Role of myofibroblasts during normal tissue repair and excessive scarring: interest of their assessment in nephropathies

Gut Microbiota, Macrophages and Diet: An Intriguing New Triangle in Intestinal Fibrosis

Intestinal fibrosis is a common complication in inflammatory bowel disease (IBD) without specific treatment. As macrophages are the key actors in inflammatory responses and the wound healing process, they have been extensively studied in chronic diseases these past decades. By their exceptional ability to integrate diverse stimuli in their surrounding environment, macrophages display a multitude of phenotypes to underpin a broad spectrum of functions, from the initiation to the resolution of inflammation following injury. The hypothesis that distinct macrophage subtypes could be involved in fibrogenesis and wound healing is emerging and could open up new therapeutic perspectives in the treatment of intestinal fibrosis. Gut microbiota and diet are two key factors capable of modifying intestinal macrophage profiles, shaping their specific function. Defects in macrophage polarisation, inadequate dietary habits, and alteration of microbiota composition may contribute to the development of intestinal fibrosis. In this review, we describe the intriguing triangle between intestinal macrophages, diet, and gut microbiota in homeostasis and how the perturbation of this discreet balance may lead to a pro-fibrotic environment and influence fibrogenesis in the gut.

Mitochondrial Pathophysiology on Chronic Kidney Disease

In healthy kidneys, interstitial fibroblasts are responsible for the maintenance of renal architecture. Progressive interstitial fibrosis is thought to be a common pathway for chronic kidney diseases (CKD). Diabetes is one of the boosters of CKD. There is no effective treatment to improve kidney function in CKD patients. The kidney is a highly demanding organ, rich in redox reactions occurring in mitochondria, making it particularly vulnerable to oxidative stress (OS). A dysregulation in OS leads to an impairment of the Electron transport chain (ETC). Gene deficiencies in the ETC are closely related to the development of kidney disease, providing evidence that mitochondria integrity is a key player in the early detection of CKD. The development of novel CKD therapies is needed since current methods of treatment are ineffective. Antioxidant targeted therapies and metabolic approaches revealed promising results to delay the progression of some markers associated with kidney disease. Herein, we discuss the role and possible origin of fibroblasts and the possible potentiators of CKD. We will focus on the important features of mitochondria in renal cell function and discuss their role in kidney disease progression. We also discuss the potential of antioxidants and pharmacologic agents to delay kidney disease progression.

Osteopontin-derived synthetic peptide SVVYGLR upregulates functional regeneration of oral and maxillofacial soft-tissue injury

Wound healing in the oral and maxillofacial region is a complicated and interactive process. Severe mucosal or skeletal muscle injury by trauma or surgery induces worse healing conditions, including delayed wound closure and repair with excessive scar tissue. These complications lead to persistent functional impairment, such as digestive behavior or suppression of maxillofacial growth in infancy. Osteopontin (OPN), expressed in a variety of cells, is multifunctional and comprises a number of functional domains. Seven amino acids sequence, SVVYGLR (SV peptide), exposed by thrombin cleavage of OPN, has angiogenic activity and promotes fibroblast differentiation into myofibroblasts and increased expression of collagen type III. Additionally, synthetic SV peptide shows faster dermal and oral mucosal wound closure by facilitating cell motility and migratory activities in dermal- or mucosal-derived keratinocytes and fibroblasts. Moreover, cell motility and differentiation in myogenic cell populations are accelerated by SV peptide, which contributes to the facilitation of matured myofibers and scarless healing and favorable functional regeneration after skeletal muscle injury. SV peptide has high affinity with TGF-β, with potential involvement of the TGF-β/Smad signaling pathway. Clinical application of single-dose SV peptide could be a powerful alternative treatment option for excessive oral and maxillofacial wound care to prevent disadvantageous events.

An immunohistochemical prostate cell identification key indicates that aging shifts procollagen 1A1 production from myofibroblasts to fibroblasts in dogs prone to prostate-related urinary dysfunction

Background

The identity and spatial distribution of prostatic cell types has been determined in humans but not in dogs, even though aging- and prostate-related voiding disorders are common in both species and mechanistic factors, such as prostatic collagen accumulation, appear to be shared between species. In this publication we characterize the regional distribution of prostatic cell types in the young intact dog to enable comparisons with human and mice and we examine how the cellular source of procollagen 1A1 changes with age in intact male dogs.

Methods

A multichotomous decision tree involving sequential immunohistochemical stains was validated for use in dog and used to identify specific prostatic cell types and determine their distribution in the capsule, peripheral, periurethral and urethral regions of the young intact canine prostate. Prostatic cells identified using this technique include perivascular smooth muscle cells, pericytes, endothelial cells, luminal, intermediate, and basal epithelial cells, neuroendocrine cells, myofibroblasts, fibroblasts, fibrocytes, and other hematolymphoid cells. To enhance rigor and transparency, all high resolution images (representative images shown in the figures and biological replicates) are available through the GUDMAP database at https://doi.org/10.25548/16-WMM4.

Results

The prostatic peripheral region harbors the largest proportion of epithelial cells. Aging does not change the density of hematolymphoid cells, fibroblasts, and myofibroblasts in the peripheral region or in the fibromuscular capsule, regions where we previously observed aging- and androgen-mediated increases in prostatic collagen abundance Instead, we observed aging-related changes the procollagen 1A1 positive prostatic cell identity from a myofibroblast to a fibroblast.

