Intermediate filaments in smooth muscle from pregnant and non-pregnant human uterus

The expression of intermediate filaments in the abomasum of ruminants: A comparative study

Intermediate filaments (IFs) are key molecular factors of the cell and have been reported to play an important role in maintaining the structural integrity and functionality of the abomasum. This study was designed to determine the regional distribution, cellular localization and expression of several IFs, including CK8, CK18, CK19, vimentin, desmin, peripherin and nestin, as well as the connective tissue component laminin, in the bovine, ovine and caprine abomasa. Immunohistochemical analyses demonstrated varying levels of expression of CK8, CK18, CK19, vimentin, desmin, nestin, peripherin and laminin in the bovine, ovine and caprine abomasa. CK8 immunoreactions were particularly evident in the luminal and glandular epithelia of the glands found in the abomasal cardia, fundus and pylorus in all three species. In the bovine abomasum, CK18 immunoreactions were stronger in the parietal cells, compared to the chief cells. In the abomasum of all three species, the smooth muscle as well as the smooth muscle cells of the vascular media in the cardiac, fundic and pyloric regions showed strong immunoreactivity. In all three species, the cardiac, fundic and pyloric regions of the abomasum showed strong peripherin and nestin immunoreactions in the luminal and glandular epithelial cells, stromal and smooth muscle cells, nervous plexuses and blood vessels. The expression patterns of IFs and laminin in the ruminant abomasum suggest that these proteins play a structural role in the cytoskeleton and are effective in maintaining abomasal tissue integrity and stability.

Differential expression of desmin in the uterine myometrium and cervix as a possible mechanism for successful parturition in rats

Expression of desmin, an intermediate filament, in the myometrium and cervix were investigated in peripartum rats (full term day 22 of pregnancy (DP22)). Des mRNA was expressed in lesser amounts in the cervix at peripartum (DP17 and 21, and day of birth 1 (DB1)), compared to those in the cervixes of ovariectomized rats. Immunohistochemical analysis revealed that desmin protein was diffusely present in the myometrium, and locally in the epithelium of the cervix. Western blot analysis showed that desmin protein levels in the myometrium increased 4- to 6-fold at DP17, 21 and DB1, and decreased rapidly at DB2 to the basal level observed in ovariectomized or non-pregnant rats. In contrast, cervical desmin protein levels increased approximately 10-fold at DP21 compared to those in ovariectomized rats, but decreased rapidly at DB1, indicating its decrease at parturition and an inconsistency between mRNA and protein expression. The administration of 17β-estradiol to ovariectomized rats increased desmin protein levels in the myometrium and cervix after 24 h. S-nitrosylated desmin protein was detected in the myometrium and cervix at DP21. The mRNA expression of inducible nitric oxide synthase was consistent with the expression of desmin protein. Thus, desmin, which is regulated by estradiol, is differentially expressed in the myometrium and cervix at peripartum possibly for successful pregnancy and parturition. In the cervix, desmin protein expression seems to be regulated by estradiol at the translational level. S-nitrosylation of desmin may have a potential role in the peripartum uterus.

Relationship between adenomyosis and endometriosis; Different phenotypes of a single disease?

Adenomyosis and endometriosis are common gynecological disorders, but their pathophysiology is still under debate. The aim of this review is to discuss whether adenomyosis and endometriosis represent two different entities or different phenotypes of a single disease. We searched PubMed electronic databases published between January 2000 and April 2020. Endometriosis is classified into three phenotypes; superficial peritoneal disease (SUP), ovarian endometrioma (OMA) and deep infiltrating endometriosis (DIE) lesions. Adenomyosis presents several different subtypes, including intrinsic adenomyosis, extrinsic adenomyosis, adenomyosis externa and focal adenomyosis located in the outer myometrium (FAOM). Human uterus is embryologically composed of archimetra, originating from the Müllerian duct, and neometra, arising from the non-Müllerian duct, and adenomyosis and endometriosis are diseases of archimetra. The outer myometrial layer of the uterus is composed of highly differentiated smooth muscle cells (SMCs), while the inner myometrial cells are immature. Inappropriate uterine contractions can cause retrograde menstruation and chronic inflammation in the pelvic cavity, then influencing the development of pelvic endometriosis. Furthermore, hyperperistalsis results in physiological and pathological changes to the endometrial-myometrial junctional barrier, allowing invagination of the normal endometrial tissue into the inner myometrial layer. This can trigger the development of intrinsic adenomyosis. There are insufficient data available to draw conclusions, but extrinsic adenomyosis may result from pelvic endometriosis and FAOM from rectal and bladder DIE/adenomyosis externa. In conclusions, this paper contributes to the debate in the possibility that adenomyosis and endometriosis represent different phenotypes of a single disease.

