Blood levels of endothelial progenitor cells in men with varying degrees of risk but no history of cardiovascular disease strongly correlate with Framingham risk factor score and clinical measures of endothelial function, according to an article in the February 13th issue of the New England Journal of Medicine.

The American team had hypothesized that this type of adult stem cell plays a role in arterial repair and that individuals with decreased numbers of endothelial progenitor cells may show progression of endothelial dysfunction and development of cardiovascular disease.

The researchers evaluated 45 healthy men (mean age 50 + 2 years), some of whom had a positive history of one or more standard cardiovascular risk factor: They found that low blood levels of progenitor cells correlated with higher cardiovascular risk as assessed by Framingham risk factor score. In addition, cells from men at higher risk aged faster in laboratory studies than those from men at lower risk. Clinically, investigators found that flow-mediated brachial artery reactivity, a measure of endothelial function, was more accurately predicted by blood level of progenitor cells than the presence or absence of conventional risk factors.

Standard heart disease risk factors are age, family history of early heart disease, smoking, hypertension, hypercholesterolemia, obesity, physical inactivity, and diabetes.

"Past research on cardiovascular disease has often focused on what causes the damage to the blood vessels," said Toren Finkel, M.D., of the National Institutes of Health and a coauthor of the study. "We looked at the other part of the equation: How does the body repair damaged blood vessels? What does that tell us about the cause of the disease?

"We believe that these endothelial progenitor cells patch damaged sites in blood vessel walls," he continued. "When the cells start to run out, cardiovascular disease worsens.
We don't yet know what causes their depletion but it may be related to the fact that the risk of cardiovascular disease increases as people age. For instance, the cells may be
used up repairing damage done by other risk factors or those risk factors could directly affect the survival of the endothelial cells themselves.

"Much more research needs to be done to better understand this finding," Finkel added. "But it's possible that, some day, doctors may be able to test a person's risk of
cardiovascular disease by taking a blood sample and measuring these cells. If the level is too low, an injection of endothelial cells might boost the body's ability to repair itself and prevent more blood vessel damage."