Adhered macrophages as an additional marker of cardiomyocyte injury in biopsies of patients with dilated cardiomyopathy

Abstract Background . As shown recently, macrophages have proved most suitable for the chronic stage of myocarditis (MCI). The study aim . Accordingly, the aim of this study was to determine the number of CD68(+) macrophages adhered to injured cardiac myocytes in biopsy of patients with dilated cardiomyopathy (DCM) and clinical suspicion of MCI. Patients and Methods . The study group consisted of 181 patients with DCM (159M, 22F, mean duration of symptoms was 1.8 years) and decreased left ventricular ejection fraction (< 40%). Immunohistochemistry on cryostat sections was performed using a Leica Bond Max autostainer and murine monoclonal antihuman antibodies anti-CD68(+) macrophages (cloneEBM11) from DAKO, Denmark. The total number of CD68(+) macrophages and the number of CD68 macrophages attached to injured cardiomyocytes were counted in at least 10 high power fields under 400x magnification and converted into the number of cells/mm 2 . Results . Two expression patterns of CD68(+) macrophages were observed: those localized freely in the interstitial space only, and cells attached to injured cardiomyocytes. The mean number of total CD68(+) macrophages and the number of those adhered to injured cardiomyocytes were 8.92 ± 4.29 and 0.89 ± 1.57, respectively. As far as CD68(+) macrophages adhered to injured cardiac myocytes are concerned, 72 out of 181 (39.8%) samples presented these cells. Importantly, in 7 positive cases for the presence of adhered macrophages, the average of total CD68(+) cells was < 14cells/mm 2 (7 out of 81, 8.64%). Spearman’s rank coefficient showed a significant correlation between the count of the total number of CD68(+) macrophages and CD68(+) cells directly adhered to injured cardiac myocytes (r = 0.53, P < 0.001). Both the total number of CD68(+) macrophages and the number of CD68(+) cells directly adhered correlated negatively with cTnT in the serum of DCM patients (Spearman’s rho, r = -0.45, P < 0.001 and r = - 0.31, P = 0.009, respectively). Conclusion . The use of the count of CD68(+) macrophages by immunohistochemistry which are attached to injured cardiomyocytes may be useful for the diagnosis of chronic inflammation in endomyocardial biopsy in patients with DCM, especially in those who did not meet the criteria for MCI.