Targeted Nanoparticle Probes for Embryonic Stem Cell Derived Progenitor Cells
David Larocca. Burnham Institute for Medical Research, La Jolla, CA Pluripotent stem cells whether from embryonic (ES) or induced (iPS) cells offer a potentially unlimited source of replacement cells for treating human degenerative diseases associated with aging such as cardiovascular disease, macular degeneration, aging skin, diabetes, Parkinson’s, and Alzheimer’s disease.
The availability of iPS cells will no doubt increase the number of research grade ES-like cell lines dramatically and may ultimately fulfill the need for patient specific stem cells. However, a significant problem and potential bottleneck to developing stem cell therapies is the development of efficient tools and technologies for directed differentiation of pluripotent stem cells toward therapeutic cell types. Currently, this process is poorly understood and often yields differentiated cells that represent only a few percent of the starting ES cells which are difficult to scale up.
Identification of surface markers of lineage specific progenitor cells would provide tools for tracking, isolating and scaling these cells to improve differentiation yields and increase our understanding of ES cell differentiation in vitro. Toward this end, we have isolated progenitor cell-targeting peptides by selecting phage display libraries on differentiating ES cells. We have used the cell-targeting peptides or peptide phage themselves to target fluorescent nanoparticles (quantum dots) to progenitors cells. The quantum dot label persists and the tagged cells can be tracked up to several weeks as they differentiate.
Peptides that bind to specific subpopulations of differentiating ES cells have been identified using variety of selection strategies and are focusing on selection of probes that target heart, blood vessel, neural crest and skin cell lineages. We are currently assessing the lineage of selected cell-targeting peptides by immunostaining with differentiation specific markers and assessing co-localization with quantum dot labeled cells.
In addition to progenitor isolation the peptide probes in development will be useful for monitoring stem cell fate in-vitro and in-vivo and as cell lineage markers in high-throughput screens for reagents that regulate differentiation.