Paracrine interactions between mesothelial and colon-carcinoma cells in a rat model

Role of IGF-1R in epithelial-mesenchymal transdifferentiation of human peritoneal mesothelial cells

BACKGROUND

Peritoneal fibrosis (PF) is caused by epithelial-mesenchymal transdifferentiation (EMT) in the peritoneum under high glucose (HG) conditions. The study aimed to explored the role of Insulin-like growth factor 1 receptor (IGF-1R) in the regulation of EMT in human peritoneal mesothelial cells (HPMCs).

METHODS

We used HG peritoneal dialysis fluid (PDF) to induce in vivo PF in mice, and treated HPMCs with HG in vitro to stimulate EMT.

RESULTS

In the mice, the higher the glucose concentration in the dialysate, the more obvious the peritoneal tissue thickening and the more that collagen was deposited. The in vitro study indicated that the expression of IGF-1R, α-SMA, vimentin was upregulated, while the expression of occludin, ZO-1, and E-cadherin was downregulated in HPMCs under HG and IGF-1R overexpression conditions. Conversely, the expression of IGF-1R, α-SMA, and vimentin was downregulated, while the expression of occludin, ZO-1, and E-cadherin was upregulated in IGF-1R-underexpressed HPMCs under HG conditions. The cell migration abilities were increased, while the cell adhesion abilities were reduced in HPMCs under HG and IGF-1R overexpression conditions. In contrast, cell migration abilities were reduced, while cell adhesion abilities were increased in IGF-1Runderexpressed HPMCs under HG conditions.

CONCLUSIONS

Targeting at IGF-1R may provide novel insights into the prevention and treatment of PF.

Ovarian Cancer-Associated Mesothelial Cells: Transdifferentiation to Minions of Cancer and Orchestrate Developing Peritoneal Dissemination

Ovarian cancer has one of the poorest prognoses among carcinomas. Advanced ovarian cancer often develops ascites and peritoneal dissemination, which is one of the poor prognostic factors. From the perspective of the "seed and soil" hypothesis, the intra-abdominal environment is like the soil for the growth of ovarian cancer (OvCa) and mesothelial cells (MCs) line the top layer of this soil. In recent years, various functions of MCs have been reported, including supporting cancer in the OvCa microenvironment. We refer to OvCa-associated MCs (OCAMs) as MCs that are stimulated by OvCa and contribute to its progression. OCAMs promote OvCa cell adhesion to the peritoneum, invasion, and metastasis. Elucidation of these functions may lead to the identification of novel therapeutic targets that can delay OvCa progression, which is difficult to cure.

Number of mesothelial cells as a measure of adequacy criteria for pleural effusions: A multi-institutional study

BACKGROUND

The development of a terminology system is essential to allow uniformity in reporting serous fluid specimens. An important topic to cover is the issue of specimen adequacy. In the present study, we aimed to evaluate whether there is a correlation between number of mesothelial cells and overall improved sensitivity and adequacy control of tests.

METHODS

Cases of negative pleural fluids with concomitant positive pleural biopsies were selected from two referral institutions, with observation of the number of mesothelial cells in 10 high-power fields, comparing the results with a control group (cases with negative biopsies, ie, true negatives). Comparisons were conducted using the nonparametric Mann-Whitney U test. Data were analysed for sensitivity and specificity derived from the receiver operating characteristics curve. For the choice of an optimal cut-off of mesothelial cells, receiver operating curve analysis was constructed and the Youden index was calculated.

RESULTS

A total of 112 pleural effusions with paired pleural biopsies were studied. There was no difference in distributions of the number of mesothelial cells between cases with a positive biopsy (false negatives) and the control group (median = 39 vs median = 30, respectively, P-value = .974). However, simple logistic regression found a cut-off of 750 cells per 10 high-power fields as an optimal number for improved sensitivity (72.7%), with fair discriminatory power.

CONCLUSIONS

Enumeration of mesothelial cells may improve the sensitivity of the cytological diagnosis of malignant pleural effusion, serving as an internal quality control for the test's overall accuracy.

