Tracking Mesenchymal Stromal Cells In Vivo Using A Sensitive Bioluminescence Method

Akaluc can achieve cell tracking at the single-cell level, so this paper hypothesized that the bioluminescence of Akaluc could be used to tracking MSC in vivo. A newly discovered imaging platform of bioluminescence which based on a red-shifted and highly deliverable luciferin analog Akaluc was used to evaluate the safety and distribution of mesenchymal stromal cells)MSCs( in vivo. After intravenous infusion in immune-deficient Nude mice with gene modified Akaluc MSC which was established by lentivirus mVenus-Akaluc infection, we tracked the MSCs in real time. Therefore, we could assess the safety of MSCs in vivo and their biodistribution and finally determine whether MSCs are suitable for further research and experiment. We genetically-engineered MSCs with Akaluc lentivirus infection and puromycine screening named Akaluc MSCs. In vitro, the Akaluc activity of Akaluc MSCs reached 6300 per 104 cells. Signals can also be observed in more than 10 cells through in vivo imaging. Within 1-5 days after injection, the cells are mainly concentrated in the lungs. A part of the cells was observed to transfer to liver on the fifth day and was mainly spread in liver after 7 days. The cells were observed to survive for 14 to 21 days in vivo. In the meantime, the nude mice behave normally, and the mesenchymal stem cells disappear after 21 days. After continuous observation over one year, no tumorigenesis and no death wea observed in the mice. Former researches showed that cells were trapped in lungs and disappeared after 7 days. In this study, we observed MSCs live for over 14 days by the tracking using Akaluc. Akaluc was proven to be more effective than other enzymes in visualizing the biodistribution of mesenchymal stem cells, and it was proven to be not having tumorigenicity, because no sign of tumorigenesis was observed in vivo after one year.