L-Cysteine Improves Growth of Human Peritoneal Mesothelial CellsIn Vitro

Objective

To improve the growth characteristics of human peritoneal mesothelial cells (HPMC).

Design

The effect of commonly used agents, L-cysteine and epidermal growth factor (EGF), added individually (“single”) or mixed with hydrocortisone and apo-transferrin (“admixture”) in the culture medium (M199) on cultured HPMC, was investigated. Methods: Growth agents were added to M199 medium along with 2% fetal bovine serum and L-glutamine. Growth was determined by the analysis of thymidine ([methyl-3H] thymidine) incorporation into deoxyribonucleic acid, total cell protein, and by cell counts. Morphology was assessed by phase contrast light microscopy and scanning electron microscopy.

Results

HPMC exposed to L-cysteine 0.25 x 10–3 mol/L (30 μg/mL) exhibited significantly improved attachment and growth. Attached cells appeared flat and well spread out shortly after seeding, and produced a tight polygonal monolayer in 14 days, in contrast to the growth of HPMC in control M199 medium, which failed to reach confluence. After an initial lag period in cell growth, EGF (0.01 μg/mL) produced a greater increase in cell growth than L-cysteine did; however, this was associated with changes in HPMC morphology. During the growth period (14 days), EGF-stimulated HPMC appeared distorted and irregular compared to L-cysteine-treated cells, which had the characteristic tight “cobblestone” appearance.

Conclusion

L-cysteine improved cell attachment with preservation of the characteristic morphology of HPMC. Epidermal growth factor improved cell growth but produced changes in morphology. The addition of L-cysteine to the culture medium has an important cell growth enhancement role due to the improved cell attachment and cell viability.

Remodeling of peritoneal-like structures by mesothelial cells: its role in peritoneal healing

BACKGROUND

Intraabdominal adhesions are a common complication following laparotomy. Since the exact mechanisms involved in this processes are unknown we have analyzed in vitro the role of mesothelial cells in peritoneal healing.

MATERIAL AND METHODS

Human mesothelial cells from omental tissue were cultivated for 2 weeks in a three-dimensional culture either on or in a collagen type I matrix. The effects of blood and collagen matrix were analyzed by exposing mesothelial cells to an overlying blood clot, simulating intraperitoneal bleeding, or a second collagen layer. The production of collagen types III and IV, fibronectin, and laminin was analyzed with immunohistochemical methods.

RESULTS

Mesothelial cells grown on a collagen matrix formed a monolayer of flat or cobblestone-like cells whereas those cultivated in a collagen matrix exhibited spindle-like morphology. Mesothelial cells failed to grow into an overlying collagen matrix, but did grow into a blood clot, emphasizing a potential role of blood clots in peritoneal adhesion formation. Independent of the culture systems mesothelial cells produced collagen type III, fibronectin, and laminin but not collagen type IV.

CONCLUSIONS

Our experiments demonstrate remodeling of peritoneal-like structures by mesothelial cells in a three-dimensional culture reflecting their putative role in the reepithelialization after serosal defects, and also in the formation of peritoneal adhesions.

Response of the human peritoneal mesothelial cell to injury: an in vitro model of peritoneal wound healing

BACKGROUND

The denudation of the peritoneal mesothelium and damage to the underlying interstitium is a frequent finding in patients receiving continuous ambulatory peritoneal dialysis as a treatment for end-stage renal failure. The response of the mesothelium to injury from repeated episodes of infection or from exposure to dialysis fluids has not been extensively studied. The present study describes a simple and reproducible method with which to investigate the response of human mesothelial cells to injury.

METHODS

The model of peritoneal injury consists of mechanically wounding a monolayer of human peritoneal mesothelial cells with a glass probe and following the repopulation of the denuded area by time-lapse photomicroscopy. In addition immunohistochemistry was used to follow the response of marker proteins for stress fibers and focal adhesions as well as macromolecules associated with the extracellular matrix.

RESULTS

Under serum-free conditions the wound (0.58 +/- 0.094 mm; mean +/- SD; N = 20) closed within 72 +/- 5 hours (N = 8). This rate of healing was enhanced by fetal calf serum, by human serum (10%) and by undiluted spent non-infected dialysate. The repair process over the first 48 hours was the result of cell migration, was independent of cell proliferation and involved the de novo synthesis of several different extracellular matrix components. An early event in the healing process was the rapid reorganization of intracellular stress fibers together with the formation of associated focal adhesions in cells at the wound edge.

CONCLUSION

This in vitro model should prove invaluable in characterizing the process of wound healing within the peritoneal cavity, thus allowing a better understanding of the response to infection as well as any effect of dialysis fluids in this pattern of cell behavior.

Host defences in continuous ambulatory peritoneal dialysis and the genesis of peritonitis

Continuous ambulatory peritoneal dialysis (CAPD) has come to be extensively used for the treatment of end-stage renal failure in children, and especially infants, such that now more than half of children on dialysis worldwide receive treatment by this means. Peritonitis, however, is commoner in children than in adults receiving treatment, and is a major source of morbidity and treatment failure in children started on CAPD. Only recently has the immunology of the normal peritoneum been studied extensively, with the need to assess the impact of the installation of large volumes of fluid into the peritoneal sac during dialysis. The main phagocytic defences of the peritoneum depend upon a unique set of macrophages which are present free in the peritoneal fluid but also in the submesothelium and in perivascular collections together with B lymphocytes in the submesothelial area. Both the number of macrophages per unit volume and the concentration of opsonic proteins, such as IgG, complement and fibronectin, are reduced to between only 1% and 5% when dialysis fluid is continuously present in the peritoneal sac. In addition, the fluids used for CAPD are toxic to both macrophages and to mesothelial cells. Thus minor degrees of contamination frequently lead to peritonitis and in addition the majority of patients have catheters inserted in their peritoneum which become colonised with organisms capable of producing exopolysaccharide (slime), which promotes adhesion of the organism to the plastic and protects them against phagocytic attack and the penetration of antibiotics. Thus the peritoneum is in a state of continual inflammation, as well as being a markedly more vulnerable site than the normal peritoneum to the entry of organisms. Whether clinical peritonitis appears in this state of chronic contamination probably depends on perturbation in the balance between host defences and the organism. Whilst Staphylococcus epidermidis is the commonest cause of peritonitis, Staphylococcus aureus and Gram-negative organisms are much more serious and more frequently lead either to temporary catheter removal or discontinuation of dialysis altogether. This review describes the peritoneal defences in relation to the genesis of peritonitis.