Transforming growth factor-beta 1 modulates myofibroblastic phenotype of rat palatal fibroblasts in vitro

Chronic Resveratrol Treatment Inhibits MRC5 Fibroblast SASP-Related Protumoral Effects on Melanoma Cells

Cellular senescence is related to organismal aging and is observed after DNA damaging cancer therapies, that induce tumor-suppressive modifications, but it is characterized by a strong increase in secreted factors, termed the "senescence-associated secretory phenotype" (SASP). Particularly, SASP from stroma senescent fibroblasts creates a cancer-favoring microenvironment, providing targets for anti-cancer interventions. In the present article, chronic treatment (5 weeks) with 5 µM resveratrol has been used to modulate senescence-related protumoral features of MRC5 fibroblasts, reducing SASP-related interleukins IL1α, IL1β, IL6, and IL8; transforming-growth-factor-β (TGFβ); matrix metallo-proteinases MMP3 and MMP2; urokinase plasminogen activator (uPA); receptor proteins uPAR, IL6R, insulin growth factor receptor-1 (IGF-1R), TGFβ-R2, and CXCR4. The cellular nuclear-factor-kB (NF-kB) protein level was also reduced, confirming its role in the induction of SASP. Resveratrol pretreated MRC5 fibroblasts were resistant to activation by TGFβ. Resveratrol treatment of senescent MRC5 induced the production of conditioned media (CM) which counteracted the protumoral effect of senescent CM on A375 and A375-M6 melanoma cell proliferation and invasiveness, and reduced the expression of epithelial-to-mesenchymal transition markers related to malignant features. This experimental approach proposes a treatment that targets the senescent stromal cell phenotype to induce an anti-tumor hosting microenvironment, which is suitable for both preventive and therapeutic purposes.

Myofibroblasts in Palatal Wound Healing: Prospects for the Reduction of Wound Contraction after Cleft Palate Repair

The surgical closure of orofacial clefts is considered to impair maxillary growth and dento-alveolar development. Wound contraction and subsequent scar tissue formation, during healing of these surgical wounds, contribute largely to these growth disturbances. The potential to minimize wound contraction and subsequent scarring by clinical interventions depends on the surgeon’s knowledge of the events responsible for these phenomena. Fibroblasts initiate wound contraction, but proto-myofibroblasts and mature myofibroblasts are by far the most important cells in this process. Myofibroblasts are characterized by their cytoskeleton, which contains alpha-smooth-muscle actin. Additionally, their contractile apparatus contains bundles of actin microfilaments and associated contractile proteins, such as non-muscle myosin. This contractile apparatus is thought to be the major force-generating element involved in wound contraction. After closure of the wound, the myofibroblasts disappear by apoptosis, and a less cellular scar is formed. A reduction of contraction and scarring might be obtained by inhibition of myofibroblast differentiation, stimulation of their de-differentiation, stimulation of myofibroblast apoptosis, or impairment of myofibroblast function. In this review, we will discuss all of these possibilities, which ultimately may lead to a better outcome of cleft palate surgery.

Role of α1 and α2 chains of type IV collagen in early fibrotic lesions of idiopathic interstitial pneumonias and migration of lung fibroblasts

Early fibrotic lesions are thought to be the initial findings of fibrogenesis in idiopathic interstitial pneumonias, but little is known about their properties. Type IV collagen comprises six gene products, α1-α6, and although it is known as a major basement membrane component, its abnormal deposition is seen in fibrotic lesions of certain organs. We studied the expression of type I and III collagen and all α chains of type IV collagen in lung specimens from patients with usual interstitial pneumonia (UIP) or organizing pneumonia (OP) via immunohistochemistry. With cultured lung fibroblasts, we analyzed the expression and function of all α chains of type IV collagen via immunohistochemistry, western blotting, real-time quantitative PCR, and a Boyden chamber migration assay after the knockdown of α1 and α2 chains. Although we observed type I and III collagens in early fibrotic lesions of both UIP and OP, we found type IV collagen, especially α1 and α2 chains, in early fibrotic lesions of UIP but not OP. Fibroblasts enhanced the expression of α1 and α2 chains of type IV collagen after transforming growth factor-β1 stimulation. Small interfering RNA against α1 and α2 chains increased fibroblast migration, with upregulated phosphorylation of focal adhesion kinase (FAK), and adding medium containing fibroblast-produced α1 and α2 chains reduced the increased levels of fibroblast migration and phosphorylation of FAK. Fibroblasts in OP were positive for phosphorylated FAK but fibroblasts in UIP were not. These results suggest that fibroblasts in UIP with type IV collagen deposition, especially α1 and α2 chains, have less ability to migrate from early fibrotic lesions than fibroblasts in OP without type IV collagen deposition. Thus, type IV collagen deposition in early fibrotic lesions of UIP may be implicated in refractory pathophysiology including migration of lesion fibroblasts via a FAK pathway.

Intra-articular decorin influences the fibrosis genetic expression profile in a rabbit model of joint contracture

OBJECTIVES

The goal of this study was to determine whether intra-articular administration of the potentially anti-fibrotic agent decorin influences the expression of genes involved in the fibrotic cascade, and ultimately leads to less contracture, in an animal model.

METHODS

A total of 18 rabbits underwent an operation on their right knees to form contractures. Six limbs in group 1 received four intra-articular injections of decorin; six limbs in group 2 received four intra-articular injections of bovine serum albumin (BSA) over eight days; six limbs in group 3 received no injections. The contracted limbs of rabbits in group 1 were biomechanically and genetically compared with the contracted limbs of rabbits in groups 2 and 3, with the use of a calibrated joint measuring device and custom microarray, respectively.

RESULTS

There was no statistical difference in the flexion contracture angles between those limbs that received intra-articular decorin versus those that received intra-articular BSA (66° vs 69°; p = 0.41). Likewise, there was no statistical difference between those limbs that received intra-articular decorin versus those who had no injection (66° vs 72°; p = 0.27). When compared with BSA, decorin led to a statistically significant increase in the mRNA expression of 12 genes (p < 0.01). In addition, there was a statistical change in the mRNA expression of three genes, when compared with those without injection.

CONCLUSIONS

In this model, when administered intra-articularly at eight weeks, 2 mg of decorin had no significant effect on joint contractures. However, our genetic analysis revealed a significant alteration in several fibrotic genes. Cite this article: Bone Joint Res 2014;3:82-8.

