Preventive effect of pirfenidone against experimental sclerosing peritonitis in rats

Inhibition of STAT3 by S3I-201 suppress peritoneal fibroblast phenotype conversion and alleviate peritoneal fibrosis

Peritoneal fibrosis is a common pathological response to long-term peritoneal dialysis (PD) and a major cause for PD discontinuation. Understanding the cellular and molecular mechanisms underlying the induction and progression of peritoneal fibrosis is of great interest. In our study, in vitro study revealed that signal transducer and activator of transcription 3 (STAT3) is a key factor in fibroblast activation and extracellular matrix (ECM) synthesis. Furthermore, STAT3 induced by IL-6 trans-signalling pathway mediate the fibroblasts of the peritoneal stroma contributed to peritoneal fibrosis. Inhibition of STAT3 exerts an antifibrotic effect by attenuating fibroblast activation and ECM production with an in vitro co-culture model. Moreover, STAT3 plays an important role in the peritoneal fibrosis in an animal model of peritoneal fibrosis developed in mice. Blocking STAT3 can reduce the peritoneal morphological changes induced by chlorhexidine gluconate. In conclusion, our findings suggested STAT3 signalling played an important role in peritoneal fibrosis. Therefore, blocking STAT3 might become a potential treatment strategy in peritoneal fibrosis.

Molecular and Cellular Markers in Chlorhexidine-Induced Peritoneal Fibrosis in Mice

Understanding the tissue changes and molecular mechanisms of preclinical models is essential for creating an optimal experimental design for credible translation into clinics. In our study, a chlorhexidine (CHX)-induced mouse model of peritoneal fibrosis was used to analyze histological and molecular/cellular alterations induced by 1 and 3 weeks of intraperitoneal CHX application. CHX treatment for 1 week already caused injury, degradation, and loss of mesothelial cells, resulting in local inflammation, with the most severe structural changes occurring in the peritoneum around the ventral parts of the abdominal wall. The local inflammatory response in the abdominal wall showed no prominent differences between 1 and 3 weeks. We observed an increase in polymorphonuclear cells in the blood but no evidence of systemic inflammation as measured by serum levels of serum amyloid A and interleukin-6. CHX-induced fibrosis in the abdominal wall was more pronounced after 3 weeks, but the gene expression of fibrotic markers did not change over time. Complement system molecules were strongly expressed in the abdominal wall of CHX-treated mice. To conclude, both histological and molecular changes were already present in week 1, allowing examination at the onset of fibrosis. This is crucial information for refining further experiments and limiting the amount of unnecessary animal suffering.

Hyperspectral evaluation of peritoneal fibrosis in mouse models

Analysis of morphological changes of the peritoneal membrane is an essential part of animal studies when investigating molecular mechanisms involved in the development of peritoneal fibrosis or testing the effects of potential therapeutic agents. Current methods, such as histology and immunohistochemistry, require time consuming sample processing and analysis and result in limited spatial information. In this paper we present a new method to evaluate structural and chemical changes in an animal model of peritoneal fibrosis that is based on hyperspectral imaging and a model of light transport. The method is able to distinguish between healthy and diseased subjects based on morphological as well as physiological parameters such as blood and scattering parameters. Furthermore, it enables evaluation of changes, such as degree of inflammation and fibrosis, that are closely related to histological findings.

Enhanced Expression of Heat Shock Protein 47 in Rat Model of Peritoneal Fibrosis

← Objective

Peritoneal fibrosis is one of the serious complications of continuous ambulatory peritoneal dialysis therapy and is characterized by collagen accumulation. Heat shock protein 47 (HSP-47) is a collagen-specific molecular chaperon and is closely associated with collagen synthesis; however, the involvement of HSP-47 in the progression of peritoneal fibrosis is not fully understood.

← Design

To examine the serial pathological alterations caused by peritoneal fibrosis, we made an experimental model of peritoneal fibrosis by daily intraperitoneal injection of chlorhexidine gluconate (CG) in rats for 28 days and examined the expression of HSP-47 together with that of types I and III collagen, alpha-smooth muscle actin (αSMA), and ED-1 (a marker for macrophages) using immunohistochemistry. Rats treated with saline containing 15% ethanol were used as the control group.

← Results

In the control group, the peritoneal tissue was slightly thickened and HSP-47 was expressed in the peritoneum at day 28. In the CG group, the peritoneal tissue serially became thickened and fibrotic. The expression of HSP-47 was evident in mesothelial cells and submesothelial connective tissue after day 7 of treatment with CG, and increased thereafter. The expression of types I and III collagen and αSMA was proportionally strengthened during our experiments. ED-1–positive cells were present in thickened areas with abundant proliferation of collagen fiber. The number of cells positive for ED-1 increased gradually and reached a maximum at day 21.

← Conclusion

Our results indicate that, in a rat experimental model of peritoneal fibrosis, the expression of HSP-47 is associated with the progression of peritoneal fibrosis.

Abdominal Cocoon: An Animal Model for a Complication of Peritoneal Dialysis

Objective

The purpose of this work was to develop an animal model of sclerosing encapsulating peritonitis, a complication of continuous ambulatory peritoneal dialysis in which the intestines are conglomerated into an ovoid cocoonlike structure.

Design

Toward this end, rats were injected with a chemical irritant (household bleach) intraperitoneally. One week later, before the resultant peritonitis could cause adhesions, 10 or 25 mL of fresh whole rat blood was injected into the peritoneal cavity. Two weeks later, the effect of the treatments was evaluated by macroscopic and microscopic study.

Results

The irritant caused a chemical peritonitis. The subsequently injected blood clotted on the surfaces of the inflamed intestines, and contraction of the clot (syneresis) was responsible for bringing the intestinal loops together. This conglomeration was made permanent by the fibrosis evoked by the chemical peritonitis. The end result was an ovoid encapsulated mass of intestines and other viscera.

Conclusion

An animal model for an abdominal cocoon has been produced. It can be used for studies of the pathogenesis and prevention of this complication of peritoneal dialysis.

