Cardiologists Ibhar Al Mheid, Arshed Quyyumi and colleagues from Emory’s Clinical Cardiovascular Research Institute recently published a paper that weaves together insights from past research on circulating progenitor cells. They tease apart the influences of age and cardiovascular disease (CVD) risk factors on these cells, whose regenerative capacity has made them the target of much investigation. From this research, one can infer that the circulatory system has a limited regenerative capacity, and stress upon the system earlier in life depletes it later.

Circulating progenitor cells are rare cells in the blood that can become white or red blood cells, as well as endothelial cells, which line blood vessels and repair them when damaged by cardiovascular disease. Quyyumi and his colleagues have sought to deliver progenitor cells, derived from the patient’s own bone marrow, to the heart – or less invasively, spur them out of the bone marrow with drugs.

They already knew that people with more CVD risk factors tend to have lower numbers of progenitor cells, and that people with CVD and lower numbers of progenitor cells have a higher mortality risk.

But it gets more complicated: physical or mental stress can stimulate these cells to emerge from the bone marrow. Some previous work from this group had shown that circulating proangiogenic cell activity actually goes UP with CVD risk.

In their new paper, published in Circulation Research, the Emory team sought to separate the influences of age and of CVD risk factors (meaning: diabetes, hypertension or high cholesterol) on progenitor cells. Put simply, does unhealthy living or time bring the levels of these cells down?

To do so, they combined two groups of study participants: mostly healthy university employees from the Emory-Georgia Tech Predictive Health Institute, and the Emory Cardiovascular Biobank — hospitalized patients undergoing cardiac catheterization.

For younger subjects (<40 years), risk factors were associated with increased PC counts, whereas for older subjects (>60 years), risk factors and CVD were associated with lower progenitor cell counts.

The authors conclude:

“Circulating progenitor cell levels do not decline with healthy aging. Risk factor exposure at a younger age stimulates progenitor cell mobilization whereas continued exposure is associated with lower progenitor cell levels in later life.”

Co-authors include: Salim S Hayek, Nima Ghasemzadeh, Greg Martin, Muhammad Hammadah, A M Zafari, Viola Vaccarino, and Edmund K Waller.