Spatiotemporal control of porcine p65RHD expression by advanced Tet-On system in PIEC cells helps regulate NFкB activity.

NFкB transcription activation leads to malfunction of endothelial cells, which is the main reason for pig xenograft rejection. Overexpression of a dominant negative mutant of porcine NFκB p65 (pp65RHD) could inhibit NFкB activation in endothelial cells. This study presents an advanced tetracycline-regulated system for pp65RHD spatiotemporal expression in porcine iliac endothelial cell line. In this system, an endothelial specific promoter ICAM-2 is used to improve pTet-On and internal ribosome entry site as well as enhanced green fluorescent protein (EGFP) elements are used to facilitate the result observation in pTRE-Tight. Through transfection and drug selection, we obtained 7 single cell clones containing the advanced Tet-On system, in which pp65RHD expression is under tight regulated by doxycycline and can be visualized easily through EGFP. The distribution of induced pp65RHD was verified by immunocytochemical assays test. Then, NFкB activity was tested. Luciferase reporter assays showed that NFкB activity in two clones was influenced by the Dox-induced pp65RHD expression, but other clones weren't influenced. Therefore, we picked up 2 cell clones from the uninfluenced clones for further investigation by immunocytochemical assays and RT-PCR detection. The final results supported the overexpression of pp65RHD in one clone could successfully inhibit NFкB activity. The success of pp65RHD spatiotemporal expression system is helpful to regulate NFкB activity and conquer cell-mediated immunity and could be used for preparation of transgenic pig, contributing to xenotransplantation.