Transient coexpression of cytokeratin and vimentin in differentiating rat Sertoli cells

Developmental expression of heat shock protein 60 (HSP60) in the rat testis and ovary

Heat shock protein 60 (HSP60), a member of the chaperonin family, has an essential role in mediating correct folding of nuclear encoded proteins imported to mitochondria. We have investigated immunocytochemical expression of HSP60 in developing fetal, newborn, postnatal, and pubertal testis and ovary, and in the adult ovary of the rat. In the fetal gonads, HSP60 was expressed in the germ cells organized into sex cords and in the developing Leydig cells of the testis. In the pubertal testis, Leydig cells were strongly, spermatogonia and premeiotic spermatocytes moderately labeled, spermatids unlabeled. In the postnatal ovary, oocytes at all stages of folliculogenesis were positive for HSP60. In the pubertal ovary, glandular theca cells, and in the mature ovary, also the cells of the corpora lutea exhibited intense cytoplasmic labeling. At the electron microscopic level, immunogold particles were localized in the mitochondrial matrix, and in the Western blot analysis the antibody detected one single band of 60 kDa. Anti-HSP60 labeling in male and female sex steroid producing cells and their progenitors seems to be coordinated with the functional differentiation of these endocrine cells of the gonad. In the oocytes, a key element required for proper folding of imported mitochondrial proteins seems to be constitutively expressed throughout folliculogenesis. However, the data suggest that in the male germ cells mitochondrial chaperonin HSP60 is either not needed during the haploid phase of spermatogenesis or its level becomes extensively reduced and therefore undetectable by the methods used in the study.

Testicular cell cytoskeleton in the newt, Triturus marmoratus marmoratus, during the annual cycle

Light and electron microscopy immunohistochemical studies and Western blotting analysis of cytoskeletal proteins have been carried out in the testis of the marbled newt (Triturus marmoratus marmoratus) during the annual testicular cycle. The present findings revealed homologies and differences with regard to those reported in the testes of mammals and other vertebrates. Changes in immunohistochemical expression have also been detected in the course of the annual cycle. Actin and tubulin, which were scanty and diffusely located in spermatogonia and spermatocytes, increased their expression and reorganized during spermiogenesis. Vimentin and keratin, undetected in spermatogonia and spermatocytes, were expressed in differentiating spermatids and spermatozoa. In these cells, actin might be related with the connection of the axial fiber to the undulating membrane and the coordination of movement by both structures, while vimentin might be involved in the maintenance of the spatial relationship between the axoneme and the marginal fiber. During the first stages of spermatogenesis, the cytoplasm of Sertoli cells (follicular cells) showed a diffuse immunoreaction to actin, myosin, and tubulin and no vimentin immunolabeling. In advanced spermiogenesis, the follicular cells showed an intense immunoreaction to actin, myosin, tubulin, and vimentin in the apical projections that surrounded the spermatid heads. These apical cytoskeletal components might be involved in spermatid elongation, since the spermatids display no manchette, and in spermatozoon positioning and grouping. The colocalization of myosin and actin in the follicular cells suggests that actin filaments from contractile bundles and that contraction might be involved in changes in the Sertoli cell shape that accompany germ cell development during spermatogenesis. The interstitial cells immunostained to actin, myosin, tubulin, and vimentin. These cells, together with follicular cells, seemed to form the glandular tissue cells which showed a similar immunophenotype. The cells that surrounded the efferent duct epithelium immunostained to desmin, and they are probably contractile cells involved in sperm evacuation.

Immunohistochemical detection of immature Sertoli cell markers in testicular tissue of infertile adult men: a preliminary study

Testicular biopsy specimens from oligozoospermic infertile patients are characterized by different types of spermatogenic impairment in adjacent seminiferous tubules, a phenomenon called mixed atrophy. In order to evaluate possible involvement of the state of Sertoli cell differentiation, the distribution pattern of anti-Müllerian hormone (AMH), vimentin and cytokeratin intermediate filament proteins was investigated by means of immunohistochemistry. AMH immunoactivity occurs in Sertoli cells of the normal postnatal prepubertal testis, but it is absent in the adult testis with normal spermatogenesis. In the case of mixed atrophy, AMH immunoactivity was found in Sertoli cells of tubules showing spermatogenic arrest at the level of spermatogonia and in tubules showing Sertoli-cell-only (SCO) syndrome. Vimentin was expressed regularly in Sertoli cells independent of spermatogenic impairment or the state of Sertoli cell differentiation. Cytokeratin immunoactivity occurs in Sertoli cells of the normal postnatal prepubertal testis. Furthermore, cytokeratin expression was found in Sertoli cells of tubules showing spermatogenic arrest at the level of spermatogonia and in some SCO tubules. Co-expression of AMH and cytokeratin suggests that spermatogenic impairment such as spermatogenic arrest and SCO syndrome in human seminiferous tubules is associated with a population of Sertoli cells showing a prepubertal stage of development. The different pattern of AMH and cytokeratin expression in SCO tubules indicates that Sertoli cells in SCO syndrome show a mosaic pattern of differentiation.

Moderate alcohol consumption and disorders of human spermatogenesis

Environmental factors are suspected to be responsible in part for the deterioration in semen quality observed worldwide during the recent few decades. Alcohol might be one factor, considering the frequent changes in testicular function associated with heavy drinking. The dose-dependent effects of alcohol on human spermatogenesis are, however, not well known. We analyzed spermatogenesis and testicular tissue morphology of 195 men, aged 35-69 years, with computer-assisted microscopy in this autopsy study. The men were categorized into controls and four "consumption groups" according to the average daily alcohol consumption, which was determined on the basis of blind interviews with relatives and acquaintances. When the average daily alcohol consumption was 40 g or less, 59 (66%) of the 90 men showed normal spermatogenesis, whereas 31 (34%) had partial spermatogenic arrest (SA). Of the 31 men with average daily intake between 40 and 80 g, 17 (54%) showed normal spermatogenesis, 13 (42%) had partial or complete SA, and 1 man exhibited more severe testicular damage-"Sertoli cell only" (SCO) syndrome. Among men with daily intake between 80 and 160 g, only 13 of 35 men showed normal spermatogenesis (37%), 19 (54%) had partial or complete SA (odds ratio = 2.92), and 3 (9%) had the SCO syndrome (odds ratio = 16.85). The frequencies of spermatogenic disorders were similar in men drinking in excess of 160 g. Both SA and the SCO syndrome showed a clear dependence on daily dose; p < 0.0001 and p < 0.0004, respectively. We conclude that long-term average daily consumption of < 40 g of alcohol seems not to be associated with disorders of spermatogenesis. Consumption of moderate amounts of alcohol may affect semen quality more often than previously thought, whereas high alcohol consumption may even be associated with serious disorders of spermatogenesis.

Switch in the expression of the K19/K18 keratin genes as a very early evidence of testicular differentiation in the rat

It has been shown previously that acidic K18 and K19 keratins display a differential immunohistochemical pattern of expression during sexual differentiation of the gonads in the rat (Fridmacher et al. (1992) Development 115, 503-517). The present results indicate that K18 and K19 gene expression is regulated at the transcriptional level. The analysis was performed by Northern Blot, reverse transcriptase polymerase chain reaction (RT-PCR) and in situ hybridization. PCR products were cloned, sequenced and used as species-specific K18 and K19 riboprobes for in situ hybridization. K19 mRNA but not K18 mRNA was detected in undifferentiated gonads and in somatic cells of ovarian cords throughout the fetal ovary development. K18 mRNA expression appeared in male gonads, at 13.5 days of gestation, at the onset of testicular differentiation, as the first Sertoli cells differentiated and aggregated to form seminiferous cords. As testicular differentiation progressed, K19 mRNA disappeared and, from 14.5 days of gestation on, fetal Sertoli cells expressed exclusively K18 mRNA. The changes in the transcriptional activity of K19 and K18 genes, observed in male gonads, occur characteristically at the very beginning of testicular differentiation. In the male pathway of sexual differentiation, the switch in K19/K18 gene expression is, in addition to the activation of the anti-Müllerian hormone gene, the most precocious regulative event occurring after the expression of the testis determining factor SRY.

