Firefly gene reporter allows scientists to track the exact fate of transplanted stem cells

Researchers from the University of Central Florida’s College of Medicine’s Burnett School of Biomedical Sciences (BSBS) and the Gazes Cardiac Research Institute at the Medical University of South Carolina have used firefly luciferase to track, in real-time, the differentiation of transplanted cardiac embryonic stem cells. They expressed the firefly luciferase reporter gene (luc) in a mouse embryonic stem (mES) cell line that constitutively expresses the enhanced yellow fluorescent protein (EYFP). Researchers were able to follow differentiation and proliferation of transplanted cardiac stem cells both in vivo and post-mortem with traditional histological assays. Steven N. Ebert, an associate professor at Burnett School of Biomedical Sciences, said, “Cardiac muscle cells are the holy grail in the cardiac world. We were able to clearly demonstrate that the stem cells were becoming heart muscle cells, and we could see that not only in histological sections, as is traditionally done; the firefly activity let us see them glow in vivo.”
With previous stem cell therapies, researchers could not monitor the activity of transplanted cells once they had been inserted into the subject. However, this dual reporter system allows researchers to observe the functionality of the cells and then even exactly document exactly where the transplanted cells wound up through histological examinations.
Ebert’s team previously attempted to track mES cells by loading the cells with super paramagnetic microparticle beads and using magnetic resonance imaging (MRI). Unfortunately even though this technique was able to determine the location of the cells and provide high-resolution images, but the beads migrated out of the target cells. Additionally, this method did not provide any new insights into the function of the cells. Ebert admitted, “Fundamentally, there’s a lot that we don’t know about how stem cells behave once they’ve been put back into the heart and become stimulated under natural conditions. An impetus behind the firefly strategy was to give us a way to see if the cells were actually becoming heart muscle by observing the functional activity.”
Although the current paper only documents the incorporation and differentiation of basic cardiac embryonic stem cells, Ebert says the reporter system can be adapted for a variety of clinical uses. His lab is testing the mES dual-reporter cell line to different application. The team is also developing new lines for more specialized investigation, such as examining the rehabilitation differences for damaged cardiac cells that produce adrenaline and those that do not.
Ebert concluded, “We’d like to put [the cardiac stem cells] into disease models where there’s actual damage to the heart and see if they can regenerate some of the cardiac muscle that has been lost. There’s a lot of potential in the field and a lot we don’t know yet, so there’s a lot more investigation to keep us busy for a while.”