STEM CELL FATES
Pantelis Tsoulfas, M.D. • Scott R. Whittemore, Ph.D.

Stem cells are among the hottest topics in regeneration research today. Stem cells are unspecialized cells that can still divide to produce more stem cells, but their progeny also can mature into many types of cells in the body. These include nerve cells and neural-support cells: astrocytes and oligodendrocytes. Before cells with such wide potential can be successfully used for spinal cord repair, we must ask whether they can form functional nerve cells, and will they do so in the injured spinal cord?

Dr. Pantelis Tsoulfas has conducted two collaborations, addressing each of these questions. The first, work with colleagues at the National Institutes of Health, showed for the first time that nerve cells derived from rat brain could express well known excitatory or inhibitory neurotransmitters. Neurotransmitters are the chemicals with which nerve cells communicate. They either excite or inhibit the firing of other nerves in the circuit. Furthermore, the researchers showed that this communication actually does take place, at synapses formed in the dish between the stem-cell derived neurons.

This promising finding has to be balanced, however, by recent findings by Dr. Tsoulfas and former Miami Project colleague Scott Whittemore (now at the University of Louisville). In their soon-to-appear study, stem cells from embryonic rat brain were grafted into the spinal cord. While these cells have the potential to form neurons in laboratory dishes, in the spinal cord they formed almost exclusively astrocytes. The investigators concluded that stem cell fates will need to be influenced in the laboratory before grafting if the needed numbers of nerve cells or oligodendrocytes are to be obtained after grafting. Some success along these lines has been reported this year by Dr. John McDonald of Washington University.