Cardiac stem cell aging and heart failure

A side effect of the medical improvements of the last centuries is the progressive aging of the world population, which is estimated to reach the impressive number of 2 billion people with more than 65 years by 2050. As a consequence, age-related diseases, such as heart failure, will affect more and more patients in the next years. To understand the biological bases of these diseases will be a crucial task in order to find better treatments, and possibly slow age-related morbidity and mortality. Cardiac stem cells have been at the center of a heated debate and their potential involvement in cardiac homeostasis has been questioned. In this review, we summarize evidence obtained by independent groups, on different animal models and humans, that strongly support the important role played by immature, cardiac resident cells in the cardioprotection against heart failure

Obese mice exposed to psychosocial stress display cardiac and hippocampal dysfunction associated with local brain-derived neurotrophic factor depletion

Introduction: Obesity and psychosocial stress (PS) co-exist in individuals of Western society. Nevertheless, how PS impacts cardiac and hippocampal phenotype in obese subjects is still unknown. Nor is it clear whether changes in local brain-derived neurotrophic factor (BDNF) account, at least in part, for myocardial and behavioral abnormalities in obese experiencing PS. Methods: In adult male WT mice, obesity was induced via a high-fat diet (HFD). The resident-intruder paradigm was superimposed to trigger PS. In vivo left ventricular (LV) performance was evaluated by echocardiography and pressure-volume loops. Behaviour was indagated by elevated plus maze (EPM) and Y-maze. LV myocardium was assayed for apoptosis, fibrosis, vessel density and oxidative stress. Hippocampus was analyzed for volume, neurogenesis, GABAergic markers and astrogliosis. Cardiac and hippocampal BDNF and TrkB levels were measured by ELISA and WB. We investigated the pathogenetic role played by BDNF signaling in additional cardiac-selective TrkB (cTrkB) KO mice. Findings: When combined, obesity and PS jeopardized LV performance, causing prominent apoptosis, fibrosis, oxidative stress and remodeling of the larger coronary branches, along with lower BDNF and TrkB levels. HFD/PS weakened LV function similarly in WT and cTrkB KO mice. The latter exhibited elevated LV ROS emission already at baseline. Obesity/PS augmented anxiety-like behaviour and impaired spatial memory. These changes were coupled to reduced hippocampal volume, neurogenesis, local BDNF and TrkB content and augmented astrogliosis. Interpretation: PS and obesity synergistically deteriorate myocardial structure and function by depleting cardiac BDNF/TrkB content, leading to augmented oxidative stress. This comorbidity triggers behavioral deficits and induces hippocampal remodeling, potentially via lower BDNF and TrkB levels. FUND: J.A. was in part supported by Rotary Foundation Global Study Scholarship. G.K. was supported by T32 National Institute of Health (NIH) training grant under award number 1T32AG058527. S.C. was funded by American Heart Association Career Development Award (19CDA34760185). G.A.R.C. was funded by NIH (K01HL133368-01). APB was funded by a Grant from the Friuli Venezia Giulia Region entitled: Heart failure as the Alzheimer disease of the heart; therapeutic and diagnostic opportunities . M.C. was supported by PRONAT project (CNR). N.P. was funded by NIH (R01 HL136918) and by the Magic-That-Matters fund (JHU). V.L. was in part supported by institutional funds from Scuola Superiore Sant\u27Anna (Pisa, Italy), by the TIM-Telecom Italia (WHITE Lab, Pisa, Italy), by a research grant from Pastificio Attilio Mastromauro Granoro s.r.l. (Corato, Italy) and in part by ETHERNA project (Prog. n. 161/16, Fondazione Pisa, Italy). Funding source had no such involvement in study design, in the collection, analysis, interpretation of data, in the writing of the report; and in the decision to submit the paper for publication

