Figure 3.

Cardiac-specific overexpression of Cisd2 at a late-life stage rescues the aging hearts of mice from age-related cardiac fibrosis and intercalated disc (ICD) defects. (A) Age-related cardiac fibrosis can be seen to be ameliorated by enhancing the expression level of Cisd2 in the aging heart. Representative immunofluorescence images of heart sections from the three groups of mice (3-mo WT, 26-mo WT, and 26-mo Cisd2 icOE) stained with antibodies against collagen I (green) and wheat germ agglutinin (red) to identify the cell membrane, with rhodamine phalloidin—to identify actin (purple), and with DAPI—to identify the cardiomyocytic nucleus. Age-related cardiac fibrosis is obvious in the 26-mo WT mice (A2). However, overexpression of cardiac Cisd2 appears to reduce cardiac fibrosis (A3). (B,C) Overexpression of Cisd2 reverses the age-related defects affecting the ICD in the aging heart. Representative immunofluorescence images of heart sections from the three groups of mice (3-mo WT, 26-mo WT, and 26-mo Cisd2 icOE) stained with antibodies against Cx43 (green) was used to localize gap junctions, against pan-cadherin (red)—to localize the ICDs, and against α-actinin (purple)—to stain muscle fibers. The sections were also stained with Hoechst (blue) to identify the nuclei. Cx43 is well-co-localized with pan-cadherin in hearts of the 3-mo WT mice (B1). However, lateralization and loss of co-localization of Cx43 with pan-cadherin were found in hearts of the 26-mo WT mice (B2). White arrows indicate lateralization of gap junctions. Maldistribution of desmosomes was found in the hearts of 26-mo WT mice (C). Co-localization of desmoplakin (green) with pan-cadherin (C1) was found within desmosomes of the 3-mo WT mice, and this was lost in hearts of the 26-mo WT mice (C2). Remarkably, defects in the ICD were reversed by cardiac-specific overexpression of Cisd2 (B3,C3).