The Role of Peritoneal Fibrosis in Encapsulating Peritoneal Sclerosis

Encapsulating peritoneal sclerosis (EPS) is a serious complication of long-term continuous peritoneal dialysis therapy. The progression of EPS has been classified into four stages by Kawanishi and colleagues: pre-EPS, and the inflammatory, encapsulating, and ileus stages. The key issue is how to diagnose EPS early enough to allow for curative treatment. In this article, we review the mechanisms of peritoneal fibrosis, especially from the perspective of collagen synthesis, and the potential role of that fibrosis in the pathogenesis of EPS.

Experimental Animal Models of Encapsulating Peritoneal Sclerosis

Encapsulating peritoneal sclerosis (EPS) is an infrequent, but extremely serious complication of long-term peritoneal dialysis. The cause of EPS is unclear, but the low incidence suggests that it is most likely multifactorial. The elucidation of developmental pathways and predictive markers of EPS would facilitate the identification and management of high-risk patients.

Animal models are often used to define pathways of disease progression and to test strategies for treatment and prevention in the patient population. Ideally such models could help to define the cause of EPS and its developmental pathways, to facilitate the identification of contributing factors and predictive markers, and to provide a system to test therapeutic strategies.

Researchers have studied several rodent models of EPS that rely on chronic chemical irritation (for example, bleach, low-pH solution, chlorhexidine gluconate) to induce peritoneal sclerosis and abdominal encapsulation. Development in all models is progressive, with inflammation giving way to peritoneal fibrosis or sclerosis with accumulating membrane damage, culminating in cocoon formation. Microscopic findings are similar to those proposed as diagnostic criteria for clinical EPS: an initial inflammatory infiltrate and submesothelial thickening, collagen deposition, and activation and proliferation of peritoneal fibroblasts. The potential to block progression of peritoneal sclerosis in these models by anti-inflammatory, antifibrotic, and antiangiogenic agents, and by inhibitors of the renin–angiotensin system have been demonstrated.

Animal models based on clinically relevant risk factors (for example, uremia, peritonitis, and long-term exposure to dialysis solutions) now represent the next step in model development.

A Historical Review of Encapsulating Peritoneal Sclerosis

Publications providing insights into the pathophysiology of, and therapeutic strategies for, EPS are the focus of the present review. Referenced publications are limited to those written in English.

Regulatory Macrophages Inhibit Alternative Macrophage Activation and Attenuate Pathology Associated with Fibrosis

Diversity and plasticity are the hallmarks of macrophages. The two most well-defined macrophage subsets are the classically activated macrophages (CAMϕs) and the IL-4-derived alternatively activated macrophages (AAMϕs). Through a series of studies, we previously identified and characterized a distinct population of macrophages with immunoregulatory functions, collectively termed regulatory macrophages (RMϕs). Although considerable advances have been made in understanding these various macrophage subsets, it is not known whether macrophages of one activation state can influence the other. In this study, we examined whether RMϕs capable of inhibiting inflammatory responses of CAMϕs could also inhibit AAMϕs and their profibrotic responses. Our results demonstrated that RMϕs significantly dampened the alternate activation phenotype of AAMϕs generated in vitro and intrinsically occurring AAMϕs from TACI^-/- macrophages. Further, RMϕs inhibited AAMϕ-promoted arginase activity and fibroblast proliferation in vitro. This inhibition occurred regardless of the strength, duration, and mode of alternative activation and was only partially dependent on IL-10. In the chlorhexidine gluconate-induced peritoneal fibrosis model, AAMϕs worsened the fibrosis, but RMϕs rescued mice from AAMϕ-mediated pathological conditions. Taken together, our study demonstrates that RMϕs are a specialized subset of macrophages with a nonredundant role in limiting overt proregenerative functions of AAMϕs, a role distinct from their well-defined role of suppression of inflammatory responses by CAMϕs.

Tamoxifen and bone morphogenic protein-7 modulate fibrosis and inflammation in the peritoneal fibrosis model developed in uremic rats

Background

Peritoneal fibrosis (PF) represents a long-term complication of peritoneal dialysis (PD), affecting peritoneal membrane (PM) integrity and function. Understanding the mechanisms underlying PF development in an uremic environment aiming alternative therapeutic strategies for treating this process is of great interest. The aim of this study was to analyze the effects of tamoxifen (TAM) and recombinant BMP7 (rBMP7) in an experimental model of PF developed in uremic rats.

Methods

To mimic the clinical situation of patients on long-term PD, a combo model, characterized by the combination of PF and CKD with severe uremia, was developed in Wistar rats. PF was induced by intraperitoneal (IP) injections of chlorhexidine gluconate (CG), and CKD was induced by an adenine-rich diet. Uremia was confirmed by severe hypertension, increased blood urea nitrogen (BUN> 120 mg/dL) and serum creatinine levels (> 2 mg/dL). Uremic rats with PF were treated with TAM (10 mg/Kg by gavage) or BMP7 (30 μg/Kg, IP). Animals were followed up for 30 days.

Results

CG administration in uremic rats induced a striking increase in PM thickness, neoangiogenesis, demonstrated by increased capillary density, and failure of ultrafiltration capacity. These morphological and functional changes were blocked by TAM or rBMP7 treatment. In parallel, TAM and rBMP7 significantly ameliorated the PM fibrotic response by reducing α-SMA, extracellular matrix proteins and TGF-ß expression. TAM or rBMP7 administration significantly inhibited peritoneal Smad3 expression in uremic rats with PF, prevented Smad3 phosphorylation, and induced a remarkable up-regulation of Smad7, an intracellular inhibitor of TGFβ/Smad signaling, contributing to a negative modulation of profibrotic genes. Both treatments were also effective in reducing local inflammation, possibly by upregulating IκB-α expression in the PM of uremic rats with PF. In vitro experiments using primary peritoneal fibroblasts activated by TGF-ß confirmed the capacity of TAM or rBMP7 in blocking inflammatory mediators, such as IL-1ß expression.

Conclusions

In conclusion, these findings indicate important roles of TGF-ß/Smad signaling in PF aggravated by uremia, providing data regarding potential therapeutic approaches with TAM or rBMP7 to block this process.

Electronic supplementary material

The online version of this article (10.1186/s10020-019-0110-5) contains supplementary material, which is available to authorized users.