Sex-dependent expression of tenascin-C in the differentiating fetal rat testis and ovary

The cellular mechanisms controlling sexual differentiation of fetal gonads are poorly understood. By examining the protein and mRNA expression of tenascin-C in correlation with the immunocytochemical detection of alpha-smooth muscle actin (alpha-SMA) and basement membrane heparan sulfate proteoglycan (HSPG) we demonstrate a clear-cut sex-and development-dependent expression pattern of tenascin-C in the rat testis, ovary and mesonephros. Immunocytochemistry and in situ hybridization of tenascin-C in 15-day-pc fetal testis and ovary showed protein and mRNA accumulation within the mesenchyme of the mesogonadal connection. In addition to the male and female mesonephros, some labeling could also be seen within the testicular tunica albuginea and intraovarian mesenchymal septa. In the 17-day-pc testis abundant accumulation of tenascin mRNA and protein appeared in the tunica and mediastinum testis, but not at all in the intratesticular mesenchyme. A similar pattern was still seen in the newborns where, however, a decrease in the anti-tenascin immunoreactivity of the tunica and mediastinum could be demonstrated. In contrast to the testis, expression of tenascin in 17-day-pc ovaries was widespread within the hilus and the entire intragonadal mesenchyme where it continued to accumulate also in newborns. Northern blot analysis of tenascin-C mRNAs showed one message of 8.0 kb in the 15-day-pc male and female gonads. An additional weak signal of 6.5 kb was seen in the female mesonephros. In the 18-day-pc testis, the 6.5-kb signal appeared stronger than the 8.0-kb signal. In contrast to the testis, the 6.5-kb message was weak in the developing ovary where the 8.0-kb signal had an intense peak on the day 18 pc. Further, in the ovary, mesenchymal accumulation of HSPG coincided with the spatial distribution of tenascin. In the testicular tunica and in the mesenchyme of the male and female genital ducts expression of tenascin was parallel with the differentiation of smooth muscle tissue, detected by labeling for alpha-SMA, which also indicated the tenascin-negative myoid cells of the testis. Our results indicate that tenascin expression in the fetal rat internal genitalia is involved in the differentiation of smooth muscle cells but not intratesticular myoid cells. In the ovarian mesenchyme, tenascin-C may have a specific function in the dynamic remodeling of the ovarian cords.

Intermediate filaments in the testis of the teleost mosquito fish Gambusia affinis holbrooki: a light and electron microscope immunocytochemical study and western blotting analysis

A light and electron microscope immunocytochemical study and Western blotting analysis has been performed on intermediate filaments (vimentin, desmin and cytokeratins) in the testis of the teleost fish Gambusia affinis holbrooki. An immunoreaction to vimentin was observed in the epithelium of the efferent ducts, testicular canal and their surrounding peritubular cells. Positive vimentin immunostaining was also observed in the cells located around seminiferous tubules (boundary cells), Leydig cells, interstitial fibroblasts, chromatophores, and blood vessel endothelial cells. In contrast to mammals, no vimentin immunoreactivity was found in the Sertoli cells. Immunoreactivity to desmin was weak in the epithelial cells of the efferent ducts and testicular canal and intense in the peritubular cells that surrounded these ducts. Desmin immunoreactivity was also observed in the seminiferous tubule boundary cells. The immunoreactivity was weak in the boundary cells that surrounded germ cell cysts containing spermatogonia or spermatocytes and intense in the boundary cells around cysts with elongated or mature spermatids. Immunoreactivity towards cytokeratins was observed only in testicular blood vessels. Cytokeratin immunolabelling was intense in the endothelium and weak in the vascular smooth muscle cells. No cytokeratin immunoreactivity was found in the Sertoli cells, germ cells, interstitial cells or in the efferent duct epithelium. The absence of intermediate filaments in the Sertoli cells, the absence of cytokeratins in the epithelium of the sperm excretory ducts, and the presence of desmin filaments in these epithelial cells are the most important differences with regards to the intermediate filament phenotype in mammalian testes.

Cytoskeleton in Sertoli cells of the mosquito fish (Gambusia affinis holbrooki)

BACKGROUND

There is little information about the distribution of cytoskeletal components in the testes of teleost fish. The aim of this paper was to know the distribution of some major cytoskeletal proteins (tubulin, actin, vimentin, desmin, and cytokeratins) in the Sertoli cells of Gambusia affinis holbrooki and in their efferent duct epithelial cells which are possibly originated from the Sertoli cells.

METHODS

Light and electron microscopic immunocytochemical studies and Western blotting analysis were performed in G. affinis testis.

RESULTS

Actin immunoreaction was observed in the Sertoli cells at all spermatogenic stages, although the intensity of this reaction varied from one stage to another. Sertoli cells that support spermatogonia or spermatocytes showed a weak immunoreaction which was uniformly distributed throughout the cytoplasm and somewhat more concentrated at the level of the inter-Sertoli specialized junctions. Immunoreaction to actin increased during the first stages of spermiogenesis and was mainly localized beneath the plasma membrane. This immunoreaction was more intense in the basal than in the apical cytoplasm of Sertoli cells. In a more advanced stage of spermiogenesis, actin immunoreaction become stronger in the apical cytoplasm where Sertoli cells displayed cytoplasmic projections around each spermatid. After sperm release, the apical Sertoli cell cytoplasm still showed an intense actin immunoreaction. Intense immunoreaction to actin was also observed in the epithelial cells lining the efferent ducts. Immunoreaction to tubulin was diffuse throughout the Sertoli cell cytoplasm. No immunoreaction to vimentin or desmin was observed in the Sertoli cells during the spermatogenic process. Immunoreaction to both vimentin and desmin was observed in the efferent duct cells. Desmin immunoreaction was also observed in the seminiferous tubule boundary cells, mainly in the sections showing germ cell cysts at the last stages of spermiogenesis and in the peritubular cells that surrounded the efferent duct epithelium. Immunoreaction to cytokeratins was found in the endothelium of testicular blood vessels but not in the Sertoli cells or in the efferent duct epithelium.

CONCLUSIONS

Immunoreaction pattern to cytoskeletal proteins in the Sertoli cells of G. affinis differs from that reported in mammalian Sertoli cells. These differences include the distribution of actin filaments and the absence of detectable vimentin immunoreaction in G. affinis Sertoli cells.

Differential distribution of the alpha 6 subunit of integrins in the development and sexual differentiation of the mouse testis

The distribution of the alpha 6 subunit of integrins in the development and sexual differentiation of mouse testis was analyzed by light and electron microscopy during the embryonic, fetal and early postnatal periods. At the pregonadal phase only the epithelial cells of the mesonephric duct and of the distal mesonephric tubules showed a reaction to alpha 6, whereas the surface epithelium and the mesenchyme of the mesonephros were negative or contained only a rudimentary amount of the alpha 6 subunit. With the formation of the gonadal ridge and the testicular blastema, the gonadal cells became positive for the alpha 6 subunit. This expression remained in embryonic cord cells and in the vascular endothelial cells, whereas the differentiating cells of the surface epithelium, tunica albuginea, the Leydig cells, and the interstitial mesenchymal cells were negative. With the fetal and postnatal differentiation, the expression of the alpha 6 subunit gradually diminished in the cord cells, and by the prepubertal phase, alpha 6 was found only at adhesion sites between some Sertoli cells. Similar changes were seen in the mesonephric duct and tubules, and in the rete cords. The presence of alpha 6 in regions undergoing developmental cell aggregation processes and their disappearance during tissue maturation, suggest that alpha 6 plays a specific but transient role in gonadal cell adhesion necessary for the histogenetic organization of the testis. In addition to its role in developing and organizing cells, alpha 6 integrin was also a prominent component in degenerating cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related changes in cytoskeletal components of the BDF1 mouse Sertoli cell

Age-related changes in mouse Sertoli cell cytoskeletal components (F-actin, vimentin and cytokeratin) were investigated by light and transmission electron microscopy and immunofluorescence using BDF1 mice from 3-33 months of age. In old mice (30 and 33 months of age), the testicular seminiferous epithelia were extremely thin, containing scarce round spermatids and spermatocytes with no elongated spermatids. In these epithelia, the Sertoli cells had lost their polarity and had become flattened. F-actin was detectable at the junction between adjoining Sertoli cells and around the spermatid head in young mice. In old mice, F-actin was distributed at the junction between adjacent Sertoli cells, around the spermatid head, and at the luminal side of the Sertoli cell cytoplasm. Vimentin was detected around the Sertoli cell nucleus and extended into the Sertoli cell trunk towards the tubular lumen in young mice. In old mice testes, however, vimentin was recognized around the Sertoli cell nucleus, but not in the Sertoli cell trunk. Additionally, sheet-like reactions of vimentin, running parallel to the basement membrane, were detected near the luminal surface. Although cytokeratin was not detected in the Sertoli cells of mice until 27 months of age, it was obvious in the extremely thin seminiferous epithelia of older mice. Cytokeratin was randomly distributed within the Sertoli cell cytoplasm. In these Sertoli cells, the expression of vimentin was concurrently detected. Detection of cytokeratin in the extremely thin seminiferous epithelia is one of the most characteristic phenomena of age-related testicular changes in Sertoli cells of older mice.

