Expression of desmin, laminin and fibronectin during in situ differentiation (decidualization) of rat uterine stromal cells

Immunocytochemical analysis of frozen rat uterine sections containing decidual tissue, formed in response to normal or artificial stimulation of uteri sensitized by endogenous or exogenous hormonal regimens, demonstrated an elevated expression of the intermediate filament protein desmin in decidual cells. Changes in the expression of extracellular matrix (ECM) components were coordinated with the elevated expression of desmin as stromal cells underwent decidualization. In parallel with the pattern of regional decidualization, as determined by elevated desmin expression, laminin accumulated in ECM of decidual cells while an apparent decrease in fibronectin was associated with altered organization at the decidual cell surface. The in situ observations confirm previous results, which indicated that the expression of desmin in decidual cells formed in vivo or in vitro is a valid marker of their differentiation, and resolve questions unanswered in the previous study: (a) desmin (and laminin) appear to be constitutively expressed in non-decidualized stroma at barely detectable levels, (b) desmin is a valid marker of stromal cell differentiation because it is expressed similarly in decidual cells, irrespective of varying experimental protocols for uterine sensitization and stimulation, and (c) desmin expression follows the same regional progression described for the process of decidualization in morphological and histochemical studies.     

Initiation and maintenance of in vitro decidualization are independent of hormonal sensitization in vivo.

The effects of in vivo hormonal sensitization on the competence of uterine stromal (US) cells to decidualize in vitro were assessed. In vitro differentiation of uterine stroma isolated from Day 4 pregnant rats, sensitized to respond to a decidual stimulus, was compared to that in nonsensitized immature, castrated or cycling rats. The initiation of in vitro decidualization--as monitored by the expression of the decidual markers desmin and laminin in rat US cells--was independent of the hormonal status of the animal from which the cells were isolated and occurred in the absence of serum in the medium. Differentiation was accelerated in high-density cultures where contact inhibition suppressed proliferation and decreased the extent of cell growth. The extent to which in vitro decidualization imitates in vivo stromal cell differentiation was assessed by comparing decidualization in the rabbit, a species with only a limited decidual cell response, and in the rat. US cells isolated from nonpregnant rabbits differentiated in vitro by expressing laminin, but not desmin. Indirect immunofluorescence of frozen uterine sections from pregnant and nonpregnant rabbits validated in vitro differentiation as a faithful reflection of the in vivo program of decidualization. Although the program of US cell differentiation may vary between the species, initiation of differentiation in vitro appeared to be independent of hormonal preparation in vivo for both the species examined.     

Developmental expression of adenosine deaminase during decidualization in the rat uterus

Adenosine deaminase (ADA) is expressed in high concentrations at the fetal-maternal interface during postimplantation stages of gestation in the mouse. The experiments reported here were designed to identify the specific uterine cells that express ADA subsequent to implantation in the rat and to determine if embryonic cells contribute to ADA expression. The results of biochemical analysis demonstrate that ADA-specific activity increases to very high levels in implantation sites, beginning approximately 72 h after blastocyst attachment. Immunocytochemical analysis localized this ADA expression to the decidualized stromal cells in the antimesometrial region of the pregnant uterus. In experimentally induced deciduoma, these cells were capable of synthesizing high levels of both ADA and mRNA for ADA in the absence of embryos. The enzyme first appeared in decidual cell cytoplasm, approximately 72 h after induction of decidualization, and later was localized in the decidual cell nuclei. Since the expression of ADA and its mRNA in decidual cells follows the appearance of desmin, a protein marker for decidualization, by at least 48 h, ADA appears to be involved in the functioning of mature decidual cells rather than in stromal cell differentiation. The expression of ADA, but not desmin, was restricted to the antimesometrial decidual cells and decreased when these cells regressed. At mid-gestation ADA activity increased and was localized principally in the fetal placenta. The results presented here demonstrate that ADA is localized to the antimesometrial decidual cell and that its expression is consequent to differentiation of the uterine stromal cell and independent of any embryonic stimulus.     

