By providing highly enriched populations of tissue-specific adult stem cells, Asymmetrex’s SACK technology makes direct adult tissue stem cell engineering practical for the first time. With SACK agent supplementation, cultures of SACK strains have stem cell fractions that range from 20% to 70%. These high fractions make special targeting for genetic engineering unnecessary; and they make it feasible to seed micro-fabricated engineered tissue architectures with high efficiency. The SACK agents also make it possible to produce clonal strains of adult tissue stem cells. Clonal derivation is an ideal capability for establishment and characterization of genetically engineered tissue stem cells for use in drug development and as cellular disease models. Recently, Asymmetrex scientists also discovered that SACK agents could be used to increase the efficiency of induced pluripotent stem cell production (iPSCs).
I. Genetically engineering SACK stem cell strains
As proof of concept for adult tissue stem cell genetic engineering, Asymmetrex has developed clonal, fluorescent protein-expressing (e.g., yellow fluorescent protein, cyan fluorescent protein) strains of SACK-produced human liver stem cells, rat liver hepatocyte stem cells, and mouse pancreatic stem cells.
II. SACK applications for Induced Pluripotent Stem Cell (iPSC) Production
Investigation and engineering of the reprogramming of differentiated tissue cells to regain pluripotency currently preoccupy many stem cell research and development efforts in both academia and industry. Although iPSCs have many advantageous applications for basic and disease research, their suitability for regenerative medicine and drug development is often overstated. Like other types of pluripotent stem cells (e.g., embryonic stem cells), iPSCs have high levels of genetic and epigenetic mutations and are tumor-forming. The inheritance of their high mutation levels by their differentiated derivatives may compromise normal cellular functions desired for drug development applications. Beyond tumorigenicity as a considerable problem for transplantation therapies, iPSCs’ lack of asymmetric self-renewal precludes their use for long term reconstitution of tissues in children and adults.
Despite the many shortcomings of iPSCs for cellular therapy, they have proven to be indispensable for cellular programming research. However, their employment in this research is limited by two challenges. Research efforts continue with the goals of increasing the efficiency of their production and making them without the use of gene transfer, which may further increase their tumorigenic potential. At Asymmetrex, we have shown that some SACK-produced adult tissue stem cells (e.g., pancreatic) can be converted directly into iPSCs without using reprogramming genes or proteins. Moreover, SACK agents like xanthine increase the efficiency of this gene-free induction process to levels comparable to reports for reprogramming genes. This enhancing technology is available for licensing to iPSC reagent supply companies.