Intermediate filament proteins and epithelial differentiation in the embryonic ovary of the rat

The development and sexual differentiation of gonads in female rat embryos and fetuses between the ages of 11 and 17 days was studied by immunocytochemical analysis of intermediate filament proteins and laminin by light and electron microscopy. In the 11-day-old pregonadal embryo, the surface epithelial cells in the ventral cortex of the mesonephros contained desmin but not cytokeratin or vimentin. The development of the gonad began on the following day by proliferative growth of the mesonephric surface cells, which like the subepithelial cells soon expressed vimentin in addition to desmin. The differentiation continued by formation of separate epithelial cell clusters, which joined into cords, irregular in shape and size. Desmin disappeared from the cord cells and cytokeratins appeared while vimentin remained in all somatic cell types. Desmin was especially abundant in some stromal cells adjacent to the epithelial tissues. After the segration of the basic ovarian tissues, vimentin and desmin decreased and cytokeratins appeared in the surface epithelial cells. New changes in cytokeratin expression appeared with the differentiation of the embryonic cords in a sex-specific manner with gradual decrease of reactivity for cytokeratin 18. No immunoreaction to the neurofilament proteins was found at the present ages, and the germ cells were negative for intermediate filaments. The results show that desmin is expressed in several primitive ovarian and mesonephric cells even though they are not myogenic.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokeratin and vimentin heterogeneity in human cornea

The body of information on cytokeratin expression in non-epithelial and epithelioid cells is steadily increasing. In this immunocytochemical study using a panel of monoclonal cytokeratin antibodies, we regularly observed cytokeratins no. 8 and 18 together with vimentin in the corneal endothelium of the human eye, but the antibodies exhibited a heterogeneous reactivity pattern. In fetal eye specimens, cytokeratins were already present at the 10th week of gestation, and disappeared at about the 22th week of fetal development. Corneal and conjunctival epithelial cells in the same specimens usually showed uniform cytokeratin 8 and 18 expression, beside the well documented presence of corneal and squamous epithelium type cytokeratins. In 2 of our 7 cases of adults, cells coexpressing cytokeratin and vimentin were observed in the corneal epithelium. The data provide another example of modulation of cytokeratin and vimentin expression, in which simplistic rules cannot be applied.

Dynamic changes in the intermediate filaments of the epithelial cells during development of the chicken's bursa of Fabricius

The development of bursal follicles and the differentiation of the follicle-associated epithelium and interfollicular epithelium were studied immunohistochemically using monoclonal anti-vimentin and anti-cytokeratin antibodies. In 10-day-old embryos the entodermal and cloacal epithelia coexpressed vimentin- and cytokeratin-intermediate filaments. Both undifferentiated and differentiated bursal surface epithelium simultaneously expressed vimentin- and cytokeratin-intermediate filaments during the entire period of embryogenesis. Vimentin expression in reticuloepithelial cells was related to bursal cell differentiation but was not linked to immune function. Sequential loss of vimentin from interfollicular epithelium, follicle-associated epithelium, and reticuloepithelial cells may reflect sequential acquisition of maturity in these three compartments. The presence of cytokeratin-intermediate filaments suggested that follicle-associated epithelium was not of mesenchymal origin. Testosterone treatment did not influence the vimentin and cytokeratin filament expression in the epithelial cell.

Utility of immunohistochemistry in distinguishing ovarian sertoli-stromal cell tumors from carcinosarcomas

Poorly differentiated Sertoli-stromal cell tumors and carcinosarcomas of the ovary both show biphasic epithelial and stromal patterns and may both show heterologous stromal elements, presenting a difficult diagnosis. We studied the immunohistochemical profile of Sertoli cell differentiation in human testes and applied these findings to the ovarian tumors. Eleven Sertoli-stromal cell tumors, six carcinosarcomas of the ovary, and 11 testes (six fetal, one infant, and four adult) were studied using antibodies to cytokeratin AE1:AE3 (AE1:3), cytokeratin CAM 5.2 (CAM), epithelial membrane antigen (EMA), vimentin, desmin, muscle-specific actin (MSA), S-100 protein (S-100), CA 19-9, CA 125, carcinoembryonic antigen monoclonal (CEA-M), carcinoembryonic antigen polyclonal (CEA-P), and placental alkaline phosphatase (PLAP). In the fetal testes, immature gonadal stroma and sex cord areas stained with vimentin (six of six cases), AE1:3 (five of six cases), and CAM (six of six cases). Sertoli cells in immature gonadal stroma areas, sex cords, and seminiferous tubules of normal fetal, infant, or adult testes never showed immunoreactivity for EMA, S-100, CA 19-9, CA 125, CEA-M, CEA-P, or PLAP. All Sertoli-stromal cell tumors stained with AE1:3 and CAM in areas of Sertoli cell differentiation (11 of 11 cases) but did not stain with EMA, PLAP, CEA-P, CEA-M, CA 19-9, CA 125, or S-100 (none of 11 cases). Carcinosarcomas expressed AE1:3 and CAM in all epithelial areas (six of six cases) and most stromal areas (five of six cases). Carcinomatous areas of carcinosarcoma also showed immunoreactivity for EMA (six of six cases), CA 125 (two of six cases), PLAP (two of six cases), CEA-P (two of six cases), and CEA-M (one of six cases), while stromal areas of carcinosarcoma expressed EMA (four of six cases) and S-100 (four of six cases). Heterologous stromal elements were present in three of 11 Sertoli-stromal cell tumors (two showed skeletal muscle and one showed both skeletal muscle and cartilage differentiation) and in four of six carcinosarcomas (one skeletal muscle, one cartilage, and two cartilage and skeletal muscle). All skeletal muscle heterologous elements expressed desmin, vimentin, and MSA. The heterologous cartilage in carcinosarcoma stained with S-100 (three of three), while the one case of heterologous cartilage in Sertoli-stromal cell tumor did not. These results suggest that ovarian Sertoli-stromal cell tumor can be distinguished from carcinosarcoma by the absence of staining for EMA, PLAP, CEA, CA 125, or CA 19-9 in epithelial areas of Sertoli-stromal cell tumor.(ABSTRACT TRUNCATED AT 400 WORDS)

Intermediate filaments and epithelial differentiation of male rat embryonic gonad

The presence and distribution of desmin, vimentin, cytokeratin, and laminin in the gonads of developing male rat embryos (11-17 days) were studied by immunocytochemistry. The findings were correlated with morphological changes of the cells and with the formation of basement membranes, as determined by electron microscopy. The surface epithelial and subepithelial cells of the meesonephros in the prospective gonadal region contained desmin. At the onset of gonadal development, vimentin appeared in the somatic cells of the thickening surface epithelium, which formed the gonadal ridge. Desmin disappeared and cytokeratins appeared in the Sertoli precursor cells at the inception of their epithelial differentiation. Simultaneously, the prospective Sertoli cells became polarized during their assembly into epithelial cell aggregates; the aggregates then fused and formed elongated testicular cords. The epithelial cell differentiation was accompanied by a deposition of basement membrane material around the cords and by an increase of desmin in the cells immediately around the cords. With further differentiation of the testicular cords, some cytokeratins from the Sertoli cells, but not from the cells of the rete cords, disappeared. On the other hand, other cytokeratin polypeptides and vimentin remained in the fetal Sertoli cells. The surface cell layer slowly differentiated towards a proper epithelium after the basic formation of the testicular cords and interstitium. Desmin and vimentin persisted in the interstitial cells throughout the entire study period. The early differentiation of the gonad is apparently under a general sex-independent initiation program. The developmental changes in intermediate filaments offer an opportunity for the further analysis of their general role in early organogenesis. In light of the genetic theory of testicular differentiation, the functions of the regulatory factor(s) include specific organization of cord cells, histological organization into looping cords rather than separated follicles, and male development of the interstitium, surface epithelium and tunica albuginea.

