Novel and simple method for isolating autologous mesothelial cells from the tunica vaginalis

Generation of mesothelial progenitor-like cells from mouse-induced pluripotent stem cells

Mesothelial cells, which cover the surface of visceral organs and serous cavities in mammals, play a crucial role in preventing adhesion. We previously reported that primary mesothelial progenitor cells (MPCs) can not only prevent postoperative adhesion but also promote liver regeneration after hepatectomy. Induced pluripotent stem cells (iPSCs) have the potential to be used for regenerative medicine. Here, we have established a differentiation protocol for mouse iPSC-derived MPCs (miMPCs) via the exposure to defined factors, as well as purification using MPC-specific cell surface antigens. Furthermore, the miMPCs had the ability to suppress postoperative adhesion and facilitate liver regeneration. This is the first report highlighting the generation of functional miMPCs, which may offer potential for de novo cell therapy.

Autologous peritoneal grafts permit rapid reperitonealization and prevent postoperative abdominal adhesions in an experimental rat study

BACKGROUND

Reperitonealization has attracted increasing attention for its potential to prevent postoperative abdominal adhesions and subsequent related complications. We studied the effect of an autologous peritoneal graft on reperitonealization and prevention of adhesions in a rat model.

METHODS

A standardized peritoneal lesion was induced on the parietal peritoneum by electrocoagulation and sutures. Twenty adult rats sustaining these lesions were randomized to 1 of 4 groups: (1) autologuous peritoneal graft with the side of mesothelial cells exposed to the abdominal cavity; (2) autologuous peritoneal graft with the side of subserosa containing fibroblasts exposed to the abdominal cavity; (3) cell sheet consisting of autologuous mesothelial cells and fibroblasts; or (4) nontreated group (Control). Fourteen days after the operation, abdominal adhesions were evaluated by macroscopic observation and histologic assessment.

RESULTS

Macroscopic observation revealed that in mesothelial cells/fibroblasts grafts, there was no adhesion on the surface of the peritoneal graft covering the lesion. In contrast, in the other 3 groups, all rats obviously revealed extended and severe adhesions. Histology showed that mesothelial cells exist on the surface of the graft in mesothelial cells/fibroblasts graft, but no mesothelial cells were observed in the samples from the other groups.

CONCLUSION

Autologous peritoneal grafts prevented postoperative abdominal adhesions in this rat model. As the mechanism of this prevention, the mesothelial cells survived and contributed to reperitonealization, only when they were transplanted as a part of the autologous peritoneal grafts and were located on the surface exposed to the abdomen.

Mesothelial cell transplantation: history, challenges and future directions

Mesothelial cells line the surface of the pleura, pericardium, peritoneum and internal reproductive organs. One of their main functions is to act as a non-adhesive barrier to protect against physical damage, however, over the past decades their physiological and pathological properties have been revealed in association with a variety of conditions and diseases. Mesothelium has been used in surgical operations in clinical settings, such as omental patching for perforated peptic ulcers and in glutaraldehyde-treated autologous pericardium for aortic valve reconstruction. Various methods for mesothelial cell transplantation have also been established and developed, particularly within the area of tissue engineering, including scaffold and non-scaffold cell sheet technologies. However, the use of mesothelial cell transplantation in patients remains challenging, as it requires additional operations under general anesthesia in order to obtain enough intact cells for culture. Moreover, the current methods of mesothelial cell transplantation are expensive and are not yet available in clinical practice. This review firstly summarizes the history of the use of mesothelial cell transplantation in tissue engineering, and then critically discusses the barriers for the clinical application of mesothelial cell transplantation. Finally, the recent developments in xenotransplantation technologies are discussed to evaluate other feasible alternatives to mesothelial cell transplantation.

Use of Mesothelial Cells and Biological Matrices for Tissue Engineering of Simple Epithelium Surrogates

Tissue-engineering technologies have progressed rapidly through last decades resulting in the manufacture of quite complex bioartificial tissues with potential use for human organ and tissue regeneration. The manufacture of avascular monolayered tissues such as simple squamous epithelia was initiated a few decades ago and is attracting increasing interest. Their relative morphostructural simplicity makes of their biomimetization a goal, which is currently accessible. The mesothelium is a simple squamous epithelium in nature and is the monolayered tissue lining the walls of large celomic cavities (peritoneal, pericardial, and pleural) and internal organs housed inside. Interestingly, mesothelial cells can be harvested in clinically relevant numbers from several anatomical sources and not less important, they also display high transdifferentiation capacities and are low immunogenic characteristics, which endow these cells with therapeutic interest. Their combination with a suitable scaffold (biocompatible, degradable, and non-immunogenic) may allow the manufacture of tailored serosal membranes biomimetics with potential spanning a wide range of therapeutic applications, principally for the regeneration of simple squamous-like epithelia such as the visceral and parietal mesothelium vascular endothelium and corneal endothelium among others. Herein, we review recent research progresses in mesothelial cells biology and their clinical sources. We make a particular emphasis on reviewing the different types of biological scaffolds suitable for the manufacture of serosal mesothelial membranes biomimetics. Finally, we also review progresses made in mesothelial cells-based therapeutic applications and propose some possible future directions.