Isolated human uterine telocytes: immunocytochemistry and electrophysiology of T-type calcium channels

Recently, telocytes (TCs) were described as a new cell type in the interstitial space of many organs, including myometrium. TCs are cells with very long, distinctive extensions named telopodes (Tps). It is suggested that TCs play a major role in intercellular signaling, as well as in morphogenesis, especially in morphogenetic bioelectrical signaling. However, TC plasma membrane is yet unexplored regarding the presence and activity of ion channels and pumps. Here, we used a combination of in vitro immunofluorescence and patch-clamp technique to characterize T-type calcium channels in TCs. Myometrial TCs were identified in cell culture (non-pregnant and pregnant myometrium) as cells having very long Tps and which were positive for CD34 and platelet-derived growth factor receptor-α. Immunofluorescence analysis of the subfamily of T-type (transient) calcium channels CaV3.1 and CaV3.2 presence revealed the expression of these ion channels on the cell body and Tps of non-pregnant and pregnant myometrium TCs. The expression in TCs from the non-pregnant myometrium is less intense, being confined to the cell body for CaV3.2, while CaV3.1 was expressed both on the cell body and in Tps. Moreover, the presence of T-type calcium channels in TCs from non-pregnant myometrium is also confirmed by applying brief ramp depolarization protocols. In conclusion, our results show that T-type calcium channels are present in TCs from human myometrium and could participate in the generation of endogenous bioelectric signals responsible for the regulation of the surrounding cell behavior, during pregnancy and labor.

Uterine smooth muscle S-nitrosylproteome in pregnancy

The molecular mechanisms involved in uterine quiescence during gestation and those responsible for induction of labor are not completely known. Nitric oxide relaxes uterine smooth muscle in a manner disparate from that for other smooth muscles because global elevation of cGMP after activation of soluble guanylyl cyclase does not relax the muscle. S-Nitrosylation, the covalent addition of an nitric oxide (NO) group to a cysteine thiol is a likely mechanism to explain the ability of NO to relax myometrium. This work is the first to describe the myometrial S-nitrosylproteome in both pregnant and nonpregnant tissue states. Using the guinea pig model, we show that specific sets of proteins involved in contraction and relaxation are S-nitrosylated in laboring and nonlaboring muscle and that many of these proteins are uniquely S-nitrosylated in only one state of the tissue. In particular, we show that S-nitrosylation of the intermediate filament protein desmin is significantly increased (5.7-fold, p < 0.005) in pregnancy and that this increase cannot be attributed solely to the increase in protein expression (1.8-fold, p < 0.005) that accompanies pregnancy. Elucidation of the myometrial S-nitrosylproteome provides a list of mechanistically important proteins that can constitute the basis of hypotheses formed to explain the regulation of uterine contraction/relaxation.

Smooth muscle cells of the bovine cervical stroma may have a secretory, rather than a contractile function during parturition

The bovine cervix contains a large amount of smooth muscle cells distributed over an outer muscular layer and within a stromal layer. The stromal layer exhibits no electromyographic (EMG) activity at parturition. This leads to the question whether the stromal smooth muscle cells of the bovine cervix are prepared to contract with parturition, or whether they have another function. To this end, cervical biopsies were repeatedly taken from 10 pregnant cows at day-185 and -275 of gestation, at spontaneous, uncomplicated calving and at 30 days after calving. The smooth muscle bundles of the stroma were immunohistochemically analysed (n = 5) with regard to their integrity and cellular density, and the degree of staining for connexin-43, smooth muscle actin alpha (SMA), desmin and vimentin. Additionally, the mRNA expression for connexin-43, SMA, desmin and vimentin was determined with RT-PCR (n = 5). The smooth muscle tissue was arranged in bundles, also at parturition. However, the cellular density of these bundles and the SMA mRNA expression were decreased at parturition. Additionally, the SMA staining and connexin-43 expression and staining remained constant during pregnancy and at parturition. This might indicate that stromal smooth muscle cells are not prepared to contract with parturition, in contrast to the myometrial smooth muscle cells. The smooth muscle cells, stained for SMA, also expressed vimentin, and the proportion of co-expression was increased at day-275 of pregnancy. This suggests that the stromal smooth muscle cells predominantly have a secretory function in cows.