Progressive Fibrosis: A Progesterone- and KLF11-Mediated Sexually Dimorphic Female Response

Progressive scarring is ubiquitous postoperatively and in an array of chronic systemic diseases. Recent studies indicate that such scarring has a high female propensity; females are also almost exclusively affected by endometriosis, a common sex steroid-dependent fibrotic disease. Endometriosis-related fibrosis is regulated epigenetically through transcription factor Krüppel-like factor 11 (KLF11). In response to surgical induction of endometriosis, Klf11-/- female mice develop significant fibrosis in contrast to wild-type mice. We therefore hypothesized that female fibrotic predilection was mediated by differential sex steroid regulation of KLF11/collagen 1a1 signaling and investigated the fibrotic response in wild-type and Klf11-/- male and female animals using a sterile peritonitis model. Fibrosis selectively developed in Klf11-/- females. Fibrosis in these animals was almost completely abrogated by ovariectomy. Ovariectomized animals were selectively supplemented with estradiol, medroxyprogesterone acetate (MPA), or dihydrotestosterone; fibrosis was only observed in mice exposed to MPA. Fibrosis therefore selectively developed in Klf11-/- female mice in response to physiological or pharmacological progesterone. The fibrotic response in these animals was also mitigated in response to antiprogestin therapy. Profibrotic gene expression was activated in a primary human peritoneal cell line in response to KLF11 short hairpin RNA and MPA but not estradiol. KLF11/collagen 1a1 signaling previously shown to be linked to fibrosis was thus selectively dysregulated in MPA-treated cells. Our in vivo and in vitro findings in an animal model and human cells, respectively, suggest that progressive fibrotic scarring is a sexually dimorphic response irrespective of etiology; moreover, it is responsive to novel, individualized therapeutic intervention.

Evaluation for Peritoneal Injury at an Early Stage Using Dual Macromolecular Markers

Long-term peritoneal dialysis (PD) frequently produces morphological and functional changes of the peritoneum, making continuation of PD difficult. Therefore, it is necessary to evaluate peritoneal injury at an early stage and develop appropriate therapies. The aims of the present study were to evaluate peritoneal injury at an early stage and assess a drug for prevention of peritoneal injury using our previously developed novel evaluation method. Peritoneal injury was induced in model animals by intraperitoneal injection of methylglyoxal (MGO) for 1 to 5 consecutive days or chlorhexidine digluconate (CG) for 1 to 14 consecutive days. Tetramethylrhodamine-dextran (RD)-10 and fluorescein isothiocyanate-dextran (FD)-2000 were then injected into the peritoneal cavity and recovered after 120 min to evaluate peritoneal injury. The ratio of the concentration of RD-10 to FD-2000 (RD-10/FD-2000 ratio) significantly decreased in animals that had been treated with MGO or CG for 1 d. Moreover, the RD-10/FD-2000 ratio significantly increased in CG- and thalidomide-treated animals. The RD-10/FD-2000 ratio can be used to evaluate peritoneal injury at an early stage and assess the drug efficacy of thalidomide for prevention of peritoneal injury. This study will contribute to the development of therapeutic treatments for peritoneal injury.

Effect of Pirfenidone on Vascular Proliferation, Inflammation and Fibrosis in an Abdominal Adhesion Rat Model

AIM

To study the efficacy of pirfenidone for prevention of postoperative adhesion formation in an adhesion rat model.

MATERIALS AND METHODS

Eighteen female Wistar rats were subjected to right-sided parietal peritoneum and right uterine horn adhesion model. Rats were randomized into three groups: group 1 (control) (closure of midline abdominal incision without any agent administration), group 2 (closure of incision after intraperitoneal administration of pirfenidone), and group 3 (closure of incision and only oral administration of pirfenidone for 14 days). Relaparotomy was performed 14 days after the first surgery. Effect of pirfenidone on adhesion formation was assessed on light microscopy by scoring vascular proliferation, inflammation, fibrosis, and collagen formation in the scarred tissue. Effect of pirfenidone on inflammation was assessed by measurement of transforming growth factor-β and interleukin-17 levels in scarred tissue.

RESULTS

The degree of vascular proliferation (1.32 ± 0.39 versus 2.34 ± 0.46, p < 0.001), inflammation (1.60 ± 0.70 versus 2.60 ± 0.52, p < 0.01), and fibrosis (1.50 ± 0.53 versus 2.40 ± 0.52, p < 0.01) were less prominent in group 2 compared to group 1, respectively. Only vascular proliferation was found to be less prominent in group 3 compared to group 1 (1.60 ± 0.42 versus 2.34 ± 0.46, p < 0.01). Intraperitoneal and oral administration of pirfenidone reduced tissue levels of inflammatory markers (TGF-β and IL-17) in parietal and visceral peritoneum compared to control group. Intraperitoneal administration of pirfenidone compared to oral administration was more effective in reducing tissue levels of inflammatory markers.

CONCLUSION

Pirfenidone is an effective agent on the prevention of postoperative vascular proliferation, inflammation and fibrosis in scarred tissue particularly with intraperitoneal administration.

Animal Models of Peritoneal Dialysis: Thirty Years of Our Own Experience

Experimental animal models improve our understanding of technical problems in peritoneal dialysis PD, and such studies contribute to solving crucial clinical problems. We established an acute and chronic PD model in nonuremic and uremic rats. We observed that kinetics of PD in rats change as the animals are aging, and this effect is due not only to an increasing peritoneal surface area, but also to changes in the permeability of the peritoneum. Changes of the peritoneal permeability seen during chronic PD in rats are comparable to results obtained in humans treated with PD. Effluent dialysate can be drained repeatedly to measure concentration of various bioactive molecules and to correlate the results with the peritoneal permeability. Additionally we can study in in vitro conditions properties of the effluent dialysate on cultured peritoneal mesothelial cells or fibroblasts. We can evaluate acute and chronic effect of various additives to the dialysis fluid on function and permeability of the peritoneum. Results from such study are even more relevant to the clinical scenario when experiments are performed in uremic rats. Our experimental animal PD model not only helps to understand the pathophysiology of PD but also can be used for testing biocompatibility of new PD fluids.