Differentiation of smooth muscle cells in the fetal rat testis and ovary: localization of alkaline phosphatase, smooth muscle myosin, F-actin, and desmin

The histochemical demonstration of alkaline phosphatase (AP) activity and localization of smooth muscle myosin (SMM), F-actin, and desmin were carried out on frozen sections of testes and ovaries from 15-day-old fetal to newborn rats. The presence of immunocytochemically localized SMM and desmin was confirmed by Western blot analysis of proteins from isolated gonads. The development of smooth muscle cells was predominant in the testis. The first SMM-positive cells with an increasing intensity for F-actin and desmin appeared in the testicular tunica albuginea and around the testicular cords by the age of 16 days. A continuous layer of SMM- and F-actin-positive (but not uniformly desmin-positive) myoid cells was detected in the newborn testis. In the early gonads and in the newborn ovary, a majority of the interstitial cells expressed desmin, indicating that, in undifferentiated tissues, non-myogenic cells may also express desmin. During fetal development, male and female gonocytes showed a decrease in F-actin content but retained their high AP activity. In the cortex of the newborn rat ovary, the observed high AP activity and the presence of desmin may be associated with the postnatal histogenesis of the follicles. The presence of SMM-containing cells in the hilus of the ovary may be required for the demarcation of the ovary from the mesonephros by the constriction of the mesovarium. The occurrence of SMM-positive cells predominantly in male fetuses suggests that the development of the contractile cells in the fetal testis may be induced by testicular androgens.

The blood-testis barrier and Sertoli cell junctions: structural considerations

In this review, a few well-established axioms have been challenged while others were viewed from a new perspective. The extensive literature on the blood-testis barrier has been scrutinized to help probe its mechanics and hopefully to promote understanding of the constant adaptation of the barrier function to germ cell development. Our principal conclusions are as follows: (1) Although the barrier zonule is topographically located at the base of the seminiferous epithelium it actually encircles the apex of the Sertoli cell. Consequently the long irregular processes specialized in holding and shaping the developing germ cells should be considered as apical appendages analogous to microvilli. (2) The development of the barrier zonule does not coincide with the appearance of a particular class of germ cells. (3) The barrier compartmentalizes the epithelium into only two cellular compartments: basal and lumenal. (4) Although the blood-testis barrier does sequester germ cells usually considered antigenic, immunoregulator factors other than the physical barrier seem to be involved in preventing autoimmune orchitis. (5) Structurally, a Sertoli cell junctional complex is composed of occluding, gap, close, and adhering junctions. The Sertoli cell membrane segments facing germ cells are presumably included in the continuum of the Sertoli cell junctional complex that extends all over the lateral and apical Sertoli cell membranes. (6) The modulation (i.e., formation and dismantling) of the junctions in a baso-apical direction is characteristic of the seminiferous epithelium and may be dictated by germ cell differentiation. The formation of tubulobulbar complexes and the following internalization of junction vesicles conceivably represent sequential steps of a single intricate junction elimination process that involves junction membrane segments from different cell types as part of a continual cell membrane recycling system. (7) The preferential association of junctional particles with one or the other fracture-face reflect a response to various stimuli including seasonal breeding. Changes in the affinity of the particles are generally coincidental with cytoskeletal changes. However, changes in the cytoskeleton are not necessarily accompanied by permeability changes. The number of strands seems to reflect neither the junctional permeability nor the transepithelial resistance. The diverse orientation of the strands seems to be related to the plasticity of the Sertoli cell occluding zonule. (8) Cooperation between all constituents (Sertoli cells, myoid cells, cell substratum, and germ cells) of the epithelium seems essential for the barrier zonule to function in synchrony with the germ cell differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)

Intermediate filaments in Sertoli cells

Using immunohistochemical techniques both at light and electron microscopic levels, the arrangement and distribution of intermediate filaments in Sertoli cells of normal testis (in rat and human), during pre- and postnatal development (in rabbit, rat, and mouse) and under experimental and pathological conditions (human, rat), have been studied and related to the pertinent literature. Intermediate filaments are centered around the nucleus, where they apparently terminate in the nuclear envelope providing a perinuclear stable core area. From this area they radiate to the plasma membranes; apically often a close association with microtubules is seen. Basally, direct contacts of the filaments with focal adhesions occur, while the relationship to the different junctions of Sertoli cells is only incompletely elucidated. In the rat (not in human) a group of filaments is closely associated with the ectoplasmic specializations surrounding the head of elongating spermatids. Both in rat and human, changes in cell shape during the spermatogenic cycle are associated with a redistribution of intermediate filaments. As inferred from in vitro studies reported in the literature, these changes are at least partly hormone-dependent (vimentin phosphorylation subsequent to FSH stimulation) and influenced by local factors (basal lamina, germ cells). Intermediate filaments, therefore, are suggested to be involved in the hormone-dependent mechanical integration of exogenous and endogenous cell shaping forces. They permit a cycle-dependent compartmentation of the Sertoli cell into a perinuclear stable zone and a peripheral trafficking zone with fluctuating shape. The latter is important with respect to the germ cell-supporting surface of the cell which seems to limit the spermatogenetic potential of the male gonad.

Sertoli cells and testicular differentiation in the rat fetus

The fetal testis is not merely a precursor of the adult organ: it is indeed an endocrine gland whose function is the masculinization of the fetus. It differs physiologically and morphologically from the adult testis. In this paper, the first stages of testicular differentiation in the rat are described, with special emphasis on the ultrastructural aspects. At the stage of 13.5 days after fertilization, the first Sertoli cells differentiate; they are characterized by a voluminous and little electron dense cytoplasm, a well-developed RER formed by vesicles and short cisternae filled with a flocculent material. Progressively, they polarize and adhere to one another by adherens-like junctions and cytoplasmic interdigitations to form the differentiating seminiferous cords. In the basal part of the Sertoli cells, a mat of microfilaments differentiates under the plasmalemma, while cytoplasmic blebs protruding in the extracellular space tend to disappear. A continuous basal lamina delineating the seminiferous cords begins to appear on day 14.5 and becomes widespread on day 15.5. These observations, when compared with other data from the literature, emphasize the fact that the differentiation of the Sertoli cells is the first morphological event during testicular differentiation. A possible role of the Sertoli cells in the subsequent organogenesis of the testis is suggested.

The fine structure of the testis, Part I

This paper presents morphological (light- and electron-microscopical) evidence for the role of the mesonephros in contributing cells to the differentiating indifferent gonad and, after sexual differentiation, to the testis. A continuous process is revealed during which segregation of cells occurs from the developing and regressing mesonephros. Additionally, the complementary role of the coelomic epithelium in gonadal ridge and testis formation is demonstrated. The differentiation of testicular cords, their remodelling from a primary reticulum, and the composition and further change of the cellular content during the period after sexual differentiation is described using a computer-aided three-dimensional reconstruction system. Apart from these morphogenetic events, cytodifferentiation in the somatic cells of the indifferent gonad and of the early differentiated testis is demonstrated using indirect immunofluorescence in combination with monoclonal antibodies to the intermediate filament proteins keratin 8 and 18 and vimentin. The immunohistochemical results show that different forms of cytodifferentiation coexist among the somatic cells present in the indifferent gonad and in the testis early after sexual differentiation.

Expression of different cytokeratin subclasses in human chordoma

A detailed immunohistochemical characterization of different cytokeratin subclasses was performed on frozen tumour tissue from three classical chordomas. Simple epithelium cytokeratins Nos 8, 18, and 19 were detected in all tumour cells while cytokeratin No. 7 was not found. Cytokeratins characteristic of squamous differentiation, including keratinization, were generally lacking, with the exception of the varying expression of cytokeratin No. 4. Vimentin was found in all the tumours, while they lacked desmin immunoreactivity. The present study indicates the co-expression of vimentin and cytokeratins, predominantly of the simple epithelium type. In addition, chordoma cells have the ability to express cytokeratins characteristic of squamous differentiation. This finding corresponds well to the electron microscopic findings of tonofilament bundles ending in well-developed desmosomes.

