PLK1 and graft versus host disease: Clinical scoring and histological analyses of representative GVHD target organs, including the small intestine, lung, kidney, and liver, revealed that injection of SHC-MSCs or PLK1-overexpressing MSCs effectively decreased immune cell infiltration and characteristic tissue injuries in GVHD mice, such as sloughing of villi in the small intestine and fibrosis in the lung and liver (Fig. 4e).