Novel Platforms to Create Labeled Stem Cells

Stem cell research offers unlimited potential for applications in regenerative medicine. Much of the excitement surrounding this area of research comes from the cells inherent qualities; the ability to self renew and generate a variety of cells within the body. In the past two decades, research on stem cells has progressed exponentially providing a vast array of tools for a large breadth of areas. As research persists, there is a growing need for faster and more effective tools to analyze the many unknown processes that will unlock the power within these cells. Delivery of genes to create labeled stem cells vastly enhances their utility as tools for basic research and drug screening but also as potential therapeutic agents. Gene transfer has been a routine method in stem cell research since scientists first began culturing stem cells in vitro. Genetic manipulation has accelerated research enabling the creation of in vitro models for drug discovery, use as a tool for dissecting basic stem cell biology and potential development of in vivo cell-based delivery strategies. Efficient gene transfer into stem cells is a critical step in the creation of engineered stem cells. Several viral and non-viral methods exist for the modification of stem cells, albeit with varying efficiencies (Colosimo et al., 2000). Each platform has its advantages and disadvantages that can be effectively utilized for specific applications. Here, we review gene delivery, cloning, and modification methods and describe in detail three platforms that enable the user to create modified stem cells that transiently or stably express one or multiple genes of interest. The three platforms described here each offer a unique feature and advantage that may be ideal for a particular cell type or application. The first is a non-integrating insect virus that is ideal for the transient short term expression of genes of interest. Second is an episomal EBV based vector method that allows for populations of transgene expressing cells to be stably maintained without genomic insertion. The third platform is a site specific integrating platform that can be clonally selected and is not subject to silencing.