Development of a murine intestinal explant model to examine immune mechanisms of graft versus host disease

Abstract Graft-versus host disease (GvHD) is a major course of mortality and morbidity in transplant recipients. Cytokine signaling plays a key role in the development of GvHD. To study the immune mechanisms relevant to intestinal pathology associated with GvHD, we developed a murine ex vivo model on intestinal explants derived from Xeno-GvHD to characterize mouse and human cytokine secretion and signaling. Intestinal tissues from Xeno-GvHD induced by transfer of human PBMC to irradiated NSG mice and control naïve mice were dissected and cultured. Histological analysis of the explants and measurement of lactate dehydrogenase (LDH) in the ex vivo culture system indicate that intestinal explants remain viable in culture for up to 72 hours, with an increased cytotoxicity developing over this time. Release of mouse proinflammatory cytokines including RANTES, IL-6, KC, and GM-CSF were significantly higher in GvHD explants compared to naïve controls. Among the human cytokines, RANTES was a key cytokine detected only from Xeno-GvHD explants. The patterns of cytokine/chemokine release were shown to be consistent in the ex vivo culture over time and on explants from different sites of intestine including ileum and colon. Furthermore, histochemical analysis of GvHD explants revealed much stronger immunoreactivity for RANTES compared to naïve explants. Overall, our results indicate inflammatory milieu in the intestines of GvHD mice leading to sustained production of proinflammatory cytokines in the ex vivo culture. These features indicate that the explant system is a relevant model for studying the mechanism(s) of inflammatory responses in intestinal GvHD.