Adipose-Derived Stromal Vascular Fraction and Cultured Stromal Cells as Trophic Mediators for Tendon Healing

Adipose-derived stromal vascular fraction (SVF) is a heterogeneous population of cells that yields a homogeneous population of plastic-adherent adipose tissue-derived stromal cells (ASC) when culture-expanded. SVF and ASC have been used clinically to improve tendon healing, yet their mechanism of action is not fully elucidated. The objective of this study was to investigate the potential for ASC to act as trophic mediators for tendon healing. Flexor digitorum superficialis tendons and adipose tissue were harvested from adult horses to obtain SVF, ASC, and tenocytes. Growth factor gene expression was quantified in SVF and ASC in serial passages and growth factors were quantified in ASC-conditioned medium (CM). Microchemotaxis assays were performed using ASC-CM. Tenocytes were grown in co-culture with autologous ASC or allogeneic SVF. Gene expression for insulin-like growth factor 1 (IGF-1), stromal cell-derived factor-1α (SDF-1α), transforming growth factor-β1 (TGF-β1) and TGF-β3 was significantly higher in SVF compared to ASC. Concentrations were significantly increased in ASC-CM compared to controls for IGF-1 (4-fold) and SDF-1α (6-fold). Medium conditioned by ASC induced significant cell migration in a dose-dependent manner. Gene expression for collagen types I and III, decorin, and cartilage oligomeric matrix protein was modestly, but significantly increased following co-culture of tenocytes with autologous ASC. Our findings support the ability of SVF and ASC to act as trophic mediators in tendon healing, particularly through chemotaxis, which stands to critically impact the intrinsic healing response. In vivo studies to further delineate the potential for SVF and/or ASC to improve tendon healing are warranted. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1429-1439, 2019.

Investigation of Metastasis-Related Genes: A Rat Model Mimicking Liver Metastasis of Colorectal Carcinoma

Liver is the main target of colorectal cancer (CRC) metastasis. Currently, the number of reports is small, which describe changes in gene expression supporting liver metastasis. Here, a rat model was used for analyzing mRNA modulations during liver colonization and compared with available literature. In the model, CC531 rat CRC cells were injected via a mesenteric vein into isogenic WAG/Rij rats and re-isolated at early, intermediate, advanced, and terminal stages of liver colonization. These cells were used for RNA isolation. Microarrays were used for analyzing mRNA profiles of expression. The number of deregulated genes is comparatively large and only part of it has been studied so far. As reported to date, claudins and insulin-like growth factor-binding proteins (IGFBPs) were found to be deregulated. The fact that the chosen method is efficient is confirmed by the study of claudins and IGFBPs, which show altered expression in the initial stages of liver colonization and then return to normalcy. In addition, cadherin was described to be downregulated in epithelial-mesenchymal transition models. It can, therefore, be concluded that the models used are helpful in finding genes, which are instrumental for metastatic liver colonization.

Malignant pleural effusion: from bench to bedside

Malignant pleural effusion (MPE) is a common but serious condition that is related with poor quality of life, morbidity and mortality. Its incidence and associated healthcare costs are rising and its management remains palliative, with median survival ranging from 3 to 12 months. During the last decade there has been significant progress in unravelling the pathophysiology of MPE, as well as its diagnostics, imaging, and management. Nowadays, formerly bed-ridden patients are genotyped, phenotyped, and treated on an ambulatory basis. This article attempts to provide a comprehensive overview of current advances in MPE from bench to bedside. In addition, it highlights unanswered questions in current clinical practice and suggests future directions for basic and clinical research in the field.

Co-culture systems and technologies: taking synthetic biology to the next level

Co-culture techniques find myriad applications in biology for studying natural or synthetic interactions between cell populations. Such techniques are of great importance in synthetic biology, as multi-species cell consortia and other natural or synthetic ecology systems are widely seen to hold enormous potential for foundational research as well as novel industrial, medical and environmental applications with many proof-of-principle studies in recent years. What is needed for co-cultures to fulfil their potential? Cell-cell interactions in co-cultures are strongly influenced by the extracellular environment, which is determined by the experimental set-up, which therefore needs to be given careful consideration. An overview of existing experimental and theoretical co-culture set-ups in synthetic biology and adjacent fields is given here, and challenges and opportunities involved in such experiments are discussed. Greater focus on foundational technology developments for co-cultures is needed for many synthetic biology systems to realize their potential in both applications and answering biological questions.