Th2-biased GATA-3 transgenic mice developed severe experimental peritoneal fibrosis compared with Th1-biased T-bet and Th17-biased RORγt transgenic mice

Encapsulating peritoneal sclerosis is one of the most serious complications of long-term peritoneal dialysis. The pathogenesis of encapsulating peritoneal sclerosis has not been elucidated, but several putative factors necessary for the development of peritoneum fibrosis (PF) have been reported. However, the roles of T helper (Th) cells in the progression of PF are unknown. The purpose of this study was to clarify the roles of Th1, Th2, and Th17 cells in the progression of PF. T-bet, GATA-3, and RORγt are Th1, Th2, and Th17 lineage commitment transcription factors, respectively. We previously generated Th1-biased (T-bet transgenic (Tg)) mice, Th2-biased (GATA-3 Tg) mice, and Th17-biased (RORγt Tg) mice. In this study, Th1, Th2, Th17-biased, and wild-type mice were administered chlorhexidine gluconate (CG) intraperitoneally and analyzed on day 21. CG-injected GATA-3 Tg mice showed a distended intestinal tract and developed marked thickening of the submesothelial space compared with the other groups. CG-injected GATA-3 Tg mice also showed significant expression of α-SMA positive cells, macrophages, and collagen III in the submesothelium. In contrast, CG-injected T-bet Tg mice only developed mild peritoneal fibrosis. Cytokines analysis in peritoneal fluid showed that IFN-γ was significantly increased in CG-injected T-bet Tg mice and that IL-13 was significantly increased in CG-injected GATA-3 Tg mice. Moreover, intraperitoneal administration of IFN-γ improved PF in GC-injected wild-type mice. Our results suggest that Th2 cells may play roles in the development of experimental PF and that Th1 cells may alleviate the severity of experimental PF.

New insights into therapeutic strategies for the treatment of peritoneal fibrosis: learning from histochemical analyses of animal models

Encapsulating peritoneal sclerosis (EPS) is a fatal complication that can occur in patients undergoing long-term peritoneal dialysis. It is characterized by bowel obstruction and marked sclerotic thickening of the peritoneal membrane. Although the mechanisms underlying the development of EPS are complex, angiogenesis, inflammation, and peritoneal fibrosis are known to be essential factors. Now, several animal models that exhibit EPS have pathophysiology similar to that of human EPS and have been proposed for use in research to provide insights into it. Recent histochemical methods also help us to understand the pathophysiology of EPS. Advances in basic research based on the findings in those animal models have enabled the development of several strategies for the prevention and treatment of EPS. We describe here interventional studies in some animal models for peritoneal fibrosis, one of the histological disorders findings characteristic to EPS, and we highlight the need for a sophisticated animal model that closely resembles human conditions.

Multiparametric and semiquantitative scoring systems for the evaluation of mouse model histopathology--a systematic review

BACKGROUND

Histopathology has initially been and is still used to diagnose infectious, degenerative or neoplastic diseases in humans or animals. In addition to qualitative diagnoses semiquantitative scoring of a lesion`s magnitude on an ordinal scale is a commonly demanded task for histopathologists. Multiparametric, semiquantitative scoring systems for mouse models histopathology are a common approach to handle these questions and to include histopathologic information in biomedical research.

RESULTS

Inclusion criteria for scoring systems were a first description of a multiparametric, semiquantiative scoring systems which comprehensibly describe an approach to evaluate morphologic lesion. A comprehensive literature search using these criteria identified 153 originally designed semiquantitative scoring systems for the analysis of morphologic changes in mouse models covering almost all organs systems and a wide variety of disease models. Of these, colitis, experimental autoimmune encephalitis, lupus nephritis and collagen induced osteoarthritis colitis were the disease models with the largest number of different scoring systems. Closer analysis of the identified scoring systems revealed a lack of a rationale for the selection of the scoring parameters or a correlation between scoring parameter value and the magnitude of the clinical symptoms in most studies.

CONCLUSION

Although a decision for a particular scoring system is clearly dependent on the respective scientific question this review gives an overview on currently available systems and may therefore allow for a better choice for the respective project.

Involvement of leptin in the progression of experimentally induced peritoneal fibrosis in mice

Leptin is a hormone mainly produced by white adipose cells, and regulates body fat and food intake by acting on hypothalamus. Leptin receptor is expressed not only in the hypothalamus but in a variety of peripheral tissues, suggesting that leptin has pleiotropic functions. In this study, we investigated the effect of leptin on the progression of peritoneal fibrosis induced by intraperitoneal injection of chlorhexidine gluconate (CG) every other day for 2 or 3 weeks in mice. This study was conducted in male C57BL/6 mice and leptin-deficient ob/ob mice. Peritoneal fluid, blood, and peritoneal tissues were collected 15 or 22 days after CG injection. CG injection increased the level of leptin in serum and peritoneal fluid with thickening of submesothelial compact zone in wild type mice, but CG-injected ob/ob mice attenuate peritoneal fibrosis, and markedly reduced the number of myofibroblasts, infiltrating macrophages, and blood vessels in the thickened submesothelial area. The 2-week leptin administration induced a more thickened peritoneum in the CG-injected C57BL/6 mice than in the PBS group. Our results indicate that an upregulation of leptin appears to play a role in fibrosis and inflammation during peritoneal injury, and reducing leptin may be a therapeutically potential for peritoneal fibrosis.

A novel role of the Sp/KLF transcription factor KLF11 in arresting progression of endometriosis

Endometriosis affects approximately 10% of young, reproductive-aged women. Disease associated pelvic pain; infertility and sexual dysfunction have a significant adverse clinical, social and financial impact. As precise disease etiology has remained elusive, current therapeutic strategies are empiric, unfocused and often unsatisfactory. Lack of a suitable genetic model has impaired further translational research in the field. In this study, we evaluated the role of the Sp/KLF transcription factor KLF11/Klf11 in the pathogenesis of endometriosis. KLF11, a human disease-associated gene is etiologically implicated in diabetes, uterine fibroids and cancer. We found that KLF11 expression was diminished in human endometriosis implants and further investigated its pathogenic role in Klf11-/- knockout mice with surgically induced endometriotic lesions. Lesions in Klf11-/- animals were large and associated with prolific fibrotic adhesions resembling advanced human disease in contrast to wildtype controls. To determine phenotype-specificity, endometriosis was also generated in Klf9-/- animals. Unlike in Klf11-/- mice, lesions in Klf9-/- animals were neither large, nor associated with a significant fibrotic response. KLF11 also bound to specific elements located in the promoter regions of key fibrosis-related genes from the Collagen, MMP and TGF-β families in endometrial stromal cells. KLF11 binding resulted in transcriptional repression of these genes. In summary, we identify a novel pathogenic role for KLF11 in preventing de novo disease-associated fibrosis in endometriosis. Our model validates in vivo the phenotypic consequences of dysregulated Klf11 signaling. Additionally, it provides a robust means not only for further detailed mechanistic investigation but also the ability to test any emergent translational ramifications thereof, so as to expand the scope and capability for treatment of endometriosis.

