A protective role of nintedanib in peritoneal fibrosis through H19-EZH2-KLF2 axis via impeding mesothelial-to-mesenchymal transition

BACKGROUND

Peritoneal fibrosis (PF), a common complication of long-term peritoneal dialysis, accounts for peritoneal ultrafiltration failure to develop into increased mortality. Nintedanib has previously been shown to protect against multi-organ fibrosis, including PF. Unfortunately, the precise molecular mechanism underlying nintedanib in the pathogenesis of PF remains elusive.

METHODS

The mouse model of PF was generated by chlorhexidine gluconate (CG) injection with or without nintedanib administration, either with the simulation for the cell model of PF by constructing high-glucose (HG)-treated human peritoneal mesothelial cells (HPMCs). HE and Masson staining were applied to assess the histopathological changes of peritoneum and collagen deposition. FISH, RT-qPCR, western blot and immunofluorescence were employed to examine distribution or expression of targeted genes. Cell viability was detected using CCK-8 assay. Cell morphology was observed under a microscope. RNA immunoprecipitation (RIP) and chromatin immunoprecipitation (ChIP) assays were applied to validate the H19-EZH2-KLF2 regulatory axis.

RESULTS

Aberrantly overexpressed H19 was observed in both the mouse and cell model of PF, of which knockdown significantly blocked HG-induced mesothelial-to-mesenchymal transition (MMT) of HPMCs. Moreover, loss of H19 further strengthened nintedanib-mediated suppressive effects against MMT process in a mouse model of PF. Mechanistically, H19 could epigenetically repressed KLF2 via recruiting EZH2. Furthermore, TGF-β/Smad pathway was inactivated by nintedanib through mediating H19/KLF2 axis.

CONCLUSION

In summary, nintedanib disrupts MMT process through regulating H19/EZH2/KLF2 axis and TGF-β/Smad pathway, which laid the experimental foundation for nintedanib in the treatment of PF.

Matrix metalloproteinase-10 deficiency has protective effects against peritoneal inflammation and fibrosis via transcription factor NFκΒ pathway inhibition

One of the most common causes of discontinued peritoneal dialysis is impaired peritoneal function. However, its molecular mechanisms remain unclear. Previously, by microarray analysis of mouse peritoneum, we showed that MMP (matrix metalloproteinase)-10 expression is significantly increased in mice with peritoneal fibrosis, but its function remains unknown. Chlorhexidine gluconate (CG) was intraperitoneally injected to wild-type and MMP-10 knockout mice to induce fibrosis to elucidate the role of MMP-10 on peritoneal injury. We also examined function of peritoneal macrophages and mesothelial cells obtained from wild-type and MMP-10 knockout mice, MMP-10-overexpressing macrophage-like RAW 264.7 cells and MeT-5A mesothelial cells, investigated MMP-10 expression on peritoneal biopsy specimens, and the association between serum proMMP-10 and peritoneal solute transfer rates determined by peritoneal equilibration test on patients. MMP-10 was expressed in cells positive for WT1, a mesothelial marker, and for MAC-2, a macrophage marker, in the thickened peritoneum of both mice and patients. Serum proMMP-10 levels were well correlated with peritoneal solute transfer rates. Peritoneal fibrosis, inflammation, and high peritoneal solute transfer rates induced by CG were all ameliorated by MMP-10 deletion, with reduction of CD31-positive vessels and VEGF-A-positive cells. Expression of inflammatory mediators and phosphorylation of NFκΒ subunit p65 at S536 were suppressed in both MMP-10 knockout macrophages and mesothelial cells in response to lipopolysaccharide stimulation. Overexpression of MMP-10 in RAW 264.7 and MeT-5A cells upregulated pro-inflammatory cytokines with phosphorylation of NFκΒ subunit p65. Thus, our results suggest that inflammatory responses induced by MMP-10 are mediated through the NFκΒ pathway, and that systemic deletion of MMP-10 ameliorates peritoneal inflammation and fibrosis caused by NFκΒ activation of peritoneal macrophages and mesothelial cells.

Effects of Hyperthermia and Hyperthermic Intraperitoneal Chemoperfusion on the Peritoneal and Tumor Immune Contexture

Hyperthermia combined with intraperitoneal (IP) drug delivery is increasingly used in the treatment of peritoneal metastases (PM). Hyperthermia enhances tumor perfusion and increases drug penetration after IP delivery. The peritoneum is increasingly recognized as an immune-privileged organ with its own distinct immune microenvironment. Here, we review the immune landscape of the healthy peritoneal cavity and immune contexture of peritoneal metastases. Next, we review the potential benefits and unwanted tumor-promoting effects of hyperthermia and the associated heat shock response on the tumor immune microenvironment. We highlight the potential modulating effect of hyperthermia on the biomechanical properties of tumor tissue and the consequences for immune cell infiltration. Data from translational and clinical studies are reviewed. We conclude that (mild) hyperthermia and HIPEC have the potential to enhance antitumor immunity, but detailed further studies are required to distinguish beneficial from tumor-promoting effects.

Macrophages Promote Ovarian Cancer-Mesothelial Cell Adhesion by Upregulation of ITGA2 and VEGFC in Mesothelial Cells

Ovarian cancer is a metastatic disease that frequently exhibits extensive peritoneal dissemination. Recent studies have revealed that noncancerous cells inside the tumor microenvironment, such as macrophages and mesothelial cells, may play a role in ovarian cancer metastasis. In this study, we found that human ovarian cancer cells (A2780 and SKOV3) adhered more to human mesothelial Met5A cells stimulated by macrophages (M-Met5A) in comparison to unstimulated control Met5A cells. The mRNA sequencing revealed that 94 adhesion-related genes, including FMN1, ITGA2, COL13A1, VEGFC, and NRG1, were markedly upregulated in M-Met5A cells. Knockdown of ITGA2 and VEGFC in M-Met5A cells significantly inhibited the adhesion of ovarian cancer cells. Inhibition of the JNK and Akt signaling pathways suppressed ITGA2 and VEGFC expression in M-Met5A cells as well as ovarian cancer-mesothelial cell adhesion. Furthermore, increased production of CC chemokine ligand 2 (CCL2) and CCL5 by macrophages elevated ovarian cancer-mesothelial cell adhesion. These findings imply that macrophages may play a significant role in ovarian cancer-mesothelial cell adhesion by inducing the mesothelial expression of adhesion-related genes via the JNK and Akt pathways.

In situ repair or reconstruction of the abdominal aorta-iliac artery by autologous fascia-peritoneum with posterior rectus sheath for the treatment of the infected abdominal aortic and iliac artery aneurysms: A case series and literature review

Background

Infected abdominal aortic and iliac artery aneurysms are considered acute and severe diseases with insidious onset, rapid development, and high mortality in vascular surgery. Currently, there is no better treatment, either anatomic or extra-anatomical repair.

Case presentation

From February 2018 to April 2022, 7 patients with infected abdominal aortic and iliac artery aneurysms did not have sufficient autologous venous material for repair. With the consent of the Ethics Committee of the hospital, it uses the autologous peritoneal fascial tissue with rectus sheath to repair or reconstruct the infected vessels in situ. There were 5 cases of infected abdominal aortic aneurysm, 1 case of an infected common iliac aneurysm, and 1 case of the infected internal iliac aneurysm. Aortoduodenal fistula was found in 3 cases, all of them were given duodenal fistula repair and gastrojejunostomy and cholecystostomy. Three cases of infected abdominal aortic aneurysms were repaired with the autologous peritoneal fascial tissue patch, and 2 cases of infected abdominal aortic aneurysms were reconstructed by the autologous peritoneal fascial tissue suture to bifurcate graft in situ, the autologous peritoneal fascial tissue suture reconstructed the rest 2 cases of infected iliac aneurysm to tubular graft in situ. It was essential that Careful debridement of all infected tissue and adequate postoperative irrigation and drainage. Antibiotics were administered perioperatively, and all patients were subsequently treated with long-term antibiotics based on bacterial culture and susceptibility results of infected tissues and blood. All 7 patients had underwent surgery successfully. But there were 2 cases died of anastomotic infection or massive hemorrhage after the operation, the other 5 cases survived. The follow-up time was 2–19 months. The enhanced CT of postoperation showed that the reconstructed arteries were smooth without obvious stenosis or expansion, and no abdominal wall hernia occurred.

Conclusion

In situ repair or reconstruction with autologous peritoneal fascial tissue with rectus sheath is a feasible treatment for the infected aneurysm patients without adequate autologous venous substitute, but it still needs long-term follow-up and a large sample to be further confirmed.

