Researchers have identified a way to expand blood-forming, adult stem cells from human umbilical cord blood (hUCB). Recent research uncovers a new approach for expanding blood-forming, adult stem cells from human umbilical cord blood.

Researchers from the Stowers Institute for Medical Research and collaborators have identified a way to expand blood-forming, adult stem cells from human umbilical cord blood (hUCB).

This development could make these cells available to more people, and be more readily accepted in those who undergo adult stem cell treatments for conditions such as leukemia, blood disorders, immune system diseases, and other types of cancers, but who do not have an appropriate available bone marrow match.

"Life-saving bone marrow transplants have been the common practice for decades, but this does not work for everybody," said Stowers Institute Investigator Linheng Li, Ph.D., study lead who is also co-leader of the cancer biology program at the University of Kansas Cancer Center and an affiliate professor of pathology and laboratory medicine at the University of Kansas School of Medicine.

Bone marrow donor

Only 30% of patients have a bone marrow donor match available in their families, according to the US Department of Health and Human Services. More than 170,000 people in the US are expected to be diagnosed in 2018 with a blood cancer (leukemia, lymphoma, or myeloma) according to the American Cancer Society.

Adult stem cells from umbilical cords are more likely to be a match for more people because there are fewer compatibility requirements than for a bone marrow transplant.

But adult patients need two cords' worth of blood per treatment, and there are not enough cord units available for everyone who needs the treatment. "If we can expand cord adult stem cells, that could potentially decrease the number of cords needed per treatment. That is a huge advantage," says Li.

In the study, published online July 31, 2018, in Cell Research, researchers zeroed in on a protein that affects multiple targets and pathways involved in hematopoietic stem cell self-renewal, a broader approach than other studies that focus on a single target or pathway in the process.

The protein, called Ythdf2, recognizes a particular type of modification on a group of mRNAs encoding key transcription factors for hematopoietic stem cell self-renewal and promotes the decay of these mRNAs within cells.

When the team knocked out Ythdf2 function in a mouse model or knocked down Ythdf2 function in hUCB cells, they observed increased expression of these transcription factors and expansion of hematopoietic stem cells, which are the major type of adult stem cells in hUCB.

They observed that impairing Ythdf2 function did not alter the types of cells that were subsequently produced, nor did it lead to increased blood cell malignancies. Also, the knockdown treatment is not permanent, thereby allowing Ythdf2's function to be restored after transplantation.

"Our approach of targeting Ythdf2 function using an RNA-based technique also helped avoid more persistent DNA-related changes such as mutations in epigenetic regulators," said Zhenrui Li, Ph.D., a predoctoral researcher at the University of Kansas Medical Center who is performing thesis research in the Linheng Li Lab and first author of the study.