Figure 3. BMSCs improved the morphological changes of thymus and spleen tissues of aging rats. (A) Morphological changes of thymus and spleen tissues were observed through naked eyes; (B) Histological changes of spleen tissue were investigated after HE staining; (C) Histological changes of thymus tissue were investigated after HE staining; (D) Histological changes of thymus tissue was investigated using transmission electron microscopy. White arrows indicate white pulp; Black arrows indicate splenic nodule; Green arrows indicate cortex; Yellow arrows indicate medulla; Red arrows indicate vacuoles in the cytoplasm of epithelial reticular cells.