The tumor immune microenvironment in peritoneal carcinomatosis

One in four patients with colorectal cancer, 40% of gastric cancer patients, and 60% of ovarian cancer patients will develop peritoneal metastases (PM) in the course of their disease. The outcome of patients with widespread PM remains poor with currently available treatments. Despite the relatively common occurrence of PM, little is known on the pathophysiology that drives the peritoneal metastatic cascade. It is increasingly recognized that the stromal components of the peritoneal microenvironment play an essential role in tumor progression. However, little is known about the specific interactions and components of the peritoneal tumor microenvironment, particularly with respect the immune cell population. We summarize the current knowledge of the tumor immune microenvironment (TIME) in peritoneal metastases originating from the three most common origins: ovarian, gastric, and colorectal cancer. Clearly, the TIME is highly heterogeneous and its composition and functional activity differ according to tumor type and, within the same patient, according to anatomical location. The TIME in PM remains to be explored in detail, and further elucidation of their immune contexture may allow biology driven design of novel immune modulating or immune targeting therapies.

Suspension culture promotes serosal mesothelial development in human intestinal organoids

Pluripotent-stem-cell-derived human intestinal organoids (HIOs) model some aspects of intestinal development and disease, but current culture methods do not fully recapitulate the diverse cell types and complex organization of the human intestine and are reliant on 3D extracellular matrix or hydrogel systems, which limit experimental control and translational potential for regenerative medicine. We describe suspension culture as a simple, low-maintenance method for culturing HIOs and for promoting in vitro differentiation of an organized serosal mesothelial layer that is similar to primary human intestinal serosal mesothelium based on single-cell RNA sequencing and histological analysis. Functionally, HIO serosal mesothelium has the capacity to differentiate into smooth-muscle-like cells and exhibits fibrinolytic activity. An inhibitor screen identifies Hedgehog and WNT signaling as regulators of human serosal mesothelial differentiation. Collectively, suspension HIOs represent a three-dimensional model to study the human serosal mesothelium.

Angiogenic Role of Mesothelium-Derived Chemokine CXCL1 During Unfavorable Peritoneal Tissue Remodeling in Patients Receiving Peritoneal Dialysis as Renal Replacement Therapy

Peritoneal dialysis (PD) is a valuable ‘home treatment’ option, even more so during the ongoing Coronavirus pandemic. However, the long-term use of PD is limited by unfavourable tissue remodelling in the peritoneal membrane, which is associated with inflammation-induced angiogenesis. This appears to be driven primarily through vascular endothelial growth factor (VEGF), while the involvement of other angiogenic signaling pathways is still poorly understood. Here, we have identified the crucial contribution of mesothelial cell-derived angiogenic CXC chemokine ligand 1 (CXCL1) to peritoneal angiogenesis in PD. CXCL1 expression and peritoneal microvessel density were analysed in biopsies obtained by the International Peritoneal Biobank (NCT01893710 at www.clinicaltrials.gov), comparing 13 children with end-stage kidney disease before initiating PD to 43 children on chronic PD. The angiogenic potential of mesothelial cell-derived CXCL1 was assessed in vitro by measuring endothelial tube formation of human microvascular endothelial cells (HMECs) treated with conditioned medium from human peritoneal mesothelial cells (HPMCs) stimulated to release CXCL1 by treatment with either recombinant IL-17 or PD effluent. We found that the capillary density in the human peritoneum correlated with local CXCL1 expression. Both CXCL1 expression and microvessel density were higher in PD patients than in the age-matched patients prior to initiation of PD. Exposure of HMECs to recombinant CXCL1 or conditioned medium from IL-17-stimulated HPMCs resulted in increased endothelial tube formation, while selective inhibition of mesothelial CXCL1 production by specific antibodies or through silencing of relevant transcription factors abolished the proangiogenic effect of HPMC-conditioned medium. In conclusion, peritoneal mesothelium-derived CXCL1 promotes endothelial tube formation in vitro and associates with peritoneal microvessel density in uremic patients undergoing PD, thus providing novel targets for therapeutic intervention to prolong PD therapy.

Amelioration of human peritoneal mesothelial cell co-culture-evoked malignant potential of ovarian cancer cells by acacetin involves LPA release-activated RAGE-PI3K/AKT signaling

Background

Ovarian cancer is a devastating gynecological malignancy and frequently presents as an advanced carcinoma with disseminated peritoneum metastasis. Acacetin exerts anti-cancerous effects in several carcinomas. Here, we sought to investigate acacetin function in ovarian cancer malignancy triggered by peritoneal mesothelial cells.

Methods

Peritoneal mesothelial cells were treated with acacetin, and then the conditioned medium was collected to treat ovarian cancer cells. Then, cell proliferation was analyzed by MTT assay. Transwell analysis was conducted to evaluate cell invasion. Protein expression was determined by western blotting. ELISA and qRT-PCR were applied to analyze inflammatory cytokine levels. The underlying mechanism was also explored.

Results

Acacetin suppressed cell proliferation and invasion, but enhanced cell apoptosis. Furthermore, mesothelial cell-evoked malignant characteristics were inhibited when mesothelial cells were pre-treated with acacetin via restraining cell proliferation and invasion, concomitant with decreases in proliferation-related PCNA, MMP-2 and MMP-9 levels. Simultaneously, acacetin reduced mesothelial cell-induced transcripts and production of pro-inflammatory cytokine IL-6 and IL-8 in ovarian cancer cells. Mechanically, acacetin decreased lysophosphatidic acid (LPA) release from mesothelial cells, and subsequent activation of receptor for advanced glycation end-products (RAGE)-PI3K/AKT signaling in ovarian cancer cells. Notably, exogenous LPA restored the above pathway, and offset the efficacy of acacetin against mesothelial cell-evoked malignancy in ovarian cancer cells, including cell proliferation, invasion and inflammatory cytokine production.

Conclusions

Acacetin may not only engender direct inhibition of ovarian cancer cell malignancy, but also antagonize mesothelial cell-evoked malignancy by blocking LPA release-activated RAGE-PI3K/AKT signaling. Thus, these findings provide supporting evidence for a promising therapeutic agent against ovarian cancer.

Graphical Abstract

STAT3/HIF-1α signaling activation mediates peritoneal fibrosis induced by high glucose

BACKGROUND

Epithelial-mesenchymal transition (EMT) of mesothelial cells is a key step in the peritoneal fibrosis (PF). Recent evidence indicates that signal transducer and activator of transcription 3 (STAT3) might mediate the process of renal fibrosis, which could induce the expression of hypoxia-inducible factor-1α (HIF-1α). Here, we investigated the effect of STAT3 activation on HIF-1α expression and the EMT of mesothelial cells, furthermore the role of pharmacological blockade of STAT3 in the process of PF during peritoneal dialysis (PD) treatment.

METHODS

Firstly, we investigated the STAT3 signaling in human peritoneal mesothelial cells (HPMCs) from drained PD effluent. Secondly, we explored the effect of STAT3 signaling activation on the EMT and the expression of HIF-1α in human mesothelial cells (Met-5A) induced by high glucose. Finally, peritoneal fibrosis was induced by daily intraperitoneal injection with peritoneal dialysis fluid (PDF) so as to explore the role of pharmacological blockade of STAT3 in this process.

RESULTS

Compared with the new PD patient, the level of phosphorylated STAT3 was up-regulated in peritoneal mesothelial cells from long-term PD patients. High glucose (60 mmol/L) induced over-expression of Collagen I, Fibronectin, α-SMA and reduced the expression of E-cadherin in Met-5A cells, which could be abrogated by STAT3 inhibitor S3I-201 pretreatment as well as by siRNA for STAT3. Furthermore, high glucose-mediated STAT3 activation in mesothelial cells induced the expression of HIF-1α and the profibrotic effect of STAT3 signaling was alleviated by siRNA for HIF-1α. Daily intraperitoneal injection of high-glucose based dialysis fluid (HG-PDF) induced peritoneal fibrosis in the mice, accompanied by the phosphorylation of STAT3. Immunostaining showed that phosphorylated STAT3 was expressed mostly in α-SMA positive cells in the peritoneal membrane induced by HG-PDF. Administration of S3I-201 prevented the progression of peritoneal fibrosis, angiogenesis, macrophage infiltration as well as the expression of HIF-1α in the peritoneal membrane induced by high glucose.

CONCLUSIONS

Taken together, these findings identified a novel mechanism linking STAT3/HIF-1α signaling to peritoneal fibrosis during long-term PD treatment. It provided the first evidence that pharmacological inhibition of STAT3 signaling attenuated high glucose-mediated mesothelial cells EMT as well as peritoneal fibrosis.

Biological Effects of XyloCore, a Glucose Sparing PD Solution, on Mesothelial Cells: Focus on Mesothelial-Mesenchymal Transition, Inflammation and Angiogenesis

Glucose-based solutions remain the most used osmotic agents in peritoneal dialysis (PD), but unavoidably they contribute to the loss of peritoneal filtration capacity. Here, we evaluated at a molecular level the effects of XyloCore, a new PD solution with a low glucose content, in mesothelial and endothelial cells. Cell viability, integrity of mesothelial and endothelial cell membrane, activation of mesothelial and endothelial to mesenchymal transition programs, inflammation, and angiogenesis were evaluated by several techniques. Results showed that XyloCore preserves mesothelial and endothelial cell viability and membrane integrity. Moreover XyloCore, unlike glucose-based solutions, does not exert pro-fibrotic, -inflammatory, and -angiogenic effects. Overall, the in vitro evidence suggests that XyloCore could represent a potential biocompatible solution promising better outcomes in clinical practice.

