Myocardial fibrillar collagen network: response to ischemia

Abstract

Both myocardial extracellular matrix as a whole and the fibrillar collagen network can alter in response to environmental stimuli such as ischemia. The aim of the study was to evaluate changes of the fibrillar collagen network in chronic ischemic myocardium and in cases of its regional losses. The percentage volume, perimeter, number of fiber foci per field of the myocardial fibrillar collagen network were estimated employing the computerized Quantimet 520 image anglysis system (Cambridge Instruments, United Kingdom) in 152 autopsied males who had died suddenly (within 6 h) of ischemic heart disease (IHD). The decedents were divided into three groups according to ischemic injury: (1) chronic ischemia – 71 males; (2) group of acute regional losses – 21 males; (3) group of formed myocardial scars – 60 males. Thirty-two males who had died within the same 6 hours following an accident served as controls. All parameters of fibrillar collagen in patients with chronic ischemia were significantly higher than those in the control group, indicating diffuse interstitial myocardial fibrosis. In patients with acute myocardial regional losses the percentage volume and the collagen-to-cardiomyocyte ratio of fibrillar collagen in the intact (remote from infarction) zone were the same as in patients with chronic ischemija alone, while the collagen fibers were found to be larger. In patients with formed scars, all fibrillar collagen parameters in the intact myocardial zone were significantly higher as compared with the corresponding indices of chronic ischemia and akute regional losses groups showing the progression of myocardial interstitial fibrosis. The relationship between the abundance of fibrillar collagen and total stenotic coronary artery lesions was determined. The occurrence and progression of myocardial fibrillar collagen accumulation together with eccentric left ventricular hypertrophy indicate a cardiac compensatory process in ischemic conditions. Keywords: fibrillar collagen, myocardium, interstitial fibrosis, ischemia