Victoria Polyakova

Progression From Compensated Hypertrophy to Failure in the Pressure-Overloaded Human Heart Structural Deterioration and Compensatory Mechanisms

Background—The progression of compensated hypertrophy to heart failure (HF) is still debated. We investigated patients with isolated valvular aortic stenosis and differing degrees of left ventricular (LV) systolic dysfunction to test the hypothesis that structural remodeling, as well as cell death, contributes to the transition to HF. Methods and Results—Structural alterations were studied in LV myectomies from 3 groups of patients (group 1: ejection fraction [EF] >50%, n=12; group 2: EF 30% to 50%, n=12; group 3: EF <30%, n=10) undergoing aortic valve replacement. Control patients were patients with mitral valve stenosis but normal LV (n=6). Myocyte hypertrophy was accompanied by increased nuclear DNA and Sc-35 (splicing factor) content. ACE and TGF-&bgr;1 were upregulated correlating with fibrosis, which increased 2.3-, 2.2-, and 3.2-fold over control in the 3 groups. Myocyte degeneration increased 10, 22, and 32 times over control. A significant correlation exists between EF and myocyte degeneration or fibrosis. Ubiquitin-related autophagic cell death was 0.5‰ in control and group 1, 1.05 in group 2, and 6.05‰ in group 3. Death by oncosis was 0‰ in control, 3‰ in group 1, and increased to 5‰ (groups 2 and 3). Apoptosis was not detectable in control and group 3, but it was present at 0.02‰ in group 1 and 0.01‰ in group 2. Cardiomyocyte mitosis was never observed. Conclusions—These structure-function correlations confirm the hypothesis that transition to HF occurs by fibrosis and myocyte degeneration partially compensated by hypertrophy involving DNA synthesis and transcription. Cell loss, mainly by autophagy and oncosis, contributes significantly to the progression of LV systolic dysfunction.

Atrial extracellular matrix remodelling in patients with atrial fibrillation

Atrial fibrillation (AF) is the most frequent clinical arrhythmia. Atrial fibrosis is an important factor in initiating and maintaining AF. However, the collagen turnover and its regulation in AF has not been completely elucidated. We tested the hypothesis that the extracellular matrix changes are more severe in patients with permanent AF in comparison with those in patients in sinus rhythm (SR). Intraoperative biopsies from the right atrial appendages (RAA) and free walls (RFW) from 24 patients with AF undergoing a mini‐Maze procedure and 24 patients in SR were investigated with qualitative and quantitative immunofluorescent and Western blot analyses. As compared with SR, all patients with AF exhibited dysregulations in collagen type I and type III synthesis/degradation. Tissue inhibitors of metalloproteinases (TIMP2) was significantly enhanced only in RAA‐AF. As compared with SR, collagen VI, matrix metalloproteinases MMP2, MMP9 and TIMP1 were significantly increased while TIMP3 and TIMP4 remained unchanged in all AF groups. Reversion‐inducing cysteine‐rich protein with Kazal motifs (RECK), a newly discovered MMPs inhibitor, was elevated in RFW as compared to RAA‐AF (P<0.05) and RFW‐SR (P<0.05). The level of transforming growth factor (TGF)‐β1 was higher in AF than SR. Smad2 and phosphorylated Smad2 showed an elevation in RFW‐AF as compared to RFW‐SR, RAA‐AF, and RAA‐SR groups (P<0.05). Conclusions: Atrial fibrosis in AF is characterized by severe alterations in collagen I and III synthesis/degradation associated with disturbed MMP/TIMP systems and increased levels of RECK. TGF‐β1 contributes to atrial fibrosis via TGF‐β1‐Smad pathway by phospho‐rylating Smad2. These processes culminate in accumulations of fibrillar and non‐fibrillar collagens leading to excessive atrial fibrosis and maintainance of AF.

Fibrosis in endstage human heart failure: severe changes in collagen metabolism and MMP/TIMP profiles.

