Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Myofibroblasts”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1993

The response of rat liver perisinusoidal lipocytes to polypeptide growth regulator changes with their transdifferentiation into myofibroblast-like cells in culture.

During culture on uncoated plastic wells rat liver perisinusoidal lipocytes change their differentiated phenotype (transdifferentiate) within 1-2 weeks and obtain a myofibroblast-like phenotype (myofibroblast-like cells). This transdifferentiation was documented by morphologic (loss of fat droplets, flat cell shape, cytoplasmic extensions, expression of iso-alpha smooth muscle actin) and biochemical criteria (loss of retinyl-palmitate, enhanced matrix synthesis). Whereas transforming growth factor alpha (TGF alpha) stimulated and transforming growth factor beta (TGF beta 1) inhibited the proliferation of perisinusoidal lipocytes (early culture) these cytokines did not effect the growth of the myofibroblast-like cells. Opposite effects were obtained with platelet-derived growth factor (PDGF) which stimulated the growth of myofibroblast-like cells only. Insulin-like growth factor (IGF1) was mitogenic in both perisinusoidal lipocytes and myofibroblast-like cells, respectively. Furthermore, whereas the expression of the mRNAs of decorin and biglycan was stimulated by TGF beta 1 in perisinusoidal lipocytes, the synthesis of these mRNAs was stimulated in myofibroblast-like cells predominantly by TGF alpha. Similar effects of TGF alpha and TGF beta 1 have been observed on the glycosaminoglycan-([35S]sulfate incorporation) and proteoglycan level ([3H]leucin incorporation into decorin and biglycan). Neither IGF1 and PDGF stimulated glycosaminoglycan synthesis in perisinusoidal lipocytes or in myofibroblast-like cells. The results demonstrate that the effects of the polypeptide growth regulators TGF alpha, TGF beta 1 and PDGF depend on the cell phenotype (stage of cell activation/transdifferentiation) and may be completely different in perisinusoidal lipocytes and its transformed counterpart the myofibroblast-like cells.

Adipose Tissue↗
PubMed1993

Nucleolar organizer regions in myofibroblasts in breast cancer. Relation to cancer cell morphometry, flow cytometry, sex steroid receptor content, tumour histology and prognosis.

The number of silver-stained nucleolar organizer regions (Ag-NORs) was counted in stromal myofibroblasts in 125 cases of breast cancer. The mean (S.E.) of Ag-NORs in stromal myofibroblasts was 4.4 (0.1). The number of Ag-NORs in myofibroblasts was related to histological grade (p = 0.028), histological type (p = 0.013), tumour necrosis (p = 0.026), mitotic frequency (p = 0.091) and S-phase fraction (p = 0.032). The number of Ag-NORs in stromal myofibroblasts predicted survival with a borderline significance (x2 = 3.4, p = 0.052) and also in axillary lymph node negative tumours (X2 = 2.8, p = 0.095). The recurrence-free survival in the entire cohort (X2 = 7.1, p = 0.0075) and in axillary lymph node negative tumours (X2 = 7.1, p = 0.0078) could be predicted on the basis of the number of Ag-NORs in stromal myofibroblasts. In axillary lymph node positive tumours the number of Ag-NORs in stromal myofibroblasts had no prognostic value. In multivariate analysis the number of Ag-NORs in stromal myofibroblasts had no independent prognostic value. The results suggest a close interaction between stromal myofibroblasts and epithelial cancer cells in breast cancer, and stromal changes are clearly a subject for further analyses.

Breast Neoplasms↗
PubMed2001

A novel model to study renal myofibroblast formation in vitro.

