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PubMed1986

[Calcium channels in smooth muscle cells].

In smooth muscle cells, the electrophysiological properties of potential-dependent calcium channels are similar to those described in other excitable cells. The calcium current is dependent on the extracellular calcium concentration; it is insensitive to external sodium removal and tetrodotoxin application. Other ions (Ba2+, Sr2+, Na+) can flow through the calcium channel. This channel is blocked by Mn2+, Co2+, Cd2+ and by organic inhibitors. The inactivation mechanism is mediated by both the membrane potential and the calcium influx. Ca2+ ions can also penetrate into the cell through receptor-operated channels. These channels show a low ionic selectivity and are generally less sensitive to organic Ca-blockers than the potential-dependent calcium channels. The finding of specific channel inhibitors as well as the study of the biochemical pathways between receptor activation and channel opening are prerequisites to further characterization of receptor-operated channels.

Animals↗
PubMed1987

Isolation and characterization of an abundant and novel 22-kDa protein (SM22) from chicken gizzard smooth muscle.

Chicken gizzard smooth muscle contains a highly abundant protein (SM22) with an apparent Mr on sodium dodecyl sulfate-polyacrylamide electrophoretic gels of 23,000. The ratio of actin:SM22:tropomyosin in this tissue is estimated to be 6.5(+/- 0.8):2.0(+/- 0.2):1.0. At least three isoelectric isoforms are present in ratios of alpha:beta:gamma of 14:5:1 with alpha the most basic and gamma the most acidic. A method for the purification of SM22 and partial separation of its isoforms is described. Amino acid analyses of purified alpha and beta demonstrate the presence of 1 and 2 half-cystines, respectively, and a lower content of basic amino acids in beta. A value of 22,000 for the Mr of alpha estimated by sedimentation equilibrium indicated its presence as a monomer at physiological ionic strengths. Estimates of the translational frictional coefficient (f/fmin) of alpha calculated from its Stokes radius (25.5 A) and Mr were consistent with its existence as a moderately asymmetric globular protein. Calculations based on its far-ultraviolet CD spectrum provided values of 37% alpha-helix, 31% beta-sheet, 5% beta-turn, and 27% random coil. SM22 was shown not to share functional properties with several proteins of similar Mr and isoelectric point such as myokinase, brain 23-kDa protein, and troponin I. We conclude that it is a novel protein not previously isolated or characterized from any tissue.

Amino Acids↗
PubMed1994

Transforming growth factor beta 1 stimulates type V collagen expression in bovine vascular smooth muscle cells.

Vascular smooth muscle cells (SMCs) produce the bulk of the connective tissue of major arteries, including collagen types I, III, and V. Recently, we have shown, they also have the capacity to synthesize the alpha 1 chain of type XI, a collagen related to type V (Brown, K., Lawrence, R., and Sonenshein, G. (1991) J. Biol. Chem. 266, 23268-23273). Furthermore, expression of types V and XI collagen were coordinately regulated with respect to serum deprivation and cell density in a fashion distinct from that for types I and III. To begin to determine the factors that influence vascular SMC production of types V/XI collagen, we have examined the effects of transforming growth factor (TGF)-beta 1, a major modulator of connective tissue expression. In serum-deprived confluent cultures of bovine pulmonary artery SMCs, TGF-beta 1 treatment increased the steady-state levels of the mRNAs of collagen types V and XI, as well as of types I and III, elastin and fibronectin. The largest increase was seen for alpha 2(V) procollagen. The increase in alpha 2(V) mRNA was detectable by 12 h after addition of 2 ng/ml TGF-beta 1, and concentrations as little as 0.5 ng/ml were effective. A similar increase in alpha 2(V) mRNA levels was observed with SMCs derived from the aortic arch and carotid artery. Type V collagen protein was found to be elevated by TGF-beta 1 treatment in both the conditioned media and the cell layer associated fraction of pulse-labeled cultures. A slight decrease in SMC proliferation as judged by DNA content, [3H]thymidine incorporation, and steady-state levels of histone H3.2 mRNA resulted from TGF-beta 1 treatment. These results suggest that the elevated levels of TGF-beta 1 in the vessel wall during atherosclerosis may be, in part, responsible for the increase in type V collagen that typifies advanced fibrotic lesions.

Animals↗
PubMed1996

[Effect of N-Nitro-L-Arginine on the concentration and relaxation of vascular smooth muscle].

