Positron emission tomography: a real-time tool to quantify early islet engraftment in a preclinical large animal model.
BACKGROUND
Clinical islet transplantation is currently being explored as a therapeutic option for persons with type I diabetes and hypoglycemic unawareness. Techniques to monitor graft survival are urgently needed to optimize the procedure. Therefore, the objective of the present study was to develop a technique for imaging survival of transplanted islets in the peritransplant and early posttransplant phase.


METHODS
Isolated porcine islets were labeled in vitro with 2-deoxy-2[F]fluoro-D-glucose ([F]FDG) and infused intraportally into anesthetized pigs (n=10). Dynamic examination was performed on a positron emission tomography/computed tomography hybrid system.


RESULTS
More than 95% of the radioactivity was confined to the islets at the time of transplantation. The peak percentage of infused radioactivity within the liver, quantified at the end of the islet infusion, was only 54+/-5.1%. The distribution of the radioactivity in the liver was found to be heterogeneous. A whole-body examination showed no accumulation in the lungs or brain; extrahepatic radioactivity was, except urinary excretion, evenly distributed in the pig body.


CONCLUSIONS
Our results imply that almost 50% of the islets were damaged to the extent that the FDG contained was release within minutes after intraportal transplantation. The distribution of radioactivity without accumulation in the brain indicates that the activity is released from lysed islet cells in the form of [F]FDG-6P rather than native [F]FDG. The presented technique shows promise to become a powerful and quantitative tool, readily available in the clinic, to evaluate initial islet engraftment and survival.
Eich
Torsten
T
Department of Radiology, Oncology and Clinical Immunology, Division of Clinical Immunology, University Hospital, Uppsala, Sweden.
Eriksson
Olof
O
Sundin
Anders
A
Estrada
Sergio
S
Brandhorst
Daniel
D
Brandhorst
Heide
H
Langstrom
Bengt
B
Nilsson
Bo
B
Korsgren
Olle
O
Lundgren
Torbjorn
T
D000818:Animals; D001345:Autoradiography; D003952:Diagnostic Imaging / Q000379:methods / Q000639:trends; D004195:Disease Models, Animal; D005947:Glucose / Q000378:metabolism; D006085:Graft Survival; D007515:Islets of Langerhans / Q000166:cytology* / Q000378:metabolism; D016381:Islets of Langerhans Transplantation / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D013552:Swine; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods
D005947:Glucose