Therapeutic targeting of redox signaling in myofibroblast differentiation and age-related fibrotic disease

Myofibroblast activation plays a central role during normal wound healing. Whereas insufficient myofibroblast activation impairs wound healing, excessive myofibroblast activation promotes fibrosis in diverse tissues (including benign prostatic hyperplasia, BPH) leading to organ dysfunction and also promotes a stromal response that supports tumor progression. The incidence of impaired wound healing, tissue fibrosis, BPH, and certain cancers strongly increases with age. This paper summarizes findings from in vitro fibroblast-to-myofibroblast differentiation systems that serve as cellular models to study fibrogenesis of diverse tissues. Supported by substantial in vivo data, a large body of evidence indicates that myofibroblast differentiation induced by the profibrotic cytokine transforming growth factor beta is driven by a prooxidant shift in redox homeostasis due to elevated production of NADPH oxidase 4 (NOX4)-derived hydrogen peroxide and supported by concomitant decreases in nitric oxide/cGMP signaling and reactive oxygen species (ROS) scavenging enzymes. Fibroblast-to-myofibroblast differentiation can be inhibited and reversed by restoring redox homeostasis using antioxidants or NOX4 inactivation as well as enhancing nitric oxide/cGMP signaling via activation of soluble guanylyl cyclases or inhibition of phosphodiesterases. Current evidence indicates the therapeutic potential of targeting the prooxidant shift in redox homeostasis for the treatment of age-related diseases associated with myofibroblast dysregulation.

Can lineage-specific markers be identified to characterize mesenchyme-derived cell populations in the human airways?

Mesenchyme-derived cells in the airway wall including airway smooth muscle cells, fibroblasts, and myofibroblasts are known to play important roles in airway remodeling. The lack of specific phenotypical markers makes it difficult to define these cell populations in primary cultures. Most relevant studies to date have used animal airway tissues, vascular tissues, or transformed cell lines with only limited studies attempting to phenotypically characterize human airway mesenchymal cells. The objectives of this study were to evaluate reported markers and identify novel markers to define these cell types. We could not identify any specific marker to define these cell populations in vitro that permitted unequivocal identification using immunocytochemistry. However, characteristic filamentous alpha-smooth muscle actin distribution was observed in a significant ( approximately 25%) proportion of human airway smooth muscle cells, whereas this was not observed in airway fibroblasts. A significantly higher proportion of airway fibroblasts expressed alpha(1)- and alpha(2)-integrin receptors compared with human airway smooth muscle cells as assessed by fluorescence activated cell sorting. Global gene expression profiling identified aldo-keto reductase 1C3 (AKR1C3) and cathepsin K as being novel markers to define airway smooth muscle cells, whereas integrin-alpha(8) (ITGA8) and thromboxane synthase 1 (TBXAS1) were identified as novel airway fibroblast-specific markers, and these findings were validated by RT-PCR. Ex vivo studies in human airway tissue sections identified high-molecular weight caldesmon and alpha-smooth muscle actin as being expressed in smooth muscle bundles, whereas ITGA8 and TBXAS1 were absent from these.

Transforming growth factor-beta1 stimulation enhances Dupuytren's fibroblast contraction in response to uniaxial mechanical load within a 3-dimensional collagen gel

PURPOSE

A function of fibroblasts is the generation of cytomechanical force within their surrounding extracellular matrix. Abnormalities in force generation may be the cause of many pathologic conditions including scarring, and some fibroproliferative disorders such as Dupuytren's disease, which is the focus of this report.

METHODS

This work investigated the cytomechanical responses of Dupuytren's-derived fibroblasts to externally applied mechanical force using a culture force monitor model, with and without stimulation with the fibrosis-linked cytokine, transforming growth factor-beta1 (TGF-beta1). We compared these responses with cytomechanical responses of fibroblasts derived from the transverse carpal ligament.

RESULTS

Dupuytren's fibroblasts display a significantly greater ability to contract a collagen matrix compared with control fibroblasts, with a maximum generated force of 131 dynes (p < .001). These cells did not exhibit a characteristic plateau phase in the contraction, which indicates a delay in achieving tensional homeostasis from Dupuytren's-derived cells. After being subjected to uniaxial overload and underload, Dupuytren's fibroblasts responded by increased force generation, whereas control fibroblasts responded by a reduction in force in response to an overload, and contraction in response to an underload. These changes were exacerbated by the addition of the profibrotic factor TGF-beta1, with a significant increase in generated force for all cell types, in particular during the early phase of fibroblast attachment and contraction, and a positive contraction gradient in response to overloading forces.

CONCLUSIONS

These data suggest that cells derived from this fibrotic disease display characteristic abnormalities in force generation profiles. Their default response to loading or underloading is contraction, or increased force generation. This work highlights the role of TGF-beta1 as a mechano-transduction cytokine, which has an influence on the early phase cell of force generation, as well as a role in mechanical responses of cells to external mechanical stimuli. This, in turn, may influence the progression of Dupuytren's disease and the high rates of recurrence seen postoperatively.

Smooth muscle alpha-actin expression and myofibroblast differentiation by TGFbeta are dependent upon MK2

Fibroblasts play a major role in processes such as wound repair, scarring, and fibrosis. Differentiation into myofibroblasts, characterized by upregulation of smooth muscle alpha-actin (smalpha) in response to profibrotic agents such as TGFbeta is believed to be an important step in fibrosis. Therefore, elucidating mechanisms of myofibroblast differentiation might reveal novel targets in treating diseases such as idiopathic pulmonary fibrosis (IPF). MK2 is a kinase substrate of p38 MAP kinase that mediates some effects of p38 activation on the actin cytoskeleton. Using mouse embryonic fibroblasts (MEF) from MK2 knockout (MK2(-/-)) mice, we demonstrate that disrupting expression of MK2 expression reduces filamentous actin and stress fibers. It also causes MK2(-/-) MEF to express less smalpha than their corresponding wild-type (WT) MEF at baseline and in response to TGFbeta. Furthermore, TGFbeta causes downregulation of smalpha in MK2(-/-) MEF, instead of upregulation observed in WT MEF. Expression of other fibroblast markers, such as collagen, is not altered in MK2(-/-) MEF. Our results further suggest that downregulation of smalpha in MK2(-/-) MEF is not due to lack of activation of serum responsive promoter elements, but probably due to reduced smalpha message stability in these cells. These results indicate that MK2 plays a key role in regulation of smalpha expression, and that targeting MK2 might present a therapeutic approach in managing conditions such as pulmonary fibrosis.

Lack of MK2 inhibits myofibroblast formation and exacerbates pulmonary fibrosis

Fibroblasts play a major role in tissue repair and remodeling. Their differentiation into myofibroblasts, marked by increased expression of smooth muscle-specific alpha-actin (alpha-SMA), is believed to be important in wound healing and fibrosis. We have recently described a role for MK2 in this phenotypic differentiation in culture. In this article, we demonstrate that MK2 also regulates myofibroblasts in vivo. Disruption of MK2 in mice prevented myofibroblast formation in a model of pulmonary fibrosis. However, MK2 disruption and consequent lack of myofibroblast formation exacerbated fibrosis rather than ameliorated it as previously postulated. When mice lacking MK2 (MK2-/-) were exposed to bleomycin, more collagen accumulated and more fibroblasts populated fibrotic regions in their lungs than in similarly treated wild-type mice. While there were many vimentin-positive cells in the bleomycin-treated MK2-/- mouse lungs, few alpha-SMA-positive cells were observed in these lungs compared with wild-type mouse lungs. siRNA against MK2 reduced alpha-SMA expression in wild-type mouse embryonic fibroblasts (MEF), consistent with its suppression in MK2-/- MEF. On the other hand expressing constitutively active MK2 in MK2-/- MEF significantly increased alpha-SMA expression. MK2-/-MEF proliferated at a faster rate and produced more collagen; however, they migrated at a slower rate than wild-type MEF. Overexpressing phosphomimicking HSP27, a target of MK2, did not reverse the effect of MK2 disruption on fibroblast migration. MK2 disruption did not affect Smad2 activation by transforming growth factor-beta. Thus, MK2 appears to mediate myofibroblast differentiation, and inhibiting that differentiation might contribute to fibrosis rather than protect against it.

