Increase in circulating bone marrow progenitor cells after myocardial infarction

Most circulating blood cells expressing the marker CD34 are bone marrow progenitor cells. These cells differentiate into cardiomyocytes, endothelial and smooth muscle cells after myocardial infarction in vivo. Mobilization of bone marrow progenitor cells into the peripheral blood after myocardial infarction may supply these cells to the heart. Rise in CD34+ cell concentrations following myocardial infarction would support the existence of myocardial-initiated mobilization.

Serial measurements of circulating CD34+ cells were made in 42 consecutive patients presenting with first ST-elevation myocardial infarction. Measurement of serum concentrations of monocyte chemoattractant protein-1, stromal derived factor-1, hepatocyte growth factor, interleukin-17 and thrombopoietin was also performed. Samples were drawn on day 1 after myocardial infarction, and on days 4, 8 and 12. Levels of CD34+ cells and cytokines were also measured in 15 controls.

By day 8, the mean concentration of CD34+ cells rose by 74% above mean control level of 2527 cells/ml, and 41% above day 1 mean (P=0.02). This rise was sustained on day 12 (P=0.05). On day 1, there was a 9.3-fold rise in hepatocyte growth factor above the control level of 589 pg/ml (P=0.002). Hepatocyte growth factor levels declined from the day 1 mean of 6061 to 1485 pg/ml on day 12 (P=0.002). No significant change in stromal derived factor-1, interleukin-17, monocyte chemoattractant protein-1 and thrombopoietin was observed. Elevations in CD34+ cells and hepatocyte growth factor were not related to infarction size as estimated on echocardiography.

Elevation in the concentration of circulating CD34+ cells after myocardial infarction suggests that myocardial initiated bone marrow progenitor cell mobilization exists in humans. The cytokines studied in our protocol are not likely to play a direct role in bone marrow progenitor cell mobilization.