Ectopic expression of Smad7 inhibits transforming growth factor-beta responses in vascular smooth muscle cells

Nuclear Smooth Muscle α-actin Participates in Vascular Smooth Muscle Cell Differentiation

Missense variants throughout ACTA2, encoding smooth muscle α-actin (αSMA), predispose to adult-onset thoracic aortic disease, but variants disrupting arginine 179 (R179) lead to Smooth Muscle Dysfunction Syndrome (SMDS) characterized by diverse childhood-onset vascular diseases. Here we show that αSMA localizes to the nucleus in wildtype (WT) smooth muscle cells (SMCs), enriches in the nucleus with SMC differentiation, and associates with chromatin remodeling complexes and SMC contractile gene promotors. The ACTA2 p.R179 αSMA variant shows decreased nuclear localization. Primary SMCs from Acta2 SMC-R179C/+ mice are less differentiated than WT SMCs in vitro and in vivo and have global changes in chromatin accessibility. Induced pluripotent stem cells from patients with ACTA2 p.R179 variants fail to fully differentiate from neuroectodermal progenitor cells to SMCs, and single-cell transcriptomic analyses of an ACTA2 p.R179H patient's aortic tissue show increased SMC plasticity. Thus, nuclear αSMA participates in SMC differentiation, and loss of this nuclear activity occurs with ACTA2 p.R179 pathogenic variants.

Up-regulation of BMP-2 antagonizes TGF-β1/ROCK-enhanced cardiac fibrotic signalling through activation of Smurf1/Smad6 complex

Rho-associated kinase (ROCK) plays a critical role in pressure overload-induced left ventricular remodelling. However, the underlying mechanism remains unclear. Here, we reported that TGF-β1-induced ROCK elevation suppressed BMP-2 level and strengthened fibrotic response. Exogenous BMP-2 supply effectively attenuated TGF-β1 signalling pathway through Smad6-Smurf-1 complex activation. In vitro cultured cardiomyocytes, mechanical stretch up-regulated cardiac TGF-β1, TGF-β1-dependent ROCK and down-regulated BMP-2, but BMP-2 level could be reversed through blocking TGF-β1 receptor by SB-431542 or inhibition of ROCK by Y-27632. TGF-β1 could also activate ROCK and suppress endogenous BMP-2 level in a dose-dependent manner. Knock-down BMP-2 enhanced TGF-β1-mediated PKC-δ and Smad3 signalling cascades. In contrast, treatment with Y-27632 or SB-431542, respectively suppressed ROCK-dependent PKC-δ and Smad3 activation, but BMP-2 was only up-regulated by Y-27632. In addition, BMP-2 silencing abolished the effect of Y-27632, but not SB-431542 on suppression of TGF-β1 pathway. Further experiments showed that Smad6 Smurf1 interaction were required for BMP-2-evoked antagonizing effects. Smad6 overexpression attenuated TGF-β1-induced activation of PKC-δ and Smad3, promoted TGF-β RI degradation in BMP-2 knock-down cardiomyocytes, and could be abolished after knocking-down Smurf-1, in which Smad6/Smurf1 complex formation was critically involved. In vivo data showed that pressure overload-induced collagen deposition was attenuated, cardiac function was improved and TGF-β1-dependent activation of PKC-δ and Smad3 was reduced after 2 weeks treatment with rhBMP-2(0.5 mg/kg) or Y-27632 (10 mg/kg) in mice that underwent surgical transverse aortic constriction. In conclusion, we propose that BMP-2, as a novel fibrosis antagonizing cytokine, may have potential beneficial effect in attenuating pressure overload-induced cardiac fibrosis.

Transforming growth factor-β in graft vessels: histology and immunohistochemistry

OBJECTIVES

The biological functions of transforming growth factor-β signaling that involves Smad proteins have not been previously investigated with respect to coronary artery bypass grafts. The aim of the present study was to observe the immunostaining of proteins that are related to this signaling pathway.

METHODS

Fifteen remnants of coronary artery bypass grafts, including nine saphenous veins, three radial arteries and three mammary arteries, were collected from 12 patients who were undergoing coronary artery bypass. Hematoxylin and eosin, Masson's trichrome, and immunohistochemical staining of transforming growth factor-β1, type I receptor of transforming growth factor-β, Smad2/3, Smad4, and Smad7 were performed.

