Umbilical cord blood cells can success fully be reprogrammed to function like embryonic stem cells, setting the basis for the creation of a comprehensive bank of tissue-matched, cord blood-derived induced pluripotent stem (iPS) cells for off-the-shelf applications, report researchers at the Salk Institute and the Center for Regenerative Medicine in Barcelona.
"Cord blood stem cells could serve as a safe, 'ready-to-use' source for the generation of iPS cells, since they are easily accessible, immunologically immature and quick to return to an embryonic stem cell-like state," says Juan-Carlos Izpisúa Belmonte, a professor in the Salk's Gene Expression Laboratory, who led the study published in the October issue of the journal Cell Stem Cell.
Worldwide, there are already more than 400,000 cord blood units banked along with immunological information. Due to their early origin, cells found in umbilical cord blood contain a minimal number of somatic mutations and possess the immunological immaturity of newborn cells, allowing the Human leukocyte antigen (HLA) donor-recipient match to be less than perfect without the risk of immune rejection of the transplant.
HLA typing is used to match patients and donors for bone marrow or cord blood transplants. HLAs are special surface markers found on most cells in the body and help the immune system to distinguish between "self" and "non-self."
"Selecting common HLA haplotypes from among already banked cord blood units to create iPS cell would significantly reduce the number of cell lines needed to provide a HLA match for a large percentage of the population," says Izpisúa Belmonte.
Since the first adult cells were converted into iPS cells, they have generated a lot excitement as an uncontroversial alternative to embryonic stem cells and as a potential source for patient-specific stem cells. Unfortunately, taking a patient's cells back in time is not only costly, but could be difficult when those cells are needed right away to mend injured spinal cords or treat acute diseases, and outright impossible when the effects of aging or chronic disease have irrevocably damaged the pool of somatic cells.
With this in mind, Belmonte and his colleagues set out to transform hematopoietic stem cells isolated from cord blood into iPS cells. They not only successfully converted them using only two out of the four most commonly used factors–OCT4 and SOX2–but also in less time than any other previously published methodology require. No matter, whether the researchers started with freshly collected cord blood or previously frozen samples, the resulting iPS cells were indistinguishable from human embryonic stem cells.