The arterial smooth muscle contractility is regulated by the free intracellular calcium concentration and by alpha 1 and alpha 2 adrenergic receptor stimulation (norepinephrine (NE), phenylephrine (PHE) and clonidine), inducing contraction, increase in vascular tension and increase in intracellular calcium concentration. This response is increased in the absence of endothelium. On the other hand, the relaxation of isolated arteries induced by acetylcholine (ACh) is endothelium-dependent and modulate by EDRF. We have studied the effect of pre incubation with N-nitro-L-arginine (L-NA) on the alpha-adrenergic-induced-contraction and ACh-induced relaxation, respectively in isolated rat toraxic aorta strips in comparison with the effect produced by 70 mM KCl which is taken as control. The results show a significant difference (p < 0.001) in the presence of L-NA on the PHE-induced contraction compared to the absence of L-NA. At the three ACh concentration used, the presence of L-NA induced relaxation less than 20%. The absence of L-NA produced 100% relaxation returning to base line. L-NA induces an increase in calcium entry through receptor modulated calcium channels, and because the inhibition of the synthesis of EDRF it would produce an increase in vascular tension. In the same way, relaxation is explained by ACh-stimulated EDRF release, which is inhibited by L-NA. Considering the vascular endothelium as a paracrine organ, is important and interesting to study the pharmacomodulation of the NO/EDRF effects and, for the same reason, to consider L-NA in the pharmacologic arsenal.

Acetylcholine↗
PubMed1991

Effects of putative modulators of relaxation microinjected into intact amphibian smooth muscle cells.

1. Single smooth muscle cells were isolated intact from the stomach of the toad Bufo marinus. The relaxation of cells following cessation of electrical stimulation was compared with those relaxed by pressure microinjection of either metal ion chelators or cyclic nucleotides. 2. Injection of either a Ca2+ chelator or 3',5'-cyclic AMP slowed or halted shortening and promoted re-extension of a cell or collapse of membrane evaginations (blebs) in a manner similar to that following cessation of electrical stimulation. Collapse of blebs occurred first and was then followed smoothly by the next stage with cells re-extending at maximum rates in one of three ranges at 22 degrees C. These rates, in order of increasing speed, were 0.005, 0.009 and 0.03 cell lengths s-1 after electrical stimulation, 3',5'-cyclic AMP and EDTA injection, respectively. On the other hand, shortening began at a maximum rate of about 0.1 cell lengths s-1 unless a Ca2+ chelator or 3',5'-cyclic AMP was injected about 30 s or less before electrical stimulation. Injection of these agents reduced the speed of shortening by about half. 3. Injection of a liquid per se (e.g. 140 mM-KCl) neither altered action potentials nor duplicated the changes produced by the aforementioned relaxing agents. Large, sustained injections of substances that were not relaxing agents (e.g. dilute KCl) ruptured the membrane without producing any bleb collapse or re-extension of a contracted cell. Blebs not only collapsed rapidly when a relaxing agent was injected but bleb collapse was a much more sensitive indication of relaxation than cell re-extension; small injections of relaxing agents could clearly collapse blebs with no associated measurable change in cell length. This supports the idea previously inferred from fixed or permeabilized cells, that filaments in smooth muscle are organized to produce force over short distances at points along the cell membrane, in addition to shortening along the long axis. 4. Physiological relaxation of smooth muscle can evidently be mimicked by 3',5'-cyclic AMP elevation. Restoring forces may develop during shortening of isolated smooth muscle cells in elements of their cytoskeleton, surface membrane, or contractile filaments. However, these putative forces may not be able to produce physiological re-extension in the absence of a rise in cyclic AMP and/or a fall in [Ca2+].

Animals↗
PubMed1995

Superficial buffer barrier function of smooth muscle sarcoplasmic reticulum.

In smooth muscle the superficial sarcoplasmic reticulum accumulates a portion of the Ca2+ that enters cells through the plasmalemma and thus functions as a buffer barrier to Ca2+ entry into the myoplasm (superficial buffer barrier or SBB). In this review Cornelis van Breemen, Qian Chen and Ismail Laher summarize experimental support for the SBB, and discuss data indicating that: (1) contraction is related more to the rate than extent of Ca2+ entry; (2) refilling of sarcoplasmic reticulum from the extracellular space is mediated by Ca2+ influx and Ca2+ pumping by the sarcoplasmic reticulum Ca2+ pump; (3) the superficial sarcoplasmic reticulum unloads Ca2+ to the extracellular space by a multi step process that involves sequentially the opening of Ca2+ and inositol 1,4,5-trisphosphate [Ins(1,4,5,)P3] sensitive channels and Ca2+ extrusion by Na(+)-Ca2+ exchange; (4) the SBB generates a peripheral Ca2+ gradient; (5) Ca(2+)-mobilizing receptor agonists generate Ins(1,4,5)P3 which short circuits the SBB to increase the effectiveness of Ca2+ influx in raising [Ca2+]i and consequently increase smooth muscle contraction. A physiologically regulated SBB is thought to enhance the informational content of Ca2+ signalling and support variable reduction of smooth muscle tone. Pharmacological modulation of Ca2+ transport in the superficial sarcoplasmic reticulum therefore presents an alternative means of controlling smooth muscle tone dependent on Ca2+ entry.