Primary human mesothelial cell culture in the evaluation of the inflammatory response to different sclerosing agents used for pleurodesis

The mechanisms of chemical pleurodesis are still not fully explained. We aimed to evaluate the feasibility of using primary biopsy‐derived human mesothelial cells to establish an in vitro culture and to assess the response of pleural mesothelial cells to different sclerosing agents. Talc, povidone‐iodine, doxycycline, and TGF‐β were used at different doses to stimulate pleural mesothelial cells. After 6 and 24 h, mRNA expression of interleukin (IL)‐1β, IL‐6, IL‐8, TGF‐β, MCP‐1, IL‐17A, and MMP9 was measured in cultured cells, and the protein level of IL‐1β, IL‐6, and IL‐8 was measured in the culture supernatant. The most pronounced response was observed after talc exposure. It was expressed as an increase in IL‐1β concentration in culture supernatant after 24 h of higher talc dose stimulation compared to 6 h of stimulation (17.14 pg/ml [11.96–33.32 pg/ml] vs. 1.84 pg/ml [1.81–1.90 pg/ml], p = 0.02). We showed that culture pleural mesothelial cells isolated from pleura biopsy specimens is feasible. Inflammatory responses of mesothelial cells to different sclerosants were highly variable with no consistent pattern of mesothelium reaction neither in terms of different sclerosing agents nor in the time of the most significant reaction. We demonstrated that pro‐inflammatory mesothelial response includes an increase in IL‐1β mRNA expression and protein production. This may suggest the role of IL‐1β in the formation and maintenance of the inflammatory response during pleurodesis.

Laparoscopic Peritoneal Wash Cytology-Derived Primary Human Mesothelial Cells for In Vitro Cell Culture and Simulation of Human Peritoneum

Peritoneal mucosa of mesothelial cells line the abdominal cavity, surround intestinal organs and the female reproductive organs and are responsible for immunological integrity, organ functionality and regeneration. Peritoneal diseases range from inflammation, adhesions, endometriosis, and cancer. Efficient technologies to isolate and cultivate healthy patient-derived mesothelial cells with maximal purity enable the generation of capable 2D and 3D as well as in vivo-like microfluidic cell culture models to investigate pathomechanisms and treatment strategies. Here, we describe a new and easily reproducible technique for the isolation and culture of primary human mesothelial cells from laparoscopic peritoneal wash cytology. We established a protocol containing multiple washing and centrifugation steps, followed by cell culture at the highest purity and over multiple passages. Isolated peritoneal mesothelial cells were characterized in detail, utilizing brightfield and immunofluorescence microscopy, flow cytometry as well as Raman microspectroscopy and multivariate data analysis. Thereby, cytokeratin expression enabled specific discrimination from primary peritoneal human fibroblasts. Raman microspectroscopy and imaging were used to study morphology and biochemical properties of primary mesothelial cell culture compared to cryo-fixed and cryo-sectioned peritoneal tissue.

Interleukin-17A derived from mast cells contributes to fibrosis in gastric cancer with peritoneal dissemination

OBJECTIVES

Interleukin-17A (IL-17A) is pro-inflammatory cytokine and acts as profibrotic factor in the fibrosis of various organs. Fibrosis tumor-like peritoneal dissemination of gastric cancer interferes with drug delivery and immune cell infiltration because of its high internal pressure. In this study, we examined the relationship between IL-17A and tissue fibrosis in peritoneal dissemination and elucidated the mechanism of fibrosis induced by IL-17A using human peritoneal mesothelial cells (HPMCs) and a mouse xenograft model.

METHODS

Seventy gastric cancer patients with peritoneal dissemination were evaluated. The correlation between IL-17A and fibrosis was examined by immunofluorescence and immunohistochemistry. A fibrosis tumor model was developed based on subcutaneous transplantation of co-cultured cells (HPMCs and human gastric cancer cell line MKN-45) into the dorsal side of nude mice. Mice were subsequently treated with or without IL-17A. We also examined the effect of IL-17A on HPMCs in vitro.

RESULTS

There was a significant correlation between IL-17A expression, the number of mast cell tryptase (MCT)-positive cells, and the degree of fibrosis (r = 0.417, P < 0.01). In the mouse model, IL-17A enhanced tumor progression and fibrosis. HPMCs treated with IL-17A revealed changes to a spindle-like morphology, decreased E-cadherin expression, and increased α-SMA expression through STAT3 phosphorylation. Moreover, HPMCs treated with IL-17A showed increased migration.

CONCLUSIONS

IL-17A derived from mast cells contributes to tumor fibrosis in peritoneal dissemination of gastric cancer. Inhibiting degranulation of mast cells might be a promising treatment strategy to control organ fibrosis.

Anatomy and histology of the foramen of ovarian bursa opening to the peritoneal cavity and its changes in autoimmune disease-prone mice

The ovarian bursa is a small peritoneal cavity enclosed by the mesovarium and mesosalpinx, which surrounds the ovaries and oviductal infundibulum in mammals. The ovarian bursa is considered as the structure facilitating the transport of ovulated oocytes into the oviduct. Our previous study revealed reduced oocyte pick-up function in the oviduct of lupus-prone MRL/MpJ-Faslpr/lpr mouse, suggesting the possibility of an escape of ovulated oocytes into the peritoneal cavity, despite the presence of an almost complete ovarian bursa in the mouse. In this study, we revealed anatomical and histological characteristics of the ovarian bursa in C57BL/6 N, MRL/MpJ, and MRL/MpJ-Faslpr/lpr mice. All strains had the foramen of ovarian bursa (FOB), with a size of approximately 0.04 to 0.12 cm2 , surrounded by the ligament of ovarian bursa (LOB), which is part of the mesosalpinx. The LOB was partially lined with the cuboidal mesothelial cells and consisted of a thick smooth muscle layer in all strains. In 6-month-old MRL/MpJ-Faslpr/lpr mice, in which the systemic autoimmune abnormality deteriorated and oocyte pick-up function was impaired, the size of the FOB tended to be larger than that of other strains. Additionally, in MRL/MpJ-Faslpr/lpr mice at 6 months of age, there was infiltration by numerous immune cells in the mesosalpinx suspending the isthmus; however, the LOB prevented severe inflammation and showed deposition of collagen fibers. These results not only indicate that the FOB is a common structure within mice, but also imply the physiological function of the LOB and its role in maintaining the microenvironment around the ovary, as well as regulating healthy reproduction.

Mesothelial Cells

♦ Background

The introduction of peritoneal dialysis (PD) as a modality of renal replacement therapy has provoked much interest in the biology of the peritoneal mesothelial cell. Mesothelial cells isolated from omental tissue have immunohistochemical markers that are identical to those of mesothelial stem cells, and omental mesothelial cells can be cultivated in vitro to study changes to their biologic functions in the setting of PD.

♦ Method

The present article describes the structure and function of mesothelial cells in the normal peritoneum and details the morphologic changes that occur after the introduction of PD. Furthermore, this article reviews the literature of mesothelial cell culture and the limitations of in vitro studies.

♦ Results

The mesothelium is now considered to be a dynamic membrane that plays a pivotal role in the homeostasis of the peritoneal cavity, contributing to the control of fluid and solute transport, inflammation, and wound healing. These functional properties of the mesothelium are compromised in the setting of PD. Cultures of peritoneal mesothelial cells from omental tissue provide a relevant in vitro model that allows researchers to assess specific molecular pathways of disease in a distinct population of cells. Structural and functional attributes of mesothelial cells are discussed in relation to long-term culture, proliferation potential, age of tissue donor, use of human or animal in vitro models, and how the foregoing factors may influence in vitro data.

♦ Conclusions

The ability to propagate mesothelial cells in culture has resulted, over the past two decades, in an explosion of mesothelial cell research pertaining to PD and peritoneal disorders. Independent researchers have highlighted the potential use of mesothelial cells as targets for gene therapy or transplantation in the search to provide therapeutic strategies for the preservation of the mesothelium during chemical or bacterial injury.

In Vitro Study of Peritoneal Fibrosis

Peritoneal fibrosis (PF) is an important issue in peritoneal dialysis (PD) because it remains one of the leading causes of patient drop-out from PD. In this review, we focus on in vitro approaches to the pathogenesis and therapeutic potential of PF and on associated clinical implications. Representative Asian studies, initiated since mid-1990s, that have investigated matrix accumulation in peritoneal tissue possibly leading to PF in the PD population will be highlighted as examples to learn how to apply this research tool. As compared with data from well-designed clinical trials, observations from in vitro models may be far from becoming solid evidence; however, they do cast new light on options for investigations into therapeutic pharmaceuticals.