Transforming Growth Factor-β Receptor Type 1 (TGFβRI) Kinase Activity but Not p38 Activation Is Required for TGFβRI-Induced Myofibroblast Differentiation and Profibrotic Gene Expression

Transforming growth factor-beta (TGFbeta) is a major mediator of normal wound healing and of pathological conditions involving fibrosis, such as idiopathic pulmonary fibrosis. TGFbeta also stimulates the differentiation of myofibroblasts, a hallmark of fibrotic diseases. In this study, we examined the underlying processes of TGFbetaRI kinase activity in myofibroblast conversion of human lung fibroblasts using specific inhibitors of TGFbetaRI (SD-208) and p38 mitogen-activated kinase (SD-282). We demonstrated that SD-208, but not SD-282, inhibited TGFbeta-induced SMAD signaling, myofibroblast transformation, and collagen gel contraction. Furthermore, we extended our findings to a rat bleomycin-induced lung fibrosis model, demonstrating a significant decrease in the number of myofibroblasts at fibroblastic foci in animals treated with SD-208 but not those treated with SD-282. SD-208 also reduced collagen deposition in this in vivo model. Microarray analysis of human lung fibroblasts identified molecular fingerprints of these processes and showed that SD-208 had global effects on reversing TGFbeta-induced genes involved in fibrosis, inflammation, cell proliferation, cytoskeletal organization, and apoptosis. These studies also revealed that although the p38 pathway may not be needed for appearance or disappearance of the myofibroblast, it can mediate a subset of inflammatory and fibrogenic events of the myofibroblast during the process of tissue repair and fibrosis. Our findings suggest that inhibitors such as SD-208 may be therapeutically useful in human interstitial lung diseases and pulmonary fibrosis.

Effect of ribozyme against transforming growth factorbeta1 on biological character of activated HSCs

Transforming growth factorbeta1 (TGFbeta1) is considered to be the principal contributor to liver fibrosis. So in this study the ribozymes against TGFbeta1 were designed. The in vitro cleavage activities of the ribozymes were assayed through incubation of (32)p-labeled target RNAs and (32)p-labeled ribozymes in different conditions. HSC-T6 cells were transfected with the eukaryotic constructs encoding ribozyme and disable ribozyme, then the stable cell clones were used to evaluate its antifibrotic characteristic through the effect of ribozyme on biological character of activated hepatic stellate cells (HSCs). The results demonstrated that two ribozymes (Rz803 and Rz1395) could cleave target RNAs into expected products effectively, Rz803 possessed better cleavage activity in vitro. Stable transfection of Rz803 into activated HSCs reduced TGFbeta1 expression in mRNA and protein level efficiently. The further studies demonstrated that Rz803 reduced deposition of collagen I, suppressed HSC proliferation, but had no effect on HSC activation in transfected HSC-T6 cells. Therefore, it indicated that Rz803 could reverse the character of activated HSCs by down-regulating TGFbeta1 expression efficiently and diminishing TGFbeta1 signaling underlying activation of hepatic stellate cells. As the consequence, it would provide a potential therapeutic approach for liver fibrosis.

Scleroderma fibroblasts demonstrate enhanced activation of Akt (protein kinase B) in situ

Recent studies suggest that, in addition to activation and hypersecretion of matrix components, fibroblasts from patients with systemic sclerosis (SSc) are relatively resistant to apoptosis. Transforming growth factor-beta (TGF)-beta is strongly implicated in the pathogenesis of SSc and we and others have shown that TGF-beta can activate Akt, a kinase with potent anti-apoptotic effects. To determine whether Akt was activated in SSc, we quantified phospho-Akt expression in skin fibroblasts in vitro by western blot analysis and a functional kinase assay. In addition, the relative proportion of fibroblasts containing activated Akt in was quantified by immunohistochemistry on skin sections insitu. Analysis of Akt phosphorylation of skin fibroblasts in vitro suggested increased phosphorylation of Akt, and evaluation of skin sections by immunohistochemistry revealed significantly higher percentages of fibroblasts that stained for phospho-Akt compared with controls (78% +/- 14.0% vs 13% +/- 9%, p < 0.001). In addition, co-incident staining of phospho-Akt and alpha-smooth muscle actin was observed in some fibroblasts. These findings indicate that Akt is activated insitu in skin fibroblasts from patients with SSc. Akt activation may contribute to resistance to apoptosis, selection of disease-inducing fibroblasts, and, possibly, myofibroblasts.

Chondroitin sulfate in palatal wound healing

Chondroitin sulfate is up-regulated in granulation tissue during wound healing. To investigate the role of chondroitin sulfate in the wound-healing process after surgical repair of cleft palate, we isolated and cultured rabbit palatal fibroblasts. Treatment with chondroitin-6-sulfate resulted in a dose-dependent increase in cell adhesion and cell proliferation, whereas the reverse effects were seen after chondroitinase degradation of chondroitin sulfate. The biological actions of chondroitin sulfate appeared to be dependent on the presence and position of sulfate groups. Inhibition of glycosaminoglycan sulfation by chlorate treatment led to reduced cell adhesion and cell proliferation and a slower rate of wound closure in vitro. Furthermore, exposure to chondroitin-4-sulfate resulted in a dose-dependent reduction in cell adhesion. Together, these results show that chondroitin sulfate is involved in palatal wound healing.

AlphaV integrins play an important role in myofibroblast differentiation

Transforming growth factor-beta1 is a potent mediator of the differentiation of fibroblasts into myofibroblasts, which is characterized by the appearance of the cytoskeletal protein alpha-smooth muscle actin. The aim of this study was to investigate the role of integrin extracellular matrix receptors in transforming growth factor-beta1-induced myofibroblast differentiation. We show that blockade of the alphav and/or beta1 integrins prevents the transforming growth factor-beta1-induced myofibroblast differentiation, seen by the increased expression of alpha-smooth muscle actin and enhanced collagen gel contraction in three human fibroblast cell lines (from the mouth, skin, and kidney). Further, blockade of alphav specific integrins alphavbeta5 and alphavbeta3 suppressed myofibroblast differentiation in fibroblasts from the mouth and skin; however, in the kidney cells, the prevention of differentiation was seen only with blockade of alphavbeta5 integrin but not alphavbeta3. A possible reason for this result may be different degrees of responsiveness to transforming growth factor-beta1 treatment seen from different anatomical origins of the cell lines. These data indicate a novel role for alphav integrins in the differentiation of human fibroblasts from the mouth, skin, and kidney into myofibroblasts and suggest that there is a common differentiation pathway.

