[Dynamic changes of peripheral blood monocyte subsets after myocardial ischemia/reperfusion in rats]

To investigate the dynamic changes of monocyte subsets after myocardial ischemia/reperfusion (I/R) in rats and their correlations with myocardial repair after I/R injury.

Sixteen male Wistar rats were randomly divided into two groups: I/R group and sham group. Myocardial I/R was induced by left anterior descending coronary artery ligation for 45 min followed by permanent reperfusion. Peripheral blood was harvested from the tail vein to evaluate the dynamics of CD172a(+);CD43(low); and CD172a(+);CD43(high); monocyte subsets by flow cytometry at baseline and on day 1, 3, 5, 7 and 14 after I/R injury. Survival rats were sacrificed on day 30, and the hearts were prepared for the evaluation of collagen deposition (Masson's trichrome staining) and myocardial hypertrophy (wheat-germ agglutinin staining).

In I/R group, there was a significant increase of CD172a(+);CD43(low); monocytes on day 1 compared with the baseline (P<0.05), followed by an increasing trend, which peaked on day 3 (P<0.01), and then underwent a gradual decreasing trend to the baseline on day 7. In sham group, a similar increasing trend of CD172a(+);CD43(low); monocytes was observed on day 1 (P<0.05) compared with the baseline, whereas this trend declined rapidly to the baseline level on day 3. The proportion of CD172a(+);CD43(low); in I/R group on day 3 was much higher than that in the sham group (P<0.01). There were no significant differences between the two groups at any other time points. A reciprocal change of CD172a(+);CD43(high); monocytes was observed during investigation. Cardiac pathological evaluation revealed that there was a significant reparative fibrosis in the infarct area (P<0.05) along with a significant myocardial hypertrophy in non-infarct area (P<0.01) in I/R group. Correlation analysis showed that the proportion of CD172a(+);CD43(low); monocytes on day 3, but not CD172a(+);CD43(high); monocytes, was positively correlated with the level of collagen deposition in the infarct area (r=0.86, P<0.05).

The study demonstrates the dynamic profile of circulating monocyte subsets following myocardial I/R injury in rats, which indicates that the proinflammatory CD172a(+);CD43(low); monocytes might be a therapeutic target to attenuate myocardial I/R injury.