Conclusions

Hematolymphoid cells and myofibroblasts are often identified as sources of collagen in tissues prone to aging-related fibrosis. We show that these are not the likely sources of pathological collagen synthesis in older intact male dogs. Instead, we identify an aging-related shift in the prostatic cell type producing procollagen 1A1 that will help direct development of cell type and prostate appropriate therapeutics for collagen accumulation.

A short peptide potentially promotes the healing of skin wound

Skin wound, a common form of skin damage in daily life, remains a serious challenge in clinical treatment. Bioactive peptides with high efficiency have been considered as potential therapeutic candidates for wound healing. In this report, a novel short linear peptide, with mature peptide sequence of 'GLLSGINAEWPC' and no obvious similarity with other known bioactive peptides, was identified by genomic method from the skin of odorous frog, Odorrana andersonii Our results suggested that OA-GL12 (OA: abbreviation of species (O. andersonii), GL: two initial amino acids, 12: peptide length) obviously accelerated the scratch-healing of keratinocytes and human fibroblasts in a time- and concentration-dependent manner. Meanwhile, OA-GL12 showed significant effect in promoting the wound healing on the full-thickness skin wound model. Inflammatory assay results demonstrated that OA-GL12 induced the secretion of tumor necrosis factor (TNF) and transforming growth factor β1 (TGF-β1) on murine macrophage cell line (RAW264.7), which might explain the powerful accelerating capacity of wound healing. Moreover, results also indicated that epidermal growth factor receptor (EGFR) was involved in the mechanisms underlying the scratch-healing promoting activity of OA-GL12. In addition, OA-GL12 showed obvious free radical scavenging activity. Results supported that OA-GL12 did not exert risk in acute toxicity, hemolytic activity, and direct antibacterial activity. The remarkable effect of OA-GL12 on promoting wound healing verified in this research made it potential to be a novel template for the development of wound healing-promoting agents.

The cardiac repair benefits of inflammation do not persist: evidence from mast cell implantation

Multiple mechanisms contribute to progressive cardiac dysfunction after myocardial infarction (MI) and inflammation is an important mediator. Mast cells (MCs) trigger inflammation after MI by releasing bio‐active factors that contribute to healing. c‐Kit‐deficient (Kit^W/W‐v) mice have dysfunctional MCs and develop severe ventricular dilatation post‐MI. We explored the role of MCs in post‐MI repair. Mouse wild‐type (WT) and Kit^W/W‐vMCs were obtained from bone marrow (BM). MC effects on fibroblasts were examined in vitro by proliferation and gel contraction assays. MCs were implanted into infarcted mouse hearts and their effects were evaluated using molecular, cellular and cardiac functional analyses. In contrast to WT, Kit^W/W‐vMC transplantation into Kit^W/W‐v mice did not improve cardiac function or scar size post‐MI. Kit^W/W‐vMCs induced significantly reduced fibroblast proliferation and contraction compared to WT MCs. MC influence on fibroblast proliferation was Basic fibroblast growth factor (bFGF)‐dependent and MC‐induced fibroblast contractility functioned through transforming growth factor (TGF)‐β. WT MCs transiently rescue cardiac function early post‐MI, but the benefits of BM cell implantation lasted longer. MCs induced increased inflammation compared to the BM‐injected mice, with increased neutrophil infiltration and infarct tumour necrosis factor‐α (TNF‐α) concentration. This augmented inflammation was followed by increased angiogenesis and myofibroblast formation and reduced scar size at early time‐points. Similar to the functional data, these beneficial effects were transient, largely vanishing by day 28. Dysfunctional Kit^W/W‐vMCs were unable to rescue cardiac function post‐MI. WT MC implantation transiently enhanced angiogenesis and cardiac function. These data suggest that increased inflammation is beneficial to cardiac repair, but these effects are not persistent.

Delayed rearterialization unlikely leads to nonanastomotic stricture but causes temporary injury on bile duct after liver transplantation

Nonanastomotic strictures (NAS) are common biliary complications after liver transplantation (LT). Delayed rearterialization induces biliary injury in several hours. However, whether this injury can be prolonged remains unknown. The correlation of this injury with NAS occurrence remains obscure. Different delayed rearterialization times were compared using a porcine LT model. Morphological and functional changes in bile canaliculus were evaluated by transmission electron microscopy and real-time PCR. Immunohistochemistry and TUNEL were performed to validate intrahepatic bile duct injury. Three months after LT was performed, biliary duct stricture was determined by cholangiography; the tissue of common bile duct was detected by real-time PCR. Bile canaliculi were impaired in early postoperative stage and then exacerbated as delayed rearterialization time was prolonged. Nevertheless, damaged bile canaliculi could fully recover in subsequent months. TNF-α and TGF-β expressions and apoptosis cell ratio increased in the intrahepatic bile duct only during early postoperative period in a time-dependent manner. No abnormality was observed by cholangiography and common bile duct examination after 3 months. Delayed rearterialization caused temporary injury to bile canaliculi and intrahepatic bile duct in a time-dependent manner. Injury could be fully treated in succeeding months. Solo delayed rearterialization cannot induce NAS after LT.