OBJECTIVES We studied fibrosis, collagen metabolism, MMPs/TIMPs and cytokine expression in various forms of human heart failure (HF) by quantitative immunofluorescent microscopy, Western blot, zymography, RT-PCR and in situ hybridization. In explanted human hearts with HF due to either dilated (DCM, n=6) or ischemic (ICM-BZ-borderzone, ICM-RZ-remote zone, n=7) or inflammatory (myocarditis, MYO, n=6) cardiomyopathy and 8 controls MMP2, 8, 9, 19, and TIMP1, 2, 3, 4 as well as procollagens I and III (PINP, PIIINP), mature collagen III (IIINTP) and the cross-linked collagen I degradation product (ICTP) were measured. RESULTS In comparison with controls, MMPs and TIMPs were significantly upregulated ranging (from highest to lowest) from ICM-BZ, DCM, ICM-RZ, MYO for all MMPs with the exception of MMP9 (highest in DCM), and for TIMPs from ICM-BZ, ICM-RZ, DCM and MYO. MMP2 and 9 were activated in all groups. The TIMP/MMP ratio was 1.3 for control, 1.9 in ICM-BZ (TIMP>MMP) and lowered to 1.0 in the other groups. Collagen I/collagen III ratio correlated significantly with the decrease in LVEDP. PINP was higher than ICTP in all groups. PIIINP elevation was present in DCM and ICM-RZ and IIINTP was up to 4-fold augmented in all groups. Fibrosin mRNA was upregulated in ICM-BZ, activin A in MYO but FGF1 and FGF2 remained unchanged. ANP mRNA was increased in all groups. CONCLUSIONS Although different degrees of severity of collagen metabolism, MMP/TIMP imbalance and cytokine expression in diverse forms of HF are present, the end product is collagen deposition. These findings suggest multiple mechanisms acting alone or in concert in fibrosis development in HF.

Therapeutic targeting of the oncostatin M receptor-β prevents inflammatory heart failure

Abstract Heart failure (HF) is a common and potentially deadly condition, which frequently develops as a consequence of various diseases of the heart. The incidence of heart failure continuously increases in aging societies illustrating the need for new therapeutic approaches. We recently discovered that continuous activation of oncostatin M (OSM), a cytokine of the interleukin-6 family that induces dedifferentiation of cardiomyocytes, promotes progression of heart failure in dilative cardiomyopathy. To evaluate whether inhibition of OSM signaling represents a meaningful therapeutic approach to prevent heart failure we attenuated OSM-receptor (Oβ) signaling in a mouse model of inflammatory dilative cardiomyopathy. We found that administration of an antibody directed against the extracellular domain of Oβ or genetic inactivation of a single allele of the Oβ gene reduced cardiomyocyte remodeling and dedifferentiation resulting in improved cardiac performance and increased survival. We conclude that pharmacological attenuation of long-lasting Oβ signaling is a promising strategy to treat different types and stages of HF that go along with infiltration by OSM-releasing inflammatory cells.

Oncostatin M Induces FGF23 Expression in Cardiomyocytes

Background: It is well-known that elevated levels of Fibroblast Growth Factor-23 (FGF23), a bone derived hormone, in circulation are associated with renal failure. Recent studies emphasize the correlation between Heart Failure (HF) and FGF23, but the ability of cardiomyocytes themselves to express and secrete this phosphatonin is yet unknown. A further factor involved in HF is the cytokine oncostatin M (OSM). The aims of our study were: 1) to analyze the myocardium of HF patients in terms of FGF23 expression in cardiomyocytes and 2) to assess whether OSM is able to induce FGF23 production in cardiomyocytes. Methods: Cultures of adult cardiomyocytes were treated with OSM and screened for the expression of FGF23 transcripts. FGF23 secretion was determined by Western blot and ELISA of cell culture supernatants. Heart explants of HF patients with Dilated Cardiomyopathy (DCM), Ischemic Cardiomyopathy (ICM) and myocarditis (Myo) were analyzed by immunofluorescence using FGF23 antibodies and compared with healthy controls. FGF23 levels were also determined in mice with a cardiac restricted overexpression of Monocyte Chemotactic Protein-1 (MCP1), which developed an “inflammatory” Heart Failure (iHF) due to macrophage infiltration. Results: OSM massively induced the expression and secretion of FGF23 in cultured adult cardiomyocytes. Confocal microscopy revealed high amounts of FGF23 positive cardiomyocytes in the myocardium of patients with ischemic heart disease (IHD), myocarditis, dilated cardiomyopathy (DCM) and in mice with iHF. Conclusions: The presence of FGF23 in the myocardium of patients with different types of HF and in mice with “inflammatory” HF suggests that macrophages are responsible for the FGF23 expression in cardiomyocytes via OSM. Whether FGF23 acts as a regeneration promoting factor and/or potentially serves as a HF/transplantation marker has to be clarified.