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Mast cells in human adipose tissue: link with morbid obesity, inflammatory status, and diabetes.

AIMS AND HYPOTHESIS
Mast cells are immune cells known for their role in several inflammatory and fibrotic diseases. Recent works in mice suggest that mast cells could be cellular actors involved in the pathophysiology of obesity, a disease characterized by white adipose tissue (WAT) and systemic inflammation. The aim of the study was to better characterize mast cells in WAT of obese with or without type 2 diabetes and lean subjects as well as to explore the relationship with WAT inflammation and fibrosis.


METHODS
Subcutaneous and omental adipose tissue from six lean subjects, 10 obese nondiabetic, and 10 diabetic patients was analyzed by immunohistochemistry and real-time PCR for inflammatory and fibrosis markers. Cytokines secretion of mast cells isolated from WAT and cultured in different conditions was estimated by cytokine array kit.


RESULTS
We found that mast cells are activated in human adipose tissue and localized preferentially in fibrosis depots, a local condition that stimulates their inflammatory state. Mast cells with tryptase(+) chymase(+) staining tended to be higher in obese omental adipose tissue. We found positive links between mast cell number and several characteristics of obese WAT including fibrosis, macrophage accumulation, and endothelial cell inflammation. Mast cell number and their inflammatory phenotype are associated with diabetes parameters.


CONCLUSION AND INTERPRETATION
Mast cells are cellular actors of WAT inflammation and possibly fibrotic state found in obesity and diabetes. Whether mast cells could be involved in the pathophysiology of diabetes needs additional study as well as the positioning of these cells in driving pathological alterations of WAT in these chronic metabolic diseases.