A Novel Tracking System For Stem Cell Transplantation

Objective: Stem cell regenerative medicine holds a great promise in clinical practices.However,the survival,retention and distribution of stem cells after transplantation need further investigation before clinical translation.The purpose of this project is to establish multimodal imaging system to track the transplanted stem cells in vivo by combining the exogenous photoacoustic imaging(PAI)and endogenous bioluminescence(BLI).Meanwhile,the dangerous cells can be removed through photothermal therapy(PTT).Methods: In this study,coexpression of Fluc,HSCttk and cop GFP from a single transcript is mediated by the 2A peptide sequence.The three reporters above are targeted to AAVS1 locus through CRISPR/Cas9-mediated homologous recombination.Meanwhile,we labeled stem cells expressing three reporters using Cu Fe Se2 nanoparticles in vitro,to detect the distribution of the transplanted cells through PAI,BLI and PTT.Results: Three reporters driven by CAG promoters were efficiently expressed in embryonic stem cells.No gene silence was observed during passage and differentiation.It allows for visualization and quantitative evaluation of the dynamic change the cells after transplantation.Stem cells incubated with Cu Fe Se2 nanoparticles in vitro can be detect through PAI and PTT.Cu Fe Se2 nanoparticles labeled human embryonic stem cells can form subcutaneous teratoma,while these cells can be removed though PTT effect of Cu Fe Se2 under 808 nm laser.The whole process can be visualized by BLI.In order to remove cell in deeper tissue,we employed myocardial infarction mouse model and tansplanted stem cells.We found PTT can remove the cells labeled with Cu Fe Se2 nanoparticles in heart tissue.The method provided a new strategy to remove the cells that cause cardiac arrhythmia and teratoma after transplantation.Conclusions: The three reporter system can be used to track the transplanted cells efficiently through BLI,fluorescence and so on.Cu Fe Se2 nanoparticles incubated cells can be monitored by PAI.PTT of Cu Fe Se2 nanoparticles can be used to eliminate the side effects after stem cells transplantation,including cardiac arrhythmia and teratoma.