Influence of monocyte-like cells on the fibrinolytic activity of peritoneal mesothelial cells and the effect of sodium hyaluronate

Role of matrix metalloproteinases in tumour invasion: immunohistochemistry of peritoneum from peritoneal carcinomatosis

Colorectal cancer is one of the most common forms of cancer. Spread of tumour to the peritoneal cavity may lead to seeding of cancer cells that adhere to and invade the peritoneal membrane causing peritoneal carcinomatosis. Matrix metalloproteinases (MMPs) play an essential role in cancer cell invasion and dissemination. The aim of this study was to evaluate the morphology and presence of matrix metalloproteinases in peritoneal carcinomatosis. Biopsy samples of the parietal peritoneum were taken from patients undergoing cytoreductive surgery for peritoneal carcinomatosis. The samples were fixed in formalin, dehydrated and embedded in paraffin prior to cutting into 4-µm slices. Staining with haematoxylin/eosin was used for morphology studies, and MMP-1, MMP-2 and TIMP-1 levels were evaluated using immunohistochemistry and light microscopy. The microscopically tumour-free areas of the peritoneal membrane were thin compared to the peripheral invasion zone and the areas invaded by tumour. Peritoneum invaded by tumour was richly vascularised and contained inflammatory cells. MMP-1 was expressed in tumour-free peritoneum and in the invasion zone between tumour and peritoneal tissue, but not in tumour-invaded areas. MMP-2 and TIMP-1 were mostly expressed in the proximity of blood vessels and inflammatory cells in tumour-invaded areas, but was not seen in tumour-free areas. MMPs play an important role in the process of cancer cell invasion of the peritoneum in peritoneal carcinomatosis. The peripheral zone of the tumour appears to be of importance for tumour invasion.

Regulation of synthesis and roles of hyaluronan in peritoneal dialysis

Hyaluronan (HA) is a ubiquitous extracellular matrix glycosaminoglycan composed of repeated disaccharide units of alternating D-glucuronic acid and D-N-acetylglucosamine residues linked via alternating β-1,4 and β-1,3 glycosidic bonds. HA is synthesized in humans by HA synthase (HAS) enzymes 1, 2, and 3, which are encoded by the corresponding HAS genes. Previous in vitro studies have shown characteristic changes in HAS expression and increased HA synthesis in response to wounding and proinflammatory cytokines in human peritoneal mesothelial cells. In addition, in vivo models and human peritoneal biopsy samples have provided evidence of changes in HA metabolism in the fibrosis that at present accompanies peritoneal dialysis treatment. This review discusses these published observations and how they might contribute to improvement in peritoneal dialysis.

Stimulation of TLRs by LMW-HA induces self-defense mechanisms in vaginal epithelium

The innate immune system is present throughout the female reproductive tract and functions in synchrony with the adaptive immune system to provide protection in a way that enhances the chances for fetal survival, while protecting against potential pathogens. Recent data show that activation of Toll-like receptor (TLR)2 and 4 by low-molecular weight hyaluronic acid (LMW-HA) in the epidermis induces secretion of the antimicrobial peptide β-defensin 2. In the present work, we show that LMW-HA induces vaginal epithelial cells to release different antimicrobial peptides, via activation of TLR2 and TLR4. Further, we found that LMW-HA favors repair of vaginal epithelial injury, involving TLR2 and TLR4, and independently from its classical receptor CD44. This wound-healing activity of LMW-HA is dependent from an Akt/phosphatidylinositol 3 kinase pathway. Therefore, these findings suggest that the vaginal epithelium is more than a simple physical barrier to protect against invading pathogens: on the contrary, this surface acts as efficient player of innate host defense, which may modulate its antimicrobial properties and injury restitution activity, following LMW-HA stimulation; this activity may furnish an additional protective activity to this body compartment, highly and constantly exposed to microbiota, ameliorating the self-defense of the vaginal epithelium in both basal and pathological conditions.

Intercellular adhesion molecule-1 and gelatinase expression in human peritoneal mesothelial cells during propagation in culture

Mesothelial cells are involved in a variety of biological processes, which include the formation of peritoneal adhesions. The cultures of human peritoneal mesothelial cells comprise an important tool to investigate the behavior and functions of mesothelial cells. Very little is known about the differences among mesothelial cells isolated from different sources and about the changes in specific functions as caused by cell propagation in vitro or that result from storage of cells at low temperatures. This study aims to characterize 2 particular cellular activities relevant for tissue repair, which include the expression of intercellular adhesion molecule-1 (ICAM-1) and the gelatinase activity; in addition, this study will assess the effect of hyaluronan, which is an antiadhesive agent, on these cellular activities. Viable cell lines were established from both omentum and peritoneal lavage fluid from 7 patients. Both ICAM-1 expression, which was measured by enzyme-linked immunosorbent assay (ELISA), and matrix metalloproteinase (MMP) bioactivity, which was measured by zymography, were measured in the 2nd and 4th passage; the latter also was measured after freezing and storing of cells in liquid nitrogen. The effects of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), phorbol myristate acetate (PMA), and hyaluronan were analyzed. ICAM-1 was constitutively expressed and stimulated by IL-1beta, TNF-alpha, and PMA. All cell lines produced both MMP-2 and MMP-9. Only the latter activity was affected by TNF-alpha and, especially so, PMA. Differences were found between the 2nd and 4th passage, as well as between cells of different lineage, mostly so if the relative stimulation by the various agents was compared. The addition of sodium hyaluronate either to control cultures or to cultures together with any of the 3 stimuli examined did not significantly change either ICAM-1 expression or gelatinase activity. The freezing and storage of cells did not affect their functions. Both the human omentum and peritoneal lavage fluid are good sources to establish mesothelial cell lines, which can be propagated also after freezing without qualitative changes in their ability to express ICAM-1 and produce the gelatinases. For omental cells, a differential effect of stimulation occurs depending on whether the cells have been passaged 2 or 4 times. The presence of hyaluronan did not affect the expression of ICAM-1 or the gelatinases.

