Mast cells and basic fibroblast growth factor in physiological aging of rat heart and kidney.

Age-related morphological and physiological changes occur in cells, tissues and organs with high metabolic or mitotic activity; these changes decrease their regenerative capacity. One such change is interstitial fibrosis. Mast cells contain basic fibroblast growth factor and have been related to pro-fibrotic activity. We investigated the role of mast cells in physiological aging of the heart and kidney. We analyzed changes in mast cell number and compared the left and right heart ventricles and kidneys of 6- and 12-month-old Wistar rats. We also evaluated the immunohistochemical expression of basic fibroblast growth factor. Finally, we analyzed changes in the extent of interstitial fibrosis and in the glomerular sclerosis index as nonspecific markers of aging and correlated these parameters with of mast cells. Mast cells were visualized by toluidine blue staining and specific immunohistochemical expression of tryptase. The expression of basic fibroblast growth factor was assessed semiquantitatively. The extent of interstitial fibrosis was investigated using Mallory's trichrome staining. Glomerular sclerosis was evaluated using periodic acid-Schiff staining. We found that the number of mast cells increased significantly in the older rats. We also found that the number of mast cells was greatest in the left ventricle followed by the right ventricle, then the kidney. The immunoreactivity of basic fibroblast growth factor also increased in older animals. Correlations between the number of mast cells and immunoreactivity of basic fibroblast growth factor, extent of interstitial fibrosis and glomerular sclerosis index demonstrated the association between mast cells and age-related tissue remodeling of the heart and kidney.