Animals↗
PubMed1976

Antigenicity of janin, a new protein from smooth muscle.

The exact nature of smooth muscle autoantibodies is still unclear. The antigen(s) which they are directed against remain unknown. Janin, a so far unknown smooth muscle protein, was obtained from smooth muscle tissue extracts and purified by means of three different procedures. Its mol. w. was estimated at 60,000 daltons. It stimulated a specific anti-janin antibody in rabbits as shown by tube test, double diffusion in agar and indirect immunofluorescence. The new protein absorbed eighteen out of 104 human smooth muscle positive sera that were not absorbed with smooth muscle actin, myosin, heavy meromyosin, light meromyosin, tropomyosin and brain tubulin. This would vindicate a view that smooth muscle autoantibodies differ from patient to patient with regard to the autoantigen(s) involved.

Antibody Formation↗
PubMed2003

Vesicle-associated protein-A is differentially expressed during intestinal smooth muscle cell differentiation.

Gastrointestinal (GI) smooth muscle diseases represent a major health concern affecting in excess of 2 million people each year. Little is currently known regarding the molecular mechanisms controlling either normal or pathogenic GI smooth muscle development. In an effort to identify the specific gene products responsible for modulating GI smooth muscle cell (SMC) differentiation, we performed differential display on distinct intestinal SMC (ISMC) phenotypes. This analysis identified over 40 unique transcripts that appeared to be differentially expressed in distinct SMC phenotypes. One such transcript that appeared to be preferentially expressed in immature smooth muscle myocytes was identified as vesicle-associated membrane protein, associated protein A (VAP-A). Northern blot analysis confirmed that VAP-A was expressed threefold higher in immature smooth muscle myocytes when compared with both smooth muscle myoblasts and mature smooth muscle myocytes. VAP-A mRNA was differentially expressed during normal rat development and showed peak levels of expression in the intestine during late embryogenesis and early neonatal development. These observations provide the first evidence that VAP-A-mediated membrane trafficking may play an important role in modulating ISMC differentiation.

Amino Acid Sequence↗
PubMed1975

Trophic influences of sympathetic nerves and cyclic AMP on differentiation and proliferation of isolated smooth muscle cells in culture.

Smooth muscle cells of the newborn guinea-pig vas deferens dispersed into single cells and grown in culture maintain their differentiation for approximately 5 days before undergoing dedifferentiation and mitosis. The presence of sympathetic nerve fibres in contact with the isolated cells delays this process by 3-7 days (Chamley et al., 1974). A similar delay in dedifferentiation of vas deferens smooth muscle cells in tissue culture in the presence of sympathetic ganglion extract is described in the present report, demonstrating that the trophic effect is elicited by a chemical substance. This effect is mimicked by the presence of either a confluent layer of RKA epithelial cells, dibutyryl cyclic AMP or theophylline. A similar, but considerably weaker, effect is also obtained with spinal cord and liver extracts and noradrenaline. Acetylcholine does not show an effect. It is suggested that a trophic substance (probably not noradrenaline) from sympathetic neurons activates the adenyl cyclase system of smooth muscle cells to increase the intracellular level of cyclic AMP which in turn promotes and maintains the differentiation of the cultured smooth muscle cells.

Acetylcholine↗
PubMed1991

Serotonin: an inducer of collagenase in myometrial smooth muscle cells.

