MicroRNA-141-3p plays a role in human mesenchymal stem cell aging by directly targeting ZMPSTE24

miR-135a modulates tendon stem/progenitor cell senescence via suppressing ROCK1

Tendon stem/progenitor cell (TSPC) senescence may lead to age-related tendon disorders and impair tendon regeneration and replacement capacity in humans. However, the mechanisms governing TSPC aging and degeneration remain obscure. Recently, it has been reported that Rho-associated coiled-coil protein kinase 1 (ROCK1) might be a key player in TSPC aging process. miRNAs are also involved in cellular senescence. In this study, whether miRNAs modulate senescence of TSPCs through targeting ROCK1 was evaluated. We found that miR-135a, which directly binds to the 3'-untranslated region of ROCK1, is significantly downregulated in aged compared with young TSPCs. Overexpression of miR-135a in young TSPCs suppresses senescence, promotes proliferation, and induces migration and tenogenic differentiation, whereas suppression of miR-135a in aged TSPCs has the opposite effects. By gain-of-function and loss-of-function studies, we confirmed that ROCK1 mediates the effects of miR-135a in TSPCs. Taken together, our data suggest that miR-135a plays an important role in TSPC senescence via targeting ROCK1.

The microRNA miR-17-3p inhibits mouse cardiac fibroblast senescence by targeting Par4

The microRNA miR-17-92 cluster plays a fundamental role in heart development. The aim of this study was to investigate the effect of a member of this cluster, miR-17, on cardiac senescence. We examined the roles of miR-17 in senescence and demonstrated that miR-17-3p attenuates cardiac aging in the myocardium by targeting Par4 (also known as PAWR). This upregulates the downstream proteins CEBPB, FAK, N-cadherin, vimentin, Oct4 and Sca-1 (also known as stem cell antigen-1), and downregulates E-cadherin. Par4 has been reported as a tumor suppressor gene that induces apoptosis in cancer cells, but not in normal cells. Repression of Par4 by miR-17-3p enhances the transcription of CEBPB and FAK, which promotes mouse cardiac fibroblast (MCF) epithelial-to-mesenchymal transition (EMT) and self-renewal, resulting in cellular senescence and apoptosis resistance. We conclude that Par4 can bind to the CEBPB promoter and inhibit its transcription. Decreased Par4 expression increases the amount of CEBPB, which binds to the FAK promoter and enhances FAK transcription. Par4, CEBPB and FAK form a senescence signaling pathway, playing roles in modulating cell survival, growth, apoptosis, EMT and self-renewal. Through this novel senescence signaling axis, miR-17-3p represses Par4 expression, acting pleiotropically as a negative modulator of cardiac aging and cardiac fibroblast cellular senescence.

Regulatory Roles of miRNAs in Aging

Aging is a biological process characterized by the progressive deterioration of physiological functions that occurs through the accumulation of macromolecular and cellular damage. This phenomenon impairs tissue function and is a risk factor for many disorders including cardiovascular disease, neurodegenerative disorders, and cancer. A recent study has enumerated nine cellular and molecular hallmarks that represent common denominators of aging and together determine the aging phenotype, highlighting the concept of aging plasticity. Among the multiple molecular mechanisms which may contribute to aging modulation, microRNAs (miRNAs) are raising enormous interest due to their ability to affect all the "Hallmarks of Aging." In this chapter, we will focus on the description of the diverse functional roles of geromiRs, the large and growing subgroup of miRNAs implicated in aging. We will also address the molecular mechanisms underlying miRNA function in aging and discuss potential strategies for managing aging and extending longevity based on geromiR modulation.

A p38 MAPK-mediated alteration of COX-2/PGE2 regulates immunomodulatory properties in human mesenchymal stem cell aging

Because human mesenchymal stem cells (hMSC) have profound immunomodulatory effects, many attempts have been made to use hMSCs in preclinical and clinical trials. For hMSCs to be used in therapy, a large population of hMSCs must be generated by in vitro expansion. However, the immunomodulatory changes following the in vitro expansion of hMSCs have not been elucidated. In this study, we evaluated the effect of replicative senescence on the immunomodulatory ability of hMSCs in vitro and in vivo. Late-passage hMSCs showed impaired suppressive effect on mitogen-induced mononuclear cell proliferation. Strikingly, late-passage hMSCs had a significantly compromised protective effect against mouse experimental colitis, which was confirmed by gross and histologic examination. Among the anti-inflammatory cytokines, the production of prostaglandin E₂ (PGE₂) and the expression of its primary enzyme, cyclooxygenase-2 (COX-2), were profoundly increased by pre-stimulation with interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α), and this response was significantly decreased with consecutive passages. We demonstrated that the impaired phosphorylation activity of p38 MAP kinase (p38 MAPK) in late-passage hMSCs led to a compromised immunomodulatory ability through the regulation of COX-2. In conclusion, our data indicate that the immunomodulatory ability of hMSCs gradually declines with consecutive passages via a p38-mediated alteration of COX-2 and PGE₂ levels.

WITHDRAWN: Nuclear matrix, nuclear envelope and premature aging syndromes in a translational research perspective

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.semcdb.2014.03.022. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Nuclear matrix, nuclear envelope and premature aging syndromes in a translational research perspective

Lamin A-related progeroid syndromes are genetically determined, extremely rare and severe. In the past ten years, our knowledge and perspectives for these diseases has widely progressed, through the progressive dissection of their pathophysiological mechanisms leading to precocious and accelerated aging, from the genes mutations discovery until therapeutic trials in affected children. A-type lamins are major actors in several structural and functional activities at the nuclear periphery, as they are major components of the nuclear lamina. However, while this is usually poorly considered, they also play a key role within the rest of the nucleoplasm, whose defects are related to cell senescence. Although nuclear shape and nuclear envelope deformities are obvious and visible events, nuclear matrix disorganization and abnormal composition certainly represent the most important causes of cell defects with dramatic pathological consequences. Therefore, lamin-associated diseases should be better referred as laminopathies instead of envelopathies, this later being too restrictive, considering neither the key structural and functional roles of soluble lamins in the entire nucleoplasm, nor the nuclear matrix contribution to the pathophysiology of lamin-associated disorders and in particular in defective lamin A processing-associated aging diseases. Based on both our understanding of pathophysiological mechanisms and the biological and clinical consequences of progeria and related diseases, therapeutic trials have been conducted in patients and were terminated less than 10 years after the gene discovery, a quite fast issue for a genetic disease. Pharmacological drugs have been repurposed and used to decrease the toxicity of the accumulated, unprocessed and truncated prelaminA in progeria. To date, none of them may be considered as a cure for progeria and these clinical strategies were essentially designed toward reducing a subset of the most dramatic and morbid features associated to progeria. New therapeutic strategies under study, in particular targeting the protein expression pathway at the mRNA level, have shown a remarkable efficacy both in vitro in cells and in vivo in mice models. Strategies intending to clear the toxic accumulated proteins from the nucleus are also under evaluation. However, although exceedingly rare, improving our knowledge of genetic progeroid syndromes and searching for innovative and efficient therapies in these syndromes is of paramount importance as, even before they can be used to save lives, they may significantly (i) expand the affected childrens' lifespan and preserve their quality of life; (ii) improve our understanding of aging-related disorders and other more common diseases; and (iii) expand our fundamental knowledge of physiological aging and its links with major physiological processes such as those involved in oncogenesis.