MYOMETRIAL ACTIVATION – COORDINATION, CONNECTIVITY AND CONTRACTILITY

One of the most important stages of pregnancy is the activation of uterine contractions that result in the expulsion of the fetus. The timely onset of labour is clearly important for a healthy start to life but incomplete understanding of the precise mechanisms regulating labour onset have prohibited the development of effective and safe treatments for preterm labour. This review explores the activation of the myometrium at labour onset, focussing on mechanisms of uterine contractility, including those proteins that play an important role in smooth muscle contractility. The review primarily focuses on human work but in the absence of human data describes animal studies. A broad overview of myometrial contraction mechanisms is provided before discussing more detailed aspects and identifying areas where uncertainty remains. Also discussed is the recent application of ‘omics’ based approaches to parturition research, which has facilitated an increase in the understanding of myometrial activation.

Physiological and pathological expression of intermediate filaments in the equine endometrium

The aim of this study was to investigate the expression of the intermediate filaments cytokeratin, vimentin and desmin in the equine endometrium by immunohistological techniques. For this purpose, endometrial biopsies of 151 mares were examined to determine physiological cycle patterns and changes resulting from endometriosis. During the physiological cycle epithelial cells and mesenchymal cells express cytokeratin and vimentin, respectively, whilst desmin and vimentin were coexpressed by the smooth muscle cells. Epithelial coexpression of cytokeratin and vimentin was seen in numerous fibrotic glands and in the uterine glands of three mares with pathologically inactive endometria. Three different staining patterns (basal, perinuclear, diffuse) of vimentin were associated with typical morphological alterations of the affected epithelia. In addition, in 14 cases a stromal coexpression of vimentin and desmin was found, indicating an atypical stromal differentiation in inactive endometria of older mares, barren for several years.

Up-regulation of Rnd1 during pregnancy serves as a negative-feedback control for Ca2+ sensitization of contractile elements in rat myometrium

We investigated the role of Rnd1, a member of the small GTP-binding Rho protein family, in the change in Ca(2+) sensitivity of contractile element in rat myometrium at estrus, gestation, and postpartum stages. In the permeabilized muscles, GTPgammaS or carbachol with GTP increased Ca(2+) sensitivity of contractile force in non-pregnant myometrium at the estrus stage, whereas these stimuli were ineffective in pregnant myometrium at day 21. After postpartum, the reduced Ca(2+) sensitization was recovered. Semi-quantitative RT-PCR analysis indicated that the expressions of RhoA, ROCKI, and ROCKII were not significantly different between non-pregnant and pregnant myometria. In contrast, the expression of Rnd1 was increased during the course of pregnancy, reaching a maximal at day 21, and rapidly declined after the delivery. On the other hand, Ca(2+) sensitization of contractile elements was decreased during the progress in gestation. These results suggest that Rnd1 may have an important role as a negative-feedback control of uterine contraction during gestation through the inhibition of RhoA-mediated increase in the Ca(2+) sensitivity of contractile elements.

Possible role of the protein kinase C/CPI-17 pathway in the augmented contraction of human myometrium after gestation

