In people who have suffered a stroke, blood flow must be restored to affected areas of the brain in order to minimize long-term effects, and death. Studies have shown that the infusion of a type of stem cell called mesenchymal stem cells (MSCs), derived from the bone marrow, can improve the motor function of laboratory rates following an experimental stroke. MSCs have the potential to develop, or differentiate, into many different types of connective tissue, and new research indicates that new blood vessel growth (angiogenesis) is largely responsible for the improvements seen with MSC therapy.

Researchers at Sapporo Medical University, Japan, and at Yale University Medical Center, New Haven and the VA Medical Center, West Haven, Connecticut, intravenously infused MSCs into rats at different time points following strokes to determine if the cells could promote new capillary growth in the brain and improve function. They found that rats that received MSCs up to 1 month after a stroke had greater angiogenesis near the borders of the damaged areas of the brain and performed better on a treadmill test than did rats that did not receive the treatment. This striking results suggests that the time window for treating stroke using MSC therapy may be as long as a month after the stroke occurs, although only rats treated earlier (7 days after stroke) had actual reductions in the size of the stroke lesion.  Conventional thinking is that treatment for stroke must occur within the first 12-24 hours after the event.

The mechanisms by which MSC therapy improves function after stroke are still being researched.  It is thought that MSCs produce multiple angiogenic growth factors, and that transfusion of these cells into areas of the brain damaged by stroke promotes the vital new blood vessel growth needed to keep brain cells from dying. For example, the protein called angiopoietin is an angiogenic factor that MSCs can deliver to facilitate localized angiogenesis and functional recovery in rats. Because improving blood flow to areas of the brain affected by stroke is critical for reducing impairment, the beneficial angiogenesis induced by MSCs could be an important new treatment option.