The effects of size and shape of the ovarian cancer spheroids on the drug resistance and migration

BACKGROUND

High fatality in ovarian cancer is attributed to metastasis, propagated by the release of multi-cellular aggregates/spheroids into the peritoneal cavity and their subsequent mesothelial invasion of peritoneal organs. Spheroids are therefore a common and clinically relevant in vitro model for ovarian cancer research. Spheroids in patients vary significantly in size and shape and display enhanced resistance to anti-cancer drugs compared to monolayers. However, there is no consensus on how spheroid size and shape affect drug resistance. Moreover, existing data regarding the influence of epithelial-to-mesenchymal transition (EMT) profile on spheroid shape and migration is inconclusive.

METHODS

We formed spheroids with OVCAR-3 and OVCAR-8 cells, chosen for their established genetic similarity to the patient tumor samples. We monitored their morphology using confocal microscope with dipping objective and fluorescent microscope. We characterized important EMT biomarkers; E-cadherin, Vimentin and Slug through western blotting in monolayers and spheroids. We treated these spheroids with Taxol and Cisplatin and investigated their migratory profile based on their morphology.

RESULTS

We report two distinct multicellular structures: loose aggregates (OVCAR-3) and compact spheroids (OVCAR-8). We attribute these different morphologies to the expression of the EMT biomarkers, and their changes upon spheroid formation. Importantly, we did not observe a difference in resistance to the anti-cancer drugs as a function of spheroid size and shape. However, migration capacity of compact spheroid (OVCAR-8) was 15-fold higher compared to that of loose aggregates (OVCAR-3).

CONCLUSIONS

These results highlight the importance of spheroid size and shape on anti-cancer drug resistance and migration profiles. The results of this study can, therefore, help to elucidate general rules for ovarian cancer studies based on 3D samples.

Mesothelial Cells Covering the Surface of Primo Vascular System Tissue

The primo vascular system (PVS) is reported to have a periductium composed of cells with spherical or spindle-shaped nuclei and abundant cytoplasm. However, little is known about these periductium cells. In this study, we examined the morphological features of cells covering the PVS tissue isolated from the surface of abdominal organs of rats. By hematoxylin and eosin (H&E) staining, we observed a layer of dark nuclei on the basement membrane at the borders of the sections of primo node (PN), primo vessel (PV), and their subunits. The nuclei appeared thin and linear (10-14 μm), elliptical (8-10 × 3-4 μm), and round (5-7 μm). The borders of the PVS tissue sections were immunostained with a selective antibody for mesothelial cells (MCs). Areas of immunoreactivity overlapped with the flattened cells are shown by hematoxylin and eosin staining. By scanning electron microscopy, we further identified elliptical (11 × 21 μm) and rectangular squamous MCs (length, 10 μm). There were numerous stomata (∼200 nm) and microparticles (20-200 nm) on the surface of the PVS MCs. In conclusion, this study presents the novel finding that the PVS periductium is composed of squamous MCs. These cells tightly line the luminal surface of the PVS tissue, including PNs, PVs, and small branches of the PVs in the abdominal cavity. These results will help us to understand the physiological roles such as hyaluronan secretion and the fine structure of PVS tissue.

Sialyl Lewisx-P-selectin cascade mediates tumor-mesothelial adhesion in ascitic fluid shear flow

Organ-specific colonization suggests that specific cell–cell recognition is essential. Yet, very little is known about this particular interaction. Moreover, tumor cell lodgement requires binding under shear stress, but not static, conditions. Here, we successfully isolate the metastatic populations of cancer stem/tumor-initiating cells (M-CSCs). We show that the M-CSCs tether more and roll slower than the non-metastatic (NM)-CSCs, thus resulting in the preferential binding to the peritoneal mesothelium under ascitic fluid shear stress. Mechanistically, this interaction is mediated by P-selectin expressed by the peritoneal mesothelium. Insulin-like growth factor receptor-1 carrying an uncommon non-sulfated sialyl-Lewis^x (sLe^x) epitope serves as a distinct P-selectin binding determinant. Several glycosyltransferases, particularly α1,3-fucosyltransferase with rate-limiting activity for sLe^x synthesis, are highly expressed in M-CSCs. Tumor xenografts and clinical samples corroborate the relevance of these findings. These data advance our understanding on the molecular regulation of peritoneal metastasis and support the therapeutic potential of targeting the sLe^x-P-selectin cascade.

Tumor cell in the peritoneum are often exposed to shear forces generated by ascitic flow during metastasis. Here, the authors show that metastatic cancer stem cells tether more and roll slower than the non-metastatic counterparts, and that sialyl-Lewis^x -P-selectin axis mediates peritoneal metastasis.

Epithelial-to-Mesenchymal Transition and Migration of Human Peritoneal Mesothelial Cells Undergoing Senescence

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) of human peritoneal mesothelial cells (HPMCs) contributes to fibrotic thickening of the peritoneum that develops in patients on peritoneal dialysis (PD). The process is thought to be largely mediated by transforming growth factor-beta (TGF-β). As TGF-β has also been implicated in senescence of HPMCs, we have performed an exploratory study to examine if senescent HPMCs can undergo EMT.

METHODS

Omentum-derived HPMCs were rendered senescent by repeated passages in culture. Features of EMT were assessed by immunostaining and quantitative polymerase chain reaction (qPCR) at various stages of the HPMC lifespan and after treatment with or without TGF-β. The motility of HPMCs was assessed in a scratch wound migration assay.

RESULTS

Replicative senescence of HPMCs was associated with a gradual increase in the constitutive expression of EMT markers, including increased production of extracellular matrix proteins. However, senescent HPMCs also retained epithelial cell features such as cytokeratin, calretinin, and E-cadherin and showed decreased, rather than increased, motility. In contrast, exposure to TGF-β resulted in an up-regulation of mesenchymal markers and down-regulation of epithelial markers. Such effects of TGF-β occurred both in young and senescent cells, although they were less pronounced in senescence.

CONCLUSIONS

Senescence of HPMCs is associated with spontaneous development of several EMT features. At the same time, senescent HPMCs preserve epithelial cell-like characteristics and are less prone to develop a full EMT phenotype in response to TGF-β. These observations may support the concept of cellular senescence being antagonistically pleiotropic with regard to EMT.

Molecular Mechanisms Regulating Organ-Specific Metastases in Epithelial Ovarian Carcinoma

Epithelial ovarian carcinoma is the most predominant type of ovarian carcinoma, the deadliest gynecologic malignancy. It is typically diagnosed late when the cancer has already metastasized. Transcoelomic metastasis is the most predominant mechanism of dissemination from epithelial ovarian carcinoma, although both hematogenously and lymphogenously spread metastases also occur. In this review, we describe molecular mechanisms known to regulate organ-specific metastasis from epithelial ovarian carcinoma. We begin by discussing the sites colonized by metastatic ovarian carcinoma and rank them in the order of prevalence. Next, we review the mechanisms regulating the transcoelomic metastasis. Within this chapter, we specifically focus on the mechanisms that were demonstrated to regulate peritoneal adhesion—one of the first steps in the transcoelomic metastatic cascade. Furthermore, we describe mechanisms of the transcoelomic metastasis known to regulate colonization of specific sites within the peritoneal cavity, including the omentum. Mechanisms underlying hematogenous and lymphogenous metastatic spread are less comprehensively studied in ovarian cancer, and we summarize mechanisms that were identified to date. Lastly, we discuss the outcomes of the clinical trials that attempted to target some of the mechanisms described in this review.

The Peritoneum: Beyond the Tissue - A Review

Background: Despite its complexity, the peritoneum is usually underestimated in classical medical texts simply as the surrounding tissue (serous membrane) of the gut. Novel findings on physiology and morphology of the peritoneum and mesothelial cell exist but they are usually focused or limited to Continuous Ambulatory Peritoneal Dialysis research and practice. This review aims to expose, describe and analyze the most recent evidence on the peritoneum’s morphology, embryology and physiology.

Materials and Methods: A literature review was performed on Pubmed and MEDLINE. With no limit of publication date, original papers and literature reviews about the peritoneum, the peritoneal cavity, peritoneal fluid, and mesothelial cells were included (n = 72).

Results: Peritoneum develops in close relationship to the gut from an early period in embryogenesis. Analyzing together the development of the primitive gut and the surrounding mesothelium helps understanding that the peritoneal cavity, the mesenteries and other structures can be considered parts of the peritoneum. However, some authors consider that structures like the mesenteries are different to the peritoneum. The mesothelial cell has a complex ultrastructural organization with intercellular junctions and apical microvilli. This complexity is further proven by the large array of functions like selective fluid and cell transport; physiological protective barrier; immune induction, modulation, and inhibition; tissue repair and scarring; preventing adhesion and tumoral dissemination; cellular migration; and the epithelial-mesenchymal transition capacity.

Conclusion: Recent evidence on the anatomy, histology, and physiology of the peritoneum, shows that this structure is more complex than a simple serous membrane. These results call for a new conceptualization of peritoneum, and highlight the need of adequate research for identifying clinical relevance of this knowledge.