Pyrrole-imidazole polyamide targeting transforming growth factor β1 ameliorates encapsulating peritoneal sclerosis

OBJECTIVE

Encapsulating peritoneal sclerosis (EPS) is a devastating fibrotic complication in patients treated with peritoneal dialysis (PD). Transforming growth factor β1 (TGF-β1) is a pivotal factor in the induction of EPS.

METHODS

To develop pyrrole-imidazole (PI) polyamide, a novel gene silencer, targeted to the TGF-β1 promoter (Polyamide) for EPS, we examined the effects of Polyamide on messenger RNA (mRNA) expression of TGF-β1, vascular endothelial growth factor (VEGF), and extracellular matrix (ECM) in mesothelial cells in vitro, and on the thickness of injured peritoneum evaluated by histology and high-resolution regional elasticity mapping in rats in vivo.

RESULTS

Polyamide significantly lowered mRNA expression of TGF-β1 and ECM in vitro. Polyamide labeled with fluorescein isothiocyanate was taken up into the injured peritoneum and was strongly localized in the nuclei of most cells. Polyamide 1 mg was injected intraperitoneally 1 or 3 times in rats receiving a daily intraperitoneal injection of chlorhexidine gluconate and ethanol (CHX) for 14 days. Polyamide significantly suppressed peritoneal thickening and the abundance of TGF-β1 and fibronectin mRNA, but did not affect expression of VEGF mRNA in the injured peritoneum. Elasticity distribution mapping showed that average elasticity was significantly lower in Polyamide-treated rats than in rats treated solely with CHX.

CONCLUSIONS

Polyamide suppressed the stiffness, ECM formation, and thickening of the injured peritoneum that occurs during EPS pathogenesis. These data suggest that PI polyamide targeted to the TGF-β1 promoter will be a specific and feasible therapeutic strategy for patients with EPS.

The antifibrotic agent pirfenidone inhibits angiotensin II-induced cardiac hypertrophy in mice

Pirfenidone (5-methyl-1-phenyl-2-[(1)H]-pyridone) is an effective drug for idiopathic interstitial pneumonia that can prevent and reverse tissue fibrosis in several organs. Therefore, we investigated whether pirfenidone has a potential role in preventing angiotensin II (Ang II)-induced cardiac hypertrophy. A cardiac hypertrophic mouse model was created using an Ang II infusion (200 ng kg(-1) min(-1)) in wild-type mice for 2 weeks. Mice were divided into the following three groups: a saline-infused (control) group, an Ang II infusion (vehicle) group and an Ang II infusion+pirfenidone-treated (PFD) group, which received pirfenidone (300 mg kg(-1) per day) by gastric gavage during the Ang II infusion. At 2 weeks, we assessed hemodynamics and cardiac function and investigated tissue fibrosis of the myocardium histologically and genetically. Blood pressure in the vehicle group was significantly increased compared to the control group. Although blood pressure was not different between the vehicle and PFD groups, heart weight was significantly decreased in the PFD group. Echocardiography revealed that left ventricular hypertrophy was significantly increased in the vehicle group vs. the control group. Interestingly, pirfenidone significantly inhibited this effect. Continuous infusion of Ang II increased the perivascular and interstitial tissue fibrosis, and pirfenidone inhibited these fibrotic changes. Pirfenidone also inhibited Ang II-induced hypertrophy. In the vehicle group, the mRNA expressions of atrial natriuretic peptide, brain natriuretic peptide and transforming growth factor-β1 were increased, which was significantly inhibited by pirfenidone. Furthermore, the expression of mineralocorticoid receptors was attenuated by pirfenidone. These results indicate that pirfenidone might be effective as an antifibrotic drug in the treatment of cardiac hypertrophy induced by hypertension.

Difference in the expression of hormone receptors and fibrotic markers in the human peritoneum--implications for therapeutic targets to prevent encapsulating peritoneal sclerosis

OBJECTIVE

Encapsulating peritoneal sclerosis (EPS) is a rare but life-threatening complication of peritoneal dialysis (PD). The optimal management of patients with EPS is uncertain. In the present study, we investigated differences in the expression of nuclear receptors [progesterone (PR), androgen (AR), vitamin D (VDR), and glucocorticoid (GCR)] in the human peritoneum. We also investigated estrogen receptor (ER), matrix metalloproteinase 9 (MMP9), and transforming growth factor β1 (TGFβ1) in the context of their potential role in tamoxifen therapy.

METHODS

We analyzed clinical and histologic characteristics of 72 peritoneal biopsy specimens (22 from EPS patients, 11 from PD patients, 15 from uremic patients, and 24 from control subjects undergoing hernia repair). For immunophenotyping, we used antibodies against VDR, GCR, ER, PR, AR, MMP9, and TGFβ1.

RESULTS

In human peritoneum, VDR and GCR are highly expressed (98.6% and 87.3% respectively). Except in the case of VDR (p = 0.0012), we observed no significant difference in receptor expression between the groups. Expression of ER and PR was sparse (11.4% and 31% respectively), with higher expression in women, and AR was absent. Minimal MMP9 expression and moderate TGFβ1 expression were observed in all groups. The differences between the groups were nonsignificant.

CONCLUSIONS

Nuclear receptors are present in human peritoneum. Except in the case of VDR, the pattern for any one group is nonspecific. Glucocorticoids, vitamin D, and angiotensin converting-enzyme inhibitors or angiotensin II receptor blockers (via the vitamin D/angiotensin II pathway) might be suitable interventions for preservation of the integrity of the peritoneal membrane. The mechanism of action of tamoxifen is still not elucidated, ER expression in the peritoneum is sparse, and data about the studied pathways (MMP9, TGFβ) are inconsistent.