BACKGROUND: In chronic renal disease, the decrease of excretory renal function closely correlates with the extent of interstitial fibrosis. A common feature of interstitial fibrosis is the occurrence of myofibroblasts, which are regarded as the predominant cells in matrix synthesis. We studied the transformation of renal fibroblasts into myofibroblasts in vitro as a model to elucidate the mechanisms underlying this process. METHODS: Primary cultures of freshly isolated rat inner medullary fibroblasts were established as reported previously. mRNA expression of myofibroblast markers and interstitial collagens was examined by Northern blot and reverse transcriptase-polymerase chain reaction (RT-PCR). Phenotypic expression was investigated by immunolabeling. Endogenous transforming growth factor-beta (TGF-beta) production was inhibited by addition of a neutralizing antibody or by TGF-beta 1 antisense oligodeoxynucleotides (ODNs). RESULTS: Initially and during the first 36 hours, primary culture cells expressed neither alpha-smooth muscle actin nor desmin mRNA. From day 2 of primary culture, we observed a strong increase in these mRNAs, as evaluated by RT-PCR, followed by the phenotypic expression of these myofibroblast markers. Collagen type I mRNA was first detectable from day 4 of primary culture and showed a strong increase in its expression level during the following days, with phenotypic expression predominantly in myofibroblasts. The transformation rate of fibroblasts to myofibroblasts largely decreased in cocultures with collecting duct cells. This effect could be reversed by reducing the seeding density. We examined in this system the effect of TGF-beta 1 to define further its putative fibrogenic activity. However, neither the addition of exogenous TGF-beta 1 nor the inhibition of endogenous TGF-beta production showed any significant effect on fibroblast transformation, suggesting that this cytokine exerts its effects at other levels or requires a cofactor. CONCLUSIONS: We present a novel model to examine the de novo expression of myofibroblast markers and collagen type I in freshly isolated fibroblasts under defined conditions in primary culture. This model could provide a strategy for the molecular characterization of myofibroblast formation and the phenomena associated with this process.

Actins↗
PubMed2002

Interleukin-1beta and tumor necrosis factor-alpha induce chemokine and matrix metalloproteinase gene expression in human colonic subepithelial myofibroblasts.

BACKGROUND: Colonic subepithelial myofibroblasts may play a role in the inflammatory responses and in extracellular matrix (ECM) metabolism. In this study, we investigated the effects of interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha on chemokine (IL-8 and monocyte chemoattractant protein (MCP)-1) and ECM turnover (proliferation of subepithelial myofibroblasts, and secretion of ECM and matrix metalloproteinases (MMPs)) in colonic subepithelial myofibroblasts. METHODS: Human colonic subepithelial myofibroblasts were isolated using the method described by Mahida et al. Chemokine and MMP expressions were determined by ELISA and Northern blotting. Nuclear factor (NF)-kappaB and NF-IL6 DNA binding activities were evaluated by electrophoretic gel mobility shift assays (EMSA). RESULTS: IL-1beta and TNF-alpha did not affect the proliferation of subepithelial myofibroblasts, but stimulated the secretion of types I and IV collagens weakly. Unstimulated subepithelial myofibroblasts secreted a large amount of MMP-2, but a small amount of IL-8, MCP-1 and MMP-1. IL-1beta and TNF-alpha both induced a dose- and time-dependent increase in IL-8, MCP-1 and MMP-1 secretion, and weakly stimulated MMP-2 secretion. IL-1beta and TNF-alpha both rapidly evoked NF-kappaB DNA-binding activity. The inhibition of NF-kappaB activation markedly blocked both IL-1beta- and TNF-alpha-induced IL-8 and MCP-1 mRNA expression, but did not affect MMP-1 mRNA expression. CONCLUSIONS: These observations indicate that chemokine secretion and ECM metabolism are collectively regulated by the proinflammatory cytokines, IL-1beta and TNF-alpha, in colonic subepithelial myofibroblasts. Thus, colonic subepithelial myofibroblasts may play an important role in the pathophysiology of inflammation in the colon.

Base Sequence↗
PubMed2003

Alpha-smooth muscle actin is crucial for focal adhesion maturation in myofibroblasts.