Balance of proliferation and cell death between thyrocytes and myofibroblasts regulates thyroid fibrosis in granulomatous experimental autoimmune thyroiditis (G-EAT)

Severe granulomatous experimental autoimmune thyroiditis (G-EAT), which progresses to fibrosis, is induced in DBA/1 mice by adoptive transfer of mouse thyroglobulin-primed and -activated spleen cells. There is extensive destruction of thyrocytes and inflammatory cell infiltration including T cells, macrophages, neutrophils, and myofibroblasts (myofbs). Suppression of transforming growth factor-beta (TGF-beta) and deficiency of interferon-gamma (IFN-gamma) inhibit fibrosis, and inflammation eventually resolves. Thyrocyte destruction in wild-type (WT) mice was a result of apoptosis, as many deoxynucleotide triphosphate nick-end labeling + apoptotic thyrocytes were present in these thyroids. The balance of apoptosis and proliferation between thyrocytes and myofbs may be important factors determining the outcome of inflammation to fibrosis versus resolution. Apoptosis and proliferation in thyrocytes versus myofbs were evaluated by dual-staining of cell-proliferating marker (Ki-67) or in situ cell death and cytokeratin or alpha-smooth muscle actin and were analyzed by confocal microscopy. Apoptotic and antiapoptotic molecules in G-EAT thyroids were detected by immunostaining. In WT thyroids, which develop fibrosis, only a few myofbs were apoptotic, and many myofbs were Ki-67+, Fas-associated death domain protein-like interleukin-1beta-converting enzyme-like inhibitory protein (FLIP)+, and Bcl-XL+. In contrast, proliferation was predominant on thyrocytes of IFN-gamma-/- mice or anti-TGF-beta-treated WT mice. These results indicate that apoptosis of inflammatory cells and regeneration of thyrocytes in IFN-gamma-/- mice and anti-TGF-beta-treated WT mice may limit development of fibrosis, whereas excessive proliferation of myofbs and loss of thyrocytes in WT mice may contribute to fibrosis.

Collagen metabolism is a novel target of the neuropeptide alpha-melanocyte-stimulating hormone

Suppression of collagen synthesis is a major therapeutic goal in the treatment of fibrotic disorders. We show here that alpha-melanocyte-stimulating hormone (alpha-MSH), a neuropeptide well known for its pigment-inducing capacity, modulates collagen synthesis and deposition. Alpha-MSH in vitro suppresses the synthesis of collagen types I, III, and V and down-regulates the secretion of procollagen type I C-terminal peptide (PICP) in human dermal fibroblasts treated with the fibrogenic cytokine transforming growth factor-beta1 (TGF-beta1). Alpha-MSH did not interfere with TGF-beta1 signaling, because TGF-beta1-induced expression of collagen mRNA was not affected, implying a posttranscriptional mechanism. Human dermal fibroblasts in vitro express a high affinity binding site for MSH, which was identified by reverse transcription PCR and immunofluorescence analysis as the melanocortin-1 receptor (MC-1R). Immunohistochemical studies on normal adult human skin confirmed MC-1R expression in distinct dermal fibroblastic cells. The MC-1R on fibroblasts appears to be functionally relevant because alpha-MSH increased the amount of intracellular cAMP, and coincubation with a synthetic peptide corresponding to the human Agouti signaling protein abrogated the inhibition of TGF-beta1-induced PICP secretion by alpha-MSH. To assess the in vivo relevance of these findings, a mouse model was used in which dermal fibrosis was induced by repetitive intracutaneous injections with TGF-beta1. The inductive activity of TGF-beta1 on collagen deposition and the number of dermal cells immunoreactive for vimentin and alpha-smooth muscle actin was significantly suppressed by injection of alpha-MSH. Melanocortins such as alpha-MSH may therefore represent a novel class of modulators with potential usefulness for the treatment of fibrotic disorders.

Antifibrotic effects of suramin in injured skeletal muscle after laceration

Muscle injuries are very common in traumatology and sports medicine. Although muscle tissue can regenerate postinjury, the healing process is slow and often incomplete; complete recovery after skeletal muscle injury is hindered by fibrosis. Our studies have shown that decreased fibrosis could improve muscle healing. Suramin has been found to inhibit transforming growth factor (TGF)-beta1 expression by competitively binding to the growth factor receptor. We conducted a series of tests to determine the antifibrotic effects of suramin on muscle laceration injuries. Our results demonstrate that suramin (50 microg/ml) can effectively decrease fibroblast proliferation and fibrotic-protein expression (alpha-smooth muscle actin) in vitro. In vivo, direct injection of suramin (2.5 mg) into injured murine muscle resulted in effective inhibition of muscle fibrosis and enhanced muscle regeneration, which led to efficient functional muscle recovery. These results support our hypothesis that prevention of fibrosis could enhance muscle regeneration, thereby facilitating more efficient muscle healing. This study could significantly contribute to the development of strategies to promote efficient muscle healing and functional recovery.

TGF-beta 3 decreases type I collagen and scarring after labioplasty

Cleft lip is a common congenital malformation, and labioplasty performed on infants to repair such defects often results in severe scar formation. Since TGF-beta 3 has been implicated in wound healing, we therefore hypothesized that TGF-beta 3 functions to reduce scarring after cleft lip repair. In this investigation, we demonstrated that exogenous TGF-beta 3 reduced scar formation in an incised and sutured mouse lip in vivo. During labioplasty, endogenous TGF-beta 3 expression was also elevated. In vitro experiments showed that exogenous TGF-beta 3 reduced type I collagen accumulation. Furthermore, TGF-beta 3 inhibited alpha-smooth-muscle actin expression, a marker for myofibroblasts. In tandem, TGF-beta 3 induced the expression and activity of MMP-9. Analysis of our data suggests that TGF-beta 3 is normally secreted following labioplastic wound healing. An elevated level of TGF-beta 3 reduces type I collagen deposition by restricting myofibroblast differentiation and thereby collagen synthesis, and by promoting collagen degradation by MMP-9. In combination, these events lead to TGF-beta 3-mediated reduced scar formation.

Temporal variations in cell migration and traction during fibroblast-mediated gel compaction

Current models used in our laboratory to assess the migration and traction of a population of cells within biopolymer gels are extended to investigate temporal changes in these parameters during compaction of mechanically constrained gels. The random cell migration coefficient, micro (t) is calculated using a windowing technique by regressing the mean-squared displacement of cells tracked at high magnification in three dimensions with a generalized least squares algorithm for a subset of experimental time intervals, and then shifting the window interval-by-interval until all time points are analyzed. The cell traction parameter, tau(0)(t), is determined by optimizing the solution of our anisotropic biphasic theory to tissue equivalent compaction. The windowing technique captured simulated sinusoidal and step changes in cell migration superposed on a persistent random walk in simulated cell movement. The optimization software captured simulated time dependence of compaction on cell spreading. Employment of these techniques on experimental data using rat dermal fibroblasts (RDFs) and human foreskin fibroblasts (HFFs) demonstrated that these cells exhibit different migration-traction relationships. Rat dermal fibroblast migration was negatively correlated to traction, suggesting migration was not the driving force for compaction with these cells, whereas human foreskin fibroblast migration was positively correlated to traction.

