Inactivation of Sox9 in fibroblasts reduces cardiac fibrosis and inflammation.

Fibrotic scarring drives the progression of heart failure after myocardial infarction (MI). Therefore, the development of specific treatment regimens to counteract fibrosis is of high clinical relevance. The transcription factor SOX9 functions as an important regulator during embryogenesis, but recent data point towards an additional causal role in organ fibrosis. We show here that SOX9 is upregulated in the scar after MI in mice. Fibroblast specific deletion of Sox9 ameliorated MI-induced left ventricular dysfunction, dilatation and myocardial scarring in vivo. Unexpectedly, deletion of Sox9 also potently eliminated persisting leukocyte infiltration of the scar in the chronic phase after MI. RNA-sequencing from the infarct scar revealed that Sox9 deletion in fibroblasts resulted in strongly downregulated expression of genes related to extracellular matrix, proteolysis and inflammation. Importantly, Sox9 deletion in isolated cardiac fibroblasts in vitro similarly affected gene expression as in the cardiac scar and reduced fibroblast proliferation, migration and contraction capacity. Together, our data demonstrate that fibroblast SOX9 functions as a master regulator of cardiac fibrosis and inflammation and might constitute a novel therapeutic target during MI.

Leukocytoclastic vasculitis associated with endocarditis in a patient with transposition of the great arteries and mechanical valve replacement.

Immunological vascular phenomena can be the initial manifestation of bacterial infection and endocarditis. Here, we report a rare case of leukocytoclastic vasculitis without immune complexes or cryoglobulinemia in a patient with infective endocarditis, congenital heart disease, and a prior mechanical valve replacement. The patient completely recovered following antibiotic therapy, and skin lesions disappeared without immune suppression, which suggested infection-mediated vasculitis. While the treatment of leukocytoclastic vasculitis typically involves immunosuppressive therapy, the treatment for infection-mediated vasculitis is eradication of the infection.

C1q-TNF-Related Protein-9 Promotes Cardiac Hypertrophy and Failure.

RATIONALE: Myocardial endothelial cells promote cardiomyocyte hypertrophy, possibly through the release of growth factors. The identity of these factors, however, remains largely unknown, and we hypothesized here that the secreted CTRP9 (C1q-tumor necrosis factor-related protein-9) might act as endothelial-derived protein to modulate heart remodeling in response to pressure overload. OBJECTIVE: To examine the source of cardiac CTRP9 and its function during pressure overload. METHODS AND RESULTS: CTRP9 was mainly derived from myocardial capillary endothelial cells. CTRP9 mRNA expression was enhanced in hypertrophic human hearts and in mouse hearts after transverse aortic constriction (TAC). CTRP9 protein was more abundant in the serum of patients with severe aortic stenosis and in murine hearts after TAC. Interestingly, heterozygous and especially homozygous knock-out C1qtnf9 (CTRP9) gene-deleted mice were protected from the development of cardiac hypertrophy, left ventricular dilatation, and dysfunction during TAC. CTRP9 overexpression, in turn, promoted hypertrophic cardiac remodeling and dysfunction after TAC in mice and induced hypertrophy in isolated adult cardiomyocytes. Mechanistically, CTRP9 knock-out mice showed strongly reduced levels of activated prohypertrophic ERK5 (extracellular signal-regulated kinase 5) during TAC compared with wild-type mice, while CTRP9 overexpression entailed increased ERK5 activation in response to pressure overload. Inhibition of ERK5 by a dominant negative MEK5 mutant or by the ERK5/MEK5 inhibitor BIX02189 blunted CTRP9 triggered hypertrophy in isolated adult cardiomyocytes in vitro and attenuated mouse cardiomyocyte hypertrophy and cardiac dysfunction in vivo, respectively. Downstream of ERK5, we identified the prohypertrophic transcription factor GATA4, which was directly activated through ERK5-dependent phosphorylation. CONCLUSIONS: The upregulation of CTRP9 during hypertrophic heart disease facilitates maladaptive cardiac remodeling and left ventricular dysfunction and might constitute a therapeutic target in the future.

Highly specific detection of myostatin prodomain by an immunoradiometric sandwich assay in serum of healthy individuals and patients.

BACKGROUND: Myostatin is a muscle derived factor that functions as a negative regulator of skeletal muscle growth. Induction of myostatin expression was observed in rodent models of muscle wasting and in cachectic patients with cancer or pulmonary disease. Therefore, there is an increasing interest to use serum myostatin as a biomarker. METHODS: We established an immunoradiometric sandwich assay (IRMA), which uses a commercially available chicken polyclonal, affinity purified antibody directed against human myostatin prodomain. We determined the serum concentrations of myostatin prodomain in 249 healthy individuals as well as 169 patients with heart failure, 53 patients with cancer and 44 patients with chronic pulmonary disease. RESULTS: The IRMA had a detection limit of 0.7ng/ml, an intraassay imprecision of ≤14.1% and an interassay imprecision of ≤ 18.9%. The specificity of our assay was demonstrated by size exclusion chromatography, detection of myostatin by Western-blotting and a SMAD-dependent transcriptional-reporter assay in the signal-rich serum fractions, as well as lack of interference by unspecific substances like albumin, hemoglobin or lipids. Myostatin prodomain was stable at room temperature and resistant to freeze-thaw cycles. Apparently healthy individuals over the age of 55 had a median myostatin prodomain serum concentration of 3.9ng/ml (25(th)-75(th) percentiles, 2-7ng/ml) and we could not detect increased levels in patients with stable chronic heart failure or cancer related weight loss. In contrast, we found strongly elevated concentrations of myostatin prodomain (median 26.9ng/ml, 25(th)-75(th) percentiles, 7-100ng/ml) in the serum of underweight patients with chronic pulmonary disease. CONCLUSIONS: We established a highly specific IRMA for the quantification of myostatin prodomain concentration in human serum. Our assay could be useful to study myostatin as a biomarker for example in patients with chronic pulmonary disease, as we detected highly elevated myostatin prodomain serum levels in underweight individuals of this group.