1. Activation of protein kinase C (PKC) by phorbol 12,13-dibutylate (PDBu, 1 microm) induced sustained contractions with no increase in [Ca2+]i in nonpregnant and pregnant human myometria. The contractile effects of PDBu in pregnant myometrium were much greater than those in nonpregnant myometrium, and the contractions in pregnant myometrium were accompanied by an increase in myosin light chain (MLC) phosphorylation at Ser19. 2. The contraction induced by PDBu in pregnant myometrium was inhibited by the inhibitors of conventional PKC isoforms, bisindolylmaleimides and indolocarbazole, such as Go6976, Go6983, and Go6850 (1 microM). LY333531 (1 microM), a specific inhibitor of PKC beta, also inhibited the PDBu-induced contraction in the pregnant myometrium. 3. In the pregnant myometrium permeabilized with alpha-toxin, PDBu increased the contractions induced at fixed Ca2+ concentration (0.3 microM) both in nonpregnant and pregnant myometria, indicating Ca2+ sensitization of contractile elements. 4. Western immunoblot analysis indicated that pregnant myometrium contained PKC isozymes such as conventional PKC (alpha, beta, gamma), novel PKC (delta, epsilon, theta), and atypical PKC (zeta but not iota and lambda). RT-PCR and real-time RT-PCR analysis indicated that, among the conventional PKC, the levels of mRNA of beta isoform in pregnant human myometrium were greater than those in nonpregnant myometrium. 5. CPI-17 is a substrate for PKC, and the phosphorylated CPI-17 is considered to inhibit myosin phosphatase. The levels of CPI-17 mRNA and protein expression were also greater in the pregnant myometrium. 6. These results suggest that the PKC-mediated contractile mechanism is augmented in human myometrium after gestation, and that this augmentation may be attributable to the increased activity of the beta PKC isoform and CPI-17.

Apparent up-regulation of stimulatory G-protein alpha subunits in the pregnant human myometrium is mimicked by elevated smoothelin expression

Sensitization of adenylyl cyclase (AC) by increased expression of large isoforms of the stimulatory G-protein Galpha(s) has been suggested as a mechanism that governs uterine quiescence during pregnancy. We quantified several components of the AC pathway in pregnant (P, n=21) and nonpregnant human myometria (NP, n=10). AC activity was approximately sevenfold higher in P than in NP under basal and stimulated conditions (MnCl(2)/GTP/GTP + isoproterenol). In addition, relative stimulation (% of basal) by 5'-guanosine-betagamma-iminotriphosphate and forskolin was twofold higher in P. beta-Adrenoceptor density was low and unaltered in P. Galpha(s) mRNA splice variants did not differ in P. Using antisera against different epitopes of Galpha(s) (carboxyl-/more amino-terminal), we found unchanged expression of Galpha(s) short and long (45, 47 kDa) in P. Two additional proteins in P (51, 59 kDa) were detectable only by the carboxyl-terminal antiserum and lacked GTP binding properties. The 59 kDa protein could be identified as a recently discovered cytoskeletal protein, smoothelin, which was 10-fold increased in P. These data indicate that the apparent up-regulation of large Galpha(s) species in P is mimicked by elevated smoothelin. Therefore, the increase in AC cannot be attributed to changes in Galpha(s)- or beta-adrenoreceptors. Epitope sharing between Galpha(s) and smoothelin should be considered in experiments on smooth muscle tissues.

Differential expression of connexin43 and desmin defines two subpopulations of medial smooth muscle cells in the human internal mammary artery

Upregulation of connexin43-gap junctions is associated with transition of contractile vascular smooth muscle cells (SMCs) to the synthetic state. To determine whether phenotypically distinct subpopulations of medial SMCs differentially express connexin43, we investigated the human distal internal mammary artery, a structurally heterogeneous vessel with features ranging from elastic to elastomuscular to muscular. Immunoconfocal microscopy combined with quantitative analysis and complemented by in situ hybridization showed that SMCs in the elastic medial regions expressed high levels of connexin43 but low levels of desmin, whereas those of muscular medial regions expressed low levels of connexin43 but high levels of desmin. Ultrastructurally, SMCs of both regions were of the contractile phenotype, but the former cells were irregular in shape with relatively prominent synthetic organelles whereas the latter were spindle shaped with fewer synthetic organelles. Vimentin, smooth muscle alpha-actin, calponin, h-caldesmon, and myosin heavy chains (SM1 and SM2) were equally highly expressed by most cells in both subpopulations. The connexin43/desmin expression pattern of SMCs in regions of intimal thickening resembled those of elastic medial regions. These findings refine the view suggested from previous studies that high levels of connexin43 expression are associated with SMCs of a less contractile/more synthetic phenotype. In the internal mammary artery, the 2 subpopulations of SMCs with markedly different connexin43 expression levels both represent a differentiated contractile phenotype, but the subpopulation showing high levels of connexin43-gap junctions is characterized by low levels of desmin and structural features that reflect a more synthetic tendency.