Intermediate filaments in normal thyrocytes: modulation of vimentin expression in primary cultures

In dog thyrocyte primary cultures, the antagonistic effects of thyrotropin (TSH) and epidermal growth factor (EGF) on differentiation expression were accompagnied by distinct long-term morphological changes: TSH-treated cells showed an epitheloid morphology; EGF reversibly induced a fusiform shape. Using indirect immunofluorescence microscopy and two-dimensional gel electrophoresis, we studied the modifications in the distribution and synthesis of the intermediate filament proteins of the cytoskeleton in response to TSH and EGF. These factors had little effect on the expression of cytokeratins 8 and 18, which were expressed in 98% of cells. However, TSH induced a profound redistribution of cytokeratins (and actin) with the appearance of a marked staining of cell junctions. Vimentin was coexpressed with cytokeratins in about 40% of cells from normal thyroid follicles freshly isolated by collagenase. During culture, immunostained vimentin network progressively developed in 90% of control and EGF-treated cells simultaneously with vimentin synthesis. In contrast, only 20% of TSH-treated cells reacted with vimentin antibody and we observed a marked decrease in vimentin synthesis in response to TSH. Therefore, vimentin synthesis, which should occur in at least some normal thyroid follicles in vivo, was inhibited in vitro by TSH which promotes differentiation expression. However, EGF-treated cells thereafter cultured with TSH regained an epitheloid morphology and differentiation in spite of the persistency of a complete network of vimentin.

K562 erythroleukemia cells express cytokeratins 8, 18, and 19 and epithelial membrane antigen that disappear after induced differentiation

The effects of differentiation-modulating drugs were studied on the expression of intermediate filaments (IFs) in the human K562 erythroleukemic cell line. The untreated cells contained typical cytoplasmic coiling bundles, positive for both vimentin and cytokeratin as judged by indirect immunofluorescence microscopy with monoclonal antibodies (Mabs). Some of the cells also showed bright immunoreactivity for epithelial membrane antigen (EMA), as revealed with a Mab and polyclonal antiserum. When exposed to hemin or to sodium butyrate, most of the cells became cytokeratin negative within 3 days and showed dispersion of vimentin fibrils. Upon exposure to the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), the amount of both vimentin and cytokeratin appeared to be greatly increased within 3 days and was found both in dispersed cytoplasmic fibrils, in large spherical, eccentric aggregates, as well as in cytoplasmic fibrils in cells spreading on fibronectin. TPA induced a complete loss of proliferation, as judged by immunostaining with the Mab Ki-67. The effects of TPA were found to be irreversible and could be induced by only a short exposure to the drug. Western blotting analysis and monoclonal antibodies to individual cytokeratins revealed that untreated K562 cells expressed Mr 52,000 (No. 8), 46,000 (No. 18), and 40,000 (No. 19) cytokeratin polypeptides, which disappeared when the cells were exposed to hemin or to sodium butyrate to induce erythroid differentiation but were greatly enhanced when exposed to TPA. The monoclonal anti EMA antibody reacted in K562 cells with a single Mr 320,000 polypeptide that was also revealed in MCF-7 breast carcinoma cells. Human bone marrow cells or other leukemic cell lines with erythroid differentiation capacity (HEL and KG-1) did not contain cytokeratin- or EMA-immunoreactive cells, suggesting that in K562 cells these properties may rather represent abnormal cytodifferentiation or retrodifferentiation toward early embryonic mesenchymal cells, than a more general expression of epithelial features in human leukemic cells.

Expression of fetal-type intermediate filaments by 17-day-old rat Sertoli cells cultured on reconstituted basement membrane

The expression of cytokeratin- and vimentin-type intermediate filaments was studied by means of immunohistochemistry in Sertoli cells cultured on two types of reconstituted basement membrane in two-compartment culture chambers. In situ, the Sertoli cells of 17-day-old rats contained only vimentin intermediate filaments. During culture, a gradual reorganization of intermediate filaments accompanied by an increased cytokeratin immunoreactivity was observed. After 6 days, Sertoli cells contained both cytokeratin and vimentin, and the same cytokeratin type as in fetal and newborn testis was revealed by electrophoresis and immunoblotting. The present study shows that the isolation and culture of Sertoli cells causes, even in an improved culture system, qualitative changes in the expression of intermediate filament proteins.

Expression of cytokeratins 8 and 18 in human Sertoli cells of immature and atrophic seminiferous tubules

Tissues of human testes, either normal (23 specimens of various developmental stages), or affected by pathological conditions (19 specimens of dystopia, atrophia and/or oligospermia) were immunohistochemically examined for the expression of different cytokeratins, using mainly frozen material. Cytokeratins 8 and 18 were found in varying amounts in Sertoli cells of fetal, prepubertal and senile testes and in all cases of pathological alteration. Cytokeratins were completely absent only in normal, mature seminiferous tubules. Therefore, the immunohistochemical detection of cytokeratins in Sertoli cells seems to provide a sensitive marker for immature or damaged testes.

The Sertoli cell cytoskeleton: a target for toxicant-induced germ cell loss

Numerous studies in recent years have elucidated fundamental properties of axoplasmic structure, biochemistry, and function. The structural role of the cytoskeletal elements, the orientation of MTs within the axon, the phenomenon of MT-dependent transport, and the identity and direction of movement of two MT motors--kinesin and MAP-1C--have been revealed. For many years to come, researchers investigating the structure and function of the Sertoli cell cytoskeleton will be able to adapt techniques gleaned from work on the axonal cytoskeleton. Innovative thinking will be required to apply these techniques to the special circumstances of the male reproductive system; however, the underlying questions are similar. For example, knowledge of several fundamental properties of transport processes in the Sertoli cell would facilitate the toxicologic evaluation of this system. What is the orientation of MTs within the Sertoli cell cytoplasm? Are the fast-growing (+) ends of all MTs in the Sertoli cell cytoplasm directed toward the lumen? This is an important question because the direction of MT-dependent transport involving known MT motors is dependent upon the MT orientation. Which of the Sertoli cell transport pathways are MT-dependent pathways? What are the MT motors involved in these pathways? Ultrastructural examination following exposure to specific cytoskeleton-disrupting agents has highlighted the importance of AFs, IFs, and MTs in the Sertoli cell. Future research will focus on the nature of those molecules which integrate these cytoskeletal components into a dynamic whole, the regulatory systems which control this integration, and the role of an integrated cytoskeleton in Sertoli cell function and testicular homeostasis. Toxicology will be an active participant in this process of scientific discovery. The selective nervous system and testicular toxicants may be useful tools in revealing similarities in the cytoskeletal organization of these apparently disparate organ systems. By searching for common targets in the testis and nervous system, the mechanisms of action of these agents may be more easily, and more confidently, determined.

Visualization of the cytoskeleton in Leydig cells in vitro. Effect of luteinizing hormone and cytoskeletal disrupting drugs

Effect of LH, vinblastine and cytochalasin B on the cytoskeleton of cultured Leydig cells was investigated using monoclonal antibodies and fluorescence microscopy. After LH addition and treatment with cytoskeletal disrupting drugs, three main effects were observed: 1) increase of androgen level secreted by cultured mouse Leydig cells, 2) changes of cell-shape towards regular and rounded, 3) increase of delta 5,3 beta-HSD activity. The results are discussed in respect to possible involvement of cytoskeleton in the regulation of steroidogenesis.

Immunohistochemical investigation of different cytokeratins and vimentin in the human epididymis from the fetal period up to adulthood

The anatomical distribution of cytokeratins and vimentin was investigated by means of immunohistochemistry in the human epididymis. Epithelial cells of the ductuli efferentes and the corpus epididymidis were positive for cytokeratins and vimentin. The expression of epithelial vimentin decreased toward the cauda epididymidis, whereas cytokeratins remained unchanged. The epithelium of the ductus deferens was negative when antibodies against vimentin were used. With monoclonal antibodies to individual cytokeratins, the presence of cytokeratins 7, 8, 18, and 19 was demonstrated histochemically throughout the epithelium of the epididymis. Monoclonal antibodies specific for cytokeratin 17 allowed immunohistochemical differentiation between the ductuli efferentes and the ductus epididymidis.