Rat myometrial smooth muscle cells in culture actively produce collagenase in medium containing fetal bovine serum, but not in medium containing newborn bovine serum or containing fetal serum adsorbed with dextran-coated charcoal. A dialyzable molecule has been isolated from fetal bovine serum, which restores the ability of the smooth muscle cells to produce collagenase. The molecule has been purified and identified as serotonin (5-hydroxytryptamine). Cells cultured in medium depleted of serotonin for 3 days fail to produce collagenase, as assessed both enzymatically and immunologically. Addition of serotonin promptly restores the ability of the cells to produce the enzyme. The EC50 for serotonin is approximately 2 microM; maximum stimulation of collagenase production is observed at 5 microM. The response is specific for serotonin: a wide variety of compounds tested, either related to serotonin or of potential reproductive significance, were without effect in the induction of collagenase production by the cells. No changes in DNA content, general protein synthesis, or cellular collagen production were observed as a consequence of serotonin depletion or restoration, suggesting a selective effect of the compound on collagenase production. The effect of serotonin was also selective to myometrial smooth muscle cells; collagenase-producing fibroblasts from skin and cervix displayed no serotonin requirement for enzyme production. Studies using specific agonists or antagonists for a variety of serotonin receptor subtypes suggest that the 5-HT-2 receptor mediates the serotonin induction of collagenase in these cells. Preliminary evidence indicates that cultured human myometrial smooth muscle cells are also dependent upon serotonin for collagenase production. The evidence in this study suggests the possibility that serotonin serves as a signal to begin the massive collagen degradation that occurs in the postpartum uterus.

Animals↗
PubMed2005

The association of caveolae, actin, and the dystrophin-glycoprotein complex: a role in smooth muscle phenotype and function?

Smooth muscle cells exhibit phenotypic and mechanical plasticity. During maturation, signalling pathways controlling actin dynamics modulate contractile apparatus-associated gene transcription and contractile apparatus remodelling resulting from length change. Differentiated myocytes accumulate abundant caveolae that evolve from the structural association of lipid rafts with caveolin-1, a protein with domains that confer unique functional properties. Caveolae and caveolin-1 modulate and participate in receptor-mediated signalling, and thus contribute to functional diversity of phenotypically similar myocytes. In mature smooth muscle, caveolae are partitioned into discrete linear domains aligned with structural proteins that tether actin to the extracellular matrix. Caveolin-1 binds with beta-dystroglycan, a subunit of the dystrophin glycoprotein complex (DGC), and with filamin, an actin binding protein that organizes cortical actin, to which integrins and focal adhesion complexes are anchored. The DGC is linked to the actin cytoskeleton by a dystrophin subunit and is a receptor for extracellular laminin. Thus, caveolae and caveolin-associated signalling proteins and receptors are linked via structural proteins to a dynamic filamentous actin network. Despite development of transgenic models to investigate caveolins and membrane-associated actin-linking proteins in skeletal and cardiac muscle function, only superficial understanding of this association in smooth muscle phenotype and function has emerged.

Actins↗
PubMed1996

Immunohistochemical study and western blotting analysis of titin-like proteins in the striated muscle of Drosophila melanogaster and in the striated and smooth muscle of the oligochaete Eisenia foetida.

The presence and distribution of titin-like proteins have been examined in transversely striated muscle of Drosophila melanogaster, in obliquely striated muscles (body wall and inner muscular layer of the pseudoheart) and smooth muscle (outer muscular layer of the pseudoheart) from the earthworm Eisenia foetida by means of Western blotting analysis, light microscopy immunohistochemistry, and electron microscopy immunogold labeling, using antibodies anti vertebrate (chicken) titin (3,000 kDa) and arthropod (D. melanogaster) mini-titin (twitchin or projectin) (700 kDa). To determine whether these antibodies immunoreact non-specifically against vertebrate titin, mouse skeletal muscle was also studied. As negative control, mouse smooth muscle was used. Immunoreaction to mini-titin was found in all the invertebrate muscles studied. For each of these muscles, Western blotting analysis of mini-titin showed a single band, at approximately 700 kDa. Electron microscopy immunolabeling to this protein was observed along the whole sarcomere length (A bands and I bands) in both transversely striated muscles of the insect and obliquely striated muscles of the earthworm, although the number of immunogold particles was more abundant in the insect muscles. Mini-titin immunolabeling was also observed in the smooth muscle cells that formed the outer layer of the earthworm pseudoheart although in lower amounts than in the obliquely striated muscle. The absence of true sarcomeres in the smooth muscle cells did not permit to determine the extension of mini-titin immunolabeling. No immunoreaction to this protein was found in the striated and smooth muscles of the mouse. Immunoreaction to titin was only observed in the mouse skeletal muscle, in which both A bands and I bands appeared immunolabeled. Present results show that mini-titin in the invertebrate muscles studied differs immunohistochemically from vertebrate titin and, in contrast with titin, mini-titin is also present in invertebrate smooth muscles.

