Combination of Viagra shows rapid method to obtain donor stem cells

Researchers at UC Santa Cruz have demonstrated a new, rapid method to obtain donor stem cells for bone marrow transplants using a combination of Viagra and a second drug called Plerixafor.

According to researchers at UC Santa Cruz, combination of Viagra and a second drug called Plerixafor may help in a new, rapid method to obtain donor stem cells for bone marrow transplants.

The new study, published October 10 in Stem Cell Reports, demonstrates an alternative regimen that mobilizes stem cells from the bone marrow in just 2 hours. It involves a single oral dose of Viagra followed two hours later by a single injection of Plerixafor.

"Our approach could significantly increase the number of patients who could benefit from bone marrow transplants," said Camilla Forsberg, professor of biomolecular engineering at UC Santa Cruz and senior author of the paper. "Even though there are already ways to do this, the standard regimen doesn't work for everyone."

Viagra, best known as a treatment for erectile dysfunction, is a safe and well-studied drug that promotes the widening of blood vessels (vasodilation), which increases blood flow to tissues. Initially developed as a treatment for high blood pressure, it is now used to treat a variety of vascular disorders, including pulmonary hypertension, altitude sickness, and preeclampsia.

Forsberg's lab decided to test Viagra's ability to help mobilize hematopoietic stem cells from the bone marrow after observing that vascular changes in a strain of mice they were studying led to increased stem cell mobilization. The mice lack the gene for a cell surface protein, Robo4, which the lab's previous research had shown regulates blood vessel integrity to keep the stem cells in the bone marrow.

Plerixafor, the other drug in the combination, is an inhibitor of Cxcr4, which is a receptor on the surface of hematopoietic stem cells that helps them stick to their niche in the bone marrow. Plerixafor mobilizes the stem cells, but is not very effective on its own.

"When you dilate the blood vessels with Viagra, the cells mobilized by Plerixafor are better able to get out into the blood stream," Smith-Berdan said.

Viagra by itself did not lead to detectable increases in hematopoietic stem cells in the blood, so patients using it for other reasons need not worry about inadvertent stem cell mobilization, the authors noted.

Why Bone Marrorw Transplants Important?

Bone marrow transplants, used mostly in the treatment of cancer, are life-saving procedures to restore the stem cells that generate new blood cells throughout a person's life. These blood-forming cells (called "hematopoietic stem cells") normally reside only in the bone marrow. Obtaining them for transplants originally required drilling into the hip bone and using a special needle to remove cells directly from the bone marrow. Now it is more common to collect the cells from the blood, using drugs to get the stem cells to move from the bone marrow into the bloodstream.