Distribution of intermediate-filament proteins in the human enamel organ: unusually complex pattern of coexpression of cytokeratin polypeptides and vimentin

We applied immunohistochemical techniques and gel electrophoresis to examine the distribution of intermediate filaments in human fetal oral epithelium and the epithelia of the human enamel organ. Both methods demonstrated that human enamel epithelia contain cytokeratins 5, 14, and 17, which are typical of the basal cells of stratified epithelia, as well as smaller quantities of cytokeratins 7, 8, 19, and in trace amounts 18, which are characteristic components of simple epithelial cells. In the external enamel epithelium and stellate-reticulum cells, most of these components appeared to be simultaneously expressed. In contrast, the parental oral epithelium was negative for cytokeratin 7, thus indicating possible "neoexpression" during the course of tooth formation. Immunohistochemical procedures using various monoclonal antibodies against vimentin revealed the transient coexpression of vimentin and cytokeratins in the external enamel epithelium and in stellate-reticulum cells during enamel development. The significance of the coexpression of cytokeratins and vimentin is discussed in relation to previous findings obtained in other normal tissues and in the light of the functional processes characteristic of these epithelia.

Cytokeratin filaments and desmosomes in the epithelioid cells of the perineurial and arachnoidal sheaths of some vertebrate species

Using electron microscopy and immunohistochemistry with a large panel of antibodies to various cytoskeletal proteins we have noted that the single- or multi-layered sheaths of epithelioid cells ("neurothelia") surrounding peripheral nerves (perineurial cells) or structures of the central nervous system, including the optic nerve (arachnoid cells), show remarkable interspecies differences in their cytoskeletal complements. In two anuran amphibia examined (Xenopus laevis, Rana ridibunda), the cells of both forms of neurothelia, i.e., perineurial and arachnoid, are interconnected by true desmosomes and are rich intermediate-sized filaments (IFs) of the cytokeratin type. Among higher vertebrates, a similar situation is found in the bovine and chicken nervous systems, in which the arachnoid cells of the meninges contain desmosomes and IFs of both the cytokeratin (apparently with restricted epitope accessibilities in the chicken) and the vimentin type, whereas the perineurial cells of many nerves contain cytokeratin IFs, often together with vimentin, but no desmosomes. In contrast, in rat arachnoidal and perineurial cells significant reactions have been observed neither for cytokeratins nor for desmosomes. In the human nervous system, cytokeratins and desmosomes have also not been seen in the various perineuria studied whereas desmosomes are frequent in arachnoidal cell layers which are dominated by vimentin IFs and only in certain small regions of the brain contain some additional cytokeratins. The occurrence of cytokeratins in the tissues found positive by immunohistochemistry has been confirmed by gel electrophoresis of cytoskeletal proteins, followed by immunoblotting. Our results emphasize both similarities and differences between the neurothelia on the one hand and epithelia or endothelia on the other, justifying classification as a separate kind of tissue, i.e., neurothelium. The observations of interspecies differences lead to the challenging conclusion that neither desmosomes nor cytokeratins are essential for the basic functions of neurothelial sheaths nor does the specific type of IF protein expressed in these cells appear to matter in this respect. The results are also discussed in relation to the cytoskeletal characteristics of other epithelioid tissues and of human neurothelium-derived tumors.

Expression of intermediate filament proteins in fetal and adult human lung tissues

The expression patterns of intermediate filament proteins in fetal and normal or nonpathological adult human lung tissues are described using (chain-specific) monoclonal antibodies. In early stages of development (9-10 weeks and 25 weeks of gestation) only so-called simple cytokeratins such as cytokeratins 7 (minor amounts). 8, 18 and 19 are detected in bronchial epithelial cells. At later stages of development, the cytokeratin expression patterns become more complex. The number of bronchial cells positive for cytokeratin 7 increases, but basal cells in the bronchial epithelium remain negative. These latter cells show, however, expression of cytokeratin 14 in the third trimester of gestation. Developing alveolar epithelial cells express cytokeratins 7, 8, 18 and 19. In adult human bronchial epithelium cytokeratins 4 (varying amounts), 7, 8, 13 (minor amounts), 14, 18 and 19 can be detected, with the main expression of cytokeratins 7, 8, and 18 in columnar cells and the main expression of cytokeratin 14 in basal cells. Vimentin is detected in all mesenchymal tissues. In addition, fetal lung expresses vimentin in bronchial epithelium, however, to a lesser extent with increasing age, resulting in the expression of vimentin in only few scattered bronchial cells at birth. Also in adult bronchial epithelium the expression of vimentin is noticed in part of the basal and columnar epithelial cells. Desmin filaments, present in smooth muscle cells of the lung, appear to alter their protein structure with age. In early stages of development smooth muscle cells surrounding blood vessels are partly reactive with some cytokeratin antibodies and with a polyclonal desmin antibody. At week 9-10 and week 25 of gestation a monoclonal antibody to desmin, however, is not reactive with blood vessel smooth muscle cells but is only reactive with smooth muscle cells surrounding bronchi. With increasing age the reactivity of cytokeratin antibodies with smooth muscle cells in blood vessels decreases, while the reactivity with the monoclonal desmin antibody increases. Our results show that during differentiation profound changes in the intermediate filament expression patterns occur in the different cell types of the developing lung.

Patterns of cytokeratin/vimentin coexpression in the guinea pig

The distribution of cytokeratin and vimentin in guinea pig tissues as seen by immunohistochemistry using monoclonal antibodies is described and a similar distribution pattern of coexpression of cytokeratin and vimentin in various cell types as compared to human tissues were found. The possible explanations for the unusual coexpression of both types of intermediate filaments in normal cells are discussed.

Expression of cytokeratin and vimentin in nucleus pulposus cells

With immunohistochemistry using monoclonal antibodies against intermediate filament proteins, nucleus pulposus cells were found to express cytokeratin(s) simultaneously with vimentin in fetal life and childhood. This finding adds to the series of human tissues showing coexpression of cytokeratins and vimentin. Surprisingly remnants of such cells were also found in the nucleus pulposus of adults, and a possible relationship of such cells to chordoma formation is discussed.

Cytoskeletons of retinal pigment epithelial cells: interspecies differences of expression patterns indicate independence of cell function from the specific complement of cytoskeletal proteins

In vertebrate tissue development a given cell differentiation pathway is usually associated with a pattern of expression of a specific set of cytoskeletal proteins, including different intermediate filament (IF) and junctional proteins, which is identical in diverse species. The retinal pigment epithelium (RPE) is a layer of polar cells that have very similar morphological features and practically identical functions in different vertebrate species. However, in biochemical and immunolocalization studies of the cytoskeletal proteins of these cells we have noted remarkable interspecies differences. While chicken RPE cells contain only IFs of the vimentin type and do not possess desmosomes and desmosomal proteins RPE cells of diverse amphibian (Rana ridibunda, Xenopus laevis) and mammalian (rat, guinea pig, rabbit, cow, human) species express cytokeratins 8 and 18 either as their sole IF proteins, or together with vimentin IFs as in guinea pig and a certain subpopulation of bovine RPE cells. Plakoglobin, a plaque protein common to desmosomes and the zonula adhaerens exists in RPE cells of all species, whereas desmoplakin and desmoglein have been identified only in RPE desmosomes of frogs and cows, including bovine RPE cell cultures in which cytokeratins have disappeared and vimentin IFs are the only IFs present. These challenging findings show that neither cytokeratin IFs nor desmosomes are necessary for the establishment and function of a polar epithelial cell layer and that the same basic cellular architecture can be achieved by different programs of expression of cytoskeletal proteins. The differences in the composition of the RPE cytoskeleton further indicate that, at least in this tissue, a specific program of expression of IF and desmosomal proteins is not related to the functions of the RPE cell, which are very similar in the various species.

Coexpression of cytokeratin and vimentin in Rathke's cysts of the human pituitary gland

Immunohistochemistry with monoclonal and polyclonal antibodies revealed the presence of cytokeratins in epithelial cells of Rathke's cysts in the pars intermedia of the human pituitary gland. With monoclonal antibodies specific for individual cytokeratins, the expression of CK 18, CK 8, CK 7, and CK 19 could be shown in these cells. Within the hypophysis, CK 19 and CK 7 were restricted to Rathke's cysts and a few epithelial cell clusters in the pars tuberalis, whereas other cytokeratins were also present in endocrine cells of the pars distalis. Furthermore, vimentin and, focally, glial fibrillary acidic protein (GFAP) were detected in the cystic epithelia. By double labelling, coexpression of cytokeratin and vimentin, GFAP and cytokeratin, and GFAP and vimentin could be demonstrated. Compiled data of all known cases of coexpression of cytokeratin and vimentin in normal cells reveal physiological correlations and suggest a functional significance of this rare type of coexpression of intermediate filament proteins.