RESULTS

The saphenous veins showed more severe intimal degeneration, more severe smooth muscle cell proliferation and more collagen deposition than the arterial grafts, as evidenced by hematoxylin and eosin and Masson's trichrome stainings. Immunohistochemical assays demonstrated that the majority of the transforming growth factor-β1 signaling cytokines were primarily localized in the cytoplasm in the medial layers of all three types of grafts, whereas ectopic transforming growth factor-β1, type I receptor of transforming growth factor-β, and Smad7 overexpressions in the interstices were observed particularly in the saphenous vein and radial arterial grafts.

CONCLUSION

Enhanced transforming growth factor-β1 signal transduction with medial smooth muscle cell proliferation and ectopic transforming growth factor-β1, the presence of the type I receptor of transforming growth factor-β, and Smad7 overexpressions in the extracellular matrix may provide primary evidence for early or late graft failure.

Smad7 blocks transforming growth factor-β1-induced gingival fibroblast-myofibroblast transition via inhibitory regulation of Smad2 and connective tissue growth factor

BACKGROUND

Transforming growth factor-β1 (TGF-β1), its downstream signaling mediators (Smad proteins), and specific targets, including connective tissue growth factor (CTGF), play important roles in tissue remodeling and fibrosis via myofibroblast activation. We investigated the effect of overexpression of Smad7, a TGF-β1 signaling inhibitor, on transition of gingival fibroblast to myofibroblast. Moreover, we analyzed the participation of CTGF on TGF-β1-mediated myofibroblast transformation.

METHODS

To study the inhibitory effect of Smad7 on TGF-β1/CTGF-mediating gingival fibroblast transition into myofibroblasts, we stably overexpressed Smad7 in normal gingival fibroblasts and in myofibroblasts from hereditary gingival fibromatosis (HGF). Myofibroblasts were characterized by the expression of the specific marker isoform α of the smooth muscle actin (α-SMA) by Western blot, flow cytometry, and immunofluorescence. Enzyme-linked immunosorbent assay for type I collagen was performed to measure myofibroblast activity. CTGF's role on myofibroblast transformation was examined by enzyme-linked immunosorbent assay and small interference RNA.

RESULTS

TGF-β1 induced the expression of α-SMA and CTGF, and small interference RNA-mediating CTGF silencing prevented fibroblast-myofibroblast switch induced by TGF-β1. In Smad7-overexpressing fibroblasts, ablation of TGF-β1-induced Smad2 phosphorylation marked decreased α-SMA, CTGF, and type I collagen expression. Similarly, HGF transfectants overexpressing Smad7 demonstrated low levels of α-SMA and phospho-Smad2 and significant reduction on CTGF and type I collagen production.

CONCLUSIONS

CTGF is critical for TGF-β1-induced gingival fibroblast-myofibroblast transition, and Smad7 overexpression is effective in the blockage of myofibroblast transformation and activation, suggesting that treatments targeting myofibroblasts by Smad7 overexpression may be clinically effective in gingival fibrotic diseases, such as HGF.

Cytokine array analysis of peritoneal fluid between women with endometriosis of different stages and those without endometriosis

Cytokines are key mediators of intercellular communication and are likely to promote the development and progression of endometriosis. Previous studies provided evidence that endometriosis develops as a result of the pathogenetic factors in the peritoneal environment, especially the peritoneal fluid (PF). We determined different cytokine expression in peritoneal fluid between women with minimal/mild and moderate/severe endometriosis and those without endometriosis using the cytokine array. As a result, 78 cytokines were found to have a threefold change, including 74 increases and four decreases in endometriosis compared with the control group; 96 cytokines had a threefold change including 91 increases and five decreases in minimal and mild endometriosis compared with the control group; 83 cytokines had a threefold change including 14 increases and 69 decreases in moderate and severe endometriosis compared with minimal and mild endometriosis. The cytokine networks were produced by Pathway Studio software and revealed that most cytokines are involved in cell binding, interaction and protein synthesis and transportation regulation. Among them activin A, Smad7 and beta-nerve growth factor are the most interesting as they may be involved in the pathogenesis of endometriosis. These results suggest that cytokines are very important factors in the development of endometriosis. The findings of differentially expressed cytokines improves our knowledge of the pathogenesis and development of endometriosis and these findings warrant further studies to develop potential targets for the diagnosis and treatment of endometriosis.

