In the 1960s, Ernest McCulloch and James Till, of the University of Toronto, defined the key functions and characteristics of stem cells for the first time. It has since upended humanity’s understanding of the traditional cognition of cytology and ushered the era of cell therapy. Stem cells are undifferentiated cells with the remarkable capacity to split into any kind of cells in our body. Types of stem cells mainly include embryonic stem cells, adult stem cells, and induced pluripotent stem cells (iPSCs). The stem cell, which is cultured in a dish by adding chemical and mechanical stimuli, is able to be differentiated into any type of cell, thereby exhibiting their nascent features and taking as biology’s blueprints.
The lab work performed signified that the combination of genome editing technologies and stem cells resulted in establishing disease models and forming genetic maps to facilitate drug discovery and develop potential curative therapies for many refractory diseases.
"This gene map provides a new functional perspective for us to study the human genome and becomes a tool for us to analyze and treat cancer and genetic diseases," said Nissim Benvenisty, a professor at the Hebrew University of Jerusalem. Specifically, through gene-editing technology, mutations from simulated diseases can be introduced into the iPSC disease model and differentiated into obtaining cells needed for research or treatment. This eliminates the risk of immune rejection from the donor because these manipulated and transplanted cells are from the same patients. Pairing these findings with further promising clinical trials can help reveal their likely permanent cures for certain diseases.
To explore the use and potential of stem cells, a powerful genome-based editing technique called Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) has been applied. To put it simply, it finds a set of tools in cellular genes that can perform the task of cutting, copying and pasting, removing unwanted gene fragments, and replacing them with desired ones, thus altering the genetic makeup of living organisms such as animals, plants and bacteria. A recent study demonstrated that gene-editing technology was successfully used to repair a disease-causing mutation in human embryos. Surprisingly, the study revealed that the embryos checked the mother's copy of the MYBP3 gene, rather than the foreign DNA, to make the corrections, allowing for the accuracy of gene-editing to be achieved. The use of the CRISPR system has also successfully avoided harmful mutations that may occur through other gene-editing techniques. Co-author Shoukhrat Mitalipov at Oregon Health & Science University in Portland states, “The use of this technology may reduce the burden of this heritable disease on the family and the entire human population”.
Another gene-editing tool, called Transcription Activator-like Effector Nucleases (TALENs), has also been used to edit stem cells. Unlike CRISPR, which can introduce multiple gene mutations concurrently with a single injection, TALENs is limited to simple mutations. Both of them can effectively correct genetic errors; however, these techniques have limitations, such as off-target effects and possible safety issues, which need to be considered when employing these techniques in humans.
Since their discovery, genome-based editing technologies have fundamentally transformed human ability to manipulate genomes. When combined with stem cells, these gene-editing tools have the power to reshape the understanding of human genetics, developmental biology and regenerative medicine. However, the debate about genome editing has never faded from discovery to use. Bioethicists and researchers generally believe that human genome editing for reproductive purposes should not be attempted at this time, and ethical considerations should be regarded as a threshold so that the study of gene therapy would continue safely and effectively.