RESUMEN
BACKGROUND AIMS: Mesenchymal stromal cells (MSCs) have been reported to be a promising cell source in cell therapy, and large amounts of MSCs can easily be isolated from human amnion. Therapeutic irradiation for intra-pelvic cancer often causes radiation proctitis; however, there is currently no effective treatment. We therefore investigated the effect of transplantation of human amnion-derived MSCs (AMSCs) in rats with radiation proctitis. METHODS: Amnion was obtained at cesarean delivery, and AMSCs were isolated and expanded. Sprague-Dawley rats were γ-irradiated (5 Gy/d) at the rectum for 5 days. On day 5, AMSCs (1 × 10(6) cells) were intravenously transplanted. Rats were killed on day 8. Histological analyses were performed, and messenger RNA expression of inflammatory mediators was measured. In vitro, after γ-irradiation of rat intestinal epithelial cells (IEC-6), the cells were cultured with AMSC-conditioned medium (CM). The effect of AMSC-CM was evaluated by measurement of caspase-3/7 activity, p53 transcription activity and quantitative reverse-transcription-polymerase chain reaction for p53-target genes. RESULTS: Histological examination demonstrated that epithelial injury and infiltration of inflammatory cells in the rectum were significantly suppressed by transplantation of AMSCs. In vitro, the cell injury in IEC-6 cells induced by γ-irradiation was inhibited by AMSC-CM, which also inhibited the upregulation of p53 transcription activity, caspase-3/7 activity and p21 expression. CONCLUSIONS: Transplantation of AMSCs improved radiation proctitis, possibly through inhibition of cell injury and inflammatory reactions. AMSC transplantation should be considered as a new treatment for radiation proctitis.