Liver morphology, cell proliferation, and apoptosis after adipose tissue-derived stem cell (ASC) treatment. (A) Liver morphology of normal rats, D-galactosamine (D-gal) induced rats, phosphate-buffered saline (PBS)-treated rats, and ASC-treated rats. (B) Liver hematoxylin-and-eosin staining sections of normal rats, D-gal induced rats, PBS-treated rats, and ASC-treated rats. The livers of ASC-treated rats showed significant morphologic improvement compared with PBS-treated rats. (C) Positive cells were observed by Ki-67 staining (brown) in the liver sections. The ASC-treated group showed more positive cells (black arrows) than the PBS-treated group, suggesting that ASC treatment promoted cell proliferation in liver. (D) Quantification analysis of the Ki-67 staining section by Image-Pro Plus software. (E) Apoptotic cells (black arrow) were observed in the untreated group by TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay. Few apoptotic cells were observed in the ASC-treated group and normal livers, indicating that ASC treatment protected liver cells from apoptosis. (F) Quantification of TUNEL-positive cells in the field of view (FOV) by digital image analysis.