Metamorphosis of mesothelial cells with active horizontal motility in tissue culture

Mesothelial cells, which have diverse roles in physiology and pathology, constitute the mesothelium along with connective tissue and the basement membrane; the mesothelium serves to shield the somatic cavities. After mesothelial injury, mesothelial cells undergo tissue recovery. However, the mechanism of mesothelial regeneration remains poorly understood. In this study, we used confocal time-lapse microscopy to demonstrate that transformed mesothelial cells (MeT5A) and mouse peritoneal mesothelial cells can randomly migrate between cells in cell culture and in ex vivo tissue culture, respectively. Moreover, peritoneal mesothelial cells changed their morphology from a flattened shape to a cuboidal one prior to the migration. Conversely, MDCKII epithelial cells forming tight cell–cell contacts with one another do not alter the arrangement of adjacent cells during movement. Our evidence complements the current hypotheses of mesothelial regeneration and suggests that certain types of differentiated mesothelial cells undergo morphological changes before initiating migration to repair injured sites.

Effects of type I interferons on IGF-mediated autocrine/paracrine growth of human neuroendocrine tumor cells

We recently demonstrated that interferon (IFN)-beta has a more potent antitumor activity than IFN-alpha in BON cells, a neuroendocrine tumor (NET) cell line. The present study showed the role of type I IFNs in the modulation of the insulin-like growth factor (IGF) system in NETs. BON cells expressed IGF-I, IGF-II, IGF-I receptor, and insulin receptor mRNA. In addition, IGF-I and IGF-II stimulated the proliferation of BON cells and induced an inhibition of DNA fragmentation (apoptosis). As evaluated by quantitative RT-PCR, treatment with IFN-alpha (100 IU/ml) or IFN-beta (100 IU/ml) inhibited the expression of IGF-II mRNA (-42% and -65%, respectively, both P < 0.001), whereas IGF-I receptor mRNA was significantly upregulated by IFN-alpha (+28%, P < 0.001) and downregulated by IFN-beta (-47%, P < 0.001). Immunoreactive IGF-II concentration decreased in the conditioned medium during IFN-alpha (-16%, P < 0.05) and IFN-beta (-69%, P < 0.001) treatment. Additionally, IGF-I receptor bioactivity was reduced (-54%) after IFN-beta treatment. Scatchard analysis of (125)I-labeled IGF-I binding to cell membrane of BON cells revealed a dramatic suppression of maximum binding capacity only in the presence of IFN-beta. Finally, the proapoptotic activity of IFN-beta was partially counteracted by the coadministration of IGF-I and IGF-II (both at 50 nM). In conclusion, these data demonstrate that the IGF system has an important role in autocrine/paracrine growth of BON cells. The more potent antitumor activity of IFN-beta compared with IFN-alpha could be explained by several effects on this system: 1) both IFNs inhibit the transcription of IGF-II, but the suppression is significantly higher after IFN-beta than IFN-alpha and 2) only IFN-beta inhibits the expression of IGF-I receptor.

Use of a novel 3D culture model to elucidate the role of mesothelial cells, fibroblasts and extra-cellular matrices on adhesion and invasion of ovarian cancer cells to the omentum

The omentum is a major site of ovarian cancer metastasis. Our goal was to establish a three-dimensional (3D) model of the key components of the omental microenvironment (mesothelial cells, fibroblasts and extracellular matrices) to study ovarian cancer cell adhesion and invasion. The 3D model comprised of primary human fibroblasts extracted from normal human omentum, mixed with ECM and covered by a layer of primary human mesothelial cells, also from normal human omentum. After addition of ovarian cancer cells, the histological appearance of the 3D culture mimicked microscopic metastases to the omentum from patients with ovarian cancer. When ovarian cancer cells, SKOV3ip.1 and HeyA8, were applied to the 3D omental culture, 60% and 68% of all cells attached, respectively, but only 18% and 25% were able to invade. Ovarian cancer cells preferentially adhered to and invaded collagen I, followed by binding to collagen IV, fibronectin, vitronectin, laminin 10 and 1. Omental mesothelial cells significantly inhibited ovarian cancer cell adhesion and invasion, while omental fibroblasts induced adhesion and invasion. This effect is clearly mediated by direct cell-cell contact, since conditioned medium from mesothelial cells or fibroblasts has a minimal, or no, effect on ovarian cancer cell adhesion and invasion. In summary, we have established a 3D model to study the early steps of ovarian cancer metastasis to the human omentum, and found that omental mesothelial cells inhibit, while omental fibroblasts and the ECM enhance, the attachment and invasion of ovarian cancer cells.

