Influence of the microenvironment dynamics on extracellular matrix evolution under hypoxic ischemic conditions in the myocardium

The extracellular matrix (ECM) consists of fibrillary and non-fibrillary components in the extracellular zone, and fulfills structural and signaling roles. Cardiac insult can lead to cardiomyocyte death, which subsequently determines dynamic changes of ECM composition and regulates cellular responses, ultimately contributing to cardiac repair. The present retrospective study on a small batch selected from the database of the Pathology Department of 'Sf. Pantelimon' Hospital aimed to determine which molecules may have a role in the dynamics of ECM using histopathology and immunohistochemistry methods. The study batch was composed of cases with cardiac ischemic conditions who died at various ages of myocardial infarcts. Tissue samples were taken from the myocardium of the left ventricle (anterior and lateral walls), and multiple series of histological sections were produced and analyzed using immunohistochemistry for collagen type I (Col-1), tenascin C (Tn-C), matrix metalloproteinase 9, CD34, and CD68. Col-1 and Tn-C showed variable patterns of fibrillar plexiform network, associated with a high micro-vascular density of newly formed capillaries revealed by CD34, and an interstitial infiltrate with histiocytes demonstrated by CD68 presence. The ECM represents therefore a polymorphic microenvironment with its own dynamics that is in continuous change, involving a large spectrum of heterogenous molecules, which play different roles in myocardium remodeling under hypoxic ischemic conditions.