Because circulating progenitor cells repair blood vessels, they are a measure of regenerative capacity in the cardiovascular system. Cardiologist Arshed Quyyumi, MD and his colleagues at Emory Clinical Cardiovascular Research Institute have intensively studied this cell type as a marker of vulnerability or resilience.
A recent paper from Quyyumi’s team in Circulation Research examines circulating progenitor cells (CPCs) through the lens of racial disparity. The authors find that African-Americans tend to have lower levels of this regenerative biomarker:
In a large well-characterized biracial cohort, we demonstrate that black participants had significantly lower CPC counts compared with whites, even after adjustment for differences in demographic factors and CVD risk factors. These results were validated in an independent cohort. Thus, on average, after adjustment for sex and other CVD risk factors, blacks have CPC levels that are ≈15% to 30% lower compared with whites, even in subjects free of risk factors. CPC levels decline with age, reaching on average half the levels at age 80 compared with age 20. We found that blacks have CPC counts equivalent to those in whites who are 14 years older. CPC levels are higher after AMI as a result of mobilization because of injury. We show for first time that blacks have 30% to 35% lower CPC mobilization in the setting of AMI.
This is a tricky area to study. How many socioeconomic and environmental factors go into the racial disparities of cardiovascular disease risk? Diet. Exercise. Geography, education, access to healthcare. Air pollution. Psychological stress and inflammation associated with discrimination. It is possible to view CPCs as summing up many of these influences, analogous to the way hemoglobin A1C measurements integrate someone’s blood sugar levels over time as a marker of diabetes.
First author Ayman Samman-Tahhan, MD says: “We examined different biomarkers that could explain the disparities in CPCs. The only significant one that could explain this was MMP-9 (matrix metalloprotease 9) which helps with progenitor cell mobilization from the bone marrow.”
The Emory analysis gathers together data from three different studies and more than 1700 people — patients from the cathetherization lab who were being examined for heart disease, the Mental Stress Ischemia group (stable coronary artery disease), and the Predictive Health cohort (mostly healthy university employees).
The authors explore more complex socioeconomic factors in their discussion. In previous research papers, members of Quyyumi’s team have taken on issues such as “food deserts” and even criminal justice reform. What might they do given the opportunity to design a new study, rather than slice and dice existing data sets?