Cultured myofibroblasts are characterized by stress fibers, containing alpha-smooth muscle actin (alpha-SMA) and by supermature focal adhesions (FAs), which are larger than FAs of alpha-SMA-negative fibroblasts. We have investigated the role of alpha-SMA for myofibroblast adhesion and FA maturation. Inverted centrifugation reveals two phases of initial myofibroblast attachment: during the first 2 h of plating microfilament bundles contain essentially cytoplasmic actin and myofibroblast adhesion is similar to that of alpha-SMA-negative fibroblasts. Then, myofibroblasts incorporate alpha-SMA in stress fibers, develop mature FAs and their adhesion capacity is significantly increased. When alpha-SMA expression is induced in 5 d culture by TGFbeta or low serum levels, fibroblast adhesion is further increased correlating with a "supermaturation" of FAs. Treatment of myofibroblasts with alpha-SMA fusion peptide (SMA-FP), which inhibits alpha-SMA-mediated contractile activity, reduces their adhesion to the level of alpha-SMA negative fibroblasts. With the use of flexible micropatterned substrates and EGFP-constructs we show that SMA-FP application leads to a decrease of myofibroblast contraction, shortly followed by disassembly of paxillin- and beta3 integrin-containing FAs; alpha5 integrin distribution is not affected. FRAP of beta3 integrin-EGFP demonstrates an increase of FA protein turnover following SMA-FP treatment. We conclude that the formation and stability of supermature FAs depends on a high alpha-SMA-mediated contractile activity of myofibroblast stress fibers.

Actins↗
PubMed1997

Myofibroblast phenotypes expression in experimental renal scarring.

BACKGROUND: Myofibroblasts have been implicated in the pathogenesis of wound healing and tissue fibrosis. A role has also been put forward for these cells in the development of experimental and clinical renal scarring. SUBJECTS AND METHODS: We examined the expression of myofibroblast phenotypes by immunohistochemistry, relying on an avidin-biotin-peroxidase method, during the course of renal scarring in rats submitted to subtotal (5/6) nephrectomy (SNx). We also attempted to identify changes in immunoreactive transforming growth factor-beta (TGF-beta) and collagen (III and IV) within remnant kidneys in order to determine their association with the expression of the myofibroblasts. RESULTS: In normal sham-operated rats, alpha-smooth muscle actin (alpha-SMA) was confined to the media of renal arteries and arterioles. In contrast, in rats with renal ablation we observed the early (day 7) appearance of myofibroblasts expressing alpha-SMA (A) in the interstitium of remnant kidneys particularly around vessels. Interstitial cells expressing alpha-SMA increased with time as tubulointerstitial fibrosis progressed. By day 30 some interstitial cells also expressed vimentin (V). Various interstitial myofibroblast phenotypes (A, V, VA) were expressed during the course of experimental renal scarring. Interstitial myofibroblasts appeared to be associated with TGF-beta as these cells' cytoplasm stained for both this growth factor and alpha-SMA. Interstitial fibrosis was also associated with increased interstitial expression of both collagen III and IV. Some atrophic tubular cells showed positive immunostaining for vimentin during the late stages of renal scarring (days 90-150). In the glomeruli, a segmental expression of alpha-SMA was noted from day 21 after SNx onward. Normal glomerular endothelial cells appeared to express vimentin while epithelial cells expressed both vimentin and desmin (D). The glomerular immunostain for vimentin increased with time but decreased as glomerulosclerosis progressed. In contrast, glomerular desmin and alpha-SMA immunostain continued to rise with progressive glomerulosclerosis. This was associated with the appearance of type III collagen within scarred glomeruli. Both vimentin and desmin appeared within the walls of the renal arterioles and increased with time from day 7 and 15, respectively. Vimentin was also expressed in the peritubular capillaries of remnant kidneys. By contrast, alpha-SMA, normally present in the media of arterioles, decreased as arteriolar sclerosis progressed. These changes cannot be exclusively attributed to systemic hypertension as they were absent in a group of age-matched, sham-operated, spontaneously hypertensive rats. DISCUSSION: Myofibroblasts may play a role in the pathogenesis of glomerulosclerosis, tubulointerstitial fibrosis and vascular sclerosis. Further, the acquisition of new myofibroblastic phenotypes by glomerular and tubular cells may contribute to renal fibrosis.

Actins↗
PubMed1979

Inhibition of myofibroblasts by skin grafts.