Rho-kinase inhibition ameliorates peritoneal fibrosis and angiogenesis in a rat model of peritoneal sclerosis

BACKGROUND

Peritoneal fibrosis (PF) and angiogenesis are typical morphological changes, leading to loss of peritoneal functions in patients undergoing peritoneal dialysis. The small G protein, Rho, and its downstream effector Rho-kinase have been shown to be involved in the tissue fibrosis process. This study was undertaken to investigate the role of Rho-kinase in the pathogenesis of these alterations.

METHODS

PF was induced by intraperitoneal administration of chlorhexidine (CHX) in male rats (CHX group). These rats were treated with a Rho-kinase inhibitor, fasudil (Fas group). Human pleural mesothelial cells, MeT-5A cells, were stimulated by glucose with or without another Rho-kinase inhibitor, Y-27632.

RESULTS

Peritoneal damage including peritoneal thickening, fibrous changes, macrophage migration and angiogenesis were evident in the CHX group and were ameliorated in the Fas group. The expression of markers of tissue fibrosis, such as transforming growth factor (TGF)-β, fibronectin and α-smooth muscle cell actin, were increased in the CHX group and were downregulated by fasudil. Similar results were also seen with an inducer of angiogenesis, vascular endothelial growth factor (VEGF). Rho-kinase was activated in the peritoneum of the CHX group, which was inhibited by fasudil. In MeT-5A cells, high glucose increased TGF-β expression and VEGF secretion, which were blocked by Y-27632.

CONCLUSIONS

The activation of Rho-kinase is involved in peritoneal damage at multiple stages including tissue fibrosis and angiogenesis. The inhibition of Rho-kinase constitutes a novel strategy for the treatment of PF.

Update on potential medical treatments for encapsulating peritoneal sclerosis; human and experimental data

Encapsulating peritoneal sclerosis (EPS) is an infrequent but serious complication of peritoneal dialysis (PD). The pathogenesis is unknown but speculation is ongoing. The current management of EPS focuses on prevention and treatment of the inflammatory and fibrotic changes at the level of the peritoneal membrane with immunosuppressive and antifibrotic agents, respectively. This article reviews the currently available human and animal data on potential agents to prevent and/or treat EPS. We propose a strategy for early diagnose EPS in an attempt to avoid the development of the full-blown and potentially life-threatening clinical syndrome of EPS. Future research should focus on studying potential prophylactic and therapeutic agents in humans in large, multicenter, randomized trials but also on early detection of EPS in the inflammatory phase by means of biomarkers and the establishment of a composite EPS score.

Pirfenidone treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a discrete clinicopathologic entity defined by the presence of usual interstitial pneumonia on high-resolution CT scan and/or open lung biopsy and the absence of an alternate diagnosis or exposure explaining these findings. There are currently no FDA-approved therapies available to treat this disease, and the 5-year mortality is ∼80%. The pyridone derivative pirfenidone has been studied extensively as a possible therapeutic agent for use in this deadly disease. This review will present the unique clinical features and management issues encountered by physicians caring for IPF patients, including the poor response to conventional therapy. The biochemistry and preclinical efficacy of pirfenidone will be discussed along with a comprehensive review of the clinical efficacy, safety, and side effects and patient-centered foci such as quality of life and tolerability. It is hoped that this information will lend insight into the complex issues surrounding the use of pirfenidone in IPF and lead to further investigation of this agent as a possible therapy in this devastating disease.

Aliskiren ameliorates chlorhexidine digluconate-induced peritoneal fibrosis in rats

BACKGROUND

Peritoneal fibrosis (PF) is a recognized complication of long-term peritoneal dialysis (PD) and can lead to ultrafiltration failure. The present study was designed to investigate the protective effects of aliskiren on chlorhexidine digluconate-induced PF in rats.

MATERIALS AND METHODS

The PF was induced in Sprague-Dawley rats by daily administration of 0.5 mL 0.1% chlorhexidine digluconate in normal saline via PD tube for 1 week. Rats received daily intravenous injections of low-dose aliskiren (1 mg kg(-1)) or high-dose aliskiren (10 mg kg(-1)) for 1 week. After 7 days, conventional 4.25% Dianeal (30 mL) was administered via a PD catheter with a dwell time of 4 h and assessed of peritoneal function. At the end of dialysis, rats were sacrificed and the liver peritoneum was harvested for microscopically and immunohistochemistry.

RESULTS

There was no significant difference in mean arterial pressure and heart rate between groups. After 4 h of PD, the D(4)/P(4) urea level was reduced, the D(4)/D(0) glucose level, serum and dialysate transforming growth factor-beta1 (TGF-beta1) level was increased, the liver peritoneum was markedly thicker, and the expression of TGF-beta1, alpha-smooth muscle actin (alpha-SMA), fibronectin, collagen, and vascular endothelial growth factor (VEGF) were elevated in the PS group compared with the vehicle group. Aliskiren decreased the serum and dialysate TGF-beta1 level, decreased the thickness of the liver peritoneum, and decreased the expression of TGF-beta1, alpha-SMA, fibronectin, collagen, and VEGF-positive cells in liver peritoneum. Moreover, high-dose aliskiren had better protective effects against PF than low dose in rats.

CONCLUSIONS

Aliskiren protected against chlorhexidine digluconate-induced PF in rats by decreasing TGF-beta1 production.

Thalidomide suppresses sclerosing encapsulating peritonitis in a rat experimental model

Peritoneal dialysis is an alternative treatment of patients with end-stage renal disease. Sclerosing encapsulating peritonitis is a life-threatening complication of continuous ambulatory peritoneal dialysis. The aim of the present study was to evaluate the effect of thalidomide, which is used for the treatment of various inflammatory and autoimmune diseases, on the development of sclerosing encapsulating peritonitis induced by chlorhexidine gluconate (CG). A peritoneal fibrosis model was established using rats treated intraperitoneally with injections of CG. Thalidomide was administered orally at a dose of 100 mg/kg three times per week. When compared with CG-treated rats, thalidomide (100 mg/kg orally)-treated mice subjected to CG-induced peritoneal fibrosis experienced a significantly lower rate in the extent and severity of histological signs of peritoneal injury. Thalidomide also caused a substantial reduction of 1) the rise in myeloperoxidase activity (mucosa); 2) the expression in the tissue of TNF-alpha, IL-1beta, transforming growth factor-beta, and vascular endothelial growth factor; 3) the increase in staining (immunohistochemistry) for nitrotyrosine and for poly(ADP ribose), as well as 4) the nuclear factor-kappaB activation caused by CG in the peritoneum. Thus, thalidomide treatment reduces the degree of peritoneal fibrosis caused by CG. We propose that this evidence may help clarify the potential therapeutic actions of thalidomide in patients with peritoneal fibrosis.

