title: Cellular bioenergetics is an important determinant of the molecular imaging signal derived from luciferase and the sodium-iodide symporter.
abstract: BACKGROUND
  Molecular imaging is useful for longitudinal assessment of engraftment. However, it is not known which factors, other than cell number, can influence the molecular imaging signal obtained from reporter genes.
  
  
  OBJECTIVE
  The effects of cell dissociation/suspension on cellular bioenergetics and the signal obtained by firefly luciferase and human sodium-iodide symporter labeling of cardiosphere-derived cells were investigated.
  
  
  RESULTS
  (18)Fluorodeoxyglucose uptake, ATP levels, (99m)Tc-pertechnetate uptake, and bioluminescence were measured in vitro in adherent and suspended cardiosphere-derived cells. In vivo dual-isotope single-photon emission computed tomography/computed tomography imaging or bioluminescence imaging (BLI) was performed 1 hour and 24 hours after cardiosphere-derived cell transplantation. Single-photon emission computed tomography quantification was performed using a phantom for signal calibration. Cell loss between 1 hour and 24 hours after transplantation was quantified by quantitative polymerase chain reaction and ex vivo luciferase assay. Cell dissociation followed by suspension for 1 hour resulted in decreased glucose uptake, cellular ATP, (99m)Tc uptake, and BLI signal by 82%, 43%, 42%, and 44%, respectively, compared with adherent cells, in vitro. In vivo (99m)Tc uptake was significantly lower at 1 hour compared with 24 hours after cell transplantation in the noninfarct (P<0.001; n=3) and infarct (P<0.001; n=4) models, despite significant cell loss during this period. The in vivo BLI signal was significantly higher at 1 hour than at 24 hours (P<0.01), with the BLI signal being higher when cardiosphere-derived cells were suspended in glucose-containing medium compared with saline (PBS).
  
  
  CONCLUSIONS
  Adhesion is an important determinant of cellular bioenergetics, (99m)Tc-pertechnetate uptake, and BLI signal. BLI and sodium-iodide symporter imaging may be useful for in vivo optimization of bioenergetics in transplanted cells.
authors.affiliation: Division of Cardiovascular Medicine, Johns Hopkins School of Medicine, Baltimore, MD, USA.
authors.forename: Connie
authors.initials: C
authors.lastname: Chang
authors.forename: Angel
authors.initials: A
authors.lastname: Chan
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Lin
authors.forename: Takahiro
authors.initials: T
authors.lastname: Higuchi
authors.forename: John
authors.initials: J
authors.lastname: Terrovitis
authors.forename: Junaid M
authors.initials: JM
authors.lastname: Afzal
authors.forename: Andrew
authors.initials: A
authors.lastname: Rittenbach
authors.forename: Dongdong
authors.initials: D
authors.lastname: Sun
authors.forename: Styliani
authors.initials: S
authors.lastname: Vakrou
authors.forename: Kirubel
authors.initials: K
authors.lastname: Woldemichael
authors.forename: Brian
authors.initials: B
authors.lastname: O'Rourke
authors.forename: Richard
authors.initials: R
authors.lastname: Wahl
authors.forename: Martin
authors.initials: M
authors.lastname: Pomper
authors.forename: Benjamin
authors.initials: B
authors.lastname: Tsui
authors.forename: M Roselle
authors.initials: MR
authors.lastname: Abraham
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion; D058948:Cell Tracking / Q000379:methods*; D004195:Disease Models, Animal; D004734:Energy Metabolism; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D007091:Image Processing, Computer-Assisted; D049409:Luciferases, Firefly / Q000235:genetics / Q000378:metabolism*; D008163:Luminescent Measurements; D008297:Male; D064847:Multimodal Imaging; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000235:genetics / Q000378:metabolism / Q000601:surgery; D032383:Myocytes, Cardiac / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000637:transplantation*; D016133:Polymerase Chain Reaction; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000378:metabolism; D051381:Rats; D011921:Rats, Inbred WKY; D012815:Signal Processing, Computer-Assisted; D013670:Sodium Pertechnetate Tc 99m / Q000378:metabolism; D018874:Spheroids, Cellular; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014162:Transfection; D000099209:Sodium-Iodide Symporters
chemical_list: D000255:Adenosine Triphosphate; D019788:Fluorodeoxyglucose F18; D049409:Luciferases, Firefly; D019275:Radiopharmaceuticals; D013670:Sodium Pertechnetate Tc 99m; D027981:Symporters; D000099209:Sodium-Iodide Symporters