Peritoneal cell sheets composed of mesothelial cells and fibroblasts prevent intra-abdominal adhesion formation in a rat model

Postoperative intra-abdominal adhesions remain an unsolved problem despite significant progress in the surgical procedures themselves. They often lead to small-bowel obstruction, chronic abdominal and pelvic pain, as well as female infertility. The loss of mesothelial cells and several components of the inflammatory system following injury to the peritoneum results in fibrin formation and angiogenesis. The remaining fibrin matrix and angiogenesis lead to replacement by fibroblasts and fibrous band formation. The aim of this study was to develop a new therapeutic method of preventing intra-abdominal adhesions. We fabricated transplantable peritoneal cell sheets from the rat peritoneum by cell sheet engineering using a temperature-responsive culture system. The peritoneal cell sheets developed were composed of an upper monolayer of mesothelial cells and underlying multilayered fibroblasts, similar to the peritoneum in vivo. Transplantation of peritoneal cell sheets prevented tissue adhesion, fibrin deposition and angiogenesis, and, moreover, lymphangiogenesis and macrophage infiltration in a rat caecum cauterization adhesion model. Copyright © 2013 John Wiley & Sons, Ltd.

Thiols stabilize cobblestone morphology of cultured mesothelial cells

Cellular thiols including GSH (glutathione) and L-Cys (L-cysteine) are essential for cell signalling, growth and differentiation. L-Cys is derived from the extracellular thiol pool and is the rate-limiting compound for intracellular GSH biosynthesis. The present study investigated the effect of thiol-supplemented medium on cell growth, phenotype and total GSH of cultured hPMCs (human peritoneal mesothelial cells). Cells were cultured in medium M199 supplemented with 2% serum, with 'plus' or without 'minus' L-Cys and compared with medium supplemented with either β-ME (β-mercaptoethanol) (0.25 mmol/l) or the receptor tyrosine kinase ligand EGF (epidermal growth factor, 100 ng/ml). β-ME produced a disproportionate increase in total GSH compared with L-Cys and other thiols tested [(procysteine (2-oxothiazolidine-4-carboxylic acid) or NAC (N-acetyl-L-cysteine)], while growth and morphology were identical. Cell behaviour of primary hPMCs is characterized by the transition of fibroblastoid to cobblestone morphology during early passage. L-Cys and β-ME promoted a rapid MET (mesenchymal-to-epithelial transition) within 3 days of culture, confirmed by the presence of cobblestone cells, intact organelles, abundant microvilli, primary cilia and cortical actin. In contrast, EGF produced a biphasic response consisting of delayed growth and retention of a fibroblastoid morphology. During a rapid log phase of growth, MET was accompanied by rapid catch-up growth. Thiols may stabilize the epithelial phenotype by engaging redox-sensitive receptors and transcription factors that modulate differentiation. These data may benefit researchers working on thiol-mediated cell differentiation and strategies to regenerate damage to serosal membranes.

Mesothelial cells from tunica vaginalis, a practical source for mesothelial transplantation

Transplantation of mesothelial cells is used to repair peritoneum that is damaged by surgery, peritonitis, and peritoneal dialysis. The largest obstacle for clinical application of mesothelial cell transplantation is the lack of a reliable source of mesothelial cells. So far, they are isolated from omentum, mesentery, parietal wall and ascites. Procedures used to obtain mesothelial cells from the omentum or mesentery are invasive, however, especially in pre-operative situations. Sufficient amounts of ascites for aspiration can not be obtained under physiological conditions. We have developed a novel method of isolating mesothelial cells from the tunica vaginalis. The tunica vaginalis originates from the peritoneum and descends into the scrotum along with the testis during fetal development. This region provides a source of mesothelial cells that is convenient to approach and free from abdominal complications. Transplantation of autologous mesothelial cells that were isolated from tunica vaginalis was effective in preventing post-operative adhesions. In this review, we summarize mesothelial cell transplantation trials and describe the method of isolating mesothelial cells form the tunica vaginalis. Mesothelial cell transplantation might be widely accepted for clinical use in the near future.

Mesothelial cell transplantation in myocardial infarction

Mesothelial cells (MCs) are accessible in human patients by excision and digestion of epiploon or from peritoneal fluid or lavage. MCs are easy to culture to obtain large quantities in vitro and they can be genetically modified with interesting therapeutic genes. The important potential of MCs in tissue engineering has been shown during epiplooplasty to different organs and also in creating artificial blood conduits. MC of epicardium is probably the precursor of coronary arteries during embryogenesis. MCs secrete a broad spectrum of angiogenic cytokines, growth factors and extracellular matrix, which could be useful for repairing damaged tissues. MCs are transitional mesodermal-derived cells and considered as progenitor stem cell, have similar morphological and functional properties with endothelial cells and conserve properties of transdifferentiation. MC therapy in myocardial infarction induced neoangiogenesis in infarcted scar and preserved heart function. In conclusion, a potential therapeutic strategy would be to implant or re-implant genetically modified MCs in post-infarction injury to enhance tissue repair and healing. Imparting therapeutic target genes such as angiogenic genes would also be useful for inducing neovascularization.