Mammalian transforming growth factor beta1 activated after ingestion by Anopheles stephensi modulates mosquito immunity

During the process of bloodfeeding by Anopheles stephensi, mammalian latent transforming growth factor beta1 (TGF-beta1) is ingested and activated rapidly in the mosquito midgut. Activation may involve heme and nitric oxide (NO), agents released in the midgut during blood digestion and catalysis of L-arginine oxidation by A. stephensi NO synthase (AsNOS). Active TGF-beta1 persists in the mosquito midgut to extended times postingestion and is recognized by mosquito cells as a cytokine. In a manner analogous to the regulation of vertebrate inducible NO synthase and malaria parasite (Plasmodium) infection in mammals by TGF-beta1, TGF-beta1 regulates AsNOS expression and Plasmodium development in A. stephensi. Together, these observations indicate that, through conserved immunological cross talk, mammalian and mosquito immune systems interface with each other to influence the cycle of Plasmodium development.

The homeodomain protein Barx2 promotes myogenic differentiation and is regulated by myogenic regulatory factors

The homeobox protein Barx2 is expressed in both smooth and skeletal muscle and is up-regulated during differentiation of skeletal myotubes. Here we use antisense-oligonucleotide inhibition of Barx2 expression in limb bud cell culture to show that Barx2 is required for myotube formation. Moreover, overexpression of Barx2 accelerates the fusion of MyoD-positive limb bud cells and C2C12 myoblasts. However, overexpression of Barx2 does not induce ectopic MyoD expression in either limb bud cultures or in multipotent C3H10T1/2 mesenchymal cells, and does not induce fusion of C3H10T1/2 cells. These results suggest that Barx2 acts downstream of MyoD. To test this hypothesis, we isolated the Barx2 gene promoter and identified DNA regulatory elements that might control Barx2 expression during myogenesis. The proximal promoter of the Barx2 gene contained binding sites for several factors involved in myoblast differentiation including MyoD, myogenin, serum response factor, and myocyte enhancer factor 2. Co-transfection experiments showed that binding sites for both MyoD and serum response factor are necessary for activation of the promoter by MyoD and myogenin. Taken together, these studies indicate that Barx2 is a key regulator of myogenic differentiation that acts downstream of muscle regulatory factors.

Evidence for fibroblast growth factor receptors in myofibroblasts during palatal mucoperiosteal repair

Fibroblast growth factors (FGFs) regulate cell growth and differentiation and play crucial roles in the process of tissue repair and remodelling. We have previously shown that basic FGF is widely expressed at the injured site. Since the presence of FGF receptors (FGFRs) determines cellular responsiveness, we examined the localisation of FGFR1, FGFR2 and FGFR3 expression by immunohistochemistry throughout the repair of full-thickness excisional wounds up to 28 days after wounding. Strong expression of FGFR1 was observed in the nuclei of myofibroblasts, which are characterised by alpha-smooth muscle (alpha-SM) actin expression. The weak expression of FGFR2 was also observed in the nuclei of myofibroblasts. In contrast, there was no staining for FGFR3 in fibroblasts through the wound healing process. In addition, transforming growth factor-beta1 (TGF-beta1), a potential inducer of myofibroblasts, enhanced the expression of FGFR1 and FGFR2 in the nuclei of palatal fibroblasts in vitro. These findings suggest that FGFR1 and FGFR2 in myofibroblasts may be responsible for the signal transduction of FGF during the wound healing process.

Mice lacking Smad3 are protected against cutaneous injury induced by ionizing radiation

Transforming growth factor-beta (TGF-beta) plays a central role in the pathogenesis of inflammatory and fibrotic diseases, including radiation-induced fibrosis. We previously reported that mice null for Smad3, a key downstream mediator of TGF-beta, show accelerated healing of cutaneous incisional wounds with reduced inflammation and accumulation of matrix. To determine if loss of Smad3 decreases radiation-induced injury, skin of Smad3+/+ [wild-type (WT)] and -/- [knockout (KO)] mice was exposed to a single dose of 30 to 50 Gy of gamma-irradiation. Six weeks later, skin from KO mice showed significantly less epidermal acanthosis and dermal influx of mast cells, macrophages, and neutrophils than skin from WT littermates. Skin from irradiated KO mice exhibited less immunoreactive TGF-beta and fewer myofibroblasts, suggesting that these mice will have a significantly reduced fibrotic response. Although irradiation induced no change in the immunohistochemical expression of the TGF-beta type I receptor, the epidermal expression of the type II receptor was lost after irradiation whereas its dermal expression remained high. Primary keratinocytes and dermal fibroblasts prepared from WT and KO mice showed similar survival when irradiated, as did mice exposed to whole-body irradiation. These results suggest that inhibition of Smad3 might decrease tissue damage and reduce fibrosis after exposure to ionizing irradiation.

Transforming growth factor beta stimulates fibroblast-collagen matrix contraction by different mechanisms in mechanically loaded and unloaded matrices

Studies were carried out to test the idea that transforming growth factor beta (TGFbeta) stimulated fibroblast contraction of collagen matrices by different mechanisms depending on mechanical loading on the cells and matrix. Under mechanically unloaded conditions (floating matrices), TGFbeta stimulated contraction directly as an agonist and indirectly by preactivating cells to express the myofibroblast phenotype. Increased contraction of floating matrices by preactivated cells appeared to result in part from an autocrine mechanism. Under mechanically loaded conditions (stressed matrices), TGFbeta had no direct agonist effect on contraction. Fibroblasts preactivated to become myofibroblasts showed increased ability to transfer tension to stressed matrices, and tension persisted even after the cells' actin cytoskeleton was disrupted. Our findings are consistent with the idea that fibroblasts activated to become myofibroblasts in vitro have increased contractile activity and indicate that multiple mechanisms that differ depending on mechanical loading on the cells and matrix are involved.

Demonstration of downregulation of alpha-smooth muscle actin in interferon-gamma-treated myofibroblast by a novel cell-capture enzyme immunoassay

We developed a simple method for determining the relative amount of alpha-smooth muscle actin (alphaSMA) produced in fibroblasts. The principle of the method is based on an enzyme immunoassay (EIA) for alphaSMA in microcultured fibroblasts. The optimized protocol of the assay is as follows. Human fibroblasts were cultured with transforming growth factor beta1 (TGFbeta1) in a microtiter plate and directly immobilized on the plate. The alphaSMA produced was labeled and subjected to indirect enzyme immunoassay using alkaline phosphatase, and optical density was measured. Semiquantitativeness was confirmed using various numbers of cells in which alphaSMA production was induced by treatment with TGFbeta1. The assay simply demonstrated that interferon-gamma (INF-gamma) inhibited the production of alphaSMA in an established cell line and that in primary cultured cells originated from the contractile nodule. Since the assay is simple and semi-quantitative, it is useful for elucidating the mechanism of contractile diseases and screening a large number of substances that have an inhibitory effect on the change in activity of myofibroblasts.

