bims-senagi 2021-10-10 papers

bims-senagi

Biomed News

on Senescence and aging

Issue of 2021–10–10
eightteen papers selected by
Maria Grazia Vizioli, Mayo Clinic

The Contribution of Physiological and Accelerated Aging to Cancer Progression Through Senescence-Induced Inflammation.
Roles of extracellular vesicles in the aging microenvironment and age-related diseases.
Modulation of fracture healing by the transient accumulation of senescent cells.
Invariant Natural Killer T cells coordinate removal of senescent cells.
Targeting senescent immune cells to rejuvenate the aging skeleton.
The potential of Senolytics in transplantation.
Senescent immune cells release grancalcin to promote skeletal aging.
Targeting senescent retinal pigment epithelial cells facilitates retinal regeneration in mouse models of age-related macular degeneration.
Nucleus-mitochondria positive feedback loop formed by ERK5 S496 phosphorylation-mediated poly (ADP-ribose) polymerase activation provokes persistent pro-inflammatory senescent phenotype and accelerates coronary atherosclerosis after chemo-radiation.
CDK2 phosphorylation of Werner protein (WRN) contributes to WRN's DNA double-strand break repair pathway choice.
Iron: an underrated factor in aging.
IER2-induced senescence drives melanoma invasion through osteopontin.
Roles and functions of antisense lncRNA in vascular aging.
Advanced Maternal Age-associated SIRT1 Deficiency Compromises Trophoblast Epithelial-Mesenchymal Transition through an Increase in Vimentin Acetylation.
High-spatial and colourimetric imaging of histone modifications in single senescent cells using plasmonic nanoprobes.
Obesity and hyperinsulinemia drive adipocytes to activate a cell cycle program and senesce.
The Impact of Ageing on the CNS Immune Response in Alzheimer's Disease.
Aging impairs human bone marrow function and cardiac repair following myocardial infarction in a humanized chimeric mouse.

Front Oncol. 2021 ;11 747822

The Contribution of Physiological and Accelerated Aging to Cancer Progression Through Senescence-Induced Inflammation.

Jorge Morales-Valencia, Gregory David.

  Senescent cells are found to accumulate in aged individuals, as well as in cancer patients that receive chemotherapeutic treatment. Although originally believed to halt cancer progression due to their characteristic growth arrest, senescent cells remain metabolically active and secrete a combination of inflammatory agents, growth factors and proteases, collectively known as the senescence-associated secretory phenotype (SASP). In this review, we discuss the contribution of senescent cells to cancer progression through their ability to alter cancer cells' properties and to generate a microenvironment that promotes tumor growth. Furthermore, recent evidence suggests that senescent cells are able resume proliferation and drive cancer relapse, pointing to the use of senolytics and SASP modulators as a potential approach to prevent tumor resurgence following treatment cessation. Thus, a better understanding of the hallmarks of senescence and the impact of the SASP will allow the development of improved targeted therapeutic strategies to leverage vulnerabilities associated with this cellular state.

Keywords:  SASP; aging; cancer; inflammation; senescence

DOI:  https://doi.org/10.3389/fonc.2021.747822
J Extracell Vesicles. 2021 Oct;10(12): e12154

Roles of extracellular vesicles in the aging microenvironment and age-related diseases.

Yujia Yin, Huihui Chen, Yizhi Wang, Ludi Zhang, Xipeng Wang.

  Cellular senescence is a persistently hypoproliferative state with diverse stressors in a specific aging microenvironment. Senescent cells have a double-edged sword effect: they can be physiologically beneficial for tissue repair, organ growth, and body homeostasis, and they can be pathologically harmful in age-related diseases. Among the hallmarks of senescence, the SASP, especially SASP-related extracellular vesicle (EV) signalling, plays the leading role in aging transmission via paracrine and endocrine mechanisms. EVs are successful in intercellular and interorgan communication in the aging microenvironment and age-related diseases. They have detrimental effects on downstream targets at the levels of immunity, inflammation, gene expression, and metabolism. Furthermore, EVs obtained from different donors are also promising materials and tools for antiaging treatments and are used for regeneration and rejuvenation in cell-free systems. Here, we describe the characteristics of cellular senescence and the aging microenvironment, concentrating on the production and function of EVs in age-related diseases, and provide new ideas for antiaging therapy with EVs.

