title: Imaging of gene expression in live pancreatic islet cell lines using dual-isotope SPECT.
abstract: We are combining nuclear medicine with molecular biology to establish a sensitive, quantitative, and tomographic method with which to detect gene expression in pancreatic islet cells in vivo. Dual-isotope SPECT can be used to image multiple molecular events simultaneously, and coregistration of SPECT and CT images enables visualization of reporter gene expression in the correct anatomic context. We have engineered pancreatic islet cell lines for imaging with SPECT/CT after transplantation under the kidney capsule.
  
  
  METHODS
  INS-1 832/13 and alphaTC1-6 cells were stably transfected with a herpes simplex virus type 1-thymidine kinase-green fluorescent protein (HSV1-thymidine kinase-GFP) fusion construct (tkgfp). After clonal selection, radiolabel uptake was determined by incubation with 5-(131)I-iodo-1-(2-deoxy-2-fluoro-beta-d-arabinofuranosyl)uracil ((131)I-FIAU) (alphaTC1-6 cells) or (123)I-FIAU (INS-1 832/13 cells). For the first set of in vivo experiments, SPECT was conducted after alphaTC1-6/tkgfp cells had been labeled with either (131)I-FIAU or (111)In-tropolone and transplanted under the left kidney capsule of CD1 mice. Reconstructed SPECT images were coregistered to CT. In a second study using simultaneous acquisition dual-isotope SPECT, INS-1 832/13 clone 9 cells were labeled with (111)In-tropolone before transplantation. Mice were then systemically administered (123)I-FIAU and data for both (131)I and (111)In were acquired simultaneously.
  
  
  RESULTS
  alphaTC1-6/tkgfp cells showed a 15-fold greater uptake of (131)I-FIAU, and INS-1/tkgfp cells showed a 12-fold greater uptake of (123)I-FIAU, compared with that of wild-type cells. After transplantation under the kidney capsule, both reporter gene expression and location of cells could be visualized in vivo with dual-isotope SPECT. Immunohistochemistry confirmed the presence of glucagon- and insulin-positive cells at the site of transplantation.
  
  
  CONCLUSIONS
  Dual-isotope SPECT is a promising method to detect gene expression in and location of transplanted pancreatic cells in vivo.
authors: Lawson Health Research Institute, London, Ontario, Canada.
authors: Joo Ho
authors: JH
authors: Tai
authors: Binh
authors: B
authors: Nguyen
authors: R Glenn
authors: RG
authors: Wells
authors: Michael S
authors: MS
authors: Kovacs
authors: Rebecca
authors: R
authors: McGirr
authors: Frank S
authors: FS
authors: Prato
authors: Timothy G
authors: TG
authors: Morgan
authors: Savita
authors: S
authors: Dhanvantari
mesh_terms: D000818:Animals; D001086:Arabinofuranosyluracil / Q000031:analogs & derivatives* / Q000378:metabolism; D002460:Cell Line; D017930:Genes, Reporter; D050416:Glucagon-Secreting Cells / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000637:transplantation; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D007205:Indium Radioisotopes / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000637:transplantation; D007457:Iodine Radioisotopes / Q000378:metabolism*; D051379:Mice; D019275:Radiopharmaceuticals / Q000378:metabolism; D013937:Thymidine Kinase / Q000096:biosynthesis / Q000235:genetics; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D014334:Tropolone / Q000378:metabolism*
chemical_list: D007205:Indium Radioisotopes; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D049452:Green Fluorescent Proteins; D001086:Arabinofuranosyluracil; C043457:fialuridine; D014334:Tropolone; D013937:Thymidine Kinase