Figure 1. RG-1 pre-activates bone marrow-derived mesenchymal stem cells (BM-MSCs) without altering the phenotype of BM-MSCs. (A) In vitro and in vivo experiment design. In vitro design: IEC-6 irradiated with 10 Gy were treated with conditioned medium from non-activated BM-MSCs (MSC-CM) or BM-MSCs pre-activated by different concentration of RG1 (RG1-MSC-CM) (0.1 μM, 1 μM, 10 μM, 100 μM), followed by cell viability test every day until day 7. In vivo experiment: Sprague-Dawley rats were randomly divided into not irradiated (control) or irradiated group (IR) with a 14 Gy abdominal radiation on day 0, followed by a course of intra peritoneal injection (1 ml/day for 4 days) with control medium (DMEM-F12), MSC-CM, RG1-MSC-CM. Rats were either sacrificed at 1, 3, 5, 7 day for histological examination or were sacrificed at 1, 3, 7 day for functional evaluation. The remaining rats were used for survival analysis throughout a 14-day experiment. (B) Flow cytometry showed that BM-MSCs pre-activated by RG1 were positive for CD29, CD44, CD90, CD105 and negative for CD34, CD45. Data represent the mean ± SD (n=3) and were analyzed by t-test or one-way ANOVA.