Animals↗
PubMed2002

Expression of smooth muscle actin in osteoblasts in human bone.

It is well known that certain connective tissue cells (viz., dermal fibroblasts) can express the gene for a muscle actin--alpha-smooth muscle actin--and can contract. This process contributes to skin wound closure and is responsible for Dupuytren's contracture. The objective of this study was to determine if human osteoblasts can also express the gene for alpha-smooth muscle actin. Immunohistochemistry using a monoclonal antibody for alpha-smooth muscle actin was performed on human cancellous bone samples obtained from 20 individuals at the time of total joint arthroplasty. The percentages of resting and active osteoblasts on the bone surfaces containing this muscle actin isoform were evaluated. Explants of human bone were also studied for the expression of alpha-smooth muscle actin in the tissue and in the outgrowing cells with time in culture. Western blot analysis was performed to quantify the alpha-smooth muscle actin content of the outgrowing cells relative to smooth muscle cell controls. Nine +/- 2% (mean +/- SEM; n = 20) of the cells classified as inactive osteoblasts and 69 +/- 3% (n = 19) of the cells identified as active osteoblasts on the bone surface contained alpha-smooth muscle actin. This difference was highly statistically significant (Student's t test, p < 0.0001). Similar profiles of alpha-smooth muscle actin-expressing cells were found in explants cultured for up to 12 weeks. Cells forming a layer on the surface of the explants and growing out from them in monolayer also contained alpha-smooth muscle actin by immunohistochemistry and Western blot analysis. Human osteoblasts can express the gene for alpha-smooth muscle actin. This expression should be considered a phenotypic characteristic of this cell type, conferred by its progenitor cells: bone marrow stromal-derived stem cells, and perhaps pericytes and smooth muscle cells.

Actins↗
PubMed1983

Immunoreactivity of paraffin-embedded normal tissues and mesenchymal tumors for smooth muscle myosin.

Immunohistochemical study of smooth muscle myosin, a protein distinct from skeletal, cardiac, or nonmyogenous myosins in paraffin-embedded normal tissues and benign and malignant mesenchymal tumors revealed its strong expression in normal smooth muscle, capillary endothelium, and pericytes. All benign smooth muscle tumors with exception of gastric leiomyomas and few other leiomyomas of the gastrointestinal tract displayed strong or moderate immunoreactivity. On the other hand, strong or moderate immunoreactivity was detected in only eight of 28 spindle-cell leiomyosarcomas, as well as in 13 out of 27 malignant fibrous histiocytomas and three out of nine malignant hemangiopericytomas, while epithelioid leiomyosarcomas, fibrosarcomas, malignant schwannomas, and synovial sarcomas were negative or only weakly positive. Our results demonstrate that, while smooth muscle myosin is a very good marker of normal smooth muscle and benign smooth muscle tumors, it is expressed in diagnostically significant amounts in less than a third of spindle-cell leiomyosarcomas and none of the studied epithelioid leiomyosarcomas.

Female↗
PubMed2005

Angiotensin II up-regulates the leukemia-associated Rho guanine nucleotide exchange factor (RhoGEF), a regulator of G protein signaling domain-containing RhoGEF, in vascular smooth muscle cells.

In vascular smooth muscle, stimulation of heterotrimeric G protein-coupled receptors (GPCRs) by various contractile agonists activates intracellular signaling molecules to result in an increase in cytosolic Ca2+ and the subsequent phosphorylation of myosin light chain (MLC) by Ca2+/calmodulin-dependent MLC kinase. In addition, a portion of agonist-induced contraction is partially mediated by the Ca2+-independent activation of the small G protein RhoA and a downstream target, Rho-kinase. The activation of RhoA is controlled by several regulatory proteins, including guanine nucleotide exchange factors (GEFs). GEFs activate RhoA by promoting the release of GDP and then facilitating the binding of GTP. There are three Rho-specific GEFs (RhoGEFs) in vascular smooth muscle that contain a binding domain [regulator of G protein signaling (RGS) domain] capable of linking GPCRs to RhoA activation: PDZ-RhoGEF, leukemia-associated RhoGEF (LARG), and p115RhoGEF. We hypothesized that RGS domain-containing RhoGEFs, especially LARG, participate in linking GPCR to RhoA activation in vascular smooth muscle. We observed that angiotensin II up-regulates LARG via the AT1 receptor, and this up-regulation is signaled via the phosphatidylinositol 3-kinase pathway. Furthermore, angiotensin II treatment caused a small, but significant, increase in the component of contractile responses sensitive to Rho-kinase antagonism. These observations support the hypothesis that RhoGEFs, particularly LARG, participate in linking GPCR to RhoA activation in vascular smooth muscle.