Thymol alleviates lipopolysaccharide-stimulated inflammatory response via downregulation of RhoA-mediated NF-κB signalling pathway in human peritoneal mesothelial cells

Thymol is one of the most important dietary constituents in the thyme species and has been shown to possess anti-inflammatory properties both in vivo and in vitro. We investigated the protective effects of thymol on the lipopolysaccharide (LPS)-induced inflammatory responses in the human peritoneal mesothelial cell line (HMrSV5) to clarify the potential mechanism. HMrSV5 cells were stimulated with LPS in the presence or absence of thymol. Our results showed that thymol markedly suppressed the production of cytokines such as tumour necrosis factor α (TNF-α), interleukin (IL)-6, monocyte chemoattractant protein 1 (MCP-1) and α-smooth muscle actin (α-SMA) in a dose-dependent manner. Western blot analysis indicated that RhoA and ROCK activation; Toll-like receptor 4 (TLR4) expression; and Nuclear factor -kappa B (NF-κB) p65, IKK and IκBα phosphorylation were also inhibited by thymol. Moreover, siRNA knockdown of RhoA suppressed the expression of pro-inflammatory cytokines and phosphorylation of NF-κB p65 and IκBα proteins in LPS-stimulated HMrSV5 cells, but did not affect TLR4 expression. In conclusion, thymol inhibits LPS-induced inflammation in HMrSV5 cells by suppressing TLR4-mediated RhoA-dependent NF-κB signalling pathway. Our study suggests that thymol may be a promising therapeutic agent against peritonitis.

Specific heparanase inhibition reverses glucose-induced mesothelial-to-mesenchymal transition

Background

Epithelial-to-mesenchymal transition (EMT) of peritoneal mesothelial cells induced by high glucose (HG) levels is a major biological mechanism leading to myofibroblast accumulation in the omentum of patients on peritoneal dialysis (PD). Heparanase (HPSE), an endoglycosidase that cleaves heparan sulfate chains, is involved in the EMT of several cell lines, and may have a major role in this pro-fibrotic process potentially responsible for the failure of dialysis. Its specific inhibition may therefore plausibly minimize this pathological condition.

Methods

An in vitro study employing several biomolecular strategies was conducted to assess the role of HPSE in the HG-induced mesothelial EMT process, and to measure the effects of its specific inhibition by SST0001, a N-acetylated glycol-split heparin with a strong anti-HPSE activity. Rat mesothelial cells were grown for 6 days in HG (200 mM) culture medium with or without SST0001. Then EMT markers (VIM, α-SMA, TGF-β) and vascular endothelial growth factor (VEGF) (a factor involved in neoangiogenesis) were measured by real-time PCR and immunofluorescence/western blotting. As a functional analysis, trans-epithelial resistance (TER) and permeability to albumin were also measured in our in vitro model using a Millicell-ERS ohmmeter and a spectrophotometer, respectively.

Results

Our results showed that 200 mM of glucose induced a significant gene and protein up-regulation of VEGF and all EMT markers after 6 days of culture. Intriguingly, adding SST0001 on day 3 reversed these biological and cellular effects. HPSE inhibition also restored the normal TER and permeability lost during the HG treatment.

Conclusion

Taken together, our data confirm that HG can induce EMT of mesothelial cells, and that HPSE plays a central part in this process. Our findings also suggest that pharmacological HPSE inhibition could prove a valuable therapeutic tool for minimizing fibrosis and avoiding a rapid decline in the efficacy of dialysis in patients on PD, though clinical studies and/or trials would be needed to confirm the clinical utility of this treatment.

Importance of human peritoneal mesothelial cells in the progression, fibrosis, and control of gastric cancer: inhibition of growth and fibrosis by tranilast

BACKGROUND

Scirrhous gastric cancer is an intractable disease with a high incidence of peritoneal dissemination and obstructive symptoms (e.g., ileus, jaundice, and hydronephrosis) arising from accompanying marked fibrosis. Microenvironmental interactions between cancer cells and cancer-associated fibroblasts are the suggested cause of the disease. We elucidated the mechanisms of tumor growth and fibrosis using human peritoneal mesothelial cells (HPMCs) and investigated the effects of tranilast treatment on cells and a xenograft mouse model of fibrosis.

METHODS

HPMCs were isolated from surgically excised omentum and their interaction with MKN-45 gastric cancer cells was investigated using co-culture. Furthermore, a fibrosis tumor model was developed based on subcutaneous transplantation of co-cultured cells into the dorsal side of nude mice to form large fibrotic tumors. Mice were subsequently treated with or without tranilast.

RESULTS

The morphology of HPMCs treated with transforming growth factor (TGF)-β1 changed from cobblestone to spindle-type. Moreover, E-cadherin was weakly expressed whereas high levels of α-smooth muscle actin expression were observed. TGF-β-mediated epithelial-mesenchymal transition-like changes in HPMCs were inhibited in a dose-dependent manner following tranilast treatment through inhibition of Smad2 phosphorylation. In the mouse model, tumor size decreased significantly and fibrosis was inhibited in the tranilast treatment group compared with that in the control group.

CONCLUSIONS

Tranilast acts on the TGF-β/Smad pathway to inhibit interactions between cancer cells and cancer-associated fibroblasts, thereby inhibiting tumor growth and fibrosis. This study supports the hypothesis that tranilast represents a novel strategy to prevent fibrous tumor establishment represented by peritoneal dissemination.

Interleukin-6 trans-signalling induces vascular endothelial growth factor synthesis partly via Janus kinases-STAT3 pathway in human mesothelial cells

AIMS

Interleukin-6 (IL-6) is a vital inflammatory factor in the peritoneal cavity of peritoneal dialysis (PD) patients. Because intraperitoneal inflammation is closely associated with angiogenesis, we sought to explore the effect of IL-6 on vascular endothelial growth factor (VEGF) synthesis and its transduction pathway in mesothelial cells.

METHODS

Human mesothelial cells (Met-5A) were incubated with different concentrations of glucose and mannitol, and the effect of glucose and mannitol on the expression of IL-6 was determined. Then, the cells were stimulated by IL-6 with or without two soluble receptors of IL-6 (sIL-6R or sgp130), and VEGF synthesis was detected. Finally, the cells were incubated with IL-6/sIL-6R combined with or without the inhibitor of Janus kinases (JAK) AG490. The phosphorylation of the signal transducer and activator of transcription 3 (STAT3) and its intracellular translocation were examined.

RESULTS

1. High glucose and mannitol could upregulate IL-6 mRNA expression and IL-6 secretion in mesothelial cells significantly, and there was no difference of its effect between high glucose and mannitol. 2. Met-5A was a cell line with a single IL-6 receptor. The IL-6/sIL-6R complex induced VEGF synthesis of mesothelial cells, which was alleviated by sgp130 or AG490. IL-6 trans-signalling could induce the phosphorylation of STAT3, which is recruited to the cellular nucleus of Met-5A cells.

CONCLUSION

The present study might provide evidence that high glucose upregulates IL-6 synthesis in Met-5A cells, to some extent, depending on its osmolality and that IL-6 trans-signalling could induce VEGF synthesis partly dependent on the JAK/STAT3 pathway.

Establishing a xenograft mouse model of peritoneal dissemination of gastric cancer with organ invasion and fibrosis

Background

The clinical prognosis of gastric cancer with peritoneal dissemination is poor because of its chemoresistance and rich fibrosis. While several gastric cancer cell lines have been used to establish models of peritoneal dissemination by intraperitoneal injection, most peritoneal tumors that form adopt a medullary pattern in microscopic appearance. This histological finding for the model differs from that in the clinical situation. This study was performed to demonstrate the contribution of human peritoneal mesothelial cells (HPMCs) to fibrotic tumor formation and to establish a new xenograft model with high potential for peritoneal dissemination with organ invasion and extensive fibrosis.

Methods

We established four types of xenograft model: i) intraperitoneal injection of MKN45-P cells alone (control group), ii) injection of MKN45-P cells co-cultured with HPMCs (co-cultured group), iii) scratching the parietal peritoneum (parietal group), and iv) scratching the visceral peritoneum (visceral group) with a cotton swab before injection of co-cultured cells. Fibrosis, α-smooth muscle actin expression, and organ invasion by tumor cells were all assessed by immunohistochemical examination.

Results

All mice developed abdominal swelling with peritoneal tumors and bloody ascites. Tumors of the control and co-cultured groups were not invasive or fibrotic. Contrastingly, tumors of the scratch groups exhibited rich stromal fibrosis and possessed increased α-smooth muscle actin (α-SMA) expression. In particular, the visceral group showed edematous and spreading tumors invading the intestinal wall.

Conclusion

We established a model of peritoneal dissemination with organ invasion and stromal fibrosis. Formation of peritoneal dissemination required a favorable environment for cell adhesion, invasion, and growth. This model may be useful for analyzing the pathogenesis and treatment of peritoneal dissemination of gastric cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2991-9) contains supplementary material, which is available to authorized users.

