Glucose metabolism in pigs expressing human genes under an insulin promoter.
BACKGROUND
Xenotransplantation of porcine islets can reverse diabetes in non-human primates. The remaining hurdles for clinical application include safe and effective T-cell-directed immunosuppression, but protection against the innate immune system and coagulation dysfunction may be more difficult to achieve. Islet-targeted genetic manipulation of islet-source pigs represents a powerful tool to protect against graft loss. However, whether these genetic alterations would impair islet function is unknown.


METHODS
On a background of α1,3-galactosyltransferase gene-knockout (GTKO)/human (h)CD46, additional genes (hCD39, human tissue factor pathway inhibitor, porcine CTLA4-Ig) were inserted in different combinations under an insulin promoter to promote expression in islets (confirmed by immunofluorescence). Seven pigs were tested for baseline and glucose/arginine-challenged levels of glucose, insulin, C-peptide, and glucagon.


RESULTS
This preliminary study did not show definite evidence of β-cell deficiencies, even when three transgenes were expressed under the insulin promoter. Of seven animals, all were normoglycemic at fasting, and five of seven had normal glucose disposal rates after challenge. All animals exhibited insulin, C-peptide, and glucagon responses to both glucose and arginine challenge; however, significant interindividual variation was observed.


CONCLUSIONS
Multiple islet-targeted transgenic expression was not associated with an overtly detrimental effect on islet function, suggesting that complex genetic constructs designed for islet protection warrants further testing in islet xenotransplantation models.
Thomas E. Starzl Transplantation Institute, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA, USA.
Martin
M
Wijkstrom
Rita
R
Bottino
Hayoto
H
Iwase
Hidetaka
H
Hara
Burcin
B
Ekser
Dirk
D
van der Windt
Cassandra
C
Long
Frederico G S
FG
Toledo
Carol J
CJ
Phelps
Massimo
M
Trucco
David K C
DK
Cooper
David
D
Ayares
D000069594:Abatacept / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D030801:Animals, Genetically Modified; D015703:Antigens, CD / Q000096:biosynthesis / Q000235:genetics*; D001081:Apyrase / Q000096:biosynthesis / Q000235:genetics*; D001120:Arginine / Q000494:pharmacology; D001786:Blood Glucose / Q000032:analysis; D002096:C-Peptide / Q000378:metabolism; D002460:Cell Line; D005215:Fasting / Q000097:blood; D005347:Fibroblasts; D005700:Galactosyltransferases / Q000172:deficiency / Q000235:genetics; D005786:Gene Expression Regulation; D055786:Gene Knockout Techniques; D005813:Genes, Synthetic; D005934:Glucagon / Q000378:metabolism; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000235:genetics*; D007515:Islets of Langerhans / Q000378:metabolism*; D008074:Lipoproteins / Q000096:biosynthesis / Q000235:genetics*; D051916:Membrane Cofactor Protein / Q000235:genetics; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D034421:Sus scrofa / Q000378:metabolism*; D013552:Swine; D019076:Transgenes
D015703:Antigens, CD; D001786:Blood Glucose; D002096:C-Peptide; C497857:CD46 protein, human; D007328:Insulin; D008074:Lipoproteins; D051916:Membrane Cofactor Protein; D011993:Recombinant Fusion Proteins; C051928:lipoprotein-associated coagulation inhibitor; D000069594:Abatacept; D005934:Glucagon; D001120:Arginine; D005700:Galactosyltransferases; C530267:alpha-1,3-galactosyltransferase 1, porcine; D001081:Apyrase; C067869:CD39 antigen; D005947:Glucose
C-peptide; IVGTT; arginine stimulation test; genetic engineering; glucagon; insulin; pig; xenotransplantation