Tissue-type plasminogen activator deficiency attenuates peritoneal fibrosis in mice

Peritoneal fibrosis (PF) is an important complication of peritoneal dialysis therapy. The present study was performed to examine the mechanisms of PF in view of the plasminogen activator (PA)/plasmin/matrix metalloproteinase (MMP) cascade. PF was induced in tissue-type PA (tPA) deficient mice and wild-type mice by intraperitoneal injection of chlorhexidine gluconate. Mice were killed on day 21, and tissue samples were taken. Histopathological studies were performed. Plasmin activity, gelatinases activity, and the levels of tPA, transforming growth factor-β1 (TGF-β1), and MMP-2 mRNA were determined. Protein levels of MMP-3, tissue inhibitor of metalloproteinases (TIMP)-1, -2, and -3, phospho-Smad3, membrane-type 1 (MT1)-MMP, and MT3-MMP were also studied. On day 21, tPA +/+ mice showed severe PF, whereas tPA −/− mice showed milder change. Submesothelial basement membranes were dissolved in tPA +/+ mice while they were relatively preserved in tPA −/− mice. The levels of macrophage infiltration, staining for α-smooth muscle actin (α-SMA) and collagen type III, and vascular density were all significantly lower in tPA −/− mice than in tPA +/+ mice. The levels of plasmin activity, pro- and active MMP-2, mRNA expression of tPA and TGF-β1, and phospho-Smad3 protein were also lower in tPA −/− mice. No difference was observed between the two groups concerning the protein levels of MMP-3, TIMP-1, TIMP-2, TIMP-3, MT1-MMP, or MT3-MMP. These results indicate that the presence of tPA enhances inflammation, angiogenesis, and fibrogenesis in the peritoneum of the PF model mice. Activation of the PA/plasmin/MMP cascade may play a pivotal role in the pathogenesis of PF.

Tissue Factor and Factor V Involvement in Rat Peritoneal Fibrosis

Objective

Fibrin deposition on the peritoneum has been frequently observed in peritoneal fibrosis induced by long-term peritoneal dialysis. The present study was conducted to clarify the contribution of factor Xa through tissue factor and factor V expression in peritoneal fibrosis.

Methods

Wistar rats were intraperitoneally injected with chlorhexidine gluconate (CG) every day. For the interventional study, the factor Xa inhibitor fondaparinux was subcutaneously administered. After 28 days of CG injection, peritoneal specimens were examined by immunohistochemical analyses and in situ hybridization.

Results

The peritoneal submesothelial compact zone was observed to be markedly thicker in the CG-injected groups than in the normal group, and that thickness was dose dependent. Immunohistochemical study revealed massive fibrin, fibronectin, and type IV collagen depositions in the CG-injected groups, which was markedly higher than that in the normal group. Macrophage infiltration and staining for tissue factor, factor V, factor X, and protease-activated receptor-2 were intense in the CG-injected groups and negative/trace in the normal group. Tissue factor and factor V mRNAs were abundant in cells in the thickened peritoneum. A double-labeling experiment revealed that tissue factor was observed mainly in macrophages, and factor V was abundantly distributed in the fibrotic tissue together with macrophages. Fondaparinux treatment decreased the thickness of submesothelial fibrotic tissue, and size and number of CD31-positive vessels.

Conclusion

These results suggest that expression of tissue factor and factor V in infiltrated macrophages, together with factor X deposition, may progress angiogenesis and accumulation of extracellular matrix components, partly via profibrotic and procoagulant mechanisms in the peritoneum after inflammatory stimulation.

An Experimental Model of Encapsulating Peritoneal Sclerosis

In Japan, only about 3% of all patients with end-stage renal disease are maintained by continuous ambulatory peritoneal dialysis (CAPD). Although the reasons for the low proportion of patients receiving CAPD are multifactorial, encapsulating peritoneal sclerosis (EPS), a fatal complication of CAPD, is a major factor. In 1995 we developed a rat model of EPS, and in 2001 also developed an EPS model in mice. These rodent EPS models are reliable, reproducible, and inexpensive and have been used by other investigators. The renin–angiotensin system negatively regulates the transforming growth factor-beta signaling pathway, which plays a major role in tissue fibrosis. To investigate the anti-EPS effect of renin–angiotensin system inhibition, an angiotensin-converting enzyme inhibitor, quinapril, was administered to an EPS model in mice. Quinapril was found to inhibit EPS, both macro- and microscopically, in a dose-dependent manner. We report our experience of developing the experimental in vivo EPS model, and the inhibitory effect of this angiotensin-converting enzyme inhibitor on EPS.

Development of a Peritoneal Sclerosis Rat Model Using a Continuous-Infusion Pump

Objective

Encapsulating peritoneal sclerosis (EPS) is a serious complication of continuous ambulatory peritoneal dialysis. Previous studies have created peritoneal sclerosis rat models using daily intraperitoneal injection of chlorhexidine gluconate (CG), but this technique is cumbersome and thickening of the peritoneum makes it difficult to evaluate the injection site. We therefore aimed to make a rat model using a continuous-infusion pump.

Methods

Various concentrations of CG (5%, 8%, 10%, 12%, and 14%) in ethanol were dissolved in saline within the infusion pumps, each of which was placed in the lower abdominal cavity of a male Wister rat. After a peritoneal equilibration test was performed, the rats were sacrificed and the lower anterior parietal and visceral peritoneum was removed. Each excised peritoneum was analyzed by macroscopic and microscopic examinations, including immunohistochemistry for the expression of transforming growth factor-beta 1 (TGF-β1), vascular endothelial growth factor (VEGF), and alpha-smooth muscle actin (αSMA). The results were compared with those of control rats injected with ethanol dissolved in saline within the infusion pump and with no-pump rats.