The use of an antifibrosis agent to improve muscle recovery after laceration

Muscle injuries are challenging problems in traumatology and the most frequent injuries in sports medicine. Muscle injuries are capable of healing, although slowly and occasionally with incomplete functional recovery. We observed that lacerated muscle undergoes a rapid process of regeneration, which is hindered by the development of fibrosis. Biologic approaches to enhance muscle regeneration and prevent fibrosis are being investigated to improve muscle healing after injuries. We observed that growth factors can improve muscle regeneration but cannot prevent muscle fibrosis. We investigated the use of an antifibrosis substance, decorin, as an approach to prevent fibrosis and thereby improve muscle healing after injury in murine muscle. We observed that direct injection of human recombinant decorin can efficiently prevent fibrosis and enhance muscle regeneration in the lacerated muscle. More importantly, decorin can improve the recovery of strength in the injured muscle to a level similar to that observed in normal noninjured muscle. These results suggest that injection of decorin improves both the muscle structure and the function of the lacerated muscle to near complete recovery. This study will contribute significantly to the development of strategies to promote efficient muscle healing and complete functional recovery after muscle injuries.

Effect of telmisartan on angiotensin II-mediated collagen gel contraction by adult rat cardiac fibroblasts

The possible contributions of the angiotensin receptor subtypes 1 and 2 on the angiotensin II-induced collagen gel contraction by adult rat cardiac fibroblasts were studied using the specific angiotensin receptor type 1 and 2 antagonists telmisartan and P-186, respectively. Cardiac fibroblasts (from normal male adult rats) from passage 2 were cultured to confluency and added to a hydrated collagen gel, with or without angiotensin II, angiotensin II plus telmisartan, or angiotensin II plus P-186 in Dulbecco's Modified Eagle's Medium containing 5% fetal bovine serum for 1, 2, or 3 days. Control gels containing adult rat cardiac fibroblasts showed a significant amount of contraction after 3 days of incubation, causing a contraction to 67.9 +/- 7.1% of the area after 1 day. Angiotensin II (10(-7) M) stimulated (p < or = 0.05) the contraction of collagen mediated by cardiac fibroblasts after 1, 2, or 3 days. Telmisartan (10(-7) M) completely blocked the angiotensin II-induced collagen contraction by cardiac fibroblasts. P-186 (10(-7) M) had no effect on the angiotensin II-induced collagen contraction by cardiac fibroblasts. Addition of telmisartan and P-186 alone did not affect the collagen gel contraction by cardiac fibroblasts. Our data demonstrate that the effects of angiotensin II on the collagen gel contraction by adult rat cardiac fibroblasts are angiotensin II type 1 receptor mediated because they were abolished by the specific angiotensin II type 1 receptor antagonist telmisartan but not by the specific angiotensin II type 2 receptor antagonist P-186.

IL-4 and IL-13 induce myofibroblastic phenotype of human lung fibroblasts through c-Jun NH2-terminal kinase-dependent pathway

BACKGROUND

Myofibroblasts play a role in the airway remodeling response of bronchial asthma. IL-4 and IL-13 are possibly involved in the airway remodeling response by inducing extracellular matrix production by fibroblasts. However, the roles of these cytokines in inducing the phenotypic modulation of human lung fibroblasts (HLFs) to myofibroblasts and the intracellular signal have not been determined.

OBJECTIVE

We examined the effect of IL-4 and IL-13 on inducing the phenotypic modulation of HLFs to myofibroblasts characterized by alpha-smooth muscle actin and examined the role of the mitogen-activated protein (MAP) kinase superfamily in inducing the myofibroblastic phenotype of the HLF to clarify these issues.

METHODS

Phosphorylation and activities of c-Jun NH(2)-terminal kinase (JNK), p38 MAP kinase, and extracellular signal-regulated kinase (Erk) were examined by using Western blotting and in vitro kinase assay. Expression of alpha-smooth muscle actin in IL-4- and IL-13-stimulated HLFs was analyzed by means of Western blotting.

RESULTS

The results showed that (1) IL-4 and IL-13 increased alpha-smooth muscle actin expression in a dose- and time-dependent manner; (2) IL-4 and IL-13 induced increases in JNK and Erk phosphorylation and activity but not p38 MAP kinase activity; (3) CEP-1347 and PD 98059 attenuated IL-4- and IL13-induced JNK and Erk activity, respectively; and (4) CEP-1347, but not PD 98059, attenuated IL-4- and IL-13-induced alpha-smooth muscle actin expression.

CONCLUSION

These results indicate that IL-4 and IL-13 are capable of inducing the phenotypic modulation of HLFs to myofibroblasts, and JNK, but not p38 MAP kinase and Erk, regulates IL-4- and IL-13-induced phenotypic modulation of HLFs to myofibroblasts.

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.

Transforming growth factor-beta(1) induces angiotensin-converting enzyme synthesis in rat cardiac fibroblasts during their differentiation to myofibroblasts

OBJECTIVES

Appearance of angiotensin-converting enzyme (ACE) in fibrotic tissue can be the result of the action either of one particular growth factor or of cross-talk between multiple factors. Transforming growth factor-beta1 (TGF-beta(1)) is an effective inducor of the differentiation of cultured fibroblasts to myofibroblasts, which are heterogeneous cells with different phenotypes. The present study investigated whether TGF-beta(1) is able to induce, in vitro, the differentiation of cultured fibroblasts to myofibroblasts with a phenotype containing ACE.

DESIGN

Adult rat cardiac ventricular fibroblasts were obtained from hearts perfused with collagenase. Cells from second passage were always used. Rat cardiac ventricular fibroblasts were incubated with TGF-beta(1) (10 ng/ml) for seven days. Cell characterisation was performed using light microscopy and indirect immunostaining. Presence of vimentin, desmin, factor VIII, alpha-smooth muscle actin, and ACE was checked with both immunostaining and Western blotting. ACE activity was measured fluorometrically with hippuryl-histidyl-leucine as substrate. Synthesis of DNA was measured as (3)H-thymidine incorporation.

RESULTS

Fibroblasts contained two types of activity of hip-his-leu degradation, namely a lisinopril-dependent activity (ACE activity) and a lisinopril-independent activity ('ACE-like' activity) which is performed by peptidase(s) other than ACE. The ACE activity constituted approximately 30% of the total activity. TGF-beta(1) induced an increase in both ACE activity and ACE protein (detected by immunoblotting) by 4.5 +/- 0.9- and 6.9 +/- 2.0-fold, respectively (p<0.05). This induction of ACE was accompanied by a profound modification of the fibroblasts phenotype, which consisted of a change in cell morphology, an enlargement of cell volume and an increase in cell protein content. TGF-beta(1) profoundly inhibited (3)H-thymidine incorporation and the number of cells in growing cultures. The induction of alpha-smooth muscle actin by TGF-beta(1) (6.8 +/- 2.8-fold increase, p<0.05) simultaneously with these modifications in cell morphology and proliferation indicates the appearance of myofibroblasts. These myofibroblasts did not contain desmin.

CONCLUSION

TGF-beta(1) is able to induce the appearance of ACE in cultures of adult rat cardiac ventricular fibroblasts. The appearance of the enzyme is accompanied by the differentiation of fibroblasts to myofibroblasts.

