Forefront: MiR-34a-Knockout Mice with Wild Type Hematopoietic Cells, Retain Persistent Fibrosis Following Lung Injury

MicroRNAs (miRs) are known to limit gene expression at the post-transcriptional level and have important roles in the pathogenesis of various conditions, including acute lung injury (ALI) and fibrotic diseases such as idiopathic pulmonary fibrosis (IPF). In this study, we found increased levels of miR-34 at times of fibrosis resolution following injury, in myofibroblasts from Bleomycin-treated mouse lungs, which correlates with susceptibility to cell death induced by immune cells. On the contrary, a substantial downregulation of miR-34 was detected at stages of evolution, when fibroblasts resist cell death. Concomitantly, we found an inverse correlation between miR-34 levels with that of the survival molecule FLICE-like inhibitory protein (FLIP) in lung myofibroblasts from humans with IPF and the experimental model. Forced upregulation of miR-34 with miR-34 mimic in human IPF fibrotic-lung myofibroblasts led to decreased cell survival through downregulation of FLIP. Using chimeric miR-34 knock-out (KO)-C57BL/6 mice with miR34KO myofibroblasts but wild-type (WT) hematopoietic cells, we found, in contrast to WT mice, increased and persistent FLIP levels with a more severe fibrosis and with no signs of resolution as detected in pathology and collagen accumulation. Moreover, a mimic of miR-34a decreased FLIP expression and susceptibility to cell death was regained in miR-34KO fibroblasts. Through this study, we show for the first time an inverse correlation between miR-34a and FLIP expression in myofibroblasts, which affects survival, and accumulation in lung fibrosis. Reprogramming fibrotic-lung myofibroblasts to regain susceptibility to cell-death by specifically increasing their miR34a and downregulating FLIP, may be a useful strategy, enabling tissue regeneration following lung injury

SIRT1 Deficiency, Specifically in Fibroblasts, Decreases Apoptosis Resistance and Is Associated with Resolution of Lung-Fibrosis

In contrast to normal regenerating tissue, resistance to Fas- and FasL-positive T cell-induced apoptosis were detected in myofibroblasts from fibrotic-lungs of humans and mice following bleomycin (BLM) exposure. In this study we show, decreased FLIP expression in lung-tissues with resolution of BLM-induced fibrosis and in isolated-lung fibroblasts, with decreased resistance to apoptosis. Using a FLIP-expression vector or a shFLIP-RNA, we further confirmed the critical need for FLIP to regain/lose susceptibility of fibrotic-lung myofibroblast to Fas-induced apoptosis. Our study further show that FLIP is regulated by SIRT1 (Sirtuin 1) deacetylase. Chimeric mice, with SIRT1-deficiency in deacetylase domain (H355Y-Sirt1y/y), specifically in mesenchymal cells, were not only protected from BLM-induced lung fibrosis but, as assessed following Ku70 immunoprecipitation, had also decreased Ku70-deacetylation, decreasedKu70/FLIP complex, and decreased FLIP levels in their lung myofibroblasts. In addition, myofibroblasts isolated from lungs of BLM-treated miR34a-knockout mice, exposed to a miR34a mimic, which we found here to downregulate SIRT1 in the luciferase assay, had a decreased Ku70-deacetylation indicating decrease in SIRT1 activity. Thus, SIRT1 may mediate, miR34a-regulated, persistent FLIP levels by deacetylation of Ku70 in lung myofibroblasts, promoting resistance to cell-death and lung fibrosis

The Significance and Management of Thrombocytopenia in Antiphospholipid Syndrome

WOS: 000351442600003PubMed ID: 25740703The association between antiphospholipid antibodies (aPL) and clinical problems goes beyond what is stated in the antiphospholipid syndrome (APS) classification criteria, namely thrombosis and pregnancy morbidity, and thrombocytopenia is the most common non-criteria hematologic manifestation of aPL with a frequency ranging from 20 to 50 %. Thrombocytopenia is rarely severe, and hemorrhage is far less common than thrombosis. However, when anticoagulation is considered, it may constitute a clinical problem with increased bleeding risk. Furthermore, thrombocytopenia represents a risk factor for thrombosis in aPL-positive patients. Therefore, it is important to understand the pathogenesis and the clinical associations of thrombocytopenia to build the right medical approach in aPL-positive patients. In this paper, we review the literature on aPL/APS-associated thrombocytopenia and briefly discuss the other conditions that can result in thrombocytopenia as they have commonalities with APS and their recognition is important to establish the most appropriate treatment strategy

Fibrosis: Sirtuins at the checkpoints of myofibroblast differentiation and profibrotic activity

Fibrotic diseases are still a serious concern for public health, due to their high prevalence, complex etiology and lack of successful treatments. Fibrosis consists of excessive accumulation of extracellular matrix components. As a result, the structure and function of tissues are impaired, thus potentially leading to organ failure and death in several chronic diseases. Myofibroblasts represent the principal cellular mediators of fibrosis, due to their extracellular matrix producing activity, and originate from different types of precursor cells, such as mesenchymal cells, epithelial cells and fibroblasts. Profibrotic activation of myofibroblasts can be triggered by a variety of mechanisms, including the transforming growth factor-β signalling pathway, which is a major factor driving fibrosis. Interestingly, preclinical and clinical studies showed that fibrotic degeneration can stop and even reverse by using specific antifibrotic treatments. Increasing scientific evidence is being accumulated about the role of sirtuins in modulating the molecular pathways responsible for the onset and development of fibrotic diseases. Sirtuins are NAD+-dependent protein deacetylases that play a crucial role in several molecular pathways within the cells, many of which at the crossroad between health and disease. In this context, we will report the current knowledge supporting the role of sirtuins in the balance between healthy and diseased myofibroblast activity. In particular, we will address the signalling pathways and the molecular targets that trigger the differentiation and profibrotic activation of myofibroblasts and can be modulated by sirtuins.</p