Imaging Gene Expression in Human Mesenchymal Stem Cells: From Small to Large Animals

Abstract

Purpose:To evaluate the feasibility of reporter gene imaging in implanted human mesenchymal stem cells (MSCs) in porcine myocardium by using clinical positron emission tomography (PET)-computed tomography (CT) scanning. Materials and Methods:Animal protocols were approved by the Institutional Administrative Panel on Laboratory Animal Care. Transduction of human MSCs by using different doses of adenovirus that contained a cytomegalovirus (CMV) promoter driving the mutant herpes simplex virus type 1 thymidine kinase reporter gene (Ad-CMV-HSV1-sr39tk) was characterized in a cell culture. A total of 2.25 ϫ 10 6 transduced (n ϭ 5) and control nontransduced (n ϭ 5) human MSCs were injected into the myocardium of 10 rats, and reporter gene expression in human MSCs was visualized with micro-PET by using the radiotracer 9-(4-[fluorine 18]-fluoro-3-hydroxymethylbutyl)-guanine (FHBG). Different numbers of transduced human MSCs suspended in either phosphatebuffered saline (PBS) (n ϭ 4) or matrigel (n ϭ 5) were injected into the myocardium of nine swine, and gene expression was visualized with a clinical PET-CT. For analysis of cell culture experiments, linear regression analyses combined with a t test were performed. To test differences in radiotracer uptake between injected and remote myocardium in both rats and swine, one-sided paired Wilcoxon tests were performed. In swine experiments, a linear regression of radiotracer uptake ratio on the number of injected transduced human MSCs was performed.

Preclinical Derivation and Imaging of Autologously Transplanted Canine Induced Pluripotent Stem Cells

“…Lentivirus Production and Transduction-Lentivirus for reprogramming transgenes or Fluc-RFP-HSVttk (firefly luciferase, red fluorescent protein, and herpes simplex truncated thymidine kinase) was collected from the supernatant of transfected 293FT cells and concentrated as described previously (11,12).…”

“…Canine Myocardial Delivery of Transfected Cells-Dogs were anesthetized, tracheally intubated, and mechanically ventilated as described previously (12). Cells were delivered by injection through the fourth and fifth intercostal spaces into three adjacent sites of the anterior left ventricular myocardium.…”

“…Clinical PET-Computed Tomography (PET/CT) ImagingImaging was performed with a clinical PET-CT scanner (Discovery LightSpeed Plus; GE Medical Systems, Waukesha, WI) as described previously (12).…”

Can Imaging Gene Expression in Human Mesenchymal Stem Cells be Successful in Large Animals?

“…The development of objective and quantitative imaging approaches for tracking stem cell fate, including stem cell location, survival, engraftment, and differentiation, may lead to better patient stratification and eventual successful translation of cardiac stem cell therapy into the clinic. The contributions of Willmann et al (1) represent an important step toward this goal.…”

Optical Imaging for Stem Cell Differentiation to Neuronal Lineage

“…The reporter-based imaging strategy endowed us with the ability to localize or monitor the migration of implanted cells, to evaluate therapeutic responses of cells and tissues to drugs, and to visualize the endogenous expression of transgenes in living subjects [10][11][12].…”