Induced pluripotent stem cells (iPSCs) come from adult cells and not embryos. By genetically engineering adult cells to express a cadre of genes that are normally found in early embryonic cells, scientists can de-differentiate the adult cells into cells that resemble embryonic stem cells in many (although not all) ways.
Generating iPSCs from human adult cells is tedious and not terribly efficient, but there are ways to increase the efficiency of iPSC generation (see here). Additionally, iPSCs can show a substantial tendency to form tumors, but this tendency is cell line-specific (see here and here). Furthermore, there are ways to screen iPSC lines for tumorgenicity.
Because iPSCs are directly from the patient’s cells, the chances of rejection by the immune system are less likely (see here). Therefore, many stem cells scientists believe that iPSCs may represent one of the best future possibilities for regenerative medicine. However, a hurdle in iPSC development is the ability to generate and evaluation iPSC lines in a rapid, but reliable manner. Once adult cells are induced to become iPSCs, the iPSC cultures are a mixed bag of iPSCs, undifferentiated adult cells that failed to make the transition to iPSCs, and partially reprogrammed cells. Selecting the iPSCs by merely eye-balling the cells through the microscope is tricky and fraught with errors. If the scientist wants to select iPSCs for toxicity studies and not partially differentiated cells, selecting the wrong cells for the experiment can be fatal to the experiment itself.
Scientists from the New York Stem Cell Foundation (NYSCF) Research Institute have developed a protocol for iPSC generation and evaluation is automated and efficient, and may bring us closer to the goal of using iPSCs in the clinic some day. This protocol is the culmination of three and a half years of work. This protocol uses a technology called “fluorescence activated cell sorting” or FACS to identify fully reprogrammed cells. FACS sorts the cells according to their expression of two specific cell surface molecules and the absence of another cell surface molecule. This negative selection for a cell surface molecule found in partially reprogrammed cells but not iPSCs is a very powerful technique for purifying iPSCs.
David Kahler, the NYSCF director of laboratory automation, said, “To date, this protocol has enabled our group to derive (and characterize over) 228 individual iPS cell lines, representing one of the largest collections derived in a single lab.” Kahler continued: “This standardized method means that these iPS cells can be compared to one another, an essential step for the use in drug screens and the development of cell therapies.”
This particular cell selection technique provides the basis for a new technology developed by NYSCF, the Global Stem Cell Array, which is a fully automated, robotic platform to generate cell lines in parallel.
Underway at the NYSCF Laboratory, the Array reprograms thousands of adult cells from kin and blood samples taken from healthy donors and diseased patients into iPSC lines. Sorting and characterizing cells at an early stage of reprogramming allows efficient development of iPSC clones and derivation of adult cell types.
“We are excited about the promise this protocol holds to the field. As stem cells move towards the clinic, Kahler’s work is a critical step to ensure safe, effective treatments for everyone.” said Susan L. Solomon, who is the Chief Executive Officer of NYSCF.