Results

Two of the 5 rats in the 12% CG group and 3 of the 5 rats in the 14% CG group died of ileus within 14 days. All the rats in the 5%, 8%, and 10% CG groups survived to 28 days. Macroscopic examination in the 10% CG group showed bowel dilatation, bowel adhesion, and bloody ascites, similar to those seen in human EPS patients. All rats in each CG group showed the same extent of thickening of the submesothelial compact zone, proliferation of collagen fibers, and presence of numerous cells and neovascularization. Within same CG groups, an equal degree of thickening was observed at all sites of the peritoneum. TGF-β1, VEGF, and αSMA were highly expressed in the peritoneum of the 10% CG group.

Conclusion

We developed a novel method of creating a peritoneal sclerosis rat model using a continuous-infusion pump. Our technique is simple and highly reproducible, and will be useful in the study of peritoneal sclerosis mechanisms.

How Can Genetic Advances Impact on Experimental Models of Encapsulating Peritoneal Sclerosis?

In this review we discuss how animal models have contributed to the understanding of pathological pathways that may be involved in the development of encapsulating peritoneal sclerosis. We review the various interventional procedures that, so far, have ameliorated disease progression in animals. Reviewing advancements in molecular biology and genetic technologies, we discuss how future experimental models may impact our understanding of the pathogenesis and treatment of this rare but complex disease.

Experimental Encapsulating Peritoneal Sclerosis Models: Pathogenesis and Treatment

Encapsulating peritoneal sclerosis (EPS) is rare but, with its high morbidity and mortality, it represents one of the most serious complications of long-term peritoneal dialysis. The pathogenesis of EPS has not been elucidated yet; therefore, there has been a growing interest in establishing appropriate animal models for EPS that would explain the pathogenesis of EPS and verify the efficacy of therapeutic agents targeting pathways such as angiogenesis and/ or fibrosis. This brief review provides an update on previously published animal experimental models of EPS. Based on this review, we discuss some aspects of pathogenesis and treatment options in patients with EPS. Experimental models of EPS cannot exactly reproduce human EPS because the latter most likely has a diverse etiology, including the influences of uremia, dialysis, and genetic factors. There is a need for new animal models that would test interventions targeting multiple risk factors while also taking into account putative genetic diversities that most likely are involved in human EPS.

Comparison between the pathology of encapsulating sclerosis and simple sclerosis of the peritoneal membrane in chronic peritoneal dialysis

Reports analyzing the histopathological differences between encapsulating peritoneal sclerosis (EPS) and simple peritoneal sclerosis (non-EPS) and those comparing the pathology of early and late EPS are limited. We present pathological comparisons between EPS and non-EPS, also between the early and late EPS stages. We compared peritoneal membrane (PM) samples (Group B) of 12 EPS patients (Group A) and 23 non-EPS cases regarding; mesothelial loss, submesothelial compact zone degenerated layer and compact zone thicknesses, densities of total and diseased vessels, fibrin stain, new membrane formation and degenerative changes. Group A was subdivided into 7 early (group A1) and 8 late (group A2) EPS cases; we compared both subgroups in the same manner and finally compared groups A1, A2, and B. No differences were found between groups A and B in the incidences of mesothelial detachment, new membrane formation and compact zone degenerative changes between the two groups. Furthermore, there were no differences in compact zone thickness, and vascular densities in the compact zone of respective vascular grade. Whereas, fibrin deposition and thickness of the submesothelial degenerated layer were significantly higher in group A than group B (P = 0.01 and 0.05, respectively), and the thickness of the compact zone was less in group A1 than in group A2 (P = 0.03). Positive fibrin stains and thick degenerative compact zone layers are important pathological findings in EPS. Angiogenesis, vasculopathy, new membrane formation, fibrosis and degenerative changes of the compact zone are not unique characteristics for EPS. Larger size studies are recommended to verify this issue.

Oral pirfenidone in patients with chronic fibrosis resulting from radiotherapy: a pilot study

BACKGROUND

Fibrosis is a common side effect after treatment with ionizing radiation. Several methods to ameliorate debilitating fibrosis have been employed but without consistent results. The goal of this pilot study is to determine if Pirfenidone, a novel regulator of cytokine gene expression, has the potential to ameliorate established radiation-induced fibrosis.

METHODS

Open label, prospective pilot study of 800 mg three times/day, orally administered Pirfenidone was administered to enrolled patients who were had completed radiation therapy and who had established radiation-induced fibrosis. Range of motion (ROM) was assessed using standard measures, and subjective measures of pain, fatigue, disability and global health were measured every three months.

RESULTS

Seven patients were enrolled of whom 3 had ROM assessments of 1 site and 2 had ROM assessments of 2 sites. Of these assessments, 6 revealed increased ROM during drug intervention while 1 revealed a decreased ROM. There was an overall improvement in the mental composite score of the SF36 while physical composite score was decreased and the vitality score was unchanged. Two patients were removed from the study because of syncopal episodes.

CONCLUSION

Several patients experienced improved function of at least 25% and reported subjective improvement. Pirfenidone may benefit patients with radiation-induced fibrosis and is worthy of a larger well controlled trial.

Influence of pirfenidone on airway hyperresponsiveness and inflammation in a Brown-Norway rat model of asthma

Pirfenidone was administered to sensitized Brown Norway rats prior to a series of ovalbumin challenges. Airway hyperresponsiveness, inflammatory cell infiltration, mucin and collagen content, and the degree of epithelium and smooth muscle staining for TGF-beta were examined in control, sensitized, and sensitized/challenged rats fed a normal diet or pirfenidone diet. Pirfenidone had no effect on airway hyperresponsiveness, but reduced distal bronchiolar cell infiltration and proximal and distal mucin content. Statistical analysis showed that the control group and sensitized/challenged pirfenidone diet group TGF-beta staining intensity scores were not significantly different from isotype controls, but that the staining intensity scores for the sensitized/challenged normal diet group was significantly different from isotype controls. These results suggest that pirfenidone treatment is effective in reducing some of the components of acute inflammation induced by allergen challenge.