The myofibroblast population was studied by electron microscopy in rat wounds healing by (1) contraction of granulation tissue, (2) by coverage with split-skin grafts, and (3) by coverage with full-thickness skin grafts. In all 3 types of wounds, myofibroblasts appeared early and reached a peak number at two weeks after wounding. At this time, 40 to 50 percent of the wound fibroblasts had myofibroblast characteristics. The granulating wounds contracted rapidly and completely, and had long persistence of myofibroblasts. Split-skin grafted wounds contracted less and had a more rapid decrease in myofibroblasts. The wounds covered with full thickness skin grafts had a minimum of contraction with a very rapid decrease in the number of myofibroblasts until by 4 weeks no myofibroblasts were present. Full-thickness skin grafts thus appeared to influence contracting wounds not by preventing the formation of myofibroblasts, but by speeding up completion of their life cycle.

Animals↗
PubMed2006

Differential expression of smooth muscle myosin, smooth muscle actin, h-caldesmon, and calponin in the diagnosis of myofibroblastic and smooth muscle lesions of skin and soft tissue.

The diagnosis of low-grade and pseudosarcomatous spindle cell lesions of skin and soft tissue can sometimes be problematic; in particular, distinction between fibroblastic, myofibroblastic, and smooth muscle proliferations can occasionally pose difficulties on routine histologic examination. We have applied a panel of immunohistochemical markers to a series of spindle cell lesions of skin and soft tissue to assess the utility of the differential expression of smooth muscle and myofibroblastic-associated markers. Twenty-eight cases of nodular fasciitis, 42 cases of fibromatosis, and 3 cases of myofibroblastic sarcoma were stained with antibodies against smooth muscle actin (SMA), smooth muscle myosin (SMMS), calponin, and high-molecular weight caldesmon (h-caldesmon). For comparison, 12 cases of cutaneous leiomyoma and 8 cases of leiomyosarcomas involving superficial soft tissues and fascia were studied with the same panel of antibodies. Thirty-eight of 42 cases of fibromatosis were positive for SMA, 42/42 cases were positive for calponin, 39/42 cases were negative for SMMS, and all cases were negative for h-caldesmon. All cases of nodular fasciitis were positive for SMA and calponin, and all were negative for h-caldesmon and SMMS. All cases of myofibroblastic sarcoma were positive for SMA and 2/3 cases for calponin, and were negative for SMMS and h-caldesmon. All cases of cutaneous leiomyoma and leiomyosarcoma were positive for all 4 markers tested. Our results demonstrate a remarkably consistent pattern of reactivity of muscle and myofibroblastic-associated markers in lesions predominantly composed of myofibroblastic spindle cells, characterized by positive staining for SMA and calponin and absence of reactivity for SMMS and h-caldesmon. Application of this panel of stains may be of aid in the differential diagnosis of low-grade myofibroblastic lesions such as nodular fasciitis and fibromatosis from smooth muscle tumors of skin and soft tissue. This panel may additionally be of assistance in the diagnosis of myofibroblastic sarcoma.

Actins↗
PubMed2006

Heterogeneous presence of myofibroblasts in hereditary gingival fibromatosis.

BACKGROUND/AIM: Hereditary gingival fibromatosis (HGF) fibroblasts are characterized by an increased production of collagen and transforming growth factor-beta1 (TGF-beta1), resulting in a fibrotic enlargement of the gingiva of affected patients. A common feature of interstitial fibrosis is the occurrence of myofibroblasts, which are regarded as the predominant cells in matrix synthesis. The goal of this article is to describe the presence of myofibroblasts in HGF in order to elucidate the mechanisms underlying HGF gingival overgrowth. MATERIALS AND METHODS: Fibroblast cell lines and gingival samples from patients of two distinct families affected by HGF and from normal gingiva (NG) were included in this study. To characterize the presence of myofibroblasts, the expression of specific myofibroblast marker smooth muscle isoform of alpha-actin (alpha-SMA) was examined by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, immunofluorescence, and flow cytometric analysis. Immunohistochemistry against the alpha-SMA antigen was performed in the gingival tissue samples. RESULTS: Our results demonstrated a significant increase in the expression of the myofibroblast marker alpha-SMA in cells from one HGF family (designed as HGF Family 2), which are also characterized by an elevated expression of type I collagen, TGF-beta1 and connective tissue growth factor (CTGF). Additionally, alpha-SMA-positive cells were broadly detected in the gingival tissue samples from HGF Family 2 patients. In contrast, alpha-SMA expression by HGF Family 1 cells was quite similar to NG cells and no myofibroblasts were detected immunohistochemically, despite the higher levels of TGF-beta1 and type I collagen in HGF Family 1 fibroblasts than in NG cells. The expression of CTGF, which has been considered a key molecule to promote the transdifferentiation of myofibroblasts via TGF-beta1 activation, by HGF Family 1 cultures was significantly lower compared with HGF Family 2 and similar to NG control cells. CONCLUSIONS: Our results suggest that the presence of myofibroblasts in HGF could be dependent on CTFG expression levels, and different biological mechanisms may account for the gingival overgrowth observed in HGF patients. This could be an underlying reason for the high variable clinical expressivity of disease.