Helium generated cold plasma finely regulates activation of human fibroblast-like primary cells

Non-thermal atmospheric pressure plasmas are being developed for a wide range of health care applications, including wound healing. However in order to exploit the potential of plasma for clinical applications, the understanding of the mechanisms involved in plasma-induced activation of fibroblasts, the cells active in the healing process, is mandatory. In this study, the role of helium generated plasma in the tissue repairing process was investigated in cultured human fibroblast-like primary cells, and specifically in hepatic stellate cells and intestinal subepithelial myofibroblasts. Five minutes after treatment, plasma induced formation of reactive oxygen species (ROS) in cultured cells, as assessed by flow cytometric analysis of fluorescence-activated 2′,7′-dichlorofluorescein diacetate probe. Plasma-induced intracellular ROS were characterized by lower concentrations and shorter half-lives with respect to hydrogen peroxide-induced ROS. Moreover ROS generated by plasma treatment increased the expression of peroxisome proliferator activated receptor (PPAR)-γ, nuclear receptor that modulates the inflammatory responses. Plasma exposure promoted wound healing in an in vitro model and induced fibroblast migration and proliferation, as demonstrated, respectively, by trans-well assay and partitioning between daughter cells of carboxyfluorescein diacetate succinimidyl ester fluorescent dye. Plasma-induced fibroblast migration and proliferation were found to be ROS-dependent as cellular incubation with antioxidant agents (e.g. N-acetyl L-cysteine) cancelled the biological effects. This study provides evidence that helium generated plasma promotes proliferation and migration in liver and intestinal fibroblast-like primary cells mainly by increasing intracellular ROS levels. Since plasma-evoked ROS are time-restricted and elicit the PPAR-γ anti-inflammatory molecular pathway, this strategy ensures precise regulation of human fibroblast activation and can be considered a valid therapeutic approach for liver and gut lesions.

A small peptide with potential ability to promote wound healing

Wound-healing represents a major health burden, such as diabetes-induced skin ulcers and burning. Many works are being tried to find ideal clinical wound-healing biomaterials. Especially, small molecules with low cost and function to promote production of endogenous wound healing agents (i.e. transforming growth factor beta, TGF-β) are excellent candidates. In this study, a small peptide (tiger17, c[WCKPKPKPRCH-NH2]) containing only 11 amino acid residues was designed and proved to be a potent wound healer. It showed strong wound healing-promoting activity in a murine model of full thickness dermal wound. Tiger17 exerted significant effects on three stages of wound healing progresses including (1) the induction of macrophages recruitment to wound site at inflammatory reaction stage; (2) the promotion of the migration and proliferation both keratinocytes and fibroblasts, leading to reepithelialization and granulation tissue formation; and (3) tissue remodeling phase, by promoting the release of transforming TGF-β1 and interleukin 6 (IL-6) in murine macrophages and activating mitogen-activated protein kinases (MAPK) signaling pathways. Considering its easy production, store and transfer and function to promote production of endogenous wound healing agents (TGF-β), tiger17 might be an exciting biomaterial or template for the development of novel wound-healing agents.

Effect of transforming growth factor Beta 1 on wound healing in induced diabetic rats

OBJECTIVE

Delayed wound healing is one of the complications of diabetes mellitus, exhibited by profound inflammation and decreased granulation tissues. The current study was carried out to evaluate wound healing in both normal and diabetic rats. In addition, it evaluated the potential protective effect of transforming growth factor β1 (TGF β1), that has the broadest spectrum of actions, affecting all cell types that are involved in all stages of wound healing to accelerate wound healing in normal & diabetic rats.

METHODS

: The present study was performed on 40 male albino rats. Each 10 rats were designed as a group. Group I saved as control. They received incisional wound in their tongues 1 cm length and 1/2 cm depth. Group II received 500 ng/kg of TGF β1 5 minutes before wounding. Group III diabetes was induced then rats were treated as second group. At the 14(th) day post wounding, sections of tongues were taken for hematoxylin and eosin and Masson's trichome staining to examine the histological changes. The intracellular actions of TGF β1 were studied by TEM.

RESULTS

A higher cell proliferation rate and a denser and more organized new extracellular matrix and complete wound closure was detected at the 14(th) days in the TGF β1 treated wound in comparison with the 14(th) days for the untreated, control groups. There were delayed wound healing in diabetic rats, decreased re-epithelialization, granulation tissue thickness, matrix density, number of infiltrated cells, and number of capillaries. In TGF β1 treated diabetic rats, showed significant healing improvement was obvious as compared with diabetic rats.

CONCLUSIONS

A single intravenous injection of TGF β1 was sufficient to enhance wound healing in rat's tongue. This approach represents a new strategy that may be applied to the treatment of incisional wounds in human diabetic patients.

