title: Assessment of tissue-engineered islet graft viability by fluorine magnetic resonance spectroscopy.
abstract: BACKGROUND
  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 ((19)F-MRS), by the noninvasive measurement of oxygen partial pressure (pO(2)) 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 (19)F-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 (19)F spin-lattice relaxation times (T1), which were converted to steady-state average pO(2) estimates using a previously determined linear calibration (R(2) = 1.000). Each condition was assessed using replicate (19)F-MRS measurements (n = 6-8).
  
  
  RESULTS
  Grafts exhibited IE dose-dependent increases in T1 and decreases in pO(2) estimates. From the difference between scaffold pO(2) estimates and ambient pO(2), 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
  (19)F-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.
authors.affiliation: Schulze Diabetes Institute, Department of Surgery, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: T M
authors.initials: TM
authors.lastname: Suszynski
authors.forename: E S
authors.initials: ES
authors.lastname: Avgoustiniatos
authors.forename: S A
authors.initials: SA
authors.lastname: Stein
authors.forename: E J
authors.initials: EJ
authors.lastname: Falde
authors.forename: B E
authors.initials: BE
authors.lastname: Hammer
authors.forename: K K
authors.initials: KK
authors.lastname: Papas
mesh_terms: D000818:Animals; D002470:Cell Survival; D003922:Diabetes Mellitus, Type 1 / Q000628:therapy; D004305:Dose-Response Relationship, Drug; D005461:Fluorine / Q000494:pharmacology; D006085:Graft Survival; D006801:Humans; D007515:Islets of Langerhans / Q000166:cytology*; D016381:Islets of Langerhans Transplantation / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008962:Models, Theoretical; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D010313:Partial Pressure; D013552:Swine; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds / Q000737:chemistry
chemical_list: D005461:Fluorine; D010100:Oxygen
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