Mesothelial progenitor cells and their potential in tissue engineering

The mesothelium consists of a single layer of flattened mesothelial cells that lines serosal cavities and the majority of internal organs, playing important roles in maintaining normal serosal integrity and function. A mesothelial 'stem' cell has not been identified, but evidence from numerous studies suggests that a progenitor mesothelial cell exists. Although mesothelial cells are of a mesodermal origin, they express characteristics of both epithelial and mesenchymal phenotypes. In addition, following injury, new mesothelium regenerates via centripetal ingrowth of cells from the wound edge and from a free-floating population of cells present in the serosal fluid, the origin of which is currently unknown. Recent findings have shown that mesothelial cells can undergo an epithelial to mesenchymal transition, and transform into myofibroblasts and possibly smooth muscle cells, suggesting plasticity in nature. Further evidence for a mesothelial progenitor comes from tissue engineering applications where mesothelial cells seeded onto tubular constructs have been used to generate vascular replacements and grafts to bridge transected nerve fibres. These findings suggest that mesothelial cell progenitors are able to switch between different cell phenotypes depending on the local environment. However, only by performing detailed investigations involving selective cell isolation, clonal analysis together with cell labelling and tracking studies, will we begin to determine the true existence of a mesothelial stem cell.

Increased expression of dipeptidyl peptidase IV in human mesothelial cells by malignant ascites from ovarian carcinoma patients

Cell surface aminopeptidases play an important role in biological processes through degradation of small peptides. There are many bioactive peptides in ascites and these peptides are involved in carcinoma cell dissemination and infiltration. In human mesothelial cells dipeptidyl peptidase IV (DPPIV) shows the highest expression mostly in four cell surface aminopeptidases: aminopeptidase A, neutral endopeptidase 24-11, aminopeptidase N and DPPIV. Since mesothelial cells are always in contact with ascites, we examined the influence of malignant ascites on DPPIV. DPPIV enzyme activity in mesothelial cells was enhanced by the addition of ascites obtained from ovarian carcinoma patients in a time- and concentration-dependent manner, and flow cytometry and immunocytochemistry also revealed an increased expression of DPPIV on the cell surface of mesothelial cells. The <3-kD fraction of malignant ascites increased the DPPIV enzyme activity to the same level as the total ascites. Northern hybridization demonstrated that DPPIV mRNA was increased 3-fold by the addition of the <3-kD malignant ascites. In conclusion, DPPIV is highly expressed in human mesothelial cells and was regulated by ascites.

Mesothelial cells: their structure, function and role in serosal repair

The mesothelium is composed of an extensive monolayer of specialized cells (mesothelial cells) that line the body's serous cavities and internal organs. Traditionally, this layer was thought to be a simple tissue with the sole function of providing a slippery, non-adhesive and protective surface to facilitate intracoelomic movement. However, with the gradual accumulation of information about serosal tissues over the years, the mesothelium is now recognized as a dynamic cellular membrane with many important functions. These include transport and movement of fluid and particulate matter across the serosal cavities, leucocyte migration in response to inflammatory mediators, synthesis of pro-inflammatory cytokines, growth factors and extracellular matrix proteins to aid in serosal repair, release of factors to promote both the deposition and clearance of fibrin, and antigen presentation. Furthermore, the secretion of molecules, such as glycosaminoglycans and lubricants, not only protects tissues from abrasion, but also from infection and possibly tumour dissemination. Mesothelium is also unlike other epithelial-like surfaces because healing appears diffusely across the denuded surface, whereas in true epithelia, healing occurs solely at the wound edges as sheets of cells. Although controversial, recent studies have begun to shed light on the mechanisms involved in mesothelial regeneration. In the present review, the current understanding of the structure and function of the mesothelium and the biology of mesothelial cells is discussed, together with recent insights into the mechanisms regulating its repair.

