title: Magnetic resonance imaging of pancreatic islets in tolerance and rejection.
abstract: BACKGROUND
  We have recently described a magnetic resonance (MR) method for detection of rat pancreatic islets transplanted into the liver after labeling with superparamagnetic iron oxide nanoparticles. The aim of this work was to study whether this technique could be applicable over a longer period after transplantation and whether it could help to detect islet rejection.
  
  
  METHODS
  Islets from Lewis and Wistar rats were cultured in the presence of iron oxide nanoparticles. Two thousand of Lewis (n=6) or Wistar (n=8) iron-labeled islets were transplanted into the portal vein of Lewis diabetic animals. Serial MR imaging of the liver were performed at 1, 2, 3, 4, 5, and 6 weeks.
  
  
  RESULTS
  Although all allogeneic islets were rejected by 12 days, syngeneic animals remained normoglycemic throughout the study. At week 1, the labeled islets were visualized on MR scans as distinct hypointense spots homogeneously distributed in the liver. While their number declined only insignificantly in the syngeneic group, in the allogeneic group the number of spots gradually decreased until approximately 35% of their initial count. Although syngeneic islets showed a normal histology, the allogeneic islets were completely rejected. Iron particles, localized in macrophages, were detected only in the syngeneic islets and were absent in the rejected islet structures. In vitro incubation tests did not reveal any differences in insulin secretion between labeled and nonlabeled islets.
  
  
  CONCLUSIONS
  MR imaging of iron-labeled pancreatic islets can be used for verification of the technical success of the transplantation procedure itself and for the detection of the decreasing relative islet mass due to rejection.
authors.affiliation: Diabetes Center, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Kriz
authors.forename: Daniel
authors.initials: D
authors.lastname: Jirák
authors.forename: Peter
authors.initials: P
authors.lastname: Girman
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Berková
authors.forename: Klara
authors.initials: K
authors.lastname: Zacharovova
authors.forename: Eva
authors.initials: E
authors.lastname: Honsova
authors.forename: Alena
authors.initials: A
authors.lastname: Lodererova
authors.forename: Milan
authors.initials: M
authors.lastname: Hajek
authors.forename: Frantisek
authors.initials: F
authors.lastname: Saudek
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D006084:Graft Rejection / Q000473:pathology*; D007515:Islets of Langerhans / Q000473:pathology*; D016381:Islets of Langerhans Transplantation / Q000473:pathology* / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D051381:Rats; D011917:Rats, Inbred Lew; D023001:Transplantation Tolerance; D014184:Transplantation, Homologous