Keywords:  age-related diseases; aging microenvironment; antiaging therapy; cellular senescence; extracellular vesicles

DOI:  https://doi.org/10.1002/jev2.12154
Elife. 2021 Oct 07. pii: e69958. [Epub ahead of print]10

Modulation of fracture healing by the transient accumulation of senescent cells.

Dominik Saul, David G Monroe, Jennifer L Rowsey, Robyn Laura Kosinsky, Stephanie J Vos, Madison L Doolittle, Joshua N Farr, Sundeep Khosla.

  Senescent cells have detrimental effects across tissues with aging but may have beneficial effects on tissue repair, specifically on skin wound healing. However, the potential role of senescent cells in fracture healing has not been defined. Here, we performed an in silico analysis of public mRNAseq data and found that senescence and senescence-associated secretory phenotype (SASP) markers increased during fracture healing. We next directly established that the expression of senescence biomarkers increased markedly during murine fracture healing. We also identified cells in the fracture callus that displayed hallmarks of senescence, including distension of satellite heterochromatin and telomeric DNA damage; the specific identity of these cells, however, requires further characterization. Then, using a genetic mouse model (Cdkn2aLUC) containing a Cdkn2aInk4a-driven luciferase reporter, we demonstrated transient in vivo senescent cell accumulation during callus formation. Finally, we intermittently treated young adult mice following fracture with drugs that selectively eliminate senescent cells ('senolytics', Dasatinib plus Quercetin), and showed that this regimen both decreased senescence and SASP markers in the fracture callus and significantly accelerated the time course of fracture healing. Our findings thus demonstrate that senescent cells accumulate transiently in the murine fracture callus and, in contrast to the skin, their clearance does not impair but rather improves fracture healing.

Keywords:  medicine; mouse

DOI:  https://doi.org/10.7554/eLife.69958
Med (N Y). 2021 Aug 13. 2(8): 938-950

Invariant Natural Killer T cells coordinate removal of senescent cells.

Shivani Arora, Peter J Thompson, Yao Wang, Aritra Bhattacharyya, Hara Apostolopoulou, Rachel Hatano, Ram P Naikawadi, Ajit Shah, Paul J Wolters, Suneil Koliwad, Mallar Bhattacharya, Anil Bhushan.

   Background: The failure of immune surveillance to remove senescent cells drive age-related diseases. Here, we target an endogenous immune surveillance mechanism that can promote elimination of senescent cells and reverse disease progression.
Methods: We identify a class of lipid-activated T cells, invariant natural killer T cells (iNKTs) are involved in the removal of pathologic senescent cells. We use two disease models in which senescent cells accumulate to test whether activation of iNKT cells was sufficient to eliminate senescent cells in vivo.
Findings: Senescent preadipocytes accumulate in white adipose tissue of chronic high-fat diet (HFD) fed mice, and activation of iNKT cells with the prototypical glycolipid antigen alpha-galactosylceramide (αGalCer) led to a reduction of these cells with improved glucose control. Similarly, senescent cells accumulate within the lungs of mice injured by inhalational bleomycin, and αGalCer-induced activation of iNKT cells greatly limited this accumulation, decreased the lung fibrosis and improved survival. Furthermore, co-culture experiments showed that the preferential cytotoxic activity of iNKT cells to senescent cells is conserved in human cells.
Conclusions: These results uncover a senolytic capacity of tissue-resident iNKT cells and pave the way for anti-senescence therapies that target these cells and their mechanism of activation.

Keywords:  Fibrosis; IPF; Metabolic dysfunction; Senescence; iNKT cells; senolytic

DOI:  https://doi.org/10.1016/j.medj.2021.04.014
Cell Metab. 2021 Oct 05. pii: S1550-4131(21)00424-1. [Epub ahead of print]33(10): 1903-1905

Targeting senescent immune cells to rejuvenate the aging skeleton.

