Desmosomes are cell–cell adhesion sites and part of the intercalated discs, which couple adjacent cardiomyocytes. The connection is formed by the extracellular domains of desmosomal cadherins that are also linked to the cytoskeleton on the cytoplasmic side. To examine the contribution of the desmosomal cadherin desmoglein 2 to cardiomyocyte adhesion and cardiac function, mutant mice were prepared lacking a part of the extracellular adhesive domain of desmoglein 2. Most live born mutant mice presented normal overall cardiac morphology at 2 weeks. Some animals, however, displayed extensive fibrotic lesions. Later on, mutants developed ventricular dilation leading to cardiac insufficiency and eventually premature death. Upon histological examination, cardiomyocyte death by calcifying necrosis and replacement by fibrous tissue were observed. Fibrotic lesions were highly proliferative in 2-week-old mutants, whereas the fibrotic lesions of older mutants showed little proliferation indicating the completion of local muscle replacement by scar tissue. Disease progression correlated with increased mRNA expression of c-myc, ANF, BNF, CTGF and GDF15, which are markers for cardiac stress, remodeling and heart failure. Taken together, the desmoglein 2-mutant mice display features of dilative cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy, an inherited human heart disease with pronounced fibrosis and ventricular arrhythmias that has been linked to mutations in desmosomal proteins including desmoglein 2.

Arrhythmogenic cardiomyopathy (AC) is an incurable genetic disease, whose pathogenesis is poorly understood. AC is characterized by arrhythmia, fibrosis, and cardiodilation that may lead to sudden cardiac death or heart failure. To elucidate AC pathogenesis and to design possible treatment strategies of AC, multiple murine models have been established. Among them, mice carrying desmoglein 2 mutations are particularly valuable given the identification of desmoglein 2 mutations in human AC and the detection of desmoglein 2 auto-antibodies in AC patients. Using two mouse strains producing either a mutant desmoglein 2 or lacking desmoglein 2 in cardiomyocytes, we test the hypothesis that inflammation is a major component of disease pathogenesis. We show that multifocal cardiomyocyte necrosis initiates a neutrophil-dominated inflammatory response, which also involves macrophages and T cells. Increased expression of Ccl2/Ccr2, Ccl3/Ccr5, and Cxcl5/Cxcr2 mRNA reflects the observed immune cell recruitment. During the ensuing acute disease phase, Mmp12⁺ and Spp1⁺ macrophages and T cells accumulate in scars, which mature from cell- to collagen-rich. The expression of Cx3cl1/Cx3cr1, Ccl2/Ccr2, and Cxcl10/Cxcr3 dominates this disease phase. We furthermore find that during chronic disease progression macrophages and T cells persist within mature scars and are present in expanding interstitial fibrosis. Ccl12 and Cx3cl1 are predominant chemokines in this disease phase. Together, our observations provide strong evidence that specific immune cell populations and chemokine expression profiles modulate inflammatory and repair processes throughout AC progression.

Class I histone deacetylases (HDACs) and acetylases (HATs) are members of transcriptional pre-initiation complexes assembled by steroid hormone receptors. Recently, HDAC inhibitors were shown to enhance differentiation of endometrial fibroblasts and endometrial adenocarcinomas. However, there is only rare information on HDAC and HAT expression in the human endometrium. HDAC-1, -2, -3 and HAT (PCAF and GCN5) mRNA expression was studied in tissue from premenopausal women undergoing hysterectomy by real-time or semiquantitative RT–PCR. HDAC protein expression was assessed by Western Blot and immunohistochemistry. In endometrial adenocarcinomas (n = 17), HDAC-1 expression was studied by immunohistochemistry. In the human endometrium, HDAC-1, -2, -3 and PCAF mRNA are expressed without cyclical changes. Western blot analysis demonstrated that HDAC-2 protein expression was slightly, but significantly elevated in the secretory phase (P < 0.01 versus day 5–8), whereas HDAC-1 and -3 protein expression was constitutive throughout the menstrual cycle. By immunohistochemistry, nuclear expression of HDAC proteins was detected in all endometrial cell types. In the case of HDAC-3, immunostaining was significantly reduced in the endometrial surface epithelium on day 6–10 (P < 0.01 versus days 15–18 and 24–28). Compared to normal endometrium, a high proportion of endometrial adenocarcinomas showed impaired HDAC-1 protein expression in the epithelial and stromal compartment. Class I HDACs and HATs are expressed in the human endometrium throughout the menstrual cycle, suggesting the cyclic endometrium as a potential target for HDAC inhibitors. We hypothesis that alterations of HDAC and/or HAT expression are potentially involved in impaired endometrial differentiation.