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Presenter: T., Anazawa, Minneapolis, USA
Authors: T. Anazawa, M. Graham, J. Abouaish, G. Loganathan, B. Hering, A.N. Balamurugan
Predicting porcine islet yield by acute C-peptide response to arginine stimulation of donor pigs and pancreas dithizone scoring system
T. Anazawa, M. Graham, J. Abouaish, G. Loganathan, B. Hering, A.N. Balamurugan
Schulze Diabetes Institute, Dept. of Surgery, University of Minnesota, Minneapolis, USA
Background: In this study, we investigated the relationship between porcine islet isolation outcome, dithizone scoring system and the insulin secretory reserve, a surrogate measure of the donor’s islet mass. As previously reported, dithizone (DTZ) scoring is effective at quantifying the number of islets in a procured pancreas. Arginine stimulation, as reported by F. Pattou (AJT. 2008; 8:1-5), is a method to indirectly quantify the number of β-cells present in a pancreas before procurement. C-peptide level after arginine stimulation was monitored and compared with the DTZ scores and islet yields from those pigs.
Methods: After overnight fasting, 70 mg/kg of 10% arginine was administered to donor pigs (n=12) and intravenous samples were drawn before and 2, 3, 4 and 5 min after the infusion for measurement of C-peptide levels. The acute C-peptide response to arginine (ACRarg) was calculated as the maximum of the 2, 3, 4 and 5 minute samples minus the prestimulus C-peptide concentration. DTZ score was calculated as previously described from pancreas biopsies after procurement. Islets were isolated using our standard protocol. A successful isolation was defined as one with >1500 IEQ/g pancreas. Student t-test was used to successful and unsuccessful isolations.
Results: The results are described in the table. The average pancreas weights for successful and unsuccessful isolations were 127.3±32.6g and 156.3±36.1g respectively. The average digest IEQ/g was 1,621±505 for successful isolations and 733±277 for unsuccessful isolations (p=0.0053). A significant difference between the stimulated C-peptide level was observed 2 minutes after injection (p=0.047). Islet yield per gram pancreas correlated strongly with DTZ scores (p=0.033). The ACRarg values for successful and unsuccessful isolations were 0.34±0.16nmol/ml and 0.23±0.07nmol/ml respectively (p=0.17).
Conclusion: DTZ scoring along with the previously reported arginine stimulation test can potentially be used to select suitable pigs for islet transplantation and to predict islet isolation outcome.
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