Mechanism of pulmonary vein stenosis in infants with normally connected veins

We used microscopy, immunohistochemistry, and cell culture to identify the mechanism of restenosis in 4 infants with isolated pulmonary vein stenosis. Recurrent obstruction appears to be due to myofibroblastic proliferation in this fatal disease.

Transforming growth factor-beta1 promotes the morphological and functional differentiation of the myofibroblast

The myofibroblast is responsible for the generation of contractile force associated with wound contraction and pathological contractures and is characterized by the presence of alpha-smooth muscle (alpha-sm) actin-containing stress fibers, vinculin-containing fibronexus adhesion complexes, and fibronectin fibrils containing the ED-A splice variant. Transforming growth factor-beta1 (TGF-beta1) can promote the expression of alpha-sm actin in myofibroblasts, but the functional significance of this increased expression is unclear. In this study, we demonstrate, using the stress-relaxed collagen lattice contraction assay, that TGF-beta1 promoted a dose-dependent increase in the generation of contractile force in myofibroblasts and a concomitant increase in the expression of alpha-sm actin. We also demonstrate that TGF-beta1 enhanced the formation of the structural elements important in myofibroblast contractile force generation and transmission, including stress fibers, vinculin-containing fibronexus adhesion complexes, and fibronectin fibrils, and that this enhancement occurred prior to, and independent of, alpha-sm actin expression. This differentiated myofibroblast phenotype was not stable. Removal of TGF-beta1 resulted in reduced expression of alpha-sm actin as well as a decreased assembly of stress fibers and vinculin-containing adhesion complexes; however, there was no reduction in fibronectin fibrils. We conclude that TGF-beta1 promotes the morphological and functional differentiation of the myofibroblast by first enhancing the formation of the structural elements characteristic of the myofibroblast followed by increased expression of alpha-sm actin and contractile force generation.

Tenascin mRNA expression at the foci of recent injury in usual interstitial pneumonia

To elucidate which cells are synthesizing tenascin in usual interstitial pneumonia (UIP) we have analyzed thoracoscopic or open lung biopsies from 30 patients with UIP by mRNA in situ hybridization, using (35)S-labeled tenascin RNA probes. The phenotype of the cells expressing tenascin mRNA was confirmed by immunohistochemical stainings of serial sections with antibodies against alpha-smooth muscle actin and human cytokeratin. The results demonstrate that tenascin is expressed at the foci of recent lesions consisting of intralumenal or incorporating loose fibrotic buds. The cells expressing tenascin mRNA were located in and underneath the newly formed epithelium. Immunohistochemical stainings showed that the cells in the newly formed epithelium were strongly cytokeratin positive, and thus evidently regenerating type 2 pneumocytes, while the cells underneath the newly formed epithelium were alpha-smooth muscle actin positive and apparently myofibroblasts. Tenascin mRNA expression was clearly stronger and more frequent in myofibroblasts than in type 2 pneumocytes, however. Weak tenascin mRNA expression was also found in metaplastic bronchiolar-type epithelium and alveolar macrophages. Our results are thus in good agreement with the previous studies showing that tenascin is actively synthesized at the early fibrotic lesions in UIP. Furthermore, results demonstrate that the interaction between the epithelium and the underlying connective tissue plays a significant role in tenascin synthesis and that myofibroblasts are mainly responsible for its synthesis in fibroblastic foci of UIP.

TGF-beta and bFGF affect the differentiation of proliferating porcine fibroblasts into myofibroblasts in vitro

Fibroblasts and myofibroblasts are involved in the foreign body reaction to biomaterials, especially in capsule formation. However, contraction or detachment of the capsule can lead to complications. Biocompatibility of biomaterials may be improved by the application of proteins regulating the differentiation or activation of (myo)fibroblasts. Myofibroblasts, differentiating from fibroblasts can be identified by the expression of alpha-smooth muscle actin (alpha-SM actin). We investigated the influence of proliferation and quiescence on the differentiation of porcine dermal cells and whether transforming growth factor-beta (TGF-beta) and basic fibroblast growth factor (bFGF) are involved in the differentiation of proliferating cells. Porcine cells were used because pigs increasingly function as in vivo models while little is known of the characteristics of their cells. Serum-free cultured, quiescent fibroblasts differentiated into myofibroblasts, while proliferating fibroblasts cultured in the presence of serum containing TGF-beta, formed alpha-SM actin-negative cell clusters. After reaching confluency, these clusters started to expressing alpha-SM actin. Moreover, these proliferating cells produced TGF-beta from day 4 onwards while bFGF did not. Differentiation into myofibroblasts was inhibited by bFGF and to an even greater extent by antibodies to TGF-beta. Further, two theories concerning the role of the myofibroblast in tissue contraction in view of two biomaterial application will be discussed.

Effects of TGFbeta2 on collagen synthesis in cultured normal and wounded fetal mouse palates

OBJECTIVE

It has been demonstrated in a number of models that fetal wounds heal with little or no scar. Since collagen is an integral part of the extracellular matrix in adult scar formation, we studied the synthesis and localization of collagen in an in vitro mouse palate model for fetal wound healing.

METHODS

Palates, dissected from fetal mice at 15, 16, and 17 days of gestation and from newborn mice, were cultured in medium containing serum (for 8 hours); this was followed by culture in serum-free medium (for 12 hours). One-half of the samples from each age group were wounded in the midline. All samples were placed in serum-free medium containing 20 microCi/mL 3H-proline for 8 hours. In addition, palates from 15-day gestation and from newborn mice were also incubated with transforming growth factor TGF-beta2 (10 ng/mL). Palates were washed with saline, homogenized, and radioactivity was counted. Proline uptake was calculated for each sample as counts per milligram of protein and was subjected to statistical analysis (three-way analysis of variance). Samples of the homogenate were subjected to sodium dodecyl sulfate-gel electrophoresis and Western blotting in order to determine the types of collagen that were synthesized. Immunohistochemical localization of collagen types I, III, and VI was carried out on paraffin-embedded samples from each group.

RESULTS

There were no significant differences in proline uptake between wounded mouse palates and nonwounded mouse palates at any age, and there was no histological evidence of regeneration of the palate at the site of the wound. Proline uptake was significantly greater in untreated wounded palates at 15 days' gestation than it was in newborns. After treatment with TGF-beta2, proline uptake was significantly greater in both wounded and nonwounded palates in the newborn group and had no effect on collagen synthesis in palates from 15-day gestation animals. Collagen types I and III were localized in histological specimens using immunohistochemistry and on nitrocellulose using Western blotting. No type VI collagen was demonstrated by Western blotting, but it was localized around blood vessels and on basement membranes using immunohistochemistry.

CONCLUSION

Treatment with TGF-beta2 significantly increased collagen synthesis, as assessed by 3H-proline uptake, in cultured palates from newborn mice as compared with palates from untreated newborn mice and from both treated and untreated palates of 15-day gestation mice. These data suggest a differential response to TGF-beta2 by mouse palates as a function of fetal development.