Expression of nidogens in rat uterus and embryo during decidualization and implantation

The purpose of this study was to demonstrate the expression of nidogen-1 and nidogen-2 and their possible role in decidualization and implantation events during early pregnancy in rats. The tissue samples were examined from pregnant animals between gestational days 1-8 using immunocytochemistry. The uterine luminal epithelium, the glandular epithelium, and the myometrial smooth muscle cells stained strongly from gestational days 1-8 with both nidogen antibodies. At day 4 the decidual reaction areas began to appear in the stromal matrix and immunostaining of both nidogens revealed that the basement membrane of the surface epithelium was discontinuous. The differentiation of stromal cells into decidual cells was seen at gestational day 5 and both nidogens were weakly expressed in the decidualizing cells. At day 6, nidogen-2 immunoreactivity was higher in the primary decidual cells close to the embryo than nidogen-1, and during development of the decidual tissue both nidogens appeared in the endometrial stromal cells. At day 7, while expression of both nidogens declined in the primary decidual cells, their expression was markedly observed in the secondary decidual cells close to the myometrium. At day 8, expression of both nidogens was also observed to increase in the primary decidual cells. While nidogen-2 expression was seen in the parietal endoderm and primary ectoderm of the rat embryos at this developmental stage, nidogen-1 expression was only detected in the parietal endoderm. These results indicate that nidogen-1 and nidogen-2 could play important roles during embryogenesis, decidualization, and implantation in the endometrium of rat uterus.     

Mouse endometrial stromal cells produce basement-membrane components

During mouse pregnancy, uterine stromal cells transform into morphologically distinct decidual cells under the influence of the implanting embryo and a proper hormonal environment. Mechanical stimulation of hormonally primed uterine stromal cells leads to the same morphologic alterations. The decidualization of stromal cells is characterized by the accumulation of pericellular basement-membrane material. Decidualized stromal cells of pregnancy differ in this respect from stromal cells obtained from nonpregnant uteri, which are not associated with any significant amounts of basement-membrane components. Mouse decidual cells isolated from 6- to 7-day pregnant uteri explanted in vitro continue to synthesize basement-membrane-like extracellular matrix. Using immunohistochemistry and metabolic labeling followed by immunoprecipitation, SDS-PAGE, and fluorography, it was shown that the decidual cells synthesize laminin, entactin, fibronectin, type-IV collagen, and heparan sulfate proteoglycan. Stromal cells isolated from nonpregnant uteri and explanted in vitro produced the same basement-membrane components. Apparently, these cells were stimulated by the procedure used during isolation and explanation to undergo pseudodecidualization. We thus showed that stromal cells from pregnant and nonpregnant mouse uteri synthesize significant amounts of basement-membrane components in vitro, and hence could serve as a good model for the study of normal basement-membrane components.     

Immunohistochemical studies on the tissue localization of collagen types I, III, IV, V and VI in schwannomas. Correlation with ultrastructural features of the extracellular matrix

The distinctive tissue localization of collagen types in typical schwannomas with Antoni type A and B areas was demonstrated immunohistochemically using affinity-purified antibodies against types I, III, IV, V and VI collagen and comparative ultrastructural studies were made on the extracellular matrix components. Antoni type A tissue, which was composed of tightly packed spindle cells with long cytoplasmic processes surrounded by a continuous basement membrane and a few fibrillar components of the extracellular matrix, was almost exclusively immunoreactive for type IV collagen, presumably representing the basement membrane. Verocay bodies, which are organoid structures of Antoni type A tissue, had a variety of more abundant extracellular fibrous components, such as banded collagen fibrils, fibrous long-spacing fibrils and microfibrils. These were positive for type I and III, as well as type IV collagen. In Antoni type B areas, where two types to tumor cells designated Schwann cell-like and fibroblast-like were scattered in large amounts of amorphous extracellular matrix containing microfibrils and thick banded collagen fibrils, type VI collagen as well as types I, III and IV collagen were consistently detected. Type V collagen was localized in dense fibrous tissue areas and around blood vessels. These findings indicate that the differently organized cellular patterns of schwannomas, identified as Antoni types A and B, are characterized not only by the ultrastructural features of the extracellular matrix, but also by the distinctive collagen types produced by neoplastic Schwann cells.     

