Search

BACKGROUND Acute humoral xenograft rejection (AHXR) is an important barrier to xenograft survival. Human tumor necrosis factor-α (hTNF-α) is one of the essential mediators of AHXR and induces activation of porcine endothelial cells (PECs), resulting in upregulation of major histocompatibility complex molecules, adhesion molecules, and proinflammatory chemokines. We investigated whether introduction of a soluble human tumor necrosis factor receptor I-Fc (shTNFRI-Fc) fusion gene can suppress activation of PECs and, more importantly, produced shTNFRI-Fc transgenic pigs. METHODS The shTNFRI-Fc gene expression vector was constructed and inserted into PECs. The inhibitory effects of shTNFRI-Fc were tested by luciferase assay, reverse-transcriptase polymerase chain reaction, and flow cytometry. A shTNFRI-Fc transgenic pig was generated by somatic cell nuclear transfer. The expression of shTNFRI-Fc in the transgenic pig was evaluated by PCR, western blot, enzyme-linked immunosorbent assay, and immunohistochemistry. The inhibitory effects of shTNFRI-Fc in the serum obtained from the transgenic pig were also tested. RESULTS In comparison with control green fluorescent protein, shTNFRI-Fc protein showed much stronger inhibitory effects on NF-κB activation in the HEK293-NF-κB-luciferase reporting cell line, expression of chemokines and adhesion molecules in PECs, and TNF-α-mediated cytotoxicity. We successfully generated shTNFRI-Fc transgenic pig. Sera obtained from the transgenic pig inhibited induction of chemokines, and E-selectin in PECs stimulated with Human TNF-α. CONCLUSIONS We have generated transgenic pigs producing shTNFRI-Fc protein that can inhibit TNF-α-mediated activation of PECs. Because TNF-α is an important mediator of xenograft rejection, the use of xenografts that can produce shTNFRI-Fc proteins de novo could be an effective approach in overcoming a considerable component of the xenograft rejection process, especially AHXR.

To elucidate the potential role of porcine RANTES (Regulated upon Activation Normal T cells Expressed and Secreted) in xenograft rejection, we investigated its chemotactic activity for human mononuclear cells, as well as the effect of human cytokines on its expression in porcine endothelial cells. Porcine RANTES cDNA was successfully cloned from aortic endothelial cells of miniature pigs, and its protein expression was induced by transfection. Its deduced amino acid sequence was 83.5% identical to that of human RANTES. Porcine RANTES triggered transmigration of human mononuclear cells across the species barrier, and this chemotactic effect was suppressed by anti-RANTES neutralizing antibodies. The chemotactic effect of porcine RANTES was most prominent on human monocytes. Human tumor necrosis factor-alpha induced significant expression of porcine RANTES messenger RNA in endothelial cells; however both human interferon-gamma and interleukin-1beta failed. These results suggest that porcine RANTES can play an important role in xenotransplant rejection, through participating in the interaction between porcine endothelial cells and human monocytes.