Effects of transforming growth factor-beta1 on cell motility, collagen gel contraction, myofibroblastic differentiation, and extracellular matrix expression of human adipose-derived stem cell

Human adipose-derived stem cells (ASCs) are adult pluripotent stem cells, and their usefulness in plastic surgery has garnered attention in recent years. Although, there have been expectations that ASCs might function in wound repair and regeneration, no studies to date have examined the role of ASCs in the mechanism that promotes wound-healing. Transforming growth factor-beta1 (TGF-β1) is a strong candidate cytokine for the triggering of mesenchymal stem cell migration, construction of extracellular matrices, and differentiation of ASCs into myofibroblasts. Cell proliferation, motility, and differentiation, as well as extracellular matrix production, play an important role in wound-healing. We have evaluated the capacity of ASCs to proliferate and their potential to differentiate into phenotypic myofibroblasts, as well as their cell motility and collagen gel contraction ability, when cultured with TGF-β1. Cell motility was analyzed using a wound-healing assay. ASCs that differentiated into myofibroblasts expressed the gene for alpha-smooth muscle actin, and its protein expression was detected immunohistochemically. The extracellular matrix expression in ASCs was evaluated using real-time RT-PCR. Based on the results, we conclude that human ASCs have the potential for cell motility, extracellular matrix gene expression, gel contraction, and differentiation into myofibroblasts and, therefore, may play an important role in the wound-healing process.

Expression of calponin in periglomerular myofibroblasts of rat kidney with experimental chronic injuries

Our previous research demonstrated that calponin-immunoreactivity was localized in myofibroblasts of the periglomerular region of human kidney specimens obtained at the time of transplantation from organ recipients. In the present study we examined calponin expression in two chronic nephropathy models, puromycin aminonucleoside (PAN) nephropathy and subtotal nephrectomy (SNx), to investigate the role of calponin in chronic renal injury. Male Sprague-Dawley rats were used, and both nephropathy models were established at 1, 2, 4, and 8 weeks after surgery. There were no periglomerular calponin-positive cells in sham, PAN 1 and 2 week, and SNx 1, 2, and 4 week groups. In SNx 8 week and PAN 4 and 8 week groups, only a few glomeruli with periglomerular calponin-reactivity, which covered half or a very small part of the periglomerular space, were observed. All glomeruli with periglomerular calponin-reactivity showed sclerotic changes, especially thickening of parietal epithelial cells (PECs). In conjunction with our previous report, this data represents the first documentation of the expression of calponin in renal myofibroblasts. We suggest that interactions between PECs and calponin-positive myofibroblasts may play a key role in the late stage of glomerulosclerosis.

Generation of easily accessible human kidney tubules on two-dimensional surfaces in vitro

The generation of tissue-like structures in vitro is of major interest for various fields of research including in vitro toxicology, regenerative therapies and tissue engineering. Usually 3D matrices are used to engineer tissue-like structures in vitro, and for the generation of kidney tubules, 3D gels are employed. Kidney tubules embedded within 3D gels are difficult to access for manipulations and imaging. Here we show how large and functional human kidney tubules can be generated in vitro on 2D surfaces, without the use of 3D matrices. The mechanism used by human primary renal proximal tubule cells for tubulogenesis on 2D surfaces appears to be distinct from the mechanism employed in 3D gels, and tubulogenesis on 2D surfaces involves interactions between epithelial and mesenchymal cells. The process is induced by transforming growth factor-β₁, and enhanced by a 3D substrate architecture. However, after triggering the process, the formation of renal tubules occurs with remarkable independence from the substrate architecture. Human proximal tubules generated on 2D surfaces typically have a length of several millimetres, and are easily accessible for manipulations and imaging, which makes them attractive for basic research and in vitro nephrotoxicology. The experimental system described also allows for in vitro studies on how primary human kidney cells regenerate renal structures after organ disruption. The finding that human kidney cells organize tissue-like structures independently from the substrate architecture has important consequences for kidney tissue engineering, and it will be important, for instance, to inhibit the process of tubulogenesis on 2D surfaces in bioartificial kidneys.

Mediators leading to fibrosis - how to measure and control them in tissue engineering

Fibrosis is the result of an excessive amount of fibrous connective tissue deposited into the extracellular matrix (ECM) space of damaged tissues from injury or disease. Collagens, particularly types I and III are the main constituents of the fibrotic scar tissue as well as a mixture of fibrotic cells. Severely fibrotic tissue will develop chronic healing problems resulting in tissue/organ dysfunction. More attention needs to be given to the fibrotic differentiation and related effects in bioengineered tissues. The current review provides an update on the mechanism behind fibrosis formation as well as technical measurements and preventions.

Transforming growth factor-β1 induces intestinal myofibroblast differentiation and modulates their migration

AIM: To investigate the effects of transforming growth factor β1 (TGF-β1) on the differentiation of colonic lamina propria fibroblasts (CLPF) into myofibroblasts in vitro.

METHODS: Primary CLPF cultures were incubated with TGF-β1 and analyzed for production of α-smooth muscle actin (α-SMA), fibronectin (FN) and FN isoforms. Migration assays were performed in a modified 48-well Boyden chamber. Levels of total and phosphorylated focal adhesion kinase (FAK) in CLPF were analyzed after induction of migration.

RESULTS: Incubation of CLPF with TGF-β1 for 2 d did not change α-SMA levels, while TGF-β1 treatment for 6 d significantly increased α-SMA production. Short term incubation (6 h) with TGF-β1 enhanced CLPF migration, while long term treatment (6 d) of CLPF with TGF-β1 reduced migration to 15%-37% compared to untreated cells. FN and FN isoform mRNA expression were increased after short term incubation with TGF-β1 (2 d) in contrast to long term incubation with TGF-β1 for 6 d. After induction of migration, TGF-β1-preincubated CLPF showed higher amounts of FN and its isoforms and lower levels of total and phosphorylated FAK than untreated cells.