Actins↗
PubMed2006

Induction of the myofibroblastic phenotype in human gingival fibroblasts by transforming growth factor-beta1: role of RhoA-ROCK and c-Jun N-terminal kinase signaling pathways.

BACKGROUND AND OBJECTIVES: Myofibroblastic differentiation is an important event in gingival wound healing and chronic inflammation. Transforming growth factor-beta 1 (TGF-beta1) is a potent growth factor that has been implicated in this process. Gingival myofibroblasts have an increased ability to remodel the extracellular matrix and this feature has been associated with changes in the distribution of F-actin and the expression of the myofibroblast marker alpha-smooth muscle actin. In the present study we have analyzed the role of TGF-beta1 and the signaling routes activated by this factor in the cytoskeletal changes that characterize the myofibroblastic differentiation process in human gingival fibroblasts. MATERIALS AND METHODS: The signalling pathways involved in myofibroblastic differentiation were studied in primary cultures of human gingival fibroblasts using several signal transduction inhibitors. RhoA activation was analyzed through a pull-down assay. Distribution of focal adhesions and actin cytoskeleton was assessed by means of immunofluorescence and western blot. A cell adhesion assay was performed in TGF-beta1-stimulated cells. Smooth muscle actin expression was studied through western blot and immunofluorescence. c-Jun N-terminal kinase phosphorylation was assessed through western blot. RESULTS: Our observations show that TGF-beta1 activated the GTPase RhoA, a key regulator of the actin cytoskeleton. As a consequence of this event, this growth factor stimulated the generation of actin stress fibers and the reinforcement of vinculin-enriched focal adhesions. These responses were blocked after inhibiting ROCK, the main target of RhoA activation. TGF-beta1 also stimulated the adhesion of fibroblasts over fibronectin, an extracellular matrix molecule involved in myofibroblastic differentiation. Finally, induction of the myofibroblast marker alpha-smooth muscle actin by TGF-beta1 was abolished by the c-Jun N-terminal protein kinase inhibitor SP600125, suggesting a role for this signaling pathway during the induction of this phenotype. CONCLUSIONS: We propose that TGF-beta1 may promote the differentiation of myofibroblasts through the stimulation of cell spreading and adhesion, the reinforcement of focal adhesions, the maturation of the actin cytoskeleton, and the induction of alpha-smooth muscle actin. Activity of RhoA-ROCK and c-Jun N-terminal protein kinase signaling pathways are probably involved in these cellular events.

Actins↗
PubMed2006

A critical role of serum response factor in myofibroblast differentiation during experimental oesophageal ulcer healing in rats.

