Connexin-43 Protein Expression Pattern Analysis in Myocardial Infarction Tissues

Abstract

Background/aim: Ischemic heart disease is a leading cause of death worldwide in comparison to malignant neoplasia. Myocardial infarction (MI) is the result of severe ischemia due to a low consumption of oxygen in the myocardium. The main pathophysiological reason is a progressive obstructive atherosclerotic endothelial lesion that causes reduction in coronary blood flow and increases the corresponding arterial stenosis. Our research aim was to investigate the role of altered expression connexin-43 (gene locus: 6q22.31) protein in MI tissue substrates with different clinico-pathological characteristics.

Materials and methods: A set of fifty (n=50) MI archival tissue sections derived from a forensic pathology file were selected and micro-sectioned. Immunohistochemistry and digital image analysis assays were implemented for detecting and measuring the levels of connexin-43, respectively.

Results: Low expression of Connexin-43 protein was detected in 16/50 (32%) cases, biphasic expression pattern (low/medium) was identified in 10/50 (20%), whereas moderate and high levels of protein expression were observed in the rest of them (24/50-48%). Connexin-43 overall expression was significantly correlated with the timing of the MI onset (recent or past) (p=0.001).

Conclusion: Connexin-43 is a critical gap junction intermediate protein in MI pathology diagnosis and research. Different Connexin-43 expression levels, including single phase or biphasic patterns, should be a reliable biomarker for determining the timing of the MI lesions inside the corresponding tissue sections. Furthermore, implementation of sophisticated, accurate computerized techniques, such as digital image analysis provide very detailed, objective results regarding protein expression as modern precise (evidence-based) medicine requires.

Keywords: Myocardium; artery; connexin 43; immunohistochemistry; infarction.

Figure 1

Connexin-43 biphasic (high/moderate) expression pattern in a case of MI. Note areas with dense brown membranous staining (right part of the image) and areas with a slighter staining (centre and left part of the image), respectively (original magnification 100×, Diaminobenzidine-DAB- chromogen).

Figure 2

Connexin-43 biphasic (moderate/low) expression pattern in a case of MI. Note mixed areas with medium brown membranous and areas with a slighter staining, respectively (original magnification 100×, Diaminobenzidine-DAB-chromogen).

Figure 3

Digitized evaluation of connexin-43 protein expression. Red areas correspond to the different levels of protein expression that lead to specific staining intensity levels in a spectrum of 0-255 continuous grey scale RGB values.