Autophagy and Inflammasome Activation in Dilated Cardiomyopathy

Background: The clinical outcome of patients affected by dilated cardiomyopathy (DCM) is heterogeneous, since its pathophysiology is only partially understood. Interleukin 1 beta levels could predict the mortality and necessity of cardiac transplantation of DCM patients. Objective: To investigate mechanisms triggering sterile inflammation in dilated cardiomyopathy (DCM). Methods: Hearts explanted from 62 DCM patients were compared with 30 controls, employing immunohistochemistry, cellular and molecular biology, as well as metabolomics studies. Results: Although misfolded protein accumulation and aggresome formation characterize DCM hearts, aggresomes failed to trigger the autophagy lysosomal pathway (ALP), with consequent accumulation of both p62(SQSTM1) and dysfunctional mitochondria. In line, DCM hearts are characterized by accumulation of lipoperoxidation products and activation of both redox responsive pathways and inflammasome. Consistently with the fact that mTOR signaling may impair ALP, we observed, an increase in DCM activation, together with a reduction in the nuclear localization of Transcription Factor EB -TFEB- (a master regulator of lysosomal biogenesis). These alterations were coupled with metabolomic alterations, including accumulation of branched chain amino acids (BCAAs), known mTOR activators. Consistently, reduced levels of PP2Cm, a phosphatase that regulates the key catabolic step of BCAAs, coupled with increased levels of miR-22, a regulator of PP2Cm levels that triggers senescence, characterize DCM hearts. The same molecular defects were present in clinically relevant cells isolated from DCM hearts, but they could be reverted by downregulating miR-22. Conclusion: We identified, in human DCM, a complex series of events whose key players are miR-22, PP2Cm, BCAA, mTOR, and ALP, linking loss of proteostasis with inflammasome activation. These potential therapeutic targets deserve to be further investigated

Autophagy and inflammation in the pathogenesis of idiopathic dilated cardiomyopathy

Background: Idiopathic dilated cardiomyopathy (iDCM) is a disease of cardiac muscle characterized by dilatation, in particular of left ventricle, and systolic dysfunction in absence of other pathological conditions note and it it is burdened by a serious morbidity and mortality. Recent literature data indicate that the loss of proteostasis is an important pathophysiological mechanism. Aims: Starting from the observation that proteins aggregate as amyloid accumulations in cardiomyocytes of patients affected by iDCM, it was evaluated the hypothesis of a defect in the ubiquitin-proteasome system (UPS). It has been shown that aggresome stimulates an increase of autophagic flow so we wanted to assess the presence of elements indicative autophagy-lysosomal pathway (ALP) alterations. For this reason, we analyzed the presence of punctae of LC3 and levels of p62. An effect of the arrest of the autophagic/lysosomal pathway follows the accumulation of dysfunctional mitochondria within the cell. We evaluated also the accumulation of mitochondria positive to Parkin1, suggesting a defect in the removal of dysfunctional mitochondria. Methods and Results: we compared 48 hearts of patients affected by iDCM, collected at the time of transplant, with 18 control hearts. We studied autophagic flux alteration, mitochondrial dysfunction, activation of the damage response to double-stranded DNA, inflammasome activation, NF-kB activation and myocyte hypertrophy. Furthermor we compared cardiac stem cells obtained by explanted hearts of iDCM patients and donors studying senescence, proliferation and lysosomal membrane permeabilization. Conclusions: data obtained suggest that patients affected by iDCM present a vicious cycle characterized by loss of proteostasis, defects of autophagic flux, accumulation of dysfunctional mitochondria, increase of free intracellular radical, activation of the cellular DNA damage response, activation of inflammatory response with further stimulus to myocyte hypertrophy and worsening proteostasis