Rodent model of reproductive tract leiomyomata. Establishment and characterization of tumor-derived cell lines

Uterine myometrial tumors are the most commonly found gynecological neoplasm in women. The underlying causes of uterine leiomyomata are poorly understood, a result in part of the absence of a good animal model system in which to study these tumors. This report describes a novel rat model (Eker rat) in which spontaneous gynecological smooth muscle tumors arise with a high frequency. Leiomyomas are the predominant reproductive tract tumor that arise in these animals, although leiomyosarcomas have also been observed. Cell lines have been established from both the benign and malignant lesions. All of the lines express smooth muscle-specific actin, and leiomyoma-derived cell lines express desmin. Two of the cell lines are tumorigenic in nude mice, and the lines are variable for expression of estrogen and progesterone receptors. These lines are the first rodent tumor-derived lines to be established from leiomyomata and are the only lines available from a hereditary form of these tumors. Together with Eker rats that spontaneously develop leiomyomata, they constitute an in vitro/in vivo model system for gaining insights into the mechanism of transformation of uterine smooth muscle cells and the role of steroid hormones and hormone receptors in myometrial tumorigenesis.

Identification and classification of interstitial cells in the canine proximal colon by ultrastructure and immunocytochemistry

The ultrastructure and immunocytochemistry of interstitial cells (ICs) in the canine proximal colon were investigated. Three types of ICs were found within the tunica muscularis. (1) ICs were located along the submucosal surface of the circular muscle (IC-SM). These cells shared many features of smooth muscle cells, including myosin thick filaments and immunoreactivity to smooth muscle gamma actin, myosin light chain, and calponin antibodies. IC-SM were clearly different from smooth muscle cells in that contractile filaments were less abundant and intermediate filaments consisted of vimentin instead of desmin. (2) ICs in the region of the myenteric plexus (IC-MY) were similar to IC-SM, but these cells had no thick filaments or immunoreactivity to smooth muscle gamma actin or calponin antibodies. (3) The fine structures and immunoreactivity of ICs within the muscle layers (IC-BU) were similar to IC-MY, but IC-BU lacked a definite basal lamina and membrane caveolae. IC-BU and IC-MY were both immunopositive for vimentin. Since all ICs were immunopositive for vimentin, vimentin antibodies may be a useful tool for distinguishing between ICs and smooth muscle cells. Each class of ICs was closely associated with nerve fibers, made specialized contacts with smooth muscle cells, and formed multicellular networks. A combination of ultrastructural and immunocytochemical techniques helps the identification and classification of ICs by revealing the fine structures and determining the "chemical coding" of each class of ICs.

Effects of long-term portal hypertension on structure, active force and content of contractile and structural proteins in smooth muscle of the rat portal vein

Growth of the smooth muscle cells in the rat portal vein was induced by a partial ligation of the vessel. The ligation caused an increase in the transmural pressure and segments of the portal vein were investigated 6 weeks after the ligation. The spontaneous contractile activity of the ligated veins was similar to that of the control veins. In the ligated vessels the active force at optimal length for force development was doubled, 22.8 +/- 1.3 compared with 12.5 +/- 1.4 mN for the controls. The cross-sectional area of the media in the ligated veins, determined on transverse sections, increased from the control value of 0.10 +/- 0.01 to 0.19 +/- 0.01 mm2. Electron microscopy revealed that the mean cross-sectional area of the smooth muscle cells in the ligated portal vein was doubled (controls: 6.4 +/- 0.6, hypertrophic: 13.6 +/- 1.8 microns2). This suggests hypertrophy of the smooth muscle cells in the vessel wall as the cause for the increase in cross-sectional area of the ligated veins. An increase in the number of intermediate filaments was observed in the hypertrophied smooth muscle. The relative contents of contractile (myosin and actin) and structural (desmin and vimentin) proteins were determined with SDS-polyacrylamide gel electrophoresis. The actin/myosin and vimentin/actin ratios were unaltered by hypertrophy. The hypertrophied veins showed an increase in the desmin/actin ratio (control: 0.20 +/- 0.01, hypertrophied: 0.27 +/- 0.03). The increased amounts of desmin correlates with the increased number of intermediate filaments observed by electron microscopy.(ABSTRACT TRUNCATED AT 250 WORDS)