Distribution of vimentin-type intermediate filaments in Sertoli cells of the human testis, normal and pathologic

The presence, distribution and spatial arrangement of vimentin-type intermediate filaments in Sertoli cells from human testis biopsies, were studied in semithin and ultrathin sections using a polyclonal rabbit antiserum. At the ultrastructural level, vimentin immunoreactivity was seen concentrated around the nuclei, along fibrillary material within the cytoplasm and at the ectoplasmic specializations of the Sertoli cell junctions, as well as throughout the periphery of the Sertoli cell processes. It is therefore well suited as a marker for Sertoli cell configuration. In computer-aided 3D reconstructions of 20 serial sections, Sertoli cells displayed particular configurations of intermediate filaments in the different stages of spermatogenesis. Two basic configurations, named AS (before spermiation, stages V, VI, I and II), and PS (after spermiation, stages III and IV) respectively, could be differentiated. In addition to the reconstruction and morphological analysis of vimentin filaments in Sertoli cells from patients with unaltered spermatogenesis (obstructive azoospermia), pathological specimens (spermatogenetic arrest, Sertoli cells only-syndrome) were studied with respect to vimentin immunohistochemistry. The results indicate that vimentin filaments play an important role in the adaptation of Sertoli cells to the varying configurations of neighbouring cells during spermatogenesis as well as under pathological conditions.

A light microscopic and morphometric analysis of the Sertoli cell during the spermatogenic cycle of the rat

Testes from 8 adult rats were perfusion-fixed with buffered glutaraldehyde and semi-thin sections of the seminiferous epithelium at all stages of the spermatogenic cycle were subjected to morphometric analysis at the light microscope level. Methods are presented to derive the volume occupied by the Sertoli cells within the total volume of the seminiferous epithelium at each stage of the cycle for a single testis. The total number of Sertoli cells present in each stage for the whole testis was calculated from a measurement of Sertoli cell numerical density and the total volume of the seminiferous tubule in the testis at each stage of the cycle. Average volume of a single Sertoli cell for each stage was derived by dividing the first set of data by the latter data. Average Sertoli cell volume exhibited a cyclic variation in relation to the stages of the spermatogenic cycle. Sertoli cells were smallest during stages VI-VIII (5300-5500 micron3) increased to maximum volume during stages XII-XIV (7700-8000 micron3) and thereafter during stages I-V, gradually contracted in volume to complete the cycle. Stage-dependent cyclic variations in Sertoli cell volume offers evidence that the morphology of the Sertoli cell undergoes structural modifications to accommodate changes in the shape and volume of the developing germ cells. Furthermore these volume changes implicate the Sertoli cells in cyclic metabolic, absorptive and secretory functions which possibly direct the maturation of germ cells during the spermatogenic cycle.

Patterns of cytokeratin and vimentin expression in the human eye

We studied the expression of the various cytokeratin (CK) polypeptides and vimentin in tissues of the human eye by applying immunocytochemical procedures using a panel of monoclonal antibodies as well as by performing biochemical analyses of microdissected tissues. Adult corneal epithelium was found to contain significant amounts of the cornea-specific CKs nos. 3 and 12 as well as CK no. 5, and several additional minor CK components. Among these last CKs, no. 19 was found to exhibit an irregular mosaic-like staining pattern in the peripheral zone of the corneal epithelium, while having a predominantly basal distribution in the limbal epithelium. Both the fetal corneal epithelium and the conjunctival epithelium were uniformly positive for CK no. 19. In the ciliary epithelium, co-expression of CKs nos. 8 and 18 and vimentin was detected, whereas in the retinal pigment epithelium, CKs nos. 8 and 18 were dominant. The present data illustrate the remarkable diversity and complexity of CK-polypeptide expression in the human eye, whose significance with respect to histogenetic and functional aspects is, as yet, only partially clear. The unusual distribution of CK no. 19 in different zones of the corneal epithelium may be related to the specific topography of corneal stem cells. The occurrence of the expression of simple-epithelium CKs in the ciliary and pigment epithelium demonstrates that, despite their neuroectodermal derivation, these are true epithelia.

Cytokeratins in certain endothelial and smooth muscle cells of two taxonomically distant vertebrate species, Xenopus laevis and man

Using immunolocalization techniques, electron microscopy, and gel electrophoresis combined with immunoblotting, we have noted remarkable interspecies differences in the expression of cytokeratins in certain nonepithelial cells. In the present study we describe, in two taxonomically distant vertebrate species, the African clawed toad Xenopus laevis and man, endothelial and smooth muscle cells which express cytokeratin intermediate filaments (IFs), in addition to vimentin and/or desmin IFs. In Xenopus, all endothelia seem to produce both vimentin and cytokeratin IFs. As well, certain smooth muscle bundles located in the periphery of the walls of the esophagus and the urinary bladder produce small amounts of cytokeratin IFs in addition to IFs containing vimentin or desmin or both. The amphibian equivalents of human cytokeratins 8 and 18 have been identified in these nonepithelial tissues. In human endothelial cells, immunocytochemical reactions with certain cytokeratin antibodies are restricted to a rare subset of blood vessels. Vessels of this type were first noted in synovial and submucosal tissues, but also occur in some other locations. Cytokeratins have also been detected in certain groups of smooth muscles, such as those present in the walls of some blood vessels in synovial tissue and umbilical cord. Here, the synthesis of low levels of cytokeratins 8 and 18, sometimes with traces of cytokeratin 19, has been demonstrated in smooth muscle cells by colocalization with myogenic marker proteins, such as desmin and/or the smooth-muscle-specific isoform of alpha-actin. Possible reasons for the differences in cytokeratin expression between adjacent endothelia in man, and smooth-muscle structures in both species, as well as biologic and histodiagnostic implications of these findings, are discussed.

Induction of cytokeratin expression in human mesenchymal cells

We studied the phenotypic features of some typical human mesenchymal cells, including decidual stromal cells and adult and fetal fibroblasts under different cell culture conditions by using antibodies to intermediate filament proteins and desmoplakins. In cell culture, the decidual stromal cells rapidly acquired typical fibroblastoid appearance with abundant arrays of vimentin filaments while the cytokeratin-positive epithelial cells, occasionally found in typical epithelioid colonies, lacked vimentin positivity and showed desmoplakin positivity. Within a few days, many of the stromal cells started to present cytokeratin positivity when cultured either in Condimed or in Chang medium. The cytokeratin positivity was first detected in small, scattered cytoplasmic dotted fibrils or in perinuclear dotlike aggregates with fibrillar projections. Later, denser cytokeratin-positive fibrillar arrays could also be seen in stromal cells, which lacked desmoplakin positivity as judged by two monoclonal antibodies. Decidual stromal cells were also cloned and in five out of ten clones some of the cells acquired a similar cytokeratin positivity when transferred into Chang or Condimed medium. Immunoblotting results indicated that cytokeratins 8, 18, and 19 can be found in these cultures. Similar cytokeratin positivity could also be seen in the same culture conditions in cultured fetal fibroblasts from skin, chorionic villi, and lung but not in young or adult skin fibroblast cultures. The present results suggest that decidual stromal cells as well as some embryonal mesenchymal cells can acquire epithelial differentiation in vitro as judged by the emergence of cytokeratin proteins. This ability appears to be lost in the corresponding adult cell. The results furthermore suggest that cytokeratin fibrils can be organized in the cytoplasm without an apparent organization center and that neither the appearance of desmoplakins nor the formation of cell-to-cell contacts are required for cytokeratin filament assembly.

Expression of type I and III collagen during morphogenesis of fetal rat testis and ovary

The distribution of interstitial collagen type I and III was studied immunocytochemically and ultrastructurally in the fetal rat testis and ovary from the undifferentiated stage (day 12) until birth. The results suggest that there is a correlation between the differentiation, organization, and abundance of the mesenchyme and the differentiation of the testicular vs. ovarian cords. Type III collagen was already present in the undifferentiated gonadal mesenchyme, and it appeared at an early stage around the organizing gonadal cords. Type I collagen appeared later in a similar mesenchymal distribution as type III collagen. Fragmentation of the subepithelial basement membrane in the gonads starting morphogenesis was considered to indicate that the surface epithelium participates in the gonadal cord formation. The expression of type III collagen at first on the surface of the developing testicular cords and later around the ovarian cords suggests that the mesenchymal premyoid cells are actively involved in the male cord formation. Focal discontinuities were found in the basement membrane of the ovarian cords, which in part were separated from each other by a ramified and relatively sparse mesenchyme. A complex linkage between the cytoskeleton and the extracellular matrix is illustrated both in the cord forming Sertoli and granulosa cells, and in the adjacent mesenchymal cells. Depletion of the mesenchyme and the basement membrane around the germ cell-granulosa cell associations of the wide ovarian medullary cords may be causal for their subsequent degeneration.

