Background-Islet transplantation is a promising treatment for type 1 diabetes. Due to a shortage of suitable human pancreata, high cost, and the large dose of islets presently required for long-term diabetes reversal; it is important to maximize viable islet yield. Traditional methods of pancreas preservation have been identified as suboptimal due to insufficient oxygenation. Enhanced oxygen delivery is a key area of improvement. In this paper, we explored improved oxygen delivery by persufflation (PSF), ie, vascular gas perfusion.

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Introduction Despite significant progress in the last decade, islet transplantation remains an experimental therapy for a limited number of patients with type 1 diabetes. Tissue-engineered approaches may provide promising alternatives to the current clinical protocol and would benefit greatly from concurrent development of graft quality assessment techniques. This study was designed to evaluate whether viability of tissue-engineered islet grafts can be assessed using fluorine magnetic resonance spectroscopy (19F-MRS), by the noninvasive measurement of oxygen partial pressure (pO2) and the subsequent calculation of islet oxygen consumption rate (OCR). Methods Scaffolds composed of porcine plasma were seeded with human islets and perfluorodecalin. Each graft was covered with the same volume of culture media in a Petri dish. Four scaffolds were seeded with various numbers (0–8000) of islet equivalents (IE) aliquoted from the same preparation. After randomizing run order, grafts were examined by 19F-MRS at 37°C using a 5T spectrometer and a single-loop surface coil placed underneath. A standard inversion recovery sequence was used to obtain characteristic 19F spin-lattice relaxation times (T1), which were converted to steady-state average pO2 estimates using a previously determined linear calibration (R2 = 1.000). Each condition was assessed using replicate 19F-MRS measurements (n = 6–8). Results Grafts exhibited IE dose-dependent increases in T1 and decreases in pO2 estimates. From the difference between scaffold pO2 estimates and ambient pO2, the islet preparation OCR was calculated to be 95 ± 12 (mean ± standard error of the mean) nmol/(min · mg DNA) using theoretical modeling. This value compared well with OCR values measured using established methods for human islet preparations. Conclusions 19F-MRS can be used for noninvasive pre- and possibly posttransplant assessment of tissue-engineered islet graft viability by estimating the amount of viable, oxygen-consuming tissue in a scaffold.

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Influences of soy protein (promine D; SP), fish protein concentrate (FPC) and Brewer's Yeast or Torula Yeast on aerobic growth of S. aureus (288) and production of enterotoxins A and D were evaluated in liquid media containing equivalent amounts (1.8%) of protein from each source. S. aureus grew faster .(29 min generation time) and reached a final population of 2-7 x lo9 /ml in yeast media as compared to soy or, fish protein concentrate; 50-56 mm generation time and a final population of 2 x lO'/ml in SP or EPC. Production of enterotqxins by S. aureus was enhanced in yeast media. Enterotoxin A was detectable in unconcentrated yeast preparations after 6 hr and both toxins (A and D) after 12 hr incubation. Enterotoxin A was detected only in FPC concentrated 50-fold and after 24 hr incubation. Neither enterotoxin A nor D was detected in SP concentrated 1OCLfold after 24 or 48-hr incubation. Addition of Brewer's Yeast (2% w/v) to whole milk enhanced production of enterotoxins A and D; there was at least a lOO-fold higher amount of enterotoxin in milk + yeast as compared to simply milk.