Analysis of mechanosensing in human cardiac stem cells

Objectives: We have shown that age and pathology impair the biological properties of stem cells isolated from human hearts (CSC) and functional assays showed differences between CSC isolated from normal (DCSC) and end-stage failing (ECSC) hearts. As alterations of mechanical properties of the myocardium, such as stiffening and increased wall stress, are crucial features of cardiac remodeling, this work addresses the biological effects exerted on CSC by mechanical stimuli. Materials and methods: DCSC and ECSC were cultured under defined conditions to mimic specific features of the pathologic condition: increased mechanical loading (up to 15%, cyclic at 1 Hz), differential substrate stiffness (ranging from 1 to 231 kPa), differential cell densities. After 24, 48 and 72 h, cells were fixed and stained for analysis of proliferation and subcellular localization of YAP or lysed for RT-PCR analysis.Results: Cyclic stretch was significantly associated with both increased proliferation of DCSC (n = 6, p<0.0001) and ECSC (n = 4, p = 0.003), and with a significant reduction of nuclear localized YAP (nYAP) as a function of time (p<0.05). However, while significant correlation between cell density and decreased nYAP (p = 0.003, r2 = 0.37) characterized ECSC, this was not evident for unstretched DCSC, suggesting a less stringent regulation of contact inhibition in DCSC. These data were further confirmed by seeding cells at differential density. As opposed to what previously shown for epithelial cell lines, DCSC did not reduce nYAP positivity as a function of cell density, when grown in serum containing medium, suggesting that soluble factors present in the serum could maintain the nuclear localization of YAP, independently from the cell density. In line, serum significantly increased the nYAP expressing cells in DCSC, while a significant positive correlation between cell density and nYAP positivity can be demonstrated in DCSC cultured in serum free medium. RT-PCR for YAP-regulated targets confirmed immuno- fluorescence data. Furthermore, independently from the pathologic status, cyclic stretch was significantly associated with a persistent YAP signaling at high cell density. Besides, tension and assembly of cytoskeletal network, induced by increasing substrate stiffness, correlates with nYAP (p<0.05) and YAP transcriptional activation (p<0.05). Conclusions: D- and ECSC differ in their mechanosensing properties. However, in the first cell type, nYAP localization is dictated by the combined action of paracrine factors and cytoskeletal tension, thus reducing the contact inhibition effect. This finding is in line with a more primitive phenotype of SC isolated from normal hearts

Cell Senescence in Cardiac Repair and Failure

Although the lack of a robust cardiomyocyte proliferative response has been considered to be a crucial determinant of cardiac pathology and Heart Failure in adult mammalians, the emerging picture is that myocardial regeneration is a complex phenotype involving many actors, including acute cellular senescence and inflammation. However, three major and interconnected events occur in response to tissue injury: loss of protein homeostasis, accumulation of dysfunctional mitochondria and chronic inflammation. These events blunt the reparative response of the heart, are associated with the accumulation of chronically senescent cells and progressively lead to cardiac dysfunction. Therefore, it is crucial to understand which are the pivotal players of this process, in order to devise strategies aimed at reducing the occurrence of chronic cell senescence in the heart in vivo

Monoclonal antibodies against pools of mono- and polyacetylated peptides selectively recognize acetylated lysines within the context of the original antigen

Post-translational modifications (PTMs) strongly influence the structure and function of proteins. Lysine side chain acetylation is one of the most widespread PTMs, and it plays a major role in several physiological and pathological mechanisms. Protein acetylation may be detected by mass spectrometry (MS), but the use of monoclonal antibodies (mAbs) is a useful and cheaper option. Here, we explored the feasibility of generating mAbs against single or multiple acetylations within the context of a specific sequence. As a model, we used the unstructured N-terminal domain of APE1, which is acetylated on Lys27, Lys31, Lys32 and Lys35. As immunogen, we used a peptide mixture containing all combinations of single or multi-acetylated variants encompassing the 24\u201339 protein region. Targeted screening of the resulting clones yielded mAbs that bind with high affinity to only the acetylated APE1 peptides and the acetylated protein. No binding was seen with the non-acetylated variant or unrelated acetylated peptides and proteins, suggesting a high specificity for the APE1 acetylated molecules. MAbs could not finely discriminate between the differently acetylated variants; however, they specifically bound the acetylated protein in mammalian cell extracts and in intact cells and tissue slices from both breast cancers and from a patient affected by idiopathic dilated cardiomyopathy. The data suggest that our approach is a rapid and cost-effective method to generate mAbs against specific proteins modified by multiple acetylations or other PTM