BACKGROUND: Myofibroblast differentiation is a key event during wound healing and is triggered primarily by transforming growth factor beta (TGFbeta). Serum response factor (SRF) is a TGFbeta-inducible transcription factor that is important for wound healing. Injection of SRF expression plasmid into rat gastric ulcers significantly accelerated restoration of epithelium and smooth muscle structures. AIM: To determine the role of SRF in oesophageal ulcer healing, especially in myofibroblast differentiation. SUBJECTS: Rats (in vivo), oesophageal epithelial cells (Het1A) and fibroblasts (Rat1-R12) (in vitro) were used. METHODS: Oesophageal ulcers were induced in rats with acetic acid and subsequently treated by local injection of plasmids expressing either SRF or SRF antisense sequence. Rats were killed at 1, 3, 6, 9 and 14 days after treatment and tissues collected. For in vitro studies, both Het1A and Rat1-R12 cells were transfected with the plasmids used in ulcer treatment. RESULTS: Upregulation of SRF increased the myofibroblast population in ulcer granulation tissue; knockdown of SRF suppressed this event. In addition, ulceration induced SRF and TGFbeta expression coordinately. In vitro studies showed that overexpression of SRF in either oesophageal epithelial cells or fibroblasts was sufficient to induce myofibroblast phenotype. Furthermore, the TGFbeta-induced myofibroblast phenotype required integrin-linked kinase (ILK)-mediated SRF activation, as either knockdown of SRF or inactivation of ILK prevented this action. CONCLUSIONS: SRF is indispensable for myofibroblast differentiation during oesophageal ulcer healing and is required for TGFbeta-induced myofibroblast transition from either epithelial cells or fibroblasts. ILK is a mediator in TGFbeta-induced SRF activation and subsequent myofibroblast differentiation. ILK is associated with SRF, and TGFbeta enhances this association.

Acetic Acid↗
PubMed1999

Normal human colonic subepithelial myofibroblasts enhance epithelial migration (restitution) via TGF-beta3.

After injury and loss of epithelial cells, intestinal barrier function is reestablished by migration of viable epithelial cells from the wound edge (restitution). Myofibroblasts are located close to the basal surface of epithelial cells. This study aimed to investigate the role of human colonic subepithelial myofibroblasts in epithelial restitution. Primary cultures of subepithelial myofibroblasts were established. Monolayers of the epithelial cell lines IEC-6 and T84 were "wounded" in a standard manner to create an in vitro model of restitution. Migration of epithelial cells across the wound edge was assessed following culture in myofibroblast-conditioned medium. Myofibroblast expression of transforming growth factor (TGF)-beta isoforms was examined using RT-PCR, and TGF-beta isoform bioactivity was assessed using Mv 1 Lu bioassay. Myofibroblast-conditioned medium, via a TGF-beta-dependent pathway, significantly enhanced migration of epithelial cells across the wound edge and significantly inhibited cell proliferation in wounded monolayers. Messenger RNA for TGF-beta1, -beta2, and -beta3 was detected in the myofibroblasts, and Mv 1 Lu bioassay showed the presence of predominantly bioactive TGF-beta3. This study shows that human colonic subepithelial myofibroblasts secrete predominantly bioactive TGF-beta3 and enhance restitution in wounded epithelial monolayers via a TGF-beta-dependent pathway.

Animals↗
PubMed2002

Apoptosis and myofibroblast expression in human glomerular disease: a possible link with transforming growth factor-beta-1.

BACKGROUND/AIMS: The pathophysiological pathways involved in the pathogenesis and evolution of renal fibrosis, have not been fully elucidated. Transforming growth factor-beta(1) (TGF-beta(1)) is involved in the development of renal scarring. Apoptosis is responsible for intrinsic cell deletion observed in end-stage kidney disease. Myofibroblasts are involved in the development of renal fibrosis. This study investigates whether there is a potential relationship between apoptosis, myofibroblast infiltration and TGF-beta(1) expression in the kidney of patients with glomerulonephritis (GN). METHODS: Forty patients with various types of GN were included in the study. Myofibroblasts and TGF-beta(1) positive cells were detected in kidney biopsies by immunohistochemistry, while apoptotic cells were detected by the in situ end labelling of fragmented DNA. RESULTS: Myofibroblasts were identified in the glomeruli of some patients with severe mesangioproliferative GN and glomerulosclerosis but a more intensive myofibroblast expression was found in the renal interstitium. TGF-beta(1) was expressed in the cytoplasm of tubular epithelial cells, in the renal interstitium and in the glomeruli of patients with GN. Apoptotic cells were mainly detected in the tubules and interstitium and were present in areas with intense myofibroblast infiltration. Positive correlations were observed between the intensity of myofibroblast expression in the interstitium and apoptosis in the tubulointerstitial area (r = 0.521, p < 0.01) as well as TGF-beta(1) expression (r = 0.462, p < 0.05) and degree of renal impairment (r = 0.430, p < 0.05). CONCLUSIONS: These observations suggest that myofibroblast infiltration and apoptosis along with TGF-beta(1) expression are associated with the development of interstitial fibrosis in patients with glomerular disease.

