Immunohistochemistry of connexin43 and zonula occludens-1 in the myocardium as markers of early ischemia in autopsy material

Abstract

Immunohistochemistry of the terminal complement complex (C5b-9) and fibronectin (FN) is useful to detect myocardial ischemia preceding necrosis in the postmortem diagnosis of sudden cardiac death. The present immunohistochemical study examined connexin43 (Cx43) and zonula occludens-1 (ZO-1) as markers of early myocardial ischemia in addition to the above-mentioned markers, using forensic autopsy cases of acute deaths due to myocardial infarction (MI, n=15) and acute ischemic heart disease (AIHD) without apparent myocardial necrosis (n=8), compared with those of acute mechanical asphyxiation (As, n=24) and drowning (D, n=10) as controls. Immunopositivities of each marker in the myocardium were semi-quantitatively graded by scoring. ZO-1, C5b-9 and FN were detected in the myocardial cytoplasm, whereas Cx43 and nonphosphorylated (np) Cx43 showed varied localizations at the intercalated disc, in the cytoplasm and along the lateral cell border. ZO-1 and FN showed a tendency to be detected more intensely in MI and IHD than in As and D. C5b-9 showed specific staining at the site of ischemia in MI (n=10/15) and AIHD (n=6/8), while the distribution of npCx43 was different in most cases of MI (n=14/15) and AIHD (n=5/8), compared with As and D; npCx43 positivity score was higher in the cytoplasm than at the intercalated disc, indicating redistribution due to myocardial ischemia. Such findings were detected in a few cases of As (n=3/24). These findings suggest that the combination of npCx43 and C5b-9 immunohistochemistry is useful for detecting early lesions of myocardial ischemia in sudden cardiac death.