CONCLUSION: Long term incubation of CLPF with TGF-β1 induced differentiation into myofibroblasts with enhanced α-SMA, reduced migratory potential and FAK phosphorylation, and increased FN production. In contrast, short term contact (6 h) of fibroblasts with TGF-β1 induced a dose-dependent increase of cell migration and FAK phosphorylation without induction of α-SMA production.

Oxidative stress mediates cardiac fibrosis by enhancing transforming growth factor-beta1 in hypertensive rats

Cardiac fibrosis represented as perivascular/interstial fibrosis occurs in patients with hypertension. Oxidative stress has been demonstrated to contribute to such structural remodeling. The underlying mechanisms, however, remain to be elucidated. Herein, we tested the hypothesis that oxidative stress mediates cardiac fibrogenesis by stimulating transforming growth factor (TGF)-beta1 expression, which in turn triggers a series of fibrogenic responses. Sprague-Dawley rats were treated with angiotensin (Ang)II (9 microg/h s) for 4 weeks with/without co-treatment of combined antioxidants, apocynin, and tempol (120 mg/kg/day each, oral). Untreated rats served as controls. Appearance of cardiac oxidative stress and its potential effect on the expression of TGF-beta1, population of myofibroblasts, collagen synthesis/degradation, and fibrosis in hearts were examined. Chronic AngII infusion elevated systemic blood pressure (210 +/- 5 mmHg). Extensive perivascular and interstitial fibrosis was found in both ventricles, which were co-localized with oxidative stress represented as upregulated NADPH oxidase (gp91(phox) subunit) expression. Co-treatment with antioxidants led to: (1) markedly decreased cardiac gp91(phox); (2) significantly attenuated gene expression of TGF-beta1, type-I collagen, and tissue inhibitors of matrix metalloproteinase (TIMP)-I/II in the heart; (3) largely reduced population of myofibroblasts at sites of fibrosis; (4) significantly reduced cardiac collagen volume; (5) and partially suppressed blood pressure (190 +/- 4 mmHg). Thus, cardiac oxidative stress promotes the development of cardiac fibrosis by upregulating TGF-beta1 expression, which subsequently enhances cardiac collagen synthesis and suppresses collagen degradation in hypertensive rats.

Regulation of galectin-3 function in mucosal fibroblasts: potential role in mucosal inflammation

Recently we identified galectin-3 (gal-3), which is secreted by colonic epithelial cells (CEC), to be a strong activator of colonic lamina propria fibroblasts (CLPF). Modulation of CLPF function may play a role during stricture and fistula formation in inflammatory bowel disease (IBD). Therefore, we investigated further the expression of gal-3 and effects on CLPF. The aim of this study is to perform a direct comparison of gal-3 between tissue from healthy controls and from patients with either Crohn's disease (CD) or ulcerative colitis (UC). CEC, CLPF and intestinal macrophages (IMAC) were isolated from control and IBD colonic tissue. Interleukin-8 secretion as a readout of CLPF activation was quantified by enzyme-linked immunosorbent assay. Gal-3 in cell cultures and tissue samples was evaluated by Western blot, immunofluorescence and immunohistochemistry. CLPF-migration was assayed in the 48-well modified Boyden chamber. Gal-3 expression was found in all segments of the colon. In the terminal ileum, less gal-3 was found compared with the colon. Immunohistochemistry and immunofluorescence revealed a homogenous distribution of gal-3 in CEC and IMAC of control mucosa and UC. However, significantly less gal-3 was found in IMAC from CD patients. In CD fistulae and stenoses, gal-3 expression was reduced significantly and barely detectable. In co-incubation studies lactose reduced significantly the CLPF-stimulatory potential of gal-3, indicating that the C-terminal domain of gal-3 is responsible for CLPF activation. Gal-3 stimulated CLPF migration in CLPF derived from fistulae. In conclusion, gal-3 expression is down-regulated in CD-fistulae and stenoses as well as in IMAC in CD patients. Gal-3 induces migration of CLPF derived from fistulae. Its role for stricture and fistula formation warrants further investigation.

Kidney fibrosis in hypertensive rats: role of oxidative stress

Fibrosis of the glomerulus and the tubulointerstitium occurs in patients with hypertension. Studies have shown that renal oxidative stress appears in hypertensive kidney disease. The potential role of oxidative stress in renal fibrogenesis remains to be elucidated. Herein, we tested the hypothesis that oxidative stress contributes to the development of renal fibrosis during hypertension.Sprague-Dawley rats received angiotensin II (AngII; 9 microg/h s.c.) for 4 weeks with/without co-treatment of antioxidants, apocynin and tempol (120 mg/kg/day each, p.o.). Untreated rats served as controls. Appearance of renal oxidative stress and its effect on the expression of transforming growth factor (TGF)-beta(1), population of myofibroblasts, collagen synthesis/degradation and fibrosis in kidneys were examined. Chronic AngII infusion elevated systemic blood pressure (228 +/- 6 mm Hg), which was accompanied with extensive renal fibrosis and oxidative stress represented as upregulated NADPH oxidase and suppressed superoxide dismutase (SOD). Co-treatment with antioxidants led to: (1) markedly decreased renal NADPH oxidase; (2) significantly attenuated gene expression of TGF-beta(1), type I collagen, and tissue inhibitors of matrix metalloproteinase (TIMP)-I/-II in the kidney; (3) largely reduced population of myofibroblasts in both the cortex and medulla; (4) significantly reduced renal collagen volume, and (5) partially suppressed blood pressure (190 +/- 8 mm Hg). Thus, prolonged AngII administration promotes renal oxidative stress, which is associated with hypertensive renal disease. AngII induces renal oxidative stress by increasing NADPH oxidase and reducing SOD in the kidney, which, in turn, upregulates collagen synthesis, while suppressing collagen degradation, thereby promoting the development of fibrosis in kidneys of hypertensive rats.