Actins↗
PubMed2002

Lovastatin downregulates renal myofibroblast function in vitro.

Interstitial fibrosis is recognised as the best histological predictor of progressive renal disease. Myofibroblasts contribute to this process through several functions including hyperproliferation, collagen and collagenase synthesis and reorganisation of extracellular matrix. Recent limited in vitro studies suggest that 3-hydroxy-3-methylglutaryl-coenzyme A (HMG CoA) reductase inhibitors may reduce renal injury not only through their lipid-lowering effects but also by antagonising myofibroblast function. This study therefore examined the effects of lovastatin on the above interstitial myofibroblast behaviours in vitro. Primary cultures of rat renal cortical myofibroblasts were grown by explantation and characterised by immunohistochemistry. Dose response effects of lovastatin (0, 15, 30 microM) in DMEM and 10% FCS were examined on myofibroblast kinetics, total collagen synthesis, collagen I lattice contraction and actin filament rearrangement. Lovastatin decreased myofibroblast proliferation and growth. Likewise, collagen I lattice contraction and actin filament rearrangement were partially inhibited when lovastatin was added at 30 microM. In addition, lovastatin decreased both collagen and collagenase synthesis. Our results suggest that myofibroblast function may be downregulated by lovastatin in vitro. Although a decrease in myofibroblast activity may offer potential benefit in the prevention of progressive scarring, further studies will be necessary to determine the relative importance of these functions.

Animals↗
PubMed2004

Valvular myofibroblast activation by transforming growth factor-beta: implications for pathological extracellular matrix remodeling in heart valve disease.

The pathogenesis of cardiac valve disease correlates with the emergence of muscle-like fibroblasts (myofibroblasts). These cells display prominent stress fibers containing alpha-smooth muscle actin (alpha-SMA) and are believed to differentiate from valvular interstitial cells (VICs). However, the biological factors that initiate myofibroblast differentiation and activation in valves remain unidentified. We show that transforming growth factor-beta1 (TGF-beta1) mediates differentiation of VICs into active myofibroblasts in vitro in a dose-dependent manner, as determined by a significant increase in alpha-SMA and the dramatic augmentation of stress fiber formation and alignment. Additionally, TGF-beta1 and increased mechanical stress function synergistically to enhance contractility. In turn, contractile valve myofibroblasts exert tension on the extracellular matrix, resulting in a dramatic realignment of extracellular fibronectin fibrils. TGF-beta1 also inhibits valve myofibroblast proliferation without enhancing apoptosis. Our results are consistent with activation of a highly contractile myofibroblast phenotype by TGF-beta1 and are the first to connect valve myofibroblast contractility with pathological valve matrix remodeling. We suggest that the activation of contractile myofibroblasts by TGF-beta1 may be a significant first step in promoting alterations to the valve matrix architecture that are evident in valvular heart disease.

Actins↗
PubMed2001

Transforming growth Factor-beta1 induces phenotypic modulation of human lung fibroblasts to myofibroblast through a c-Jun-NH2-terminal kinase-dependent pathway.

Myofibroblasts play an important role in the fibrogenic process of pulmonary fibrosis. Transforming growth factor (TGF)-beta is well known to induce the phenotypic modulation of fibroblasts to myofibroblasts; however, the intracellular signal regulating induction of the myofibroblastic phenotype of human lung fibroblasts (HLF) has not been determined. In the present study, we examined the role of the mitogen-activated protein kinase (MAPK) superfamily in inducing the phenotypic modulation of HLF to myofibroblasts characterized by alpha-smooth-muscle actin expression, in order to clarify this issue. The results showed that: (1) TGF-beta1 caused the phenotypic modulation of HLF to myofibroblasts in a dose- and a time-dependent manner; (2) TGF-beta1 induced increases in c-Jun-NH2- terminal kinase (JNK), p38 MAPK, and extracellular signal-regulated kinase (Erk) phosphorylation and activity; (3) the inhibitors CEP-1347, SB 203580, and PD 98059 attenuated TGF-beta1-induced JNK, p38 MAPK, and Erk activity, respectively; and (4) CEP-1347, but not SB 203580 or PD 98059, attenuated the TGF-beta1-induced phenotypic modulation of HLF to myofibroblasts in a dose-dependent manner. These results indicate that TGF-beta1 is capable of inducing the myofibroblastic phenotype of HLF, and that JNK regulates the phenotypic modulation of TGF-beta1-stimulated HLF to myofibroblasts.

