spermatogenesis in November and December the testes were located in the inguinal canal.     

Postnatal developmental changes in immunohistochemical localization of alpha-smooth muscle actin (SMA) and vimentin in bovine testes

The present study demonstrates the postnatal developmental changes in immunohistochemical localization of alpha-smooth muscle actin (SMA) and vimentin in the bovine testis. In the peritubular myoid cells of seminiferous tubules and the sub-epithelial and stromal cells of straight tubules and the rete testis, alpha-SMA starts appearing at around 4 months of age. Peritubular alpha-SMA attains the continuous mature pattern at around 5 months of age whereas sub-epithelial and stromal alpha-SMA increases with advancing age. Vimentin is localized in the perinuclear zone of Sertoli cells, peritubular and vascular wall cells, a few interstitial cells, and in the basal part of the epithelia of straight and rete tubules. Developmental changes are only evident in the Sertoli cell vimentin, which is basal and weak at birth and increases moderately until 4 months of age. From around 5 to 8 months of age when the Sertoli cells are under morphological transformation, vimentin intensity is considerably increased and the characteristic vimentin extensions connect the Sertoli nuclei to the basal membrane. These extensions get shorter at around 9 month of age as the Sertoli nuclei are positioned basally. The mature Sertoli cell perinuclear vimentin is strong and stable without infranuclear extension. In conclusion, the age of appearance of alpha-SMA coincides with the onset of postnatal division of spermatogonia, and vimentin may play a key role in stabilizing Sertoli cell nuclei during their transformation in bovine.     

Immunohistochemical Demonstration of Cytoskeletal Proteins in the Testis of the Japanese Black Bear, Ursus thibetanus japonicus

The seasonal changes of the cytoskeletal protein expressions were immunohistochemically investigated in the testes of Japanese black bear, Ursus thibetanus japonicus. A strong immunoreaction for α-smooth muscle actin is restricted to the vascular smooth muscle cells and the peritubular cells which surround the seminiferous tubules by several layers throughout the year. Weak immunoreactions for B4 antigen and desmin were observed in the vascular smooth muscle cells and in a part of peritubular cells throughout the year. A strong immunoreaction for vimentin was also detected in the fibroblasts and Leydig cells, in addition to the vascular smooth muscle and epithelial cells and the peritubular cells throughout the year. A strong α-tubulin immunoreaction was detected in the elongating spermatids during the acrosome phase of spermiogenesis in May and June. The cytoplasm of several Sertoli cells was faintly immunoreacted for vimentin in the basal and lateral region, while an intense α-tubulin reaction was seen in the entire cytoplasm in May, April and June. In November, January and March, the immunoreactions for vimentin and α-tubulin strongly accumulate in a perinuclear region of Sertoli cells when developmental spermatids are not seen in the seminiferous tubules. These accumulations in the immunoreactions for vimentin and α-tubulin seem to be caused by the reduction in size of Sertoli cells cytoplasm with season. However, the seasonal changes of distributions in the cytoskeletal proteins are obscure in the bear testes. These results suggest that the contents of cytoskeletal proteins may not change in relation to the morphological differences with season in the testes of the seasonal breeders.     

Vimentin expression in testes of Arabian stallions

Reasons for performing study: Specific patterns of cytoskeletal filaments reflect a functional state of the cell. In testicular cells intermediate filaments (IFs) are of the vimentin type. Since it is known that Sertoli cells regulate the spermatogenic function in the male gonad, it became important to propose a system that could quantify the state of seminiferous tubular quality. To date, a Johnsen score system has never been used to equine testes. Objectives: To demonstrate the expression pattern of vimentin in testes of mature Arabian stallions and correlate its distribution with grade of seminiferous tubule impairment as indicated by a Johnsen score. Methods: For histological examination by the Johnsen method, routine haematoxylin‐eosin staining was used. Vimentin expression and its presence in testicular sections and testicular homogenates were detected by immunohistochemistry and western blot, respectively. Both analyses were performed qualitatively and quantitatively and further validated by ANOVA tests. Results: Distinct morphology of seminiferous tubules was found in testes harvested from 3 stallions. Vimentin in IFs was immunolocalised to the cytoplasm of Sertoli, Leydig and peritubular‐myoid cells. The intensity and pattern of the IFs staining was different in individual seminiferous tubules suggesting a correlation between vimentin expression and the severity of tubule degeneration. Qualitative results by immunohistochemistry and western blot were confirmed by further quantitative analyses. Conclusions: In equine testes, differential expression of vimentin was found to be correlated with the impairment of seminiferous tubules indicated by a decrease in Johnsen score. Potential relevance: The Johnsen score system may be a useful method to facilitate the identification of tubular alterations in the stallion testes. Combined histological and immunohistochemical approach may provide a detailed phenotypic classification of stallions with decreased fertility.     

