The influence of MSC on brain inflammatory cell infiltration and microglia numbers. Iba-1+ microglia cells/macrophages and MPO+ neutrophils were identified by immunohistochemistry 72 h after ICH to test the effects of MSC treatment on the number of peripheral infiltrating and brain-resident immune cells. Both the numbers of Iba-1+ microglia cells/macrophages (A, C) and infiltrated MPO+ neutrophils (B, D) were reduced in the MSC-treated group when compared with the PBS-treated group. The sign of arrow indicates the edge of the hematoma. n = 6 per group. Data are presented as the mean ± SD. Bar = 50 μm. **P < 0.01. MPO, myeloperoxidase; MSCs, mesenchymal stem cells; PBS, phosphate-buffered saline.