Effect of inflammatory cytokines and growth factors on tumour cell adhesion to the peritoneum

In this experimental study, the effect of inflammatory cytokines and growth factors on tumour cell adhesion to the peritoneum was investigated. A reproducible in vitro assay was developed to study the adhesion of CC531 colon carcinoma cells to an autologous monolayer of rat mesothelial cells. Tumour cell adhesion to mesothelium pre-incubated with interleukin-1beta (IL-1beta) and epidermal growth factor (EGF) resulted in at least 60% more tumour cell adhesion at maximal stimulation (p</=0.001). Transforming growth factor-beta (TGF-beta) pre-incubation resulted in minor, though significant stimulation of cell adhesion (maximal 16%, p<0.05). The effect of IL-1beta was time- and dose-dependent. No mesothelial cell proliferation took place after pretreatment with IL-1beta, indicating that enhanced adhesion was not based on an increase in the number of mesothelial cells. Pretreatment with EGF stimulated mesothelial cell growth as measured by DNA analysis. This effect on cell growth and adhesion was dose-dependent. Additional blocking experiments with anti-IL-1beta resulted in statistically significant inhibition of IL-1beta-stimulated tumour cell adhesion (p</=0.01), demonstrating the specificity of this effect. Interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), IL-6, and insulin-like growth factor (IGF-I) pre-incubation had no effect on tumour cell adhesion. These results prove that IL-1beta and EGF are significant promoting factors in tumour cell adhesion to mesothelium in vitro and may therefore account for tumour recurrence in the peritoneum in vivo.

Co-culture of human monocytes and thyrocytes in bicameral chamber: monocyte-derived IL-1alpha impairs the thyroid epithelial barrier

Pro-inflammatory cytokines are important mediators in tissue responses to a wide range of endogenous (e.g. autoantigens) and exogenous (e.g. infections, wounds, biomaterials) stimuli. The complex interactions taking place between different cell types in such processes are difficult to examine in vivo. Here we studied the effect of human monocytes on thyroid epithelial cells co-cultured in bicameral chambers. Freshly isolated monocytes (1x10(6)/ml) added to the basal compartment reduced the transepithelial resistance (from 300-600 to <100 Omega.cm(2)) and caused a disruption of the tight junctions in apically grown thyrocyte monolayers after co-culture for 24 h. The barrier function was further attenuated by monocytes exposed to lipopolysaccharide (10 microg/ml) or polystyrene microspheres (size: 3 microm; 1x10(7)/ml). Loss of transepithelial resistance was accompanied by release of interleukin 1alpha (maximally 550 pg/ml) from the monocytes. Conversely, the resistance remained high when co-cultures were simultaneously incubated with neutralizing anti-human interleukin 1alpha antibodies. The results show that the integrity of cultured thyroid epithelium is impaired by monocytes without requirement of direct cell-to-cell contact. This action, mediated by interleukin-1alpha, suggests a mechanism by which hidden (lumenal) autoantigens might be exposed to interstitial antigen-presenting cells in autoimmune thyroid disease. In perspective, the model provides a tool in which humoral and cell-cell dependent processes generated by bioactive agents and particulate materials, for instance, during the healing and repair of tissue around biomaterials and hybrid implants, can be selectively examined.

Red blood cells inhibit tumour cell adhesion to the peritoneum

BACKGROUND

Perioperative blood transfusion has been associated with increased tumour recurrence and poor prognosis in colorectal cancer. Blood loss in the peritoneal cavity might be a tumour-promoting factor for local recurrence. The aim of this study was to investigate whether blood in the peritoneal cavity affects local tumour recurrence.

METHODS

In an established in vivo rat model the effect of 1.5 ml syngeneic whole blood on tumour cell adhesion and tumour growth was investigated. In the same model the effect of 1.5 ml pure red blood cell (RBC) concentrate and 1.5 ml RBC-derived substances on tumour cell adhesion was studied. In an established in vitro model the effect of increasing numbers of RBCs (0-250 bx 10(6)) on tumour cell adhesion and tumour growth was assessed.

RESULTS

Both the presence of blood and RBC concentrate in the peritoneal cavity prevented tumour cell adhesion in vivo (overall P </= 0.001 and P </= 0.05 respectively), rather than promoting adherence. RBC concentrate and RBC-derived substances had a comparable inhibitory effect on tumour cell adhesion. In in vitro studies RBCs inhibited tumour cell adhesion but not tumour growth.

CONCLUSION

RBC-derived factors prevent tumour cell adhesion to the peritoneum, and consequently tumour recurrence.