Hepatic sinusoidal endothelium upregulates IL-1alpha, IFN-gamma, and iNOS in response to discordant xenogeneic islets in an in vitro model of xenoislet transplantation.
BACKGROUND
Data indicate that early islet graft failure is due to nonspecific inflammatory mechanisms that occur prior to T-cell-mediated rejection. The role of the host hepatic endothelium in mediating this immediate islet injury has not been elucidated. The endothelial cell may be important in this process because it is essentially the first cellular barrier encountered by intraportally introduced islets. We have characterized the initial response of hepatic endothelium to xenogeneic islets by measuring the expression of Il-1alpha, TNF-alpha, IFN-gamma, and iNOS in an in vitro dog-to-pig model of xenoislet transplantation.


METHODS
Dog islets (500 islet equivalents) were cocultured with either porcine hepatic endothelium or porcine aortic endothelium over a 24-h period in serum-free medium. RNA was extracted at eight time points (0, 1, 2, 4, 6, 8, 12, and 24 h). Reverse-transcriptase polymerase chain reaction was performed on each sample. Polymerase chain reaction was done on the cDNA in order to visualize Il-1alpha, TNF-alpha, IFN-gamma, and iNOS expression. Bands were semiquantitated by comparison to an external standard (GAPDH) using band densitometry.


RESULTS
Hepatic endothelium had early (1 h) expression of IL-1alpha, IFN-gamma, and iNOS. IL-1alpha peaked at 2 h, IFN-gamma at 12 h, and iNOS at 1 and 12 h. Aortic endothelium expressed low levels of IL-1alpha and TNF-alpha, but not IFN-gamma or iNOS.


CONCLUSIONS
We have demonstrated that xenogeneic islets are able to activate host endothelial cells without serum or immune cells. The observed endothelial response corresponds with known islet toxic substances. Furthermore, the response differs between hepatic and aortic endothelial cells, suggesting that these differences may be important in choosing suitable implantation sites for islets. Our findings suggest that host endothelium may play an important part in early injury of islet xenotransplants.
Tan
Michael
M
Department of Surgery, McGill University Health Centre, Montreal, Canada.
Di Carlo
Antonio
A
Liu
Shu Qing
SQ
Tector
A Joseph
AJ
Tchervenkov
Jean I
JI
Metrakos
Peter
P
D000818:Animals; D001011:Aorta / Q000276:immunology; D004285:Dogs; D004730:Endothelium, Vascular / Q000276:immunology; D015870:Gene Expression / Q000276:immunology; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000235:genetics*; D007375:Interleukin-1 / Q000235:genetics*; D016381:Islets of Langerhans Transplantation / Q000276:immunology*; D008099:Liver / Q000276:immunology*; D019001:Nitric Oxide Synthase / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000032:analysis; D013552:Swine; D014183:Transplantation, Heterologous; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics; D015854:Up-Regulation / Q000276:immunology
D007375:Interleukin-1; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II