Fibroblast growth factor represses Smad-mediated myofibroblast activation in aortic valvular interstitial cells

This study aimed to identify signaling pathways that oppose connective tissue fibrosis in the aortic valve. Using valvular interstitial cells (VICs) isolated from porcine aortic valve leaflets, we show that basic fibroblast growth factor (FGF-2) effectively blocks transforming growth factor-β1 (TGF-β1)-mediated myofibroblast activation. FGF-2 prevents the induction of α-smooth muscle actin (αSMA) expression and the exit of VICs from the cell cycle, both of which are hallmarks of myofibroblast activation. By blocking the activity of the Smad transcription factors that serve as the downstream nuclear effectors of TGF-β1, FGF-2 treatment inhibits fibrosis in VICs. Using an exogenous Smad-responsive transcriptional promoter reporter, we show that Smad activity is repressed by FGF-2, likely an effect of the fact that FGF-2 treatment prevents the nuclear localization of Smads in these cells. This appears to be a direct effect of FGF signaling through mitogen-activated protein kinase (MAPK) cascades as the treatment of VICs with the MAPK/extracellular regulated kinase (MEK) inhibitor U0126 acted to induce fibrosis and blocked the ability of FGF-2 to inhibit TGF-β1 signaling. Furthermore, FGF-2 treatment of VICs blocks the development of pathological contractile and calcifying phenotypes, suggesting that these pathways may be utilized in the engineering of effective treatments for valvular disease.—Cushing, M. C., Mariner, P. D., Liao, J. T., Sims, E. A., Anseth, K. S. Fibroblast growth factor represses Smad-mediated myofibroblast activation in aortic valvular interstitial cells.

TGFbeta1 induces epithelial-mesenchymal transition, but not myofibroblast transdifferentiation of human kidney tubular epithelial cells in primary culture

The origin and fate of renal interstitial myofibroblasts (MFs), the effector cells of renal fibrosis, are still debated. Experimental evidence suggests that renal MFs derive from tubular epithelial cells throughout the epithelial-mesenchymal transition (EMT) process. Primary human tubular epithelial cells (HUTECs) were cultured for 4 and 6 days on plastic or type I collagen-coated plates with 1, 5, 10 and 50 ng/ml of transforming growth factor beta1 (TGFbeta1). The EMT process was monitored by morphology and immunophenotyping for alphaSMA, cytokeratin 8-18, E-cadherin, vimentin and collagen III. Quantitative comparative RT/PCR and real-time PCR were used to evaluate the expression of collagen III and IV, fibronectin, tenascin, MMP-2, CTGF, E-cadherin and cadherin 11 genes, as well as those of the Smad signalling pathway. TGFbeta1 was found capable of reactivating the mesenchymal programme switched off during tubulogenesis, but it induced no de novo expression of alphaSMA gene or myofibroblast phenotype. We demonstrate that the EMT process is conditioned by the extracellular matrix and characterized by TGFbeta1-driven Smad3 downregulation. Our study results suggest that TGFbeta1 could function as a classic embryonal inducer, initiating a cascade of de-differentiating events that might be further controlled by other factors in the cellular environment.

Mechanism of benign biliary stricture: A morphological and immunohistochemical study

AIM: To explore the mechanism of benign biliary stricture.

METHODS: A model of trauma of bile duct was established in 28 dogs. The anastomosed tissues were resected and examined by light and electron microscopes on day 3, in wk 1, 3 and mo 3, 6 after operation. CD68, TGF-β1 and α-SMA were examined by immunohistochemical staining, respectively.

RESULTS: The mucosal epithelium of the bile duct was slowly recovered, chronic inflammation lasted for a long time, fibroblasts proliferated actively, extracellular matrix was over-deposited. Myofibroblasts functioned actively and lasted through the whole process. The expression of macrophages in lamina propria under mucosa, TGF-β1 in granulation tissue, fibroblasts and endothelial cells of blood vessels, α-SMA in myofiroblasts were rather strong from the 1st wk to the 6th mo after operation.

CONCLUSION: The type of healing occurring in bile duct belongs to overhealing. Myofibroblasts are the main cause for scar contracture and stricture of bile duct. High expressions of CD68, TGF-β1 and α-SMA are closely related to the active proliferation of fibroblasts, extracellular matrix over-deposition and scar contracture of bile duct.

