Fig. 5

Hypoxic rat mesenchymal stem cells (HMSCs) modulated macrophage phenotypes, reduced tubular apoptosis, and enhanced tubular proliferation in the ischemia-reperfusion (I/R)-injured rat kidneys. a–f Representative immunohistochemical photomicrographs showed that the phosphate-buffered saline (PBS) group had more infiltrated ED1-positive and inducible nitric oxide synthase (iNOS)-positive macrophages, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive apoptotic tubular cells as compared to the sham-operated (Sham) group. Intra-renal arterial (IA) and intraperitoneal (IP) administration of the HMSCs as well as intraperitoneal injection of the 100-fold concentrated HMSC-conditioned medium (CM) decreased the numbers of infiltrated iNOS-positive macrophages and TUNEL-positive apoptotic tubular cells. By contrast, renal I/R injury did not increase the number of arginase 1 (Arg1)-positive macrophages. IP administration of HMSCs as well as HMSC-CM significantly increased the number of Arg1-positive macrophages in I/R-injured rat kidneys. Only the IA-HMSC group had an increased number of proliferating cell nuclear antigen (PCNA)-positive tubular cells. Scale = 100 μm. *p < 0.05, **p < 0.01, ***p < 0.001 by one-way ANOVA with Tukey’s post hoc comparison, ns, nonsignificant, n = 4–5 for the sham group, n = 5–6 for other groups. g–l Western blot analyses showed that the I/R+PBS group had a higher ratio of Bax/Bcl-2 expressions and increased levels of active caspase 3 (CPP32), interleukin-1β (IL-1β) as well as caspase 1 in the I/R-injured rat kidneys. IA-HMSC, IP-HMSC, and HMSC-CM groups reduced the I/R-injury-induced elevation of Bax/Bcl2 ratio, CPP32, and IL-1β levels. Only IA-HMSC group supressed the I/R-injured-induced expression of caspase 1. *p < 0.05, ***p < 0.001 as compared to the sham-operated (sham) group; ^#p < 0.05, ^##p < 0.01, ^###p < 0.001 as compared to the I/R+PBS group, by one-way ANOVA with Tukey’s post hoc comparison, n = 6 per group