Angiotensin II↗
PubMed1983

Bimodal distribution of the prostaglandin I2 synthase antigen in smooth muscle cells.

Vascular and nonvascular smooth muscles in 12 different organs from the gastrointestinal, respiratory, and urogenital tracts of the rabbit, cow, dog, sheep, pig, and rat were examined for prostaglandin I2 (PGI2) synthase immunoreactivity by indirect immunocytofluorescence using monoclonal antibodies against the enzyme. Each of 35 different smooth muscle layers tested stained for the PGI2 synthase antigen except the circular smooth muscle of the rabbit large intestine. Interestingly, PGI2 synthase-positive fluorescent staining of smooth muscle was always observed to be associated with both the nuclear and plasma membranes. Our results indicate that most smooth muscle, both vascular and nonvascular, has the capacity to synthesize PGI2. Moreover, the fact that the PGI2 synthase antigen is associated with at least two different organelles in each cell suggests that there are two independent PGI2-synthesizing systems in smooth muscle; one on the nuclear membrane, and one on the plasma membrane. PGI2 formed at these different sites may subserve different functions within the same cell.

Animals↗
PubMed2003

Interleukin-4 and -13 expression is co-localized to mast cells within the airway smooth muscle in asthma.

BACKGROUND: Airway smooth muscle infiltration by mast cells is a feature of asthma and not eosinophilic bronchitis. In asthma, Th2 cytokines have been implicated as playing a critical role in the development of airway inflammation and hyper-responsiveness. Whether inflammatory cells within the airway smooth muscle release these cytokines is unknown. METHODS: We have undertaken a comparative immunohistochemical study in bronchial biopsies from 14 subjects with asthma, 10 with eosinophilic bronchitis and eight normal controls recruited from two centres. RESULTS: The median number of IL-4+ cells/mm2 smooth muscle was significantly higher in subjects with asthma than eosinophilic bronchitis and normal controls for both the anti-IL-4 mAb 3H4 (2.4, 0, 0, respectively; P=0.001) and anti-IL-4 mAb 4D9 (1.6, 0, 0, respectively; P=0.02). There were no group differences in the number of IL-5+ cells (P=0.31). In six subjects with asthma, IL-13 expression by cells within the airway smooth muscle was studied. The median (range) of IL-13+cells was 2 (0.9-2.7). Ninety-four percent of the cells expressing IL-4 (3H4), 92% of those expressing IL-4 (4D9) and 100% expressing IL-13 in the airway smooth muscle were mast cells. Fifty-five percent of the mast cells within the airway smooth muscle co-localized to IL-4 (3H4), 29% to IL-4 (4D9) and 17% to IL-13. CONCLUSIONS: In asthma, IL-4+ and IL-13+ cells were present within the airway smooth muscle and were expressed predominantly by mast cells, suggesting that IL-4 and IL-13 may play an important role in mast cell-airway smooth muscle interactions.

Adult↗
PubMed1995

Gene expression and vascular smooth muscle cell phenotype.

Vascular smooth muscle cells (VSMCs) are involved in a number of vascular disease processes including hypertension and atherosclerosis. However, their role in the pathogenesis of vascular disease is largely undetermined. We and others have studied rat VSMCs in cell culture as a model for VSMC behaviour in vivo. In recent experiments we have applied molecular biological techniques to compare genes expressed by normal contractile VSMCs with those expressed by VSMCs which have undergone several passages in cell culture. Using differential screening of a cDNA library derived from cultured rat aortic VSMC RNA we identified seven genes which are preferentially expressed by contractile VSMCs; alpha-smooth muscle actin, gamma-smooth muscle actin, calponin, phospholamban, tropoelastin, SM22 alpha and CHIP28, and two which are preferentially expressed in passaged cells which have down-regulated their contractile proteins; osteopontin (OP) and matrix Gla protein (MGP). In situ hybridization studies have confirmed that calponin and SM22 alpha, are highly expressed by medial VSMCs in human coronary arteries with little or no expression in the atheromatous intima whilst the converse is true for OP and MGP. Studies by ourselves and others have confirmed that OP is a marker for proliferating rat VSMCs both in vitro and in vivo. However, the evidence that OP is expressed by proliferating human VSMCs is less convincing.

Animals↗