Chorioallantoic placenta formation in the rat: I. Luminal epithelial cell death and extracellular matrix modifications in the mesometrial region of implantation chambers.

On days 7 and 8 of pregnancy, mesometrial regions of rat gestation sites were examined by light microscopy and transmission electron microscopy to determine what changes occur before the chorioallantoic placenta forms in that region. By day 7, gestation sites contained a uterine lumen mesometrially and an antimesometrial extension of the uterine lumen, the implantation chamber. The implantation chamber consisted of a mesometrial chamber between the uterine lumen and the conceptus, an antimesometrial chamber that contained the conceptus, and a decidual crypt antimesometrial to the conceptus. Stromal cells that formed the walls of the implantation chamber were closely packed decidual cells, while those that surrounded the uterine lumen were loosely arranged. Late on day 7, a portion of the epithelium lining the mesometrial chamber was degenerating, but this area of initial degeneration was never adjacent to the antimesometrial chamber. By early day 8, most of the epithelial cells lining the mesometrial chamber were degenerating and were being sloughed into the chamber lumen. Although degeneration of these epithelial cells morphologically resembled necrosis, it was precisely controlled, since adjacent epithelial cells lining the uterine lumen remained healthy. The space that separated the denuded luminal surface of the mesometrial chamber from underlying decidual cells became wider and was occupied by an extracellular matrix rich in cross-banded collagen fibrils. Decidual cell processes, that earlier had penetrated the basal lamina beneath healthy epithelial cells, protruded into this matrix and penetrated the basal lamina at the luminal surface. By late day 8, large areas of denuded chamber wall were covered with decidual cell processes, little remained of the basal lamina, and cross-banded collagen fibrils were scarce in the area occupied by decidual cell processes. During the times studied, uterine tissues that formed the walls of the mesometrial chamber were not in direct contact with the conceptus. This study indicates that trophoblast does not play a direct role in epithelial degeneration, basal lamina penetration, or extracellular matrix modifications in the mesometrial region of implantation chambers where part of the chorioallantoic placenta forms, although trophoblast may be required to trigger or modulate some of the changes.     

Molecular assembly, secretion, and matrix deposition of type VI collagen

Monoclonal antibodies reactive with the tissue form of type VI collagen were used to isolate the type VI collagen polypeptides from cultured fibroblasts and muscle cells. Two [35S]methionine-labeled polypeptides of 260 and 140 kD were found intracellularly, in the medium, and in the extracellular matrix of metabolically labeled cells. These polypeptides were disulfide cross-linked into very large complexes. The 260- and 140-kD polypeptides were intimately associated and could not be separated from each other by reduction without denaturation. In the absence of ascorbic acid, both polypeptides accumulated inside the cell, and their amounts in the medium and in the matrix were decreased. These results suggest that both the 260- and the 140-kD polypeptides are integral parts of the type VI collagen molecule. Examination of type VI collagen isolated from the intracellular pool by electron microscopy after rotary shadowing revealed structures corresponding to different stages of assembly of type VI collagen. Based on these images, a sequence for the intracellular assembly of type VI collagen could be discerned. Type VI collagen monomers are approximately 125 nm long and are composed of two globules separated by a thin strand. The monomers assemble into dimers and tetramers by lateral association. Only tetramers were present in culture media, whereas both tetramers and multimers were found in extracellular matrix extracts. The multimers appeared to have assembled from tetramers by end-to-end association into filaments that had prominent knobs and a periodicity of approximately 110 nm. These results show that, unlike other collagens, type VI collagen is assembled into tetramers before it is secreted from the cells, and they also suggest an extracellular aggregation mechanism that appears to be unique to this collagen.     