The Expression of Epidermal Growth Factor (EGF) and its Receptor (EGFR) During Post‐Natal Testes Development in the Yak

Growth factors play critical role in cell proliferation, regulate tissue differentiation and modulate organogenesis. Several growth factors have been identified in the testes of various mammalian species in last few years. In present investigation, the objective was to determine the expression of epidermal growth factor (EGF) and the epidermal growth factor receptor (EGFR) in yak testicular tissue by relative quantitative real time polymerase chain reaction (RT‐PCR), Western blot (WB) and immunohistochemistry (IHC) from mRNA and protein levels. The testicular tissues were collected from male yak at 6 and 24 months old. Results of RT‐PCR and WB showed that the expression quantity of EGF and EGFR at 24 months of age was higher than at 6 months, and the increase rate of EGFR on mRNA and protein levels was higher than the increase rate EGF during post‐natal testes development. Positive staining for EGF and EGFR was very low and mainly localized to Leydig cells testes at 6 months of age with immunohistochemistry, and seminiferous tubules were not observed. At 24 month of age, both the EGF and EGFR could be detected in Leydig cells, peritubular myoid cells, sertoli cells and germ cells of the yak testes. However, EGF and EGFR were localized to preferential adluminal compartment and basal compartment in the seminiferous tubules, respectively. In conclusion, the findings in present studies suggest that EGF and EGFR as important paracrine and/or autocrine regulators in yak testes development and spermatogenesis.     

Alterations in the immunohistochemical localization patterns of alpha-smooth muscle actin (SMA) and vimentin in the postnatally developing bovine cryptorchid testis

Previously, we reported the normal postnatal developmental changes in immunohistochemical localization of alpha-smooth muscle actin (SMA) and vimentin in the bovine testis. In this study, we demonstrate the alterations of these cytoskeletal proteins in the bovine cryptorchid testis as compared to the contralateral scrotal testis during postnatal development. Seminiferous peritubular alpha-SMA did not appear in the cryptorchid testis until 8 months of age, except for very weak intermittent filaments in relatively larger seminiferous tubules. However, a similar peritubular pattern was observed in the 18-month-old cryptorchid and scrotal testes. Moreover, weak expression of alpha-SMA in the straight tubules and rete testes at 5 months of age did not improve until 18 months of age in the cryptorchid testes. The Sertoli cell vimentin in the cryptorchid testes revealed a highly immature pattern at 5 months of age, a pattern similar to a transforming pattern with infranuclear vimentin extensions at 8 months of age, and a pattern that was almost a transforming pattern, but with considerable weakening of the vimentin filaments, at 18 months of age. In conclusion, cryptorchidism may cause considerable delay in testicular myoid cell differentiation and in attainment of the transforming pattern of the Sertoli cell vimentin, which weakens and fails to attain the mature pattern in the cryptorchid testis. These alterations may be related to the structural immaturity and functional failure of postnatally developing bovine testes exposed continuously to body heat.     

Carcinosarcoma mimicking a feline injection‐site sarcoma in a cat

A 15‐year‐old spayed female domestic short‐haired cat with cutaneous/subcutaneous well‐circumscribed, alopecic mass approximately 25 × 30 mm in diameter, localized to the left shoulder region was brought to the veterinary surgery department. Despite the suggestive location and macroscopic appearance, feline injection‐site sarcoma was not suspected based on the cytologic examination of fine‐needle aspirates. The tumor was surgically resected, and tissue sections were evaluated microscopically. The tumor was found to be nonencapsulated with a distinct border between the neoplastic parenchyma and surrounding connective tissue. The neoplastic tissue consisted of 2 cell populations: elongated to spindle‐shaped cells arranged in bands and cords and malignant epithelial‐like cells. Both populations showed microscopic features of malignancy. Multinucleate giant cells with irregular cytoplasm were scattered among the neoplastic cells. The spindle‐shaped cells strongly expressed vimentin but did not express α‐smooth muscle actin (α‐SMA) or cytokeratin. Desmin was strongly expressed in about 0‐5% of cells. Epithelial‐like cells expressed cytokeratin, but not vimentin, desmin, or α‐SMA. Multinucleate giant cells expressed vimentin, but did not α‐SMA, desmin, or cytokeratin. Based on microscopic observations and IHC results, the final diagnosis was carcinosarcoma with histologic features compatible with feline injection‐site sarcoma, but without the clinical aggressiveness of this tumor.     