Carbazoles↗
PubMed2005

Negative regulation of myofibroblast differentiation by PTEN (Phosphatase and Tensin Homolog Deleted on chromosome 10).

RATIONALE: Myofibroblasts are primary effector cells in idiopathic pulmonary fibrosis (IPF). Defining mechanisms of myofibroblast differentiation may be critical to the development of novel therapeutic agents. OBJECTIVE: To show that myofibroblast differentiation is regulated by phosphatase and tensin homolog deleted on chromosome 10 (PTEN) activity in vivo, and to identify a potential mechanism by which this occurs. METHODS: We used tissue sections of surgical lung biopsies from patients with IPF to localize expression of PTEN and alpha-smooth muscle actin (alpha-SMA). We used cell culture of pten(-/-) and wild-type fibroblasts, as well as adenoviral strategies and pharmacologic inhibitors, to determine the mechanism by which PTEN inhibits alpha-SMA, fibroblast proliferation, and collagen production. RESULTS: In human lung specimens of IPF, myofibroblasts within fibroblastic foci demonstrated diminished PTEN expression. Furthermore, inhibition of PTEN in mice worsened bleomycin-induced fibrosis. In pten(-/-) fibroblasts, and in normal fibroblasts in which PTEN was inhibited, alpha-SMA, proliferation, and collagen production was upregulated. Addition of transforming growth factor-beta to wild-type cells, but not pten(-/-) cells, resulted in increased alpha-SMA expression in a time-dependent fashion. In pten(-/-) cells, reconstitution of PTEN decreased alpha-SMA expression, proliferation, and collagen production, whereas overexpression of PTEN in wild-type cells inhibited transforming growth factor-beta-induced myofibroblast differentiation. It was observed that both the protein and lipid phosphatase actions of PTEN were capable of modulating the myofibroblast phenotype. CONCLUSIONS: The results indicate that in IPF, myofibroblasts have diminished PTEN expression. Inhibition of PTEN in vivo promotes fibrosis, and PTEN inhibits myofibroblast differentiation in vitro.

Actins↗
PubMed2003

Involvement of serum response factor isoforms in myofibroblast differentiation during bleomycin-induced lung injury.

Serum response factor (SRF) is a transcription factor essential for smooth muscle (SM) myogenesis. Its role in myofibroblast differentiation is, however, unknown. We studied the expression and the localization of SRF in bleomycin-induced pulmonary fibrosis, where myofibroblasts are abundant. We found that SRF levels were upregulated in bleomycin-exposed mouse lungs mainly due to de novo synthesis of SRFDelta5, a less myogenic SRF isoform. Before myofibroblast differentiation, SRF/SRFDelta5 was immunolocalized mostly in the cytoplasm of scattered fibroblasts at lesion sites. With the development of myofibroblasts, however, SRF/SRFDelta5 was found in myofibroblast nuclei. cDNA array analysis showed that SRFDelta5 and SRF induced expression of transforming growth factor-beta1, a critical factor in myofibroblast differentiation. This was accompanied by de novo expression of several inflammatory cell-specific mRNAs. The latter was confirmed by reverse transcriptase-polymerase chain reaction. Treatment of lung fibroblasts with tumor necrosis factor-alpha, which is produced early in the bleomycin model, induced SRFDelta5 expression and SRF/SRFDelta5 cytoplasmic accumulation, whereas addition of transforming growth factor-beta1 caused SRF/SRFDelta5 nuclear translocation followed by SM alpha-actin synthesis. Interleukin-4, another cytokine involved in myofibroblast differentiation, did not affect SRF or induce SRFDelta5 expression. Our studies therefore suggested a new mechanism whereby SRF and SRFDelta5 contribute to the emergence of myofibroblasts in lung injury and fibrosis.

Animals↗