Advanced glycation end products induce tubular epithelial-myofibroblast transition through the RAGE-ERK1/2 MAP kinase signaling pathway

Advanced glycation end products (AGEs) have been shown to play a role in tubular epithelial-myofibroblast transdifferentiation (TEMT) in diabetic nephropathy, but the intracellular signaling pathway remains unknown. We report here that AGEs signal through the receptor for AGEs (RAGE) to induce TEMT, as determined by de novo expression of a mesenchymal marker (alpha-smooth muscle actin, alpha-SMA) and loss of epithelial marker (E-cadherin), directly through the MEK1-ERK1/2 MAP kinase pathway, which is TGF-beta independent. This is supported by the following findings: AGEs induced de novo alpha-SMA mRNA expression as early as 2 hours followed by a loss of E-cadherin before TGF-beta mRNA expression at 24 hours and occurred in the absence of TGF-beta and AGE-induced activation of ERK1/2 MAP kinase at 15 minutes and TEMT at 24 hours were completely blocked by a neutralizing RAGE antibody, a soluble RAGE receptor, an ERK1/2 MAP kinase inhibitor (PD98059), and DN-MEK1, but not by a neutralizing TGF-beta antibody. Thus, this study demonstrates that AGEs activate the RAGE-ERK1/2 MAP kinase pathway to mediate the early TEMT process. The findings from this study suggest that targeting the RAGE or the ERK MAP kinase pathway may provide new therapeutic strategies for diabetic nephropathy and shed new light on the pathogenesis of diabetic nephropathy.

Keratocyte phenotype mediates proteoglycan structure: a role for fibroblasts in corneal fibrosis

In pathological corneas, accumulation of fibrotic extracellular matrix is characterized by proteoglycans with altered glycosaminoglycans that contribute to the reduced transparency of scarred tissue. During wound healing, keratocytes in the corneal stroma transdifferentiate into fibroblasts and myofibroblasts. In this study, molecular markers were developed to identify keratocyte, fibroblast, and myofibroblast phenotypes in primary cultures of corneal stromal cells and the structure of glycosaminoglycans secreted by these cells was characterized. Quiescent primary keratocytes expressed abundant protein and mRNA for keratocan and aldehyde dehydrogenase class 3 and secreted proteoglycans containing macromolecular keratan sulfate. Expression of these marker compounds was reduced in fibroblasts and also in transforming growth factor-beta-induced myofibroblasts, which expressed high levels of alpha-smooth muscle actin, biglycan, and the extra domain A (EDA or EIIIA) form of cellular fibronectin. Collagen types I and III mRNAs were elevated in both fibroblasts and in myofibroblasts. Expression of these molecular markers clearly distinguishes the phenotypic states of stromal cells in vitro. Glycosaminoglycans secreted by fibroblasts and myofibroblasts were qualitatively similar to and differed from those of keratocytes. Chondroitin/dermatan sulfate abundance, chain length, and sulfation were increased as keratocytes became fibroblasts and myofibroblasts. Fluorophore-assisted carbohydrate electrophoresis analysis demonstrated increased N-acetylgalactosamine sulfation at both 4- and 6-carbons. Hyaluronan, absent in keratocytes, was secreted by fibroblasts and myofibroblasts. Keratan sulfate biosynthesis, chain length, and sulfation were significantly reduced in both fibroblasts and myofibroblasts. The qualitatively similar expression of glycosaminoglycans shared by fibroblasts and myofibroblasts suggests a role for fibroblasts in deposition of non-transparent fibrotic tissue in pathological corneas.

Pathways to recovery and loss of nephrons in anti-Thy-1 nephritis

The present histopathologic study of anti-Thy-1.1 models of mesangioproliferative glomerulonephritis in rats provides a structural analysis of damage development and of pathways to recovery and to nephron loss. As long as the disease remains confined to the endocapillary compartment, the damage may be resolved or recover with a mesangial scar. Irreversible lesions with loss of nephrons emerge from extracapillary processes with crucial involvement of podocytes, leading to tuft adhesions to Bowman's capsule (BC) and subsequent crescent formation. Two mechanisms appeared to be responsible: (1) Epithelial cell proliferation at BC and the urinary orifice and (2) misdirected filtration and filtrate spreading on the outer aspect of the nephron. Both may lead to obstruction of the tubule, disconnection from the glomerulus, and subsequent degeneration of the entire nephron. No evidence emerged to suggest that the kind of focal interstitial proliferation associated with the degeneration of injured nephrons was harmful to a neighboring healthy nephron.

Structural and functional changes in heparan sulfate proteoglycan expression associated with the myofibroblastic phenotype

The principal cells implicated as the source of the extracellular matrix in areas of progressive fibrosis are fibroblasts with the phenotypic appearance of myofibroblasts. This report describes differences in heparan sulfate proteoglycan expression between myofibroblasts and normal fibroblasts, associated with impaired responses to fibroblast growth factor-2 (FGF-2). Although both cell types responded to platelet-derived growth factor, myofibroblasts, unlike fibroblasts, did not proliferate to FGF-2. A response was acquired, however, when myofibroblasts were incubated with FGF-2 in the presence of heparan sulfate (HS) and heparin. Selective digestion with pronase, NaOH/NaBH(4), heparinase I, or low pH nitrous acid showed that each HS-glycosaminoglycan region comprised a pronase-resistant peptide separating two HS chains. The HS-glycosaminoglycan chains from myofibroblasts were larger (K(av), 0.32; molecular weight, 50 kd) than those from fibroblasts (K(av), 0.4; molecular weight, 33 kd), although their disaccharide composition was identical. The chains from myofibroblasts, however, contained three, compared to two, heparinase 1-resistant sequences separated by larger contiguous areas of low sulfation. Furthermore, although there was no difference in FGF-2-binding affinity between the two cell types, the chains secreted by myofibroblasts had twice the binding capacity of those from fibroblasts. Thus, it is likely that the difference in response to FGF-2 is because of a difference in FGF-2 sequestration and receptor interaction with FGF-2-HS complexes. A comparative investigation into HS fine structure is being undertaken to examine these findings in more detail.

