This week researchers reported two groundbreaking findings that could greatly advance the use of stem cells in the treatment of a multitude of human diseases.
Researchers at the Samuel Lunenfeld Research Institute and the University of Edinburgh reported in a letter to Nature that they successfully reprogrammed adult human cells to a pluripotent state without infection, by using an engineered virus. Embryonic stem cells are naturally pluripotent, capable of transforming into any type of adult cell.
Previously, the only method of reverting adult cells into a state of pluripotency was through genetically programmed viruses, which insert four specific genes, called Yamanaka factors, into the adult cell’s genome. Any virus that can perform this function will inevitably cause other changes to the reprogrammed cell’s DNA, resulting in a greater risk of that cell becoming cancerous. Thus, such virally reprogrammed cells cannot be used in medical treatments.
These researchers instead inserted a chain of DNA containing these Yamanaka factors and a gene called piggyBAC into the adult cells. The piggyBAC gene allows the chain to jump into the cells’ DNA. After the cells are reprogrammed, the enzyme transposase is used to extract the chain from their genomes, leaving a genetically unaltered pluripotent stem cell, which does not pose an increased risk of becoming cancerous.
Researchers from Stanford and NYU’s Langone Medical Center have developed a method of supporting the three-dimensional growth of stem cells in a tissue matrix. Tissues containing skin, blood vessels and fat, called free flaps, were excised from the groin areas of rats. Stem cells were inserted into these tissues and then implanted back into the rats. The stem cells in the implanted tissues continued to grow and were not rejected.
In future studies, these researchers plan to induce the stem cells to differentiate into specialized organ cells. They predict that a re-implanted free flap tissue containing these organ and stem cells will grow into a fully functional organ within the organism without being rejected.
The production of stem cells from adult cells has two major advantages. First, these reprogrammed cells are free from the ethical controversy surrounding embryonic stem cells. They can be derived from adult skin cells and do not require the creation or destruction of embryos.
Second, reprogrammed stem cells can be derived from the patient they will be used to treat. Unlike embryonic stem cells, these reprogrammed stem cells contain the patient’s DNA and recognition proteins, greatly lowering their risk of an immunological rejection response to the implanted cells. This discovery has almost limitless implications.
The combination of these two discoveries will soon allow for the creation of organs for patients who require transplants from their own skin cells. Such organs would be the patient’s own, genetically and immunologically, and thus virtually guaranteed not to be rejected.
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