Cancer-associated peritoneal mesothelial cells lead the formation of pancreatic cancer peritoneal dissemination

The interaction between the cancer cells and the peritoneal mesothelial cells (PMCs) plays an important role in the peritoneal dissemination in several types of cancer. However, the role of PMCs in the peritoneal dissemination of pancreatic cancer remains unclear. In the present study, we investigated the interaction between the pancreatic cancer cells (PCCs) and the PMCs in the formation of peritoneal dissemination in vitro and in vivo. The tumor-stromal interaction of PCCs and PMCs significantly enhanced their mobility and invasiveness and enhanced the proliferation and anoikis resistance of PCCs. In a 3D organotypic culture model of peritoneal dissemination, co-culture of PCCs and PMCs significantly increased the cells invading into the collagen gel layer compared with mono-culture of PCCs. PMCs pre-invaded into the collagen gel, remodeled collagen fibers, and increased parallel fiber orientation along the direction of cell invasion. In the tissues of peritoneal dissemination of the KPC (LSL-KrasG12D/+; LSL-Trp53R172H/+;Pdx-1-Cre) transgenic mouse, the monolayer of PMCs was preserved in tumor-free areas, whereas PMCs around the invasive front of peritoneal dissemination proliferated and invaded into the muscle layer. In vivo, intraperitoneal injection of PCCs with PMCs significantly promoted peritoneal dissemination compared with PCCs alone. The present data suggest that the cancer-associated PMCs have important promoting roles in the peritoneal dissemination of PCCs. Therapy targeting cancer-associated PMCs may improve the prognosis of patients with pancreatic cancer.

Colorectal cancer-promoting activity of the senescent peritoneal mesothelium

Gastrointestinal cancers metastasize into the peritoneal cavity in a process controlled by peritoneal mesothelial cells (HPMCs). In this paper we examined if senescent HPMCs can intensify the progression of colorectal (SW480) and pancreatic (PSN-1) cancers in vitro and in vivo. Experiments showed that senescent HPMCs stimulate proliferation, migration and invasion of SW480 cells, and migration of PSN-1 cells. When SW480 cells were injected i.p. with senescent HPMCs, the dynamics of tumor formation and vascularization were increased. When xenografts were generated using PSN-1 cells, senescent HPMCs failed to favor their growth. SW480 cells subjected to senescent HPMCs displayed up-regulated expression of transcripts for various pro-cancerogenic agents as well as increased secretion of their products. Moreover, they underwent an epithelial-mesenchymal transition in the Smad 2/3-Snail1-related pathway. The search for mediators of senescent HPMC activity showed that increased SW480 cell proliferation was stimulated by IL-6, migration by CXCL8 and CCL2, invasion by IL-6, MMP-3 and uPA, and epithelial-mesenchymal transition by TGF-β1. Secretion of these agents by senescent HPMCs was increased in an NF-κB- and p38 MAPK-dependent mechanism. Collectively, our findings indicate that in the peritoneum senescent HPMCs may create a metastatic niche in which critical aspects of cancer progression become intensified.

Isolation and Propagation of Rat Peritoneal Mesothelial Cells

With the development of peritoneal dialysis in many countries, there has been much interest in the cell biology of peritoneal mesothelial cells. In this chapter we describe a reliable and reproducible method for the culture of rat primary mesothelial cells (RPMCs). This chapter outlines how to isolate mesothelial cells from rat peritoneum. The subculture of primary peritoneal mesothelial cells and the characterization by immunofluorescence is also described in detail.

Peritoneal VEGF-A expression is regulated by TGF-β1 through an ID1 pathway in women with endometriosis

VEGF-A, an angiogenic factor, is increased in the peritoneal fluid of women with endometriosis. The cytokine TGF-β1 is thought to play a role in the establishment of endometriosis lesions. Inhibitor of DNA binding (ID) proteins are transcriptional targets of TGF-β1 and ID1 has been implicated in VEGF-A regulation during tumor angiogenesis. Herein, we determined whether peritoneal expression of VEGF-A is regulated by TGF-β1 through the ID1 pathway in women with endometriosis. VEGF-A was measured in peritoneal fluid by ELISA (n = 16). VEGF-A and ID1 expression was examined in peritoneal biopsies (n = 13), and primary peritoneal and immortalized mesothelial cells (MeT5A) by immunohistochemistry, qRT-PCR and ELISA. VEGF-A was increased in peritoneal fluid from women with endometriosis and levels correlated with TGF-β1 concentrations (P < 0.05). VEGF-A was immunolocalized to peritoneal mesothelium and TGF-β1 increased VEGFA mRNA (P < 0.05) and protein (P < 0.05) in mesothelial cells. ID1 was increased in peritoneum from women with endometriosis and TGF-β1 increased concentrations of ID1 mRNA (P < 0.05) in mesothelial cells. VEGF-A regulation through ID1 was confirmed by siRNA in MeT5A cells (P < 0.05). Our data supports role for ID1 in the pathophysiology of endometriosis, as an effector of TGFβ1 dependent upregulation of VEGF-A, and highlights a novel potential therapeutic target.

Senescence-Associated Changes in Proteome and O-GlcNAcylation Pattern in Human Peritoneal Mesothelial Cells

INTRODUCTION

Senescence of peritoneal mesothelial cells represents a biological program defined by arrested cell growth and altered cell secretory phenotype with potential impact in peritoneal dialysis. This study aims to characterize cellular senescence at the level of global protein expression profiles and modification of proteins with O-linked N-acetylglucosamine (O-GlcNAcylation).

METHODS

A comparative proteomics analysis between young and senescent human peritoneal mesothelial cells (HPMC) was performed using two-dimensional gel electrophoresis. O-GlcNAc status was assessed by Western blot under normal conditions and after modulation with 6-diazo-5-oxo-L-norleucine (DON) to decrease O-GlcNAcylation or O-(2-acetamido-2-deoxy-D-glucopyranosylidene) amino N-phenyl carbamate (PUGNAc) to increase O-GlcNAcylation.

RESULTS

Comparison of protein pattern of senescent and young HPMC revealed 29 differentially abundant protein spots, 11 of which were identified to be actin (cytoplasmic 1 and 2), cytokeratin-7, cofilin-2, transgelin-2, Hsp60, Hsc70, proteasome β-subunits (type-2 and type-3), nucleoside diphosphate kinase A, and cytosolic 5'(3')-deoxyribonucleotidase. Although the global level of O-GlcNAcylation was comparable, senescent cells were not sensitive to modulation by PUGNAc.

DISCUSSION

This study identified changes of the proteome and altered dynamics of O-GlcNAc regulation in senescent mesothelial cells. Whereas changes in cytoskeleton-associated proteins likely reflect altered cell morphology, changes in chaperoning and housekeeping proteins may have functional impact on cellular stress response in peritoneal dialysis.

Vascular endothelial growth factor receptor-3 is a novel target to improve net ultrafiltration in methylglyoxal-induced peritoneal injury

Appropriate fluid balance is important for good clinical outcomes and survival in patients on peritoneal dialysis. We recently reported that lymphangiogenesis associated with fibrosis developed in the peritoneal cavity via the transforming growth factor-β1-vascular endothelial growth factor-C (VEGF-C) pathway. We investigated whether VEGF receptor-3 (VEGFR-3), the receptor for VEGF-C and -D, might be a new target to improve net ultrafiltration by using adenovirus-expressing soluble VEGFR-3 (Adeno-sVEGFR-3) in rodent models of peritoneal injury induced by methylglyoxal (MGO). We demonstrated that lymphangiogenesis developed in these MGO models, especially in the diaphragm, indicating that lymphangiogenesis is a common feature in the peritoneal cavity with inflammation and fibrosis. In MGO models, VEGF-D was significantly increased in the diaphragm; however, VEGF-C was not significantly upregulated. Adeno-sVEGFR-3, which was detected on day 50 after administration via tail vein injections, successfully suppressed lymphangiogenesis in the diaphragm and parietal peritoneum in mouse MGO models without significant effects on fibrosis, inflammation, or neoangiogenesis. Drained volume in the peritoneal equilibration test using a 7.5% icodextrin peritoneal dialysis solution (the 7.5% icodextrin peritoneal equilibration test) was improved by Adeno-sVEGFR-3 on day 22 (P<0.05) and day 50 after reduction of inflammation (P<0.01), indicating that the 7.5% icodextrin peritoneal equilibration test identifies changes in lymphangiogenesis. The solute transport rate was not affected by suppression of lymphangiogenesis. In human peritoneal dialysis patients, the dialysate to plasma ratio of creatinine positively correlated with the dialysate VEGF-D concentration (P<0.001). VEGF-D mRNA was significantly higher in the peritoneal membranes of patients with ultrafiltration failure, indicating that VEGF-D is involved in the development of lymphangiogenesis in peritoneal dialysis patients. These results indicate that VEGFR-3 is a new target to improve net ultrafiltration by suppressing lymphatic absorption and that the 7.5% icodextrin peritoneal equilibration test is useful for estimation of lymphatic absorption.

p70 S6 kinase drives ovarian cancer metastasis through multicellular spheroid-peritoneum interaction and P-cadherin/b1 integrin signaling activation

Peritoneal dissemination as a manifestation of ovarian cancer is an adverse prognostic factor associated with poor clinical outcome, and is thus a potentially promising target for improved treatment. Sphere forming cells (multicellular spheroids) present in malignant ascites of patients with ovarian cancer represent a major impediment to effective treatment. p70 S6 kinase (p70^S6K), which is a downstream effector of mammalian target of rapamycin, is frequently hyperactivated in human ovarian cancer. Here, we identified p70^S6K as an important regulator for the seeding and successful colonization of ovarian cancer spheroids on the peritoneum. Furthermore, we provided evidence for the existence of a novel crosstalk between P-cadherin and β1 integrin, which was crucial for the high degree of specificity in cell adhesion. In particular, we demonstrated that the upregulation of mature β1 integrin occurred as a consequence of P-cadherin expression through the induction of the Golgi glycosyltransferase, ST6Gal-I, which mediated β1 integrin hypersialylation. Loss of p70^S6K or targeting the P-cadherin/β1-integrin interplay could significantly attenuate the metastatic spread onto the peritoneum in vivo. These findings establish a new role for p70^S6K in tumor spheroid-mesothelium communication in ovarian cancer and provide a preclinical rationale for targeting p70^S6K as a new avenue for microenvironment-based therapeutic strategy.

