title: Allogeneic renal graft rejection in a rat model: in vivo MR imaging of the homing trait of macrophages.
abstract: OBJECTIVE
  To evaluate the feasibility of MR imaging to depict the in vivo recruitment of superparamagnetic iron oxide (SPIO)-labeled macrophages and to aid diagnosis of graft rejection in kidney transplantation.
  
  
  METHODS
  This study was approved by the institution's committee on animal research. Eighteen male Lewis rats received a kidney transplant; 12 had an F344 rat donor and six had a Lewis rat donor. Peritoneal macrophages were harvested from thioglycollate-treated Lewis rats, cultured, and labeled with SPIO. After resuspension of macrophages in a concentration of 1 x 10(7) cells per milliliter of Hanks balanced salt solution, 5 x 10(6) of SPIO-labeled macrophages was administered through the tail vein 2 or 5 days after transplantation in each group. The transplanted kidneys were imaged on a 4.7-T MR imager 24 hours after macrophage administration. The Wilcoxon signed rank test was performed for evaluating the differences between the relative signal intensity (SI) before and after SPIO-labeled macrophage administration.
  
  
  RESULTS
  A low-SI zone was predominantly noted in the medulla of the transplanted kidneys, and the relative SI decreased significantly from 1.40 to 0.53 (P < .001) in the allogeneic transplants following SPIO-labeled macrophage administration 5 days after the allogeneic transplantation. In the syngeneic group, the lower-SI zone was not noted in the grafts. At histopathologic examination, the lower-SI zone corresponded to the distribution of the SPIO-labeled macrophages.
  
  
  CONCLUSIONS
  This study demonstrates that the homing of intravenously administered SPIO-labeled macrophages can be monitored in the allograft rejection model on in vivo MR images.
authors: Department of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Songpagu, Seoul, South Korea.
authors: Eun Young
authors: EY
authors: Chae
authors: Eun Ju
authors: EJ
authors: Song
authors: Jin Young
authors: JY
authors: Sohn
authors: Sang-Tae
authors: ST
authors: Kim
authors: Chul Woong
authors: CW
authors: Woo
authors: Gyungyub
authors: G
authors: Gong
authors: Hee Jung
authors: HJ
authors: Kang
authors: Jin Seong
authors: JS
authors: Lee
mesh_terms: D000818:Animals; D003287:Contrast Media / Q000493:pharmacokinetics*; D003911:Dextrans; D005240:Feasibility Studies; D052203:Ferrosoferric Oxide / Q000493:pharmacokinetics*; D006084:Graft Rejection / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D016030:Kidney Transplantation; D008264:Macrophages; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D008297:Male; D023421:Models, Animal; D051381:Rats; D011917:Rats, Inbred Lew; D018709:Statistics, Nonparametric; D014184:Transplantation, Homologous
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; C065507:ferumoxides; D052203:Ferrosoferric Oxide