Transplantation of BMSCs reduces the age-associated cardiac hypertrophy and fibrosis. (A): Representative images of hematoxylin and eosin staining at a magnification of ×200. (B): Summarized data of cross-sectional area in different groups. (C): Representative sections of heart with Masson trichrome staining at a magnification of ×200. Fibrotic tissues were stained blue, and cardiomyocytes were stained red. (D): Collagen deposition was quantified with an automated image analyzer and is expressed as percentage of tissue area. The data are expressed as means ± SEM, n = 5 for each group. ∗∗, p < .01 versus young control; #, p < .05; ##, p < .01 versus old control. Abbreviation: BSMC, bone marrow mesenchymal stem cell.