New strategies to improve results of mesh surgeries for vaginal prolapses repair--an update

The use of meshes has become the first option for the treatment of soft tissue disorders as hernias and stress urinary incontinence and widely used in vaginal prolapse's treatment. However, complications related to mesh issues cannot be neglected. Various strategies have been used to improve tissue integration of prosthetic meshes and reduce related complications. The aim of this review is to present the state of art of mesh innovations, presenting the whole arsenal which has been studied worldwide since composite meshes, coated meshes, collagen's derived meshes and tissue engineered prostheses, with focus on its biocompatibility and technical innovations, especially for vaginal prolapse surgery.

AMA1-deficient Toxoplasma gondii parasites transiently colonize mice and trigger an innate immune response that leads to long-lasting protective immunity

The apical membrane antigen 1 (AMA1) protein was believed to be essential for the perpetuation of two Apicomplexa parasite genera, Plasmodium and Toxoplasma, until we genetically engineered viable parasites lacking AMA1. The reduction in invasiveness of the Toxoplasma gondii RH-AMA1 knockout (RH-AMA1(KO)) tachyzoite population, in vitro, raised key questions about the outcome associated with these tachyzoites once inoculated in the peritoneal cavity of mice. In this study, we used AMNIS technology to simultaneously quantify and image the parasitic process driven by AMA1(KO) tachyzoites. We report their ability to colonize and multiply in mesothelial cells and in both resident and recruited leukocytes. While the RH-AMA1(KO) population amplification is rapidly lethal in immunocompromised mice, it is controlled in immunocompetent hosts, where immune cells in combination sense parasites and secrete proinflammatory cytokines. This innate response further leads to a long-lasting status immunoprotective against a secondary challenge by high inocula of the homologous type I or a distinct type II T. gondii genotypes. While AMA1 is definitively not an essential protein for tachyzoite entry and multiplication in host cells, it clearly assists the expansion of parasite population in vivo.

Protein-bound polysaccharide K suppresses tumor fibrosis in gastric cancer by inhibiting the TGF-β signaling pathway

Peritoneal carcinomatosis (PC) is the most frequent metastatic pattern of gastric cancer and its prognosis is extremely poor. PC is characterized by rich fibrosis and the development of obstructive disorders such as ileus, jaundice and hydronephrosis. Epithelial-mesenchymal transition (EMT) is one of the major causes of tissue fibrosis and transforming growth factor β (TGF-β) has a pivotal function in the progression of EMT. Protein-bound polysaccharide K (PSK) is a biological response modifier that can modulate the TGF-β/Smad signaling pathway in vitro. In the present study, we established a fibrotic tumor model using human peritoneal mesothelial cells (HPMCs) and a human gastric cancer cell line to evaluate whether PSK attenuates tumor fibrosis. HPMCs exposed to PSK did not undergo the morphological change from a cobblestone-like pattern to a spindle-shape pattern normally induced by treatment with TGF-β. Immunofluorescence further demonstrated that PSK suppressed TGF-β-induced overexpression of α-SMA in the HPMCs. We further showed that HPMCs contributed to the proliferation of tumor fibrosis by using a mouse xenograft model. Additionally, PSK treatment of these mice significantly reduced the area of observable tumor fibrosis. These results suggest that seeded cancer cells transformed HPMCs into myofibroblast-like cells through their release of TGF-β in the microenvironment, facilitating the development of fibrous tumors in organs covered with HPMCs. Therefore, our study indicates that PSK has potential utility as an anti-fibrotic agent in the treatment of gastric cancer patients with PC.

Can highly purified collagen coating modulate polypropylene mesh immune-inflammatory and fibroblastic reactions? Immunohistochemical analysis in a rat model

INTRODUCTION AND HYPOTHESIS

Collagen has been proposed to be a useful biomaterial, but previous attempts to combine meshes with a collagen membrane have failed. The objective was to verify the effect of high-purified collagen gel coating in the immune-inflammatory response, host collagen metabolism, and angiogenesis around polypropylene mesh.

METHODS

In 20 female Wistar rats were implanted, at one side of the abdominal wall, a monofilament polypropylene mesh (PP), and, on the other side, a mesh coated with a new highly purified collagen gel (PPC). The animals were divided into sub-groups and euthanized at 7, 14, 21, and 90 days after implantation. Immunohistochemical analysis was performed using interleukin 1 (IL-1), matrix metalloproteinases (MMP-2, MMP-3), surface antigen CD-31, and tumor necrosis factor (TNF-α). Objective analysis (percent reactive area, average density, and vessels concentration) was performed using AxioVision Software.

RESULTS

Comparative analysis showed: higher vessel density in the PPC group after 14 days (p = 0.002); a decrease in the average density of MMP-2 in the PPC group after 21 and 90 days (p = 0.046); more stability in the behavior of MMP-3 in the PPC group throughout the periods with the percentage reactive area for MMP-3 showing a significant decrease just in the PP group after 14 and 90 days (p = 0.017), and also for MMP-3 average density, in which reduction was significant after 21 days in the PP group, but not until after 90 days in PPC group (p < 0.001).

CONCLUSIONS

Highly purified collagen coating causes significant changes in angiogenesis and in the immune reaction of metalloproteinase around mesh implants in rats. These findings can be useful for improving mesh biocompatibility for pelvic floor surgery if such effects could be properly controlled.

Peritoneal mesothelium promotes the progression of ovarian cancer cells in vitro and in a mice xenograft model in vivo

The role of mesothelial cells in the intraperitoneal spread of ovarian cancer is still elusive. In particular, it is unclear whether these cells constitute a passive barrier preventing cancer cell progression or perhaps act as an active promoter of this process. In this report we show that omental human peritoneal mesothelial cells (HPMCs) stimulate adhesion and proliferation of ovarian cancer cells (A2780, OVCAR-3, SKOV-3). The latter was associated with the paracrine activity of GRO-1, IL-6, and IL-8 released to the environment by HPMCs. Furthermore, the growth dynamics of ovarian cancer xenografts produced in response to i.p. injection of ovarian cancer cells together with HPMCs was remarkably greater than for implantation of cancer cells alone. A layer of peritoneal mesothelium was consistently present in close proximity to the tumor mass in every xenograft model. In conclusion, our results indicate that HPMCs play a supporting role in the intraperitoneal invasiveness of ovarian malignancy, whose effect may be attributed to their ability to stimulate adhesion and proliferation of cancer cells.

Janus kinase signaling activation mediates peritoneal inflammation and injury in vitro and in vivo in response to dialysate

Peritoneal membrane pathology limits long-term peritoneal dialysis (PD). Here, we tested whether JAK/STAT signaling is implicated and if its attenuation might be salutary. In cultured mesothelial cells, PD fluid activated, and the pan-JAK inhibitor P6 reduced, phospho-STAT1 and phospho-STAT3, periostin secretion, and cleaved caspase-3. Ex vivo, JAK was phosphorylated in PD effluent cells from long-term but not new PD patients. MCP-1 and periostin were increased in PD effluent in long term compared with new patients. In rats, twice daily, PD fluid infusion induced phospho-JAK, mesothelial cell hyperplasia, inflammation, fibrosis, and hypervascularity after 10 days of exposure to PD fluid. Concomitant instillation of a JAK1/2 inhibitor virtually completely attenuated these changes. Thus, our studies directly implicate JAK/STAT signaling in the mediation of peritoneal membrane pathology as a consequence of PD.

Resveratrol inhibits ovarian cancer cell adhesion to peritoneal mesothelium in vitro by modulating the production of α5β1 integrins and hyaluronic acid

OBJECTIVE

Resveratrol (Res) is known to inhibit adhesion of numerous malignancies though its effect on an adherence of ovarian cancer cells to peritoneal mesothelium remains undefined.

METHODS

To address this issue, ovarian cancer cells (A2780, OVCAR-3, SKOV-3) were subjected to Res (10, 50, 100 μM), and then their adhesion to omentum-derived human peritoneal mesothelial cells (HPMCs) was assayed.