Histone deacetylase 4 is required for TGFbeta1-induced myofibroblastic differentiation

Transforming Growth Factor beta1 (TGFbeta1) is a crucial cytokine triggering myofibroblastic (MF) differentiation, a process involved in tissue healing as well as in pathologic conditions such as fibrosis and cancer. Together with cell shape modifications, TGFbeta1-mediated differentiation of fibroblasts into myofibroblasts is characteristically associated with the neo-expression of smooth muscle alpha-actin (alpha-SMA), a cytoskeletal protein that enhances their contractile activity. Several cellular differentiation programs have been linked to epigenetic regulation of gene expression, including gene methylation and histone acetylation. Herein, we sought to investigate the role of histone deacetylases (HDAC) in TGFbeta1-induced MF differentiation. We found that TSA, a global inhibitor of class I and class II HDACs, prevented alpha-SMA transcript and protein expression and morphological changes mediated by TGFbeta1 in cultured human skin fibroblasts. In order to identify the HDAC(s) participating in MF differentiation, the impact of specific HDAC silencing (HDAC1 through HDAC8) using RNA interference was investigated in fibroblasts exposed to TGFbeta1. Among the eight HDACs tested, silencing of HDAC4, HDAC6, and HDAC8 expression impaired TGFbeta1-induced alpha-SMA expression. HDAC4 silencing most efficiently abrogated alpha-SMA expression and also prevented TGFss1-mediated morphological changes. Forced down-regulation of HDAC4 stimulated the expression of 5'-TG-3'-Interacting Factor (TGIF) and TGIF2 homeoproteins, two known endogenous repressors of the TGFbeta signaling pathway, but not of the inhibitory Smad7. Collectively, these data suggest that HDAC4 is an essential epigenetic regulator of MF differentiation and unveil HDAC4 as a potential target for treating MF-related disorders.

Regulation of collagen synthesis by inhibitory Smad7 in cardiac myofibroblasts

Transforming growth factor-beta(1) (TGF-beta(1)) signal and downstream Smads play an important role in tissue fibrosis and matrix remodeling in various etiologies of heart failure. Inhibitory Smad7 (I-Smad7) is an inducible regulatory Smad protein that antagonizes TGF-beta(1) signal mediated via direct abrogation of R-Smad phosphorylation. The effect of ectopic I-Smad7 on net collagen production was investigated using hydroxyproline assay. Adenovirus-mediated I-Smad7 gene (at 100 multiplicity of infection) transfer was associated with significant decrease of collagen synthesis in the presence and absence of TGF-beta(1) in primary rat cardiac myofibroblasts. In I-Smad7-infected cells, we also observed the ablation of TGF-beta(1)-induced R-Smad2 phosphorylation vs. LacZ controls. Overdriven I-Smad7 was associated with significantly increased expression of immunoreactive 65-kDa matrix metalloproteinase-2 (MMP-2) protein in culture medium of myofibroblast compared with LacZ-infected cells. Expression of the 72-kDa MMP-2 variant, e.g., the inactive form, was not altered by exogenous I-Smad7 transfection/overexpression. Furthermore, I-Smad7 overexpression was associated with a significant increase and decrease in expression of p27 and phospho-Rb protein, respectively, as well as reduced [(3)H]thymidine incorporation vs. Ad-LacZ-infected controls. We suggest that negative modulation of R-Smad phosphorylation by ectopic I-Smad7 may contribute to the downregulation of collagen in cardiac myofibroblasts and may suppress the proliferation of these cells. Thus treatments targeting the collagen deposition by overexpression of I-Smad7 may provide a new therapeutic strategy for cardiac fibrosis.