Distribution of laminin,vimentin and desmin in the rat uterus during initial stages of implantation

The aim of this study was to investigate the immunohistochemical distribution of laminin, vimentin and desmin during the implantation period in the rat since ECM remodelling and the expression of intermediate filaments (Ifs) is essential for successful decidualization and implantation. On day 4 of pregnancy, laminin was found in a few endometrial stromal cells (ESC), the basement membrane of the numerous endometrial blood vessels, in endometrial glands and as well as in the uterine epithelium. The localization of vimentin on day 4 of pregnancy was widespread in the ESC. However, desmin immunoreactivity was low in ESC on this day of pregnancy. On day 6 of pregnancy, laminin and vimentin were localized in the decidual area underlying luminal epithelium and around the implanting embryo. Additionally, desmin was found to be present densely in decidual cells of the anti-mesometrial region where implantation takes place. Finally, on day 8 of pregnancy, laminin was present in decidual and parietal endodermal cells, whereas vimentin was immunolocalized in primary and secondary decidual regions in the endometrium. In contrast, desmin was detected in some parts of the secondary decidual zone. In conclusion, these proteins could have crucial roles in decidualization and implantation.     

Intermediate filament protein as a marker of uterine stromal cell decidualization

An increase in intermediate filaments has been reported in rat uterine stromal cells undergoing decidualization in vivo and in vitro. In order to identify biochemical correlates of this morphological change, we have identified (two dimensional gel electrophoresis, Western blots, indirect immunofluorescent staining) the constitutive intermediate filament proteins of stromal cells decidualizing in vivo and isolated stroma decidualizing in vitro as vimentin and desmin. Vimentin is common to all uterine stromal cells but increases, proportional to total cell protein, in decidualized stroma. Barely detectable in nondecidualized stroma, desmin, unlike vimentin, increases during decidualization at a rate greater than the increase in total cell protein. Neither the increase in vimentin or desmin is observed in hormonally sensitized, nondecidual stromal cells. Desmin, because it is selectively expressed in decidualizing stroma, could be considered unique enough to serve as a marker of decidual cell differentiation.     

In vitro decidualization of human endometrial stromal cells.

Stromal cells isolated from proliferative human endometrium undergo morphologic and biochemical changes when exposed to a mixture of ovarian hormones, acquiring characteristics of decidual cells. In addition to the previously reported progestin-induced secretion of prolactin (PRL) by explants of human proliferative endometrium, and of PRL and laminin by stromal cells in culture, "in vitro" induction of several other decidual cell products was demonstrated in the present study, using cultures of stromal cells isolated from proliferative endometrium. Incubation of stromal cells with a mixture of estradiol, medroxyprogesterone acetate and relaxin, at a concentration reported to yield maximal stimulation of PRL production, resulted in changes from elongated to rounder cells, approx. 90% of which showed immunostaining for PRL under these conditions. Immunocytochemical procedures were carried out on cytospins of decidual cells isolated from decidual tissue adherent to fetal membranes collected at delivery (positive controls), and on stromal cells cultured in Lab-Tek chamber-slides, in the absence (negative controls) or in the presence of added hormones. Antibodies to 24K (a heat-shock protein also named HRP27), desmin (present in intermediate filaments), p29 (a protein associated with the estrogen receptor), and PP12 (an insulin growth factor-1 binding protein), did not react with stromal cells isolated from proliferative endometrium but showed immunostaining of the rounder cells obtained after hormonal treatment when tested with the peroxidase-labeled second antibody complex. In another series of similar experiments, in which the same decidualization end-points were employed, changes in 24K, desmin and PP12 expression were obtained by adding to the insulin-containing medium PRL instead of the hormonal mixture, a finding suggesting sequential steps during the decidualization process.     