Practical limitations of bioresorbable membranes in the prevention of intra-abdominal adhesions

INTRODUCTION

Intra-abdominal adhesions are a significant source of postoperative morbidity. Bioresorbable barriers composed of hyaluronic acid and carboxymethylcellulose (HA/CMC) reduce adhesion formation by physically separating injured or healing peritoneal surfaces. To assess whether the efficacy of a physical barrier can extend beyond the site of application, we evaluated the effectiveness of an HA/CMC barrier in preventing adhesions distal to the site of placement.

METHODS

Adhesions were induced in rats by creating peritoneal ischemic buttons on either side of a midline incision. An HA/CMC barrier (Seprafilm Genzyme) was intraoperatively placed either under the midline incision, unilaterally over half the ischemic buttons, or bilaterally over all ischemic buttons. Control buttons received no HA/CMC. On day 7 adhesions were scored. In similar experiments, peritoneal fluid was collected at 24 h to assess the effects of HA/CMC on tissue plasminogen activator activity.

RESULTS

Placement of HA/CMC under the midline incision did not reduce adhesion formation to distal ischemic buttons (72 +/- 7%) compared to controls (80 +/- 8%). Unilateral placement of HA/CMC significantly (p < 0.05) reduced adhesion formation to those ischemic buttons over which the barrier was applied (35 +/- 7%) compared to both contralateral (83 +/- 9%) and control (80 +/- 8%) ischemic buttons. The bilateral application of HA/CMC also significantly (p < 0.05) reduced adhesion formation to all ischemic buttons compared to controls (22 +/- 7% vs. 66 +/- 7%, respectively). HA/CMC did not affect peritoneal tPA activity.

CONCLUSIONS

Effective adhesion reduction by the physical barrier HA/CMC appears to be limited to the site of application in this rat model. Despite the presence of a bioresorbable membrane at predicted sites of adhesion formation in the peritoneal cavity, adhesions readily form to distal unprotected sites.

Use of barrier products in the prevention of adhesion formation following surgery

Postoperative adhesion formation is a significant health-care problem with no universally accepted method of prevention. Barrier methods of prevention have been extensively tested and licensed, and this article examines the evidence.

Low molecular weight hyaluronic acid increases the self-defense of skin epithelium by induction of beta-defensin 2 via TLR2 and TLR4

In sites of inflammation or tissue injury, hyaluronic acid (HA), ubiquitous in the extracellular matrix, is broken down into low m.w. HA (LMW-HA) fragments that have been reported to activate immunocompetent cells. We found that LMW-HA induces activation of keratinocytes, which respond by producing beta-defensin 2. This production is mediated by TLR2 and TLR4 activation and involves a c-Fos-mediated, protein kinase C-dependent signaling pathway. LMW-HA-induced activation of keratinocytes seems not to be accompanied by an inflammatory response, because no production of IL-8, TNF-alpha, IL-1beta, or IL-6 was observed. Ex vivo and in vivo treatments of murine skin with LMW-HA showed a release of mouse beta-defensin 2 in all layers of the epidermal compartment. Therefore, the breakdown of extracellular matrix components, for example after injury, stimulates keratinocytes to release beta-defensin 2, which protects cutaneous tissue at a time when it is particularly vulnerable to infection. In addition, our observation might be important to open new perspectives in the development of possible topical products containing LMW-HA to improve the release of beta-defensins by keratinocytes, thus ameliorating the self-defense of the skin for the protection of cutaneous tissue from infection by microorganisms.

Human peritoneal mesothelial cells isolated from spent dialysate fluid maintain contaminating macrophages via production of macrophage colony stimulating factor

BACKGROUND

Human peritoneal mesothelial cells (HPMC) are useful for the analysis of peritoneal reactions to various insults and to peritoneal dialysate. HPMC can be readily obtained from spent dialysis fluid, but leucocyte contamination is a major problem when using these cells for in vitro experiments. Therefore, we examined the persistence of leucocyte contamination in HPMC cultures obtained from spent dialysate.

METHODS

Cells were obtained from spent patient dialysate bags by centrifugation and analysed for specific cell phenotypes by flow cytometry at the initial collection and during sequential passages in cell culture. Cell proliferation was assessed by either bromodeoxyuridine incorporation or a dehydrogenase assay. Cytokine secretion was analysed by enzyme-linked immunosorbent assay.

RESULTS

Spent dialysate bags contained two major cell populations: CD45+ leucocytes and cytokeratin-8/18+ cells. Initially, most collected cells were CD45+, but their numbers decreased rapidly during the first week of culture. However, a persistent contamination of CD45+ leucocytes, approximately 20% of cells, was evident during the next three passages. This persistent CD45+ contamination was identified as CD68+ macrophages and contained bromodeoxyuridine + proliferating cells. These macrophages could be removed by fluorescence-activated cell sorting using anti-CD45 antibody, resulting in highly purified HPMC which expressed cytokeratin-8/18 and calretinin. Supernatant obtained from these purified HPMC contained macrophage colony stimulating factor and induced proliferation of bone marrow-derived macrophages.

CONCLUSION

Spent dialysate contains macrophages which persist in culture and are associated with HPMC secretion of macrophage colony stimulating factor and macrophage proliferation. Therefore, contaminating macrophages should be specifically removed from HPMC preparations before performing in vitro studies.