FGF22及其受体在庆阳黑山羊正常睾丸与隐睾中的表达比较

试验旨在研究成纤维生长因子22（fibroblast growth factor 22,FGF22）及其受体2（fibroblast growth factor receptor 2,FGFR2）、硫酸乙酰肝素糖蛋白（heparan sulfate proteoglycans,HSPG）在庆阳黑山羊正常睾丸与隐睾中的分布与表达,探究其在山羊睾丸发育和隐睾形成中的作用。采用HE和特殊染色观察其组织学结构特征,进而以免疫组织化学及免疫荧光法结合形态计量学统计研究FGF22、FGFR2和HSPG在山羊正常睾丸及隐睾中的定位。结果表明,山羊隐睾较正常睾丸生精小管缩窄,腔内各级生精细胞排列紊乱,间质的胶原纤维和网状纤维增多,糖原类物质阳性反应较弱,FGF22在隐睾组织的Leydig、Sertoli细胞、管周肌样细胞及血管内皮细胞整体表达密度相较于正常睾丸显著减弱（P<0.05）。HSPG在正常睾丸表达显著强于隐睾（P<0.05）,间质组织变化尤其明显。FGFR2在隐睾组表达显著增高（P<0.05）,且以Sertoli细胞强阳性表达为主。庆阳黑山羊隐睾较正常睾丸发育异常,间质组织有纤维化趋势,糖原类物质含量减少;FGF22及HSPG表达降低应与隐睾局部环境温度变化密切相关;FGFR2在隐睾组表达增高提示其在发生隐睾时可能通过Sertoli细胞进行适应性调节。     

Endocrine and sperminogenic testicular function. 8. Relationships between testicular and plasma testosterone concentrations as well as between the number of Leydig cells in testicular tissue and their cell nucleus volume in boars of different ages]

Testicular tissue and blood samples (V. spermatica interna) were taken from 32 boars during castration. The animals were different age groups. Against this background, studies were conducted into the correlations between testicular and plasma testosterone, on the one hand, and the amount of interstitial cells of Leydig in testicular tissue as well as the latters' cell nuclei volumes, on the other. The results seemed to support the conclusion that any age-dependent increase of testicular and plasma testosterone concentrations was caused unambigously by an absolute increase in volume of androgenic testicular tissue, in concomitance with testicular growth, in other words, by rise in the total number of interstitial cells of Leydig.     

Changes in Testicular Interstitial Connective Tissue of Hamsters (Mesocricetus auratus) During Ageing and After Exposure to Short Photoperiod

The testicular interstitium of Syrian hamster (Mesocricetus auratus) was studied during ageing and in testicular regression after exposure to a short photoperiod, in relation to the interstitial cells and their connective tissue. This tissue was assessed histochemically using Masson's trichrome technique and the expression of Heat Shock Protein 47 (HSP‐47) and collagen IV (α5) was assessed in Leydig cells. Finally, an ultrastructural analysis of some cells of the testicular interstitium was made. Leydig cells were positive for HSP‐47 and collagen IV (α5). Ageing did not change the parameters studied while the short photoperiod altered the synthetic activity of Leydig cells. The positivity index of these cells for HSP‐47 was significantly higher in the regressed testis, but was lower for collagen IV (α5). During ageing no change were observed. Ultrastructural Leydig cells showed a discontinuous basal lamina that did not change during ageing. The basal lamina was not identified in Leydig cells regressed by exposure to a short photoperiod. In conclusion; the intertubular connective tissue suffers little change with age. By contrast, in the testis regressed after exposure to a short photoperiod the studied parameters related to the intertubular connective tissue were altered. These changes are probably related with the low synthetic activity of regressed Leydig cell.     

Plasticity of endometrial epithelial and stromal cells—A new approach towards the pathogenesis of equine endometrosis

Equine endometrosis, a frequent cause of subfertility, is characterized by periglandular fibrosis, and no treatment exists. Endometrial biopsies not only contain diseased glands, but also contain healthy glands and stroma. Myoepithelial (ME) and myofibroblastic (MF) markers are calponin, smooth muscle actin (SMA), desmin and glial fibrillary acidic protein (GFAP). Epithelial vimentin expression indicates epithelial to mesenchymal transition (EMT). The aim of this immunohistochemical study was to investigate whether biopsies with endometrosis express MF and ME markers and vimentin. Compared to healthy areas, significantly higher percentages of endometrotic glands were lined by calponin‐ and vimentin‐positive epithelial cells, whereas periglandular fibrosis contained significantly higher percentages of stromal cells positive for vimentin, desmin and SMA and significantly less calponin‐positive stromal cells. The rare GFAP expression was restricted to endometrotic glands. Of these, the most frequent features of endometrotic glands were higher percentages of SMA‐ and vimentin‐positive stromal cells and the prominent epithelial calponin staining that occurred in 100%, 93% and 95% of examined biopsies. Results indicate plasticity of equine endometrial epithelial and stromal cells. Particularly, endometrotic glands show evidence for ME differentiation and EMT. The different expression of MF markers between stromal cells from healthy and endometrotic areas suggests functional differences. The characteristic changes in the expression of SMA, vimentin and calponin between endometrotic glands and healthy areas can be helpful to confirm early stages of endometrosis. The characterization of cellular differentiation may help to decipher the pathogenesis of endometrosis and could lead to therapeutic strategies.