Basic proteins of the perinuclear theca of mammalian spermatozoa and spermatids: a novel class of cytoskeletal elements

The nuclei of bovine spermatids and spermatozoa are surrounded by dense cytoplasmic webs sandwiched between the nuclear envelope and the acrosome and plasma membrane, respectively, filling most of the cytoplasmic space of the sperm head. This web contains a complex structure, the perinuclear theca, which is characterized by resistance to extractions in nondenaturing detergents and high salt buffers, and can be divided into two major subcomponents, the subacrosomal layer and the postacrosomal calyx. Using calyces isolated from bull and rat spermatozoa we have identified two kinds of basic proteins as major constituents of the thecal structure and have localized them by specific antibodies at the light and electron microscopic level. These are an Mr 60,000 protein, termed calicin, localized almost exclusively to the calyx, and a group of multiple-band polypeptides (MBP; Mr 56,000-74,000), which occur in both the calyx and the subacrosomal layer. The polypeptides of the MBP group are immunologically related to each other, but unrelated, by antibody reactions and peptide maps, to calicin. We show that these basic cytoskeletal proteins are first detectable in the round spermatid stage. As we have not detected any intermediate filament proteins and proteins related to nuclear lamins of somatic cells in sperm heads, we conclude that the perinuclear theca and its constituents, calicin and MBP proteins, are the predominant cytoskeletal elements of the sperm head. Immunologically cross-reacting polypeptides with similar properties have been identified in the heads of rat and human spermatozoa. We speculate that these insoluble basic proteins contribute, during spermiogenesis, to the formation of the perinuclear theca as an architectural element involved in the shape changes and the intimate association of the nucleus with the acrosome and the plasma membrane.

The mesonephric (wolffian) and paramesonephric (müllerian) ducts of golden hamsters express different intermediate-filament proteins during development

We analysed the expression of intermediate-filament proteins in the developing mesonephric duct (the precursor of the male genital ducts) and the paramesonephric duct (the precursor of the female genital ducts) of golden-hamster embryos using immunohistochemical methods. Embryos were investigated from the early stages of duct development, i.e. at 9.5 days post conceptionem (dpc), through sexual differentiation, until birth (15.5 dpc). Monospecific antibodies to vimentin or keratins 7, 8, 18 or 19 as well as two keratin antibodies that are pan-epithelial in human tissues were tested. Both ducts expressed vimentin to some degree from their early stages (mesonephric duct from 9.5 dpc onwards; paramesonephric duct from 10.5 dpc onwards) until birth. No keratins were detectable at these earliest stages. In the mesonephric duct, keratins 7, 18 and 19 appeared simultaneously at 10.5 dpc and persisted until birth. In the paramesonephric duct, only keratin 18 was detectable at first (at 12.0 dpc), with the expression of keratins 7 and 19 being delayed until 14.5 dpc. This feature was irrespective of sexual differentiation, which begins at 11.0 dpc, so that, in males, these keratins appeared on cue, even though the paramesonephric duct was regressing at this time. The expression of keratin 8 could not be demonstrated in either duct using the antibodies tested in our study. By 14.5 dpc, the differentiated male mesonephric duct and the differentiated female paramesonephric duct exhibited the same intermediate-filament protein pattern (weak vimentin expression and strong expression of keratins 7, 18 and 19), in spite of differences in the intermediate-filament protein patterns exhibited by the two ducts during early development. These different programmes of intermediate-filament protein regulation do not support the concept that the mesonephric duct makes a cellular contribution to the paramesonephric duct during the development of the latter.

Changes in the distribution of intermediate-filament types in Japanese quail embryos during morphogenesis

We examined the distribution of intermediate filaments in early quail embryos in order to determine whether these cytoskeletal proteins play a role in the epithelial-mesenchymal transitions that commonly occur during embryogenesis, e.g., the separation of neural-crest cells from the neural epithelium. The distribution of cytokeratins, vimentin, and desmin was examined in frozen sections of quail embryos at stages during which dramatic reorganizations of tissues take place. All embryonic tissues were found to contain either vimentin or cytokeratins, but the distribution of these cytoskeletal proteins was characteristic neither of the cellular organization (e.g., epithelium vs. mesenchyme) nor of the germ-layer derivation of the tissues. Cytokeratin monoclonal antibodies stained most embryonic epithelia (defined here as being sheet-like tissue with an underlying basement membrane), including epidermis and extraembryonic membranes derived in part from the ectoderm, splanchnopleure and kidney tubules derived from mesoderm, and endoderm. Cytokeratin antibodies did not stain some epithelia, including the neural tube, neural plate, and dermatome/myotome. Whereas the cytokeratin antibodies exclusively stained epithelia, the vimentin antibodies labeled both epithelial (the neural tube, dermatome/myotome, and somatic and splanchnic mesoderm) and mesenchymal tissues (the sclerotome and neural-crest cells), regardless of their germ-layer derivation. In early embryos, antibodies against desmin only stained the myotome and, in 4-day embryos, the heart and mesenchyme around the pharynx. As the distribution of intermediate-filament types did not reflect tissue organization or germ-layer derivation, we propose that the distribution of intermediate filaments in early avian embryos reflects the motile capacity of an embryonic cell and/or the presence of specialized cell junctions, i.e., desmosomes.

Hormonal regulation of Sertoli cell function

The Sertoli cell is clearly influenced, directly and indirectly, by hormones. Among these are FSH, T, insulin and Vitamin A, but others may also be involved. Mechanisms are still not well understood. The biochemical effects of these hormones can be divided into quantitative and qualitative influences, with the former predominating. Specific cellular and secretory proteins and metabolites are affected, in many cases by more than one hormone. Often these same functions are influenced by other factors in the environment of the testis as well. Hormonal responsiveness of the Sertoli cell is determined in part by the maturational state of the cell. Some secreted products bind to specific cell types in the testis and epididymis and may influence the process of spermatogenesis. However, detailed mechanisms are not known at the present time. Understanding Sertoli cell function at the biochemical level and its control by hormones is clearly of key importance in understanding the control of the spermatogenic process.

Epithelial and mesenchymal cell differentiation in the fetal rat genital ducts: changes in the expression of cytokeratin and vimentin type of intermediate filaments and desmosomal plaque proteins

Mesonephric and paramesonephric ducts develop in different ways in male and female fetuses. We have analyzed the changes in the expression of cytokeratin and vimentin type of intermediate filaments and desmosomal plaque proteins in progressing and regressing genital ducts of rat fetuses. The concomitant changes in the basement membranes were detected by laminin antibody. Epithelial cells of the indifferent (Day 15) male and female mesonephric and paramesonephric ducts contained faint vimentin positivity which, however, later disappeared. Indifferent mesonephric duct epithelium stained strongly for cytokeratin, whereas in the corresponding paramesonephric duct only a weak and spotty positivity was seen. Immunocytochemical localization of cytokeratin filaments and desmosomal plaque proteins correlated with the ultrastructural differences in the apical junctional complexes of the mesonephric and paramesonephric ducts. Regardless of the ongoing regression of the male paramesonephric duct, cytokeratin positivity increased in the disorganizing epithelium; the most weak and a granular immunoreaction was seen in the cells found in the intensively vimentin-positive periductal mesenchyme. In the regressing female mesonephric duct cytokeratin positivity was lost before the final dissolution of the basement membrane. Immunoblotting analysis of cytokeratin and vimentin polypeptides of the individual genital ducts were in agreement with the immunocytochemical results obtained in 15- and 16-day-old fetuses. The results suggest that the expression of vimentin type intermediate filaments is an indication of the mesothelial origin of the genital ducts. The increase in cytokeratin positivity of the regressing paramesonephric duct epithelium suggests that the degenerative changes are initiated by the mesenchyme. Cytokeratin-positive cells found in the periductal mesenchyme of the male paramesonephric duct may be epithelial cells transforming into mesenchyme. The results emphasize a close relationship between the changes of the intermediate filament system and extracellular matrix upon differentiation of the fetal genital ducts.