Evidence for apoptosis induction in myofibroblasts during palatal mucoperiosteal repair

Apoptosis is thought to be a requisite event for maintaining kinetic homeostasis within continually renewing tissues such as the oral mucosa and skin. However, no systematic study of the apoptotic process in fibroblasts in the oral mucosa following injury has been performed. In this study, we have assessed the expression of transforming growth factor-beta1 (TGF-beta1) and basic fibroblast growth factor (bFGF), which are among the most important modulators of wound repair, during wound healing following mucoperiosteal injury in the rat palate. In addition, we have investigated fibroblast differentiation and apoptosis by immunohistochemical analysis for alpha-smooth-muscle (alpha-SM) actin or DNA strand breaks, respectively, to clarify the mechanisms of the wound healing process. TGF-beta1-positive cells were noted in the subepithelium from Day 2 to Day 14 after injury, by which time the wounds were completely reepithelialized. Strong expression of bFGF was observed, mainly in macrophages and monocytes at the injured site, from Day 10 to Day 14 after injury. TGF-beta1 and bFGF-immunostaining was significantly lower during the later phase of wound healing. In addition, the number of myofibroblasts expressing alpha-SM actin increased (peak at Day 14), and thereafter gradually decreased. In parallel, the apoptosis in myofibroblasts was prominent on Day 14. These results suggest that TGF-beta1 and bFGF may be potential stimulators of apoptosis in myofibroblasts after re-epithelialization in the palatal wound healing process. The regulation of apoptotic phenomena during wound healing may be important in scar establishment and development of pathological scarring.

Interferon-gamma inhibits the myofibroblastic phenotype of rat palatal fibroblasts induced by transforming growth factor-beta1 in vitro

Interferon-gamma (IFN-gamma), a multifunctional cytokine, has been noted as a potential therapeutic agent for various fibrotic disorders, including excessive scar tissue formation. We previously reported that transforming growth factor-beta1 (TGF-beta1) induced the myofibroblastic phenotype in palatal fibroblasts derived from palatal mucosa, and that such effects might have a close link to palatal scar formation. In the present study, we examined the effects of IFN-gamma on TGF-beta1-pretreated palatal fibroblasts for the purpose of clarifying the suppressive potency against myofibroblastic phenotype expression in vitro. IFN-gamma significantly altered the spindle morphology of TGF-beta1-pretreated palatal fibroblasts into the polygonal one that was similar to the non-treated palatal fibroblasts. This change was parallel with a decrease in the expression of alpha-smooth muscle actin protein, a marker for myofibroblast, as determined by immunoblot analysis. Northern blot analysis showed that IFN-gamma inhibited proalpha2(I) collagen mRNA expression that was stimulated by TGF-beta1 pretreatment for 24 h. Furthermore, IFN-gamma decreased the cell contractility enhanced by TGF-beta1 pretreatment for 24 h in a three-dimensional collagen gel culture system. These results suggest that IFN-gamma may have negative effects with regard to controlling the myofibroblastic phenotype induced by TGF-beta1 in palatal fibroblasts.

Immunohistochemical findings type I and type II collagen in prenatal mouse mandibular condylar cartilage compared with the tibial anlage

In growing animals the mandibular condylar cartilage serves not only as an articular but also as a growth cartilage, yet, condylar cartilage has some characteristic features that are not found in growth cartilage. For example, some reports suggest that type I collagen, which is not seen in the growth plate cartilage of long bones, is present in the extracellular matrix of condylar cartilage postnatally. Here, the condylar and limb bud cartilage of fetal mice was examined. The distribution of type I and type II collagen in condylar cartilage was already different from that in the limb bud at the first appearance of the cartilage. Type I collagen was demonstrated in the extracellular matrix of the condylar cartilage that first appeared on day 15 of gestation. However, the reaction for type II collagen was much weaker than that for type I collagen. On day 18 of gestation, type I collagen was still found throughout the cell layers but became gradually weaker with depth. Type II collagen was limited exclusively to the deeper layers at this stage. These findings are different from those in the limb bud cartilage, indicating a characteristic feature of the cells in the condylar cartilage present from the prenatal period.

Expression of interleukin-10 by in vitro and in vivo activated hepatic stellate cells

Activated hepatic stellate cells (HSC) participate in matrix remodeling and deposition in liver fibrosis. The present study demonstrates that interleukin (IL)-10 is expressed by HSC upon activation in vitro or in vivo and that autocrine effects of this cytokine include inhibition of collagen production. Culture activation of HSC caused a distinct increase in IL-10 mRNA level compared with freshly isolated quiescent HSC. Treatment of cultured HSC with tumor necrosis factor-alpha, transforming growth factor-beta, or lipopolysaccharide further increased IL-10 mRNA by 2-fold and resulted in the release of IL-10 protein into the medium. HSC isolated from rats after bile duct ligation (BDL) showed prominent increases in IL-10 mRNA (x 100) and protein (x 30) levels at 7 days after BDL, but such induction disappeared in advanced liver fibrosis (19 days after BDL). IL-10 expression correlated positively with mRNA expression of interstitial collagenase and inversely with that of alpha1(I) collagen. Addition of anti-IL-10 IgG to cultured HSC caused enhanced collagen production under a basal or stimulated condition with TGF-beta, tumor necrosis factor-alpha, or lipopolysaccharide. These effects were associated with increased alpha1(I) collagen mRNA and reciprocally reduced collagenase mRNA levels. Co-transfection of HSC with an IL-10 expression vector and collagen reporter genes showed a 40% inhibition of alpha1(I) collagen promoter activity. These results demonstrate that activation of HSC causes enhanced autocrine expression of IL-10 which possesses a negative autoregulatory effect on HSC collagen production mediated at least in part by alpha1(I) collagen transcriptional inhibition and stimulation of collagenase expression. These findings, along with the demonstrated early induction of HSC IL-10 expression and its late disappearance during biliary liver fibrosis, suggest its in vivo role in matrix remodeling and a possibility that failure for HSC to sustain IL-10 expression underlies pathologic progression to liver cirrhosis.

Basic fibroblast growth factor induces apoptosis in myofibroblastic cells isolated from rat palatal mucosa

The effect of basic fibroblast growth factor (bFGF) on apoptosis in normal rat palatal fibroblasts and rat palatal scar fibroblasts was examined by the TUNEL method in order to clarify the mechanism of apoptosis induction in myofibroblasts during the scar formation process. A percentage of scar fibroblasts undergoing apoptosis was significantly higher than that of palatal fibroblasts when they were treated with bFGF succeeding to serum starvation. Palatal fibroblasts, phenotypically modulated into myofibroblasts by the pretreatment with transforming growth factor-beta 1 (TGF-beta 1), similarly showed a higher level of apoptosis induction by bFGF-treatment. TGF-beta 1 elevated protein and mRNA level of FGF receptor (FGFR) in palatal fibroblasts. Tyrosine autophosphorylation of FGFR upon stimulation by bFGF was significantly higher in scar fibroblasts than in normal palatal fibroblasts. These findings suggested that bFGF may be a potential stimulator of apoptosis in myofibroblasts during palatal scar formation and that FGFR may be responsible for this process.