Differentiation of muscle-derived cells into myofibroblasts in injured skeletal muscle

Injured muscle can initiate regeneration promptly by activating myogenic cells that proliferate and differentiate into myotubes and myofibers. However, the recovery of the injured skeletal muscle often is hindered by the development of fibrosis. We hypothesized that the early-appearing myogenic cells in the injured area differentiate into myofibroblasts and eventually contribute to the development of fibrosis. To investigate this, we transplanted a genetically engineered clonal population of muscle-derived stem cells (MC13 cells) into the skeletal muscle of immunodeficient SCID mice, which were lacerated 4 weeks after transplantation. The MC13 cells regenerated numerous myofibers in the nonlacerated muscle and these myogenic cells were gradually replaced by myofibroblastic cells in the injured muscle. Our results suggest that the release of local environmental stimuli after muscle injury triggers the differentiation of myogenic cells (including MC13 cells) into fibrotic cells. These results demonstrate the potential of muscle-derived stem cells to differentiate into different lineages and illustrate the importance of controlling the local environment within the injured tissue to optimize tissue regeneration via the transplantation of stem cells.

Mycophenolate mofetil inhibits regenerative repair in uranyl acetate-induced acute renal failure by reduced interstitial cellular response

We recently reported that transient appearance of interstitial myofibroblasts and infiltrating macrophages might play a role in cellular recovery in uranyl acetate (UA)-induced acute renal failure (ARF). Here we tested the effects of mycophenolate mofetil (MMF), which attenuates infiltration of lymphocytes, macrophages, and myofibroblasts, but does not suppress epithelial regeneration, on renal tissue repair. Rats treated with MMF (20 mg/kg/day) or vehicle were sacrificed at 2, 5, and 7 days after induction of ARF by injection of 5 mg/kg UA. Renal tissues were immunostained for bromodeoxyuridine (BrdU) and Ki67, alpha-smooth muscle actin (alpha-SMA), ED1, and CD43. The expression levels of alpha-SMA mRNA were examined by reverse transcription-polymerase chain reaction. Body weight loss or serum albumin levels were similar in MMF and vehicle rats during the experiment. In vehicle group, serum creatinine (Scr) significantly increased after day 5, but proximal tubular (PT) damage score increased as early as day 2 after UA injection. BrdU- or Ki67-positive regenerating tubular cells, ED1-positive macrophages and alpha-SMA-positive myofibroblasts significantly increased in the interstitium after day 5. In MMF-treated rats, Scr and PT damage score significantly increased at day 7 and the number of regenerating PT were significantly reduced compared with vehicle-treated rats at days 5 and 7. The numbers of macrophages and myofibroblasts and the expression of alpha-SMA mRNA were significantly lower in MMF than in vehicle rats at day 5, indicating that reduced interstitial cellular response is linked to the inhibition of regenerative repair. CD43-positive lymphocytes were significantly reduced in MMF group than in vehicle group at day 7, suggesting that lymphocyte infiltration does not seem to contribute to early regenerative response of proximal tubules. The transient appearance of myofibroblasts and macrophages in the interstitium may promote regenerative repair in UA-induced ARF in rats.

Proteoglycan expression during transforming growth factor beta -induced keratocyte-myofibroblast transdifferentiation

Keratocytes of the corneal stroma secrete a unique population of proteoglycan molecules considered essential for corneal transparency. In healing corneal wounds, keratocytes exhibit a myofibroblastic phenotype in response to transforming growth factor beta (TGF-beta), characterized by expression of alpha-smooth muscle actin. This study examined proteoglycan and collagen expression by keratocytes in vitro during the TGF-beta-induced keratocyte-myofibroblast transition. TGF-beta-treated primary bovine keratocytes developed myofibroblastic features, including actin stress fibers anchored to paxillin-containing focal adhesions, cell-associated fibronectin, alpha(5) integrin, and alpha-smooth muscle actin. Collagen I and III protein and mRNA increased in response to TGF-beta. Secretion of [(35)S]sulfate-labeled keratan sulfate proteoglycans decreased markedly in response to TGF-beta. Dermatan sulfate proteoglycans, however, increased in size and abundance. Protein and mRNA transcripts for normal stromal proteoglycans (lumican, keratocan, mimecan, and decorin) all decreased in response to TGF-beta, but protein expression and mRNA for biglycan, a proteoglycan present in fibrotic tissue, was markedly up-regulated. These results show that TGF-beta in vitro induces a proteoglycan expression pattern similar to that of corneal scars in vivo. This altered proteoglycan expression occurred coordinately with transdifferentiation of keratocytes to the myofibroblastic phenotype, implicating these cells as the source of fibrotic tissue in nontransparent corneal scars.