Transforming growth factor-beta regulation of epithelial tight junction proteins enhances barrier function and blocks enterohemorrhagic Escherichia coli O157:H7-induced increased permeability

Enterohemorrhagic Escherichia coli O157:H7 (EHEC) is an enteric pathogen that causes potentially fatal symptoms after intimate adhesion, modulation of intestinal epithelial signal transduction, and alteration of epithelial function (eg, barrier disruption). Although the epithelial barrier is critical to gut homeostasis, only a few agents, such as transforming growth factor (TGF)-beta, can enhance or protect epithelial barrier function. Our aims were to delineate the mechanism(s) behind TGF-beta-induced barrier enhancement and to determine whether TGF-beta could prevent EHEC-induced barrier disruption. Using monolayers of the human T84 colonic epithelial cell line, we found that TGF-beta induced a significant increase in transepithelial electrical resistance (a measure of paracellular permeability) through activation of ERK MAPK and SMAD signaling pathways and up-regulation of the tight junction protein claudin-1. Additionally, TGF-beta pretreatment of epithelia blocked the decrease in transepithelial electrical resistance and the increase in transepithelial passage of [(3)H]-mannitol caused by EHEC infection. EHEC infection was associated with reduced expression of zonula occludens-1, occludin, and claudin-2 (but not claudin-1 or claudin-4); TGF-beta pretreatment prevented these changes. These studies provide insight into EHEC pathogenesis by illustrating the mechanisms underlying TGF-beta-induced epithelial barrier enhancement and identifying TGF-beta as an agent capable of blocking EHEC-induced increases in epithelial permeability via maintenance of claudin-2, occludin, and zonula occludens-1 levels.

Smad7 Gene Transfer Attenuates Adventitial Cell Migration and Vascular Remodeling After Balloon Injury

Objective— Migration of adventitial fibroblasts contributes to arterial remodeling after angioplasty. This study used vascular gene transfer of smad7 to investigate whether antagonism of transforming growth factor-β1 signaling alters luminal loss and adventitial cell migration after balloon injury in rat carotid arteries.

Methods and Results— Adenoviruses coordinating expression of β-galactosidase (β-gal) and smad7 or β-gal and green fluorescent protein (GFP) were applied to the perivascular surface of common carotid arteries. Balloon injury was performed 4 days after gene transfer, and animals were killed at 3, 7, and 14 days after injury. Uninjured arteries only expressed adventitial β-gal positive cells; however, after balloon injury in β-gal- and GFP-transfected arteries, β-gal-positive cells were observed within the medial layer of vessels and contributed to the population of cells within the neointima at 7 to 14 days. Overexpression of smad7 and β-gal resulted in a significant reduction in the number of β-gal–labeled cells in the neointima, concomitant with reduced luminal loss and decreased adventitial collagen content.

Conclusions— We provide the first evidence that vascular smad7 overexpression attenuates remodeling and contribution of adventitial fibroblasts to neointima formation after balloon angioplasty. Smad7 may represent a novel therapeutic target to reduce the incidence of restenosis.

Transforming growth factor-beta1 signaling contributes to development of smooth muscle cells from embryonic stem cells

Knockout of transforming growth factor (TGF)-beta1 or components of its signaling pathway leads to embryonic death in mice due to impaired yolk sac vascular development before significant smooth muscle cell (SMC) maturation occurs. Thus the role of TGF-beta1 in SMC development remains unclear. Embryonic stem cell (ESC)-derived embryoid bodies (EBs) recapitulate many of the events of early embryonic development and represent a more physiological context in which to study SMC development than most other in vitro systems. The present studies showed induction of the SMC-selective genes smooth muscle alpha-actin (SMalphaA), SM22alpha, myocardin, smoothelin-B, and smooth muscle myosin heavy chain (SMMHC) within a mouse ESC-EB model system. Significantly, SM2, the SMMHC isoform associated with fully differentiated SMCs, was expressed. Importantly, the results showed that aggregates of SMMHC-expressing cells exhibited visible contractile activity, suggesting that all regulatory pathways essential for development of contractile SMCs were functional in this in vitro model system. Inhibition of endogenous TGF-beta with an adenovirus expressing a soluble truncated TGF-beta type II receptor attenuated the increase in SMC-selective gene expression in the ESC-EBs, as did an antibody specific for TGF-beta1. Of interest, the results of small interfering (si)RNA experiments provided evidence for differential TGF-beta-Smad signaling for an early vs. late SMC marker gene in that SMalphaA promoter activity was dependent on both Smad2 and Smad3 whereas SMMHC activity was Smad2 dependent. These results are the first to provide direct evidence that TGF-beta1 signaling through Smad2 and Smad3 plays an important role in the development of SMCs from totipotential ESCs.