Levels of Early Circulating Angiogenic Cells Associated with Geographic Metrics of Roadway Exposure

Background: Multiple epidemiological investigations have established that roadway proximity is associated with adverse cardiovascular conditions. Recent literature indicates circulating angiogenic cells (CACs), types vascular progenitor cells, may be indicators of exposure to roadway-generated pollutants. Our study advances cardiovascular science by describing associations between CACs and geographic roadway exposure metrics.

Methods: Peripheral blood CAC levels of participants in the Louisville, KY Healthy Heart Study (n=240) were quantified using flow cytometry. Roadway exposure was assessed by utilizing GIS to measure distance to nearest roadway, total length of major roadways, total length of all roadways, and vehicle distance travelled, all within buffer areas between 50 and 300 meter intervals from subject residences. Generalized Linear Modeling was used to assess associations between roadway exposure and CAC levels.

Results: CACs positive for early progenitor cell marker, AC133⁺, were elevated in blood of individuals residing closer to major roadways (p<0.05). Associations of all early CACs were significantly higher in subjects living within 50m of a major roadway. Levels of some AC133⁺positive cells also were significantly associated with total roadway length and vehicle distance travelled within buffer. Associations were found with CACs in all exposure metrics. Strength of associations was dependent on size of assessed buffer areas.

Discussion: These findings suggest that early CACs are increased as residential distance to major roadways decreases. Distance at which specific CAC associations become significant may indicate what types of exposures from roadways may be leading to associations. CACs are mobilized by some environmental insults as a means of vascular protection.