ENDOTOXIN CONTAMINATION MAY BE RESPONSIBLE FOR THE UNEXPLAINED FAILURE OF HUMAN PANCREATIC-ISLET TRANSPLANTATION

Clinical transplantation of human islets has a disappointingly low rat e of success. We report here the identification of a possible causativ e factor: endotoxin present in the collagenase preparations used to di sperse the pancreatic tissue before islet purification and transplanta tion. Supporting evidence includes (1) detection of unexpectedly high levels of endotoxin in most collagenase solutions currently used to di gest human pancreases; (2) demonstration that supernatants generated d uring islet separation are able to induce the inflammatory cytokines i nterleukin (IL)-1, IL-6, and tumor necrosis factor-alpha (TNF-alpha) i n macrophages; and (3) induction of IL-1, IL-6, and TNF-alpha in the i slets during the separation procedure, Cytokine expression was assesse d by reverse transcription-polymerase chain reaction and, for TNF-alph a, confirmed by enzyme-linked immunoabsorbent assay, It is proposed th at endotoxin and locally induced cytokines carried over with the graft activate the endothelium and promote lymphomonocytic infiltration of grafted islets and surrounding liver tissue favoring primary nonfuncti on and early rejection, These results also have implications for the n umerous experimental procedures that use collagenase, and they point t o possible ways to improve islet preparation and transplantation proto cols.