RESULTS

The study showed that Res inhibits adhesion of all ovarian cancer cell lines investigated. More importantly, this effect was evident either when cancer cells were directly treated with Res (cell-dependent activity) or when intact cancer cells were pretreated with conditioned medium (CM) generated by their counterparts subjected to Res (medium-dependent activity). Cell-dependent activity of Res has been recognized to be linked with decreased level of cellular α5β1 integrins which decreased functionality corresponds with reduced efficiency of cancer cell adhesion. Medium-related effects have been, in turn, associated with up-regulated secretion of soluble HA to environment (CM). The experiments with exogenous HA revealed the inverse relation between HA concentration in CM and cancer cell adhesion. When the CM from cells subjected with Res (with elevated HA) was supplemented with hyaluronidase, the restoration of cell adhesive capabilities occurred.

CONCLUSIONS

Our studies evidenced that Res affects ovarian cancer cell adhesion to HPMCs by decreasing cellular α5β1 integrin level and by increasing the secretion of HA to environment.

Alterations of intercellular junctions in peritoneal mesothelial cells from patients undergoing dialysis: effect of retinoic Acid

BACKGROUND

Dialysis patients are classified according to their peritoneal permeability as low transporter (LT, low solute permeability) or high transporter (HT, high solute permeability). Tight junction (TJ) proteins are critical to maintain ions, molecules and water paracellular transport through peritoneum. Exposure to peritoneal dialysis solutions causes damage to TJ in human peritoneal mesothelial cells (HPMCs). We analyzed the quantity, distribution and function of TJ proteins: claudin-1, -2 and -8, ZO-1 and occludin, in HPMC cultures from LT and HT patients. Since all-trans retinoic acid (ATRA) might modify the expression of TJ proteins, we studied its effect on HPMCs.

METHODS

Control HPMCs were isolated from human omentum, while HT or LT cells were obtained from dialysis effluents. Cells were cultured in presence of ATRA 0, 50 or 100 nM. Transepithelial electrical resistance (TER) measurement, immunostaining and Western blot analyses were performed.

RESULTS

HT exhibited lower TER than control and LT monolayers. Immunofluorescence for TJ was weak and discontinuous along the cell contour, in LT and HT. Furthermore, claudin-1, occludin and ZO-1 expressions were decreased. In all groups, claudin-2 was localized at nuclei. We observed that ATRA improved TJ distribution and increased TJ expression in HT. This retinoid did not modify claudin-2 and -8 expressions. All-trans retinoic acid decreased TER in HT, but had no effect in LT.

CONCLUSIONS

Tight junctions were altered in HPMCs from dialyzed patients. The HT monolayer has lower TER than LT, which might be associated with the peritoneal permeability in these patients. ATRA might be a therapeutic alternative to maintain mesothelial integrity, since it improved TJ localization and expression.

CD90(+)CD45(-) intraperitoneal mesothelial-like cells inhibit T cell activation by production of arginase I

In this study, we analyzed intraperitoneal cells recovered from human samples and found that CD90(+)CD45(-) cells exist as a minor population but vigorously grow in culture, showing the morphological features of mesothelial cells (MC). Interestingly, the MC highly expressed arginase I and markedly suppressed T cell proliferation with the reduction of CD3 ζ chain expression in T cells stimulated by coated anti-CD3 mAb. The addition of nor-NOHA (500 μM), or L-arginine (1 mM) mostly restored the inhibitory effect of MC on T cell proliferation as well as the reduced expression of CD3 ζ chain. The expression level of CD3 ζ chain in T cells in the peritoneal cavity was significantly down-regulated from circulating T cells. These results suggest that intraperitoneal free MC have immunomodulatory functions through the control of L-arginine level, and thus may play significant roles in the pathogenesis of various diseases in the peritoneal cavity.

Retinoic acid improves morphology of cultured peritoneal mesothelial cells from patients undergoing dialysis

Patients undergoing continuous ambulatory peritoneal dialysis are classified according to their peritoneal permeability as low transporter (low solute permeability) or High transporter (high solute permeability). Factors that determine the differences in permeability between them have not been fully disclosed. We investigated morphological features of cultured human peritoneal mesothelial cells from low or high transporter patients and its response to All trans retinoic Acid (ATRA, vitamin A active metabolite), as compared to non-uremic human peritoneal mesothelial cells. Control cells were isolated from human omentum. High or low transporter cells were obtained from dialysis effluents. Cells were cultured in media containing ATRA (0, 50, 100 or 200 nM). We studied length and distribution of microvilli and cilia (scanning electron microscopy), epithelial (cytokeratin, claudin-1, ZO-1 and occludin) and mesenchymal (vimentin and α-smooth muscle actin) transition markers by immunofluorescence and Western blot, and transforming growth factor β1 expression by Western blot. Low and high transporter exhibited hypertrophic cells, reduction in claudin-1, occludin and ZO-1 expression, cytokeratin and vimentin disorganization and positive α-smooth muscle actin label. Vimentin, α-smooth muscle actin and transforming growth factor-β1 were overexpressed in low transporter. Ciliated cells were diminished in low and high transporters. Microvilli number and length were severely reduced in high transporter. ATRA reduced hypertrophic cells number in low transporter. It also improved cytokeratin and vimentin organization, decreased vimentin and α-smooth muscle actin expression, and increased claudin 1, occludin and ZO-1 expression, in low and high transporter. In low transporter, ATRA reduced transforming growth factor-β1 expression. ATRA augmented percentage of ciliated cells in low and high transporter. It also augmented cilia length in high transporter. Alterations in structure, epithelial mesenchymal markers and transforming growth factor-β1 expression were differential between low and high transporter. Beneficial effects of ATRA were improved human peritoneal mesothelial cells morphology tending to normalize structures.

Collagen/Polypropylene composite mesh biocompatibility in abdominal wall reconstruction

BACKGROUND

Intraperitoneal placement of polypropylene mesh leads to extensive visceral adhesions and is contraindicated. Different coatings are used to improve polypropylene mesh properties. Collagen is a protein with unique biocompatibility and cell ingrowth enhancement potential. A novel acetic acid extracted collagen coating was developed to allow placement of polypropylene mesh in direct contact with viscera. The authors' aim was to evaluate the long-term influence of acetic acid extracted collagen coating on surgical aspects and biomechanical properties of polypropylene mesh implanted in direct contact with viscera, including complications, adhesions with viscera, strength of incorporation, and microscopic inflammatory reaction.

METHODS

Forty adult Wistar rats were divided into two groups: experimental (polypropylene mesh/acetic acid extracted collagen coating) and control (polypropylene mesh only). Astandardized procedure of mesh implantation was performed. Animals were killed 3 months after surgery and analyzed for complications, mesh area covered by adhesions, type of adhesions, strength of incorporation, and intensity of inflammatory response.

RESULTS

The mean adhesion area was lower for polypropylene mesh/acetic acid extracted collagen coating (14.5 percent versus 69.9 percent, p < 0.001). Adhesion severity was decreased in the experimental group: grades 0 and 1 were more frequent (p < 0.04 and p < 0.002, respectively) and grade 3 was less frequent (p < 0.0001). An association between adhesion area and severity was found (p < 0.0001). Complications, strength of incorporation, and intensity of inflammatory response to the mesh were similar.

CONCLUSIONS

Visceral adhesions to polypropylene mesh are significantly reduced because of acetic acid extracted collagen coating. The collagen coating does not increase complications or induce alterations of polypropylene mesh incorporation.

The proto-oncogene c-Fos transcriptionally regulates VEGF production during peritoneal inflammation

Vascular endothelial growth factor (VEGF) and transforming growth factor-β1 (TGF-β1) are key mediators of adverse peritoneal membrane remodeling in peritoneal dialysis eventually leading to ultrafiltration failure. Both are pleiotropic growth factors with cell type-dependent regulation of expression and biological effects. Here we studied regulation of TGF-β1-induced VEGF expression in human peritoneal mesothelial cells in the absence or presence of proinflammatory stimuli, tumor necrosis factor-α (TNF-α) or interleukin-1β (IL-1β). Quiescent human peritoneal mesothelial cells secreted only trace amounts of VEGF. Stimulation with TGF-β1 resulted in time- and dose-dependent increases in VEGF mRNA expression and protein release. TNF-α and IL-1β alone had minimal effects but acted in synergy with TGF-β1. Combined stimulation led to induction of transcription factor c-Fos and activation of the VEGF promoter region with high-affinity binding sites for c-Fos. Inhibition of c-Fos by small interfering RNA interference or by pharmacological blockade with SR-11302 decreased VEGF promoter activity and downregulated its expression and release. Exposure of human peritoneal mesothelial cells to dialysate effluent containing increased levels of TGF-β1, TNF-α, and IL-1β obtained during peritonitis resulted in a dose-dependent VEGF induction that was significantly attenuated by SR-11302. Thus, dialysate TGF-β1, IL-1β, and TNF-α act through c-Fos to synergistically upregulate VEGF production in peritoneal mesothelium and may represent an important regulatory link between inflammation and angiogenesis in the peritoneal membrane.