Spring 2011: Measuring Viral Titer to Analyze Transduction Efficiency in Induced Pluripotent Stem Cells
By Dr. X. Cindy Tian, Yong Tang, and Michael Tassavor
Stem cells have the ability to dramatically change the medical landscape, allowing regrowth and regeneration of tissues previously irreparable to modern science. Severe burns, spinal breakages, and muscle damage all can benefit, as well as more abstract diseases such as Parkinson’s, Multiple Sclerosis, and cancer. Until quite recently, however, sources for stem cells were limited to embryonic material.
In 2007, researchers managed to convert specialized adult cells to pluripotent stem cells capable of taking any somatic form in mice. This is highly useful in that it negates any need for embryonic stem cells in stem cell therapy, sidestepping legal and moral issues, as well as public outcry. Furthermore, it allows customized cells grown from the patient’s own cells, preventing immune rejection. Non-embryonic stem cells also have the benefit of allowing research to proceed with government grants, which, depending on the state and federal agencies involved, prohibit embryonic stem cell research.
The method used to produce induced pluripotent stem cells is the utilization of viral vectors to integrate genetic material that codes for proteins that initiate conversion to stem cells. The expression of certain genes, such as those out of the Sox family, and their associated proteins initiates the transformation of somatic cells into stem cells close in nature to embryonic stem cells.
Boosting the efficiency of the vectors is important in making this process clinically useful. Thus, the lab is currently tweaking the process to improve integration and make results more consistent and allow more reproducible results. However, currently the lab is unable to determine efficiency in an accurate or timely manner. By determining viral titer, one can correlate the amount of viral material used and the outcome, allowing better analysis of transduction and the overall efficiency of the process. The goal is to determine just exactly how much integration each exact amount of viral material achieves in the adult cells.
This experiment is essentially an assay and will involve the measurement of viral titer at known amounts to create a verifiable standard curve. Once established, accurate measurement of viral content in research samples will be measured to allow critical analysis of the transduction procedure currently employed in the lab.