YKL-40 secreted from adipose tissue inhibits degradation of type I collagen

Obesity is considered a chronic low-grade inflammatory status and the stromal vascular fraction (SVF) cells of adipose tissue (AT) are considered a source of inflammation-related molecules. We identified YKL-40 as a major protein secreted from SVF cells in human visceral AT. YKL-40 expression levels in SVF cells from visceral AT were higher than in those from subcutaneous AT. Immunofluorescence staining revealed that YKL-40 was exclusively expressed in macrophages among SVF cells. YKL-40 purified from SVF cells inhibited the degradation of type I collagen, a major extracellular matrix of AT, by matrix metalloproteinase (MMP)-1 and increased rate of fibril formation of type I collagen. The expression of MMP-1 in preadipocytes and macrophages was enhanced by interaction between these cells. These results suggest that macrophage/preadipocyte interaction enhances degradation of type I collagen in AT, meanwhile, YKL-40 secreted from macrophages infiltrating into AT inhibits the type I collagen degradation.     

Production of type VI collagen by human macrophages: a new dimension in macrophage functional heterogeneity

Macrophages derived from human blood monocytes perform many tasks related to tissue injury and repair. The main effect of macrophages on the extracellular matrix is considered to be destructive in nature, because macrophages secrete metalloproteinases and ingest foreign material as part of the remodeling process that occurs in wound healing and other pathological conditions. However, macrophages also contribute to the extracellular matrix and hence to tissue stabilization both indirectly, by inducing other cells to proliferate and to release matrix components, and directly, by secreting components of the extracellular matrix such as fibronectin and type VIII collagen, as we have recently shown. We now report that monocytes and macrophages express virtually all known collagen and collagen-related mRNAs. Furthermore, macrophages secrete type VI collagen protein abundantly, depending upon their mode of activation, stage of differentiation, and cell density. The primary function of type VI collagen secreted by macrophages appears to be modulation of cell-cell and cell-matrix interactions. We suggest that the production of type VI collagen is a marker for a nondestructive, matrix-conserving macrophage phenotype that could profoundly influence physiological and pathophysiological conditions in vivo.     

Deficiency of tenascin-X causes a decrease in the level of expression of type VI collagen

Tenascin-X (TNX) is an extracellular matrix glycoprotein. We previously demonstrated that TNX-null fibroblasts exhibit decreased cell-matrix and cell-cell adhesion. In this study, we used a differential display technique to determine the genes involved in this process. Differential display analysis of wild-type and TNX-null fibroblasts revealed that mRNA expression level of type VI collagen alpha3 is predominantly decreased in TNX-null fibroblasts. Expression levels of mRNAs of other subunits of type VI collagen, alpha2 and alpha3 chains, were also remarkably decreased in TNX-null fibroblasts. The protein level of alpha3 chain of type VI collagen was also reduced in TNX-null fibroblasts. However, the organization of type VI collagen in the extracellular matrix of TNX-null fibroblasts was similar to that of wild-type fibroblasts. Transient expression of TNX in Balb3T3 cells caused an increase in the level of mRNA of type VI collagen compared with that in vector control and increased the promoter activity of type VI collagen alpha1 subunit gene. In addition, the expression levels of type I collagen and other collagen fibril-associated molecules such as type XII and type XIV collagens, decorin, lumican and fibromodulin in wild-type and TNX-null fibroblasts were compared. It was found that the mRNA expression levels of type I collagen and collagen fibril-associated molecules other than decorin were decreased and that the expression level of decorin was increased in TNX-null fibroblasts. The results suggest the possibility that TNX mediates not only cell-cell and cell-matrix interactions but also fibrillogenesis via collagen fibril-associated molecules.     

Localization in situ of type VI collagen protein and its mRNA in mesangial proliferative glomerulonephritis using renal biopsy sections

 Extracellular matrix accumulation is crucial in the pathogenesis of glomerulosclerosis in mesangial proliferative glomerulonephritis (GN). In an attempt to explore the distribution of type VI collagen and its synthesizing cells in normal and diseased glomeruli, we investigated mRNA and protein expression of type VI collagen in renal biopsy sections, histologically diagnosed as mesangial proliferative GN. Five renal biopsies from patients diagnosed as having minor glomerular abnormalities and one surgical renal tissue were also simultaneously examined as controls. Immunohistochemical studies revealed type VI collagen immunostaining in the mesangium and glomerular basement membrane of the control glomeruli. Compared to the control, increased deposition of type VI collagen was noted in the mesangial proliferative and sclerotic lesions in GN. To identify the cells responsible for the synthesis of type VI collagen mRNA, renal sections were hybridized in situ with digoxigenin-labeled antisense oligo-DNA probe complementary to a part of α1 (VI) mRNA. Occasionally intraglomerular cells hybridized with digoxigenin-labeled antisense pro α1 (VI) oligo-DNA in control glomeruli. An increased number of intraglomerular cells (mostly epithelial cells) were, however, positive for α1 (VI) mRNA expression in GN sections. The present study documents the distribution of type VI collagen in the normal glomeruli and provides further evidence of accelerated synthesis of this collagen in mesangial proliferative GN. Accepted: 21 July 1998     

Collagen VI deficiency affects the organization of fibronectin in the extracellular matrix of cultured fibroblasts.

Fibronectin is one of the main components of the extracellular matrix and associates with a variety of other matrix molecules including collagens. We demonstrate that the absence of secreted type VI collagen in cultured primary fibroblasts affects the arrangement of fibronectin in the extracellular matrix. We observed a fine network of collagen VI filaments and fibronectin fibrils in the extracellular matrix of normal murine and human fibroblasts. The two microfibrillar systems did not colocalize, but were interconnected at some discrete sites which could be revealed by immunoelectron microscopy. Direct interaction between collagen VI and fibronectin was also demonstrated by far western assay. When primary fibroblasts from Col6a1 null mutant mice were cultured, collagen VI was not detected in the extracellular matrix and a different pattern of fibronectin organization was observed, with fibrils running parallel to the long axis of the cells. Similarly, an abnormal fibronectin deposition was observed in fibroblasts from a patient affected by Bethlem myopathy, where collagen VI secretion was drastically reduced. The same pattern was also observed in normal fibroblasts after in vivo perturbation of collagen VI-fibronectin interaction with the 3C4 anti-collagen VI monoclonal antibody. Competition experiments with soluble peptides indicated that the organization of fibronectin in the extracellular matrix was impaired by added soluble collagen VI, but not by its triple helical (pepsin-resistant) fragments. These results indicate that collagen VI mediates the three-dimensional organization of fibronectin in the extracellular matrix of cultured fibroblasts.     

Uterine extracellular matrix components are altered during defective decidualization in interleukin-11 receptor α deficient mice

Background

Implantation of the embryo and successful pregnancy are dependent on the differentiation of endometrial stromal cells into decidual cells. Female interleukin-11 receptor α (IL-11Rα) deficient mice are infertile due to disrupted decidualization, suggesting a critical role for IL-11 and its target genes in implantation. The molecular targets of IL-11 in the uterus are unknown, but it is likely that IL-11 signaling modifies the expression of other genes important in decidualization. This study aimed to identify genes regulated by IL-11 during decidualization in mouse uterus, and to examine their expression and localization as an indication of functional significance during early pregnancy.

Methods

Decidualization was artificially induced in pseudopregnant wild type (IL11Ra^+/+) and IL-11Rα deficient (IL11Ra^-/-) littermates by oil injection into the uterine lumen, and gene expression analyzed by NIA 15K cDNA microarray analysis at subsequent time points. Quantitative real-time RT-PCR was used as an alternative mRNA quantitation method and the expression and cellular localization of the protein products was examined by immunohistochemistry.

Results

Among 15,247 DNA probes, 13 showed increased and 4 decreased expression in IL11Ra^-/- uterus at 48 h of decidualization. These included 4 genes encoding extracellular matrix proteins; collagen III α1, secreted acidic cysteine-rich glycoprotein (SPARC), biglycan and nidogen-1 (entactin). Immunohistochemistry confirmed increased collagen III and biglycan protein expression in IL11Ra^-/- uterus at this time. In both IL11Ra^-/- and wild type uterus, collagen III and biglycan were primarily localized to the outer connective tissue and smooth muscle cells of the myometrium, with diffuse staining in the cytoplasm of decidualized stromal cells.

Conclusion

These data suggest that IL-11 regulates changes in the uterine extracellular matrix that are necessary for decidualization.