Hormone released by bone marrow cells may hasten recovery from brain injury

Bone marrow stromal cells release a blood vessel-dilating hormone found in the brain — a finding that suggests the hormone may be tapped to help with recovery from stroke or other neurological injuries disrupting blood flow to the central nervous system, researchers at the University of South Florida and James A. Haley Veterans’ Hospital report for the first time. The hormone is known as brain natriuretic peptide.

The laboratory study was published in the January 2004 issue of the journal Experimental Neurology.

“We’re suggesting that transplanted bone marrow stromal cells may hasten recovery by releasing brain natriuretic peptide and other factors that improve blood flow to the brain and decrease swelling and pressure around the site of injury,” said lead investigator Juan Sanchez-Ramos, MD, PhD, professor of neurology and research director at the USF Center for Aging and Brain Repair. “By helping irrigate, or restore the blood circulation to the brain, brain natriuretic factor may reduce the extent of damage from stroke or spinal cord injuries.”

Researchers at USF and other institutions have demonstrated that some cells from adult bone marrow can be converted with growth factors and other agents into immature nerve cells — both in the laboratory and following transplant into animals. Furthermore, rats suffering from stroke or other traumatic brain injury recover neurological function quicker following intravenous infusions of bone marrow stromal cells.

However, no one has proven that this recovery results from converted bone marrow cells directly replacing or repairing damaged neurons. A growing number of scientists, including Dr. Sanchez-Ramos, hypothesize that growth factors, cytokines and other substances secreted by bone marrow cells may play a more important role than first realized in recovery from neurological injuries.

The USF researchers identify bone marrow-derived brain natriuretic factor (BNP) as a potential candidate for treating stroke, spinal cord injury and other neurological damage. Although found in the brain, BNP belongs to a family of atrial natriuretic peptides, hormones made by the heart that exhibit powerful diuretic and blood pressure-lowering characteristics. In rat models of stroke, these atrial natriuretic peptides have been reported to decrease brain swelling or edema.

Human bone marrow is capable of producing significant amounts of BNP, the USF researchers demonstrated. Bone marrow stromal cells grown in the laboratory secreted levels of BNP far exceeding the amounts normally found in circulating blood and spinal fluid.

The researchers next plan to measure the effects of BNP from bone marrow cells transplanted into rats with strokes and spinal cord injuries.