Ge Zhang, Jin Liu.

Accumulation of senescent cells in the bone marrow leads to age-related bone degeneration. Identifying the key senescent cell types and the factors they release that are responsible for skeletal aging is of keen interest. In a new study by Li et al. (2021), it is shown that immune cells, including neutrophils and macrophages, are critical cell types in this aging process, and that they secrete grancalcin to promote such aging.

DOI: https://doi.org/10.1016/j.cmet.2021.09.005
Mech Ageing Dev. 2021 Oct 01. pii: S0047-6374(21)00154-8. [Epub ahead of print]200 111582

The potential of Senolytics in transplantation.

Tomohisa Matsunaga, Jasper Iske, Andreas Schroeter, Haruhito Azuma, Hao Zhou, Stefan G Tullius.

  Older organs provide a substantial unrealized potential with the capacity to close the gap between demand and supply in organ transplantation. The potential of senolytics in improving age-related conditions has been shown in various experimental studies and early clinical trials. Those encouraging data may also be of relevance for transplantation. As age-differences between donor and recipients are not uncommon, aging may be accelerated in recipients when transplanting older organs; young organs may, at least in theory, have the potential to 'rejuvenate' old recipients. Here, we review the relevance of senescent cells and the effects of senolytics on organ quality, alloimmune responses and outcomes in solid organ transplantation.

Keywords:  Aging; Immunosenescence; Old donors; SASP; Senescent cells; Senolytics; Transplantation

DOI:  https://doi.org/10.1016/j.mad.2021.111582
Cell Metab. 2021 Oct 05. pii: S1550-4131(21)00372-7. [Epub ahead of print]33(10): 1957-1973.e6

Senescent immune cells release grancalcin to promote skeletal aging.

Chang-Jun Li, Ye Xiao, Yu-Chen Sun, Wen-Zhen He, Ling Liu, Mei Huang, Chen He, Min Huang, Kai-Xuan Chen, Jing Hou, Xu Feng, Tian Su, Qi Guo, Yan Huang, Hui Peng, Mi Yang, Guang-Hui Liu, Xiang-Hang Luo.

  Skeletal aging is characterized by low bone turnover and marrow fat accumulation. However, the underlying mechanism for this imbalance is unclear. Here, we show that during aging in rats and mice proinflammatory and senescent subtypes of immune cells, including macrophages and neutrophils, accumulate in the bone marrow and secrete abundant grancalcin. The injection of recombinant grancalcin into young mice was sufficient to induce premature skeletal aging. In contrast, genetic deletion of Gca in neutrophils and macrophages delayed skeletal aging. Mechanistically, we found that grancalcin binds to the plexin-b2 receptor and partially inactivates its downstream signaling pathways, thus repressing osteogenesis and promoting adipogenesis of bone marrow mesenchymal stromal cells. Heterozygous genetic deletion of Plexnb2 in skeletal stem cells abrogated the improved bone phenotype of Gca-knockout mice. Finally, we developed a grancalcin-neutralizing antibody and showed that its treatment of older mice improved bone health. Together, our data suggest that grancalcin could be a potential target for the treatment of age-related osteoporosis.

Keywords:  bone marrow mesenchymal stromal cells; bone remodeling; grancalcin; immune cells; immunoregulation; linage fate; plexin-b2 pathway; senescence; skeletal aging

DOI:  https://doi.org/10.1016/j.cmet.2021.08.009
Geroscience. 2021 Oct 02.

Targeting senescent retinal pigment epithelial cells facilitates retinal regeneration in mouse models of age-related macular degeneration.

Jae-Byoung Chae, Hyoik Jang, Chanok Son, Chul-Woo Park, Huyeon Choi, Seongeon Jin, Ho-Yeon Lee, Hyungwoo Lee, Ja-Hyoung Ryu, Namshin Kim, Chaekyu Kim, Hyewon Chung.

  Although age-related macular degeneration (AMD) is a multifactorial disorder with angiogenic, immune, and inflammatory components, the most common clinical treatment strategies are antiangiogenic therapies. However, these strategies are only applicable to neovascular AMD, which accounts for less than 20% of all AMD cases, and there are no FDA-approved drugs for the treatment of dry AMD, which accounts for ~ 80% of AMD cases. Here, we report that the elimination of senescent cells is a potential novel therapeutic approach for the treatment of all types of AMD. We identified senescent retinal pigment epithelium (RPE) cells in animal models of AMD and determined their contributions to retinal degeneration. We further confirmed that the clearance of senescent RPE cells with the MDM2-p53 inhibitor Nutlin-3a ameliorated retinal degeneration. These findings provide new insights into the use of senescent cells as a therapeutic target for the treatment of AMD.

Keywords:  Age-related macular degeneration; Aging; Cellular senescence; Retina; Senolytic

DOI:  https://doi.org/10.1007/s11357-021-00457-4
Redox Biol. 2021 Sep 20. pii: S2213-2317(21)00291-3. [Epub ahead of print]47 102132

Nucleus-mitochondria positive feedback loop formed by ERK5 S496 phosphorylation-mediated poly (ADP-ribose) polymerase activation provokes persistent pro-inflammatory senescent phenotype and accelerates coronary atherosclerosis after chemo-radiation.

Sivareddy Kotla, Aijun Zhang, Masaki Imanishi, Kyung Ae Ko, Steven H Lin, Young Jin Gi, Margie Moczygemba, Sevinj Isgandarova, Keri L Schadler, Caroline Chung, Sarah A Milgrom, Jose Banchs, Syed Wamique Yusuf, Diana N Amaya, Huifang Guo, Tamlyn N Thomas, Ying H Shen, Anita Deswal, Joerg Herrmann, Eugenie S Kleinerman, Mark L Entman, John P Cooke, Giovanni Schifitto, Sanjay B Maggirwar, Elena McBeath, Anisha A Gupte, Sunil Krishnan, Zarana S Patel, Yisang Yoon, Jared K Burks, Keigi Fujiwara, Paul S Brookes, Nhat-Tu Le, Dale J Hamilton, Jun-Ichi Abe.

  The incidence of cardiovascular disease (CVD) is higher in cancer survivors than in the general population. Several cancer treatments are recognized as risk factors for CVD, but specific therapies are unavailable. Many cancer treatments activate shared signaling events, which reprogram myeloid cells (MCs) towards persistent senescence-associated secretory phenotype (SASP) and consequently CVD, but the exact mechanisms remain unclear. This study aimed to provide mechanistic insights and potential treatments by investigating how chemo-radiation can induce persistent SASP. We generated ERK5 S496A knock-in mice and determined SASP in myeloid cells (MCs) by evaluating their efferocytotic ability, antioxidation-related molecule expression, telomere length, and inflammatory gene expression. Candidate SASP inducers were identified by high-throughput screening, using the ERK5 transcriptional activity reporter cell system. Various chemotherapy agents and ionizing radiation (IR) up-regulated p90RSK-mediated ERK5 S496 phosphorylation. Doxorubicin and IR caused metabolic changes with nicotinamide adenine dinucleotide depletion and ensuing mitochondrial stunning (reversible mitochondria dysfunction without showing any cell death under ATP depletion) via p90RSK-ERK5 modulation and poly (ADP-ribose) polymerase (PARP) activation, which formed a nucleus-mitochondria positive feedback loop. This feedback loop reprogramed MCs to induce a sustained SASP state, and ultimately primed MCs to be more sensitive to reactive oxygen species. This priming was also detected in circulating monocytes from cancer patients after IR. When PARP activity was transiently inhibited at the time of IR, mitochondrial stunning, priming, macrophage infiltration, and coronary atherosclerosis were all eradicated. The p90RSK-ERK5 module plays a crucial role in SASP-mediated mitochondrial stunning via regulating PARP activation. Our data show for the first time that the nucleus-mitochondria positive feedback loop formed by p90RSK-ERK5 S496 phosphorylation-mediated PARP activation plays a crucial role of persistent SASP state, and also provide preclinical evidence supporting that transient inhibition of PARP activation only at the time of radiation therapy can prevent future CVD in cancer survivors.

Keywords:  Antioxidants; Atherosclerosis; ERK5; Efferocytosis; Ionizing radiation; Mitochondrial stunning; Poly (ADP-Ribose) polymerase; Senescence-associated secretory phenotype (SASP); Telomere length; p90RSK

DOI:  https://doi.org/10.1016/j.redox.2021.102132
Aging Cell. 2021 Oct 06. e13484

CDK2 phosphorylation of Werner protein (WRN) contributes to WRN's DNA double-strand break repair pathway choice.

Jong-Hyuk Lee, Raghavendra A Shamanna, Tomasz Kulikowicz, Nima Borhan Fakouri, Edward W Kim, Louise S Christiansen, Deborah L Croteau, Vilhelm A Bohr.

  Werner syndrome (WS) is an accelerated aging disorder characterized by genomic instability, which is caused by WRN protein deficiency. WRN participates in DNA metabolism including DNA repair. In a previous report, we showed that WRN protein is recruited to laser-induced DNA double-strand break (DSB) sites during various stages of the cell cycle with similar intensities, supporting that WRN participates in both non-homologous end joining (NHEJ) and homologous recombination (HR). Here, we demonstrate that the phosphorylation of WRN by CDK2 on serine residue 426 is critical for WRN to make its DSB repair pathway choice between NHEJ and HR. Cells expressing WRN engineered to mimic the unphosphorylated or phosphorylation state at serine 426 showed abnormal DSB recruitment, altered RPA interaction, strand annealing, and DSB repair activities. The CDK2 phosphorylation on serine 426 stabilizes WRN's affinity for RPA, likely increasing its long-range resection at the end of DNA strands, which is a crucial step for HR. Collectively, the data shown here demonstrate that a CDK2-dependent phosphorylation of WRN regulates DSB repair pathway choice and cell cycle participation.

Keywords:  DNA double strand break; DNA repair; Werner Syndrome; aging; phosphorylation

DOI:  https://doi.org/10.1111/acel.13484
Aging (Albany NY). 2021 Oct 06. 13(undefined):

Iron: an underrated factor in aging.

Dennis Mangan.

  Iron is an essential element for virtually all living organisms, but its reactivity also makes it potentially harmful. Iron accumulates with aging, and is associated with many age-related diseases; it also shortens the lifespans of several model organisms. Blocking iron absorption through drugs or natural products extends lifespan. Many life-extending interventions, such as rapamycin, calorie restriction, and old plasma dilution can be explained by the effects they have on iron absorption, excretion, and metabolism. Control of body iron stores so that they remain in a low normal range may be an important, lifespan- and healthspan-extending intervention.

Keywords:  aging; calorie restriction; iron; oxidative stress; plasma dilution

DOI:  https://doi.org/10.18632/aging.203612
Oncogene. 2021 Oct 05.

IER2-induced senescence drives melanoma invasion through osteopontin.

Lenka Kyjacova, Rafael Saup, Kerstin Rönsch, Sabine Wallbaum, Stefanie Dukowic-Schulze, Amelia Foss, Sandra D Scherer, Melanie Rothley, Antje Neeb, Nicole Grau, Wilko Thiele, Sonja Thaler, Natascha Cremers, Carsten Sticht, Norbert Gretz, Boyan K Garvalov, Jochen Utikal, Jonathan P Sleeman.

Expression of the immediate-early response gene IER2 has been associated with the progression of several types of cancer, but its functional role is poorly understood. We found that increased IER2 expression in human melanoma is associated with shorter overall survival, and subsequently investigated the mechanisms through which IER2 exerts this effect. In experimental melanoma models, sustained expression of IER2 induced senescence in a subset of melanoma cells in a p53/MAPK/AKT-dependent manner. The senescent cells produced a characteristic secretome that included high levels of the extracellular phosphoglycoprotein osteopontin. Nuclear localization of the IER2 protein was critical for both the induction of senescence and osteopontin secretion. Osteopontin secreted by IER2-expressing senescent cells strongly stimulated the migration and invasion of non-senescent melanoma cells. Consistently, we observed coordinate expression of IER2, p53/p21, and osteopontin in primary human melanomas and metastases, highlighting the pathophysiological relevance of IER2-mediated senescence in melanoma progression. Together, our study reveals that sustained IER2 expression drives melanoma invasion and progression through stimulating osteopontin secretion via the stochastic induction of senescence.

DOI: https://doi.org/10.1038/s41388-021-02027-6
Ageing Res Rev. 2021 Sep 30. pii: S1568-1637(21)00227-0. [Epub ahead of print] 101480

Roles and functions of antisense lncRNA in vascular aging.

Xing-Yu Cui, Jun-Kun Zhan, You-Shuo Liu.

  Vascular aging is a major cause of morbidity and mortality in the elderly population. Endothelial cells (ECs) and vascular smooth muscle cells (VSMCs), forming the intima and media layers of the vessel wall respectively, are closely associated with the process of vascular aging and vascular aging-related diseases. Numerous studies have revealed the pathophysiologic mechanism through which lncRNA contributes to vascular aging, hence more attention is now paid to the role played by antisense long non-coding RNA (AS-lncRNA) in the pathogenesis of vascular aging. Nonetheless, only a small number of studies focus on the specific mechanism through which AS-lncRNA mediates vascular aging. In this review, we summarize the roles and functions of AS-lncRNA with regards to the development of vascular aging and vascular aging-related disease. We also aim to deepen our understanding of this process and provide alternative therapeutic modalities for vascular aging-related diseases.

Keywords:  AS-lncRNA; ECs; VSMCs; disease; vascular aging

DOI:  https://doi.org/10.1016/j.arr.2021.101480
Aging Cell. 2021 Oct 03. e13491

Advanced Maternal Age-associated SIRT1 Deficiency Compromises Trophoblast Epithelial-Mesenchymal Transition through an Increase in Vimentin Acetylation.

Liling Xiong, Xuan Ye, Zhi Chen, Huijia Fu, Sisi Li, Ping Xu, Jiaxiao Yu, Li Wen, Rufei Gao, Yong Fu, Hongbo Qi, Mark D Kilby, Richard Saffery, Philip N Baker, Chao Tong.

  Advanced maternal age (AMA) pregnancies are rapidly increasing and are associated with aberrant trophoblast cell function, poor placentation, and unfavorable pregnancy outcomes, presumably due to premature placental senescence. SIRT1 is an NAD+ -dependent deacetylase with well-known antiaging effects, but its connection with placental senescence is unreported. In this study, human term placentas and first-trimester villi were collected from AMA and normal pregnancies, and a mouse AMA model was established by cross breeding young and aged male and female C57 mice. SIRT1 expression and activity in HTR8/SVneo cells were genetically or pharmacologically manipulated. Trophoblast-specific Sirt1-knockout (KO) mouse placentas were generated by mating Elf5-Cre and Sirt1fl/fl mice. Trophoblast cell mobility was assessed with transwell invasion and wound-healing assays. SIRT1-binding proteins in HTR8/SVneo cells and human placental tissue were identified by mass spectrometry. We identified SIRT1 as the only differentially expressed sirtuin between AMA and normal placentas. It is downregulated in AMA placentas early in the placental life cycle and is barely impacted by paternal age. SIRT1 loss upregulates P53 acetylation and P21 expression and impairs trophoblast invasion and migration. Sirt1-KO mouse placentas exhibit senescence markers and morphological disruption, along with decreased fetal weight. In trophoblasts, SIRT1 interacts with vimentin, regulating its acetylation. In conclusion, SIRT1 promotes trophoblast epithelial-mesenchymal transition (EMT) to enhance invasiveness by modulating vimentin acetylation. AMA placentas are associated with premature senescence during placentation due to SIRT1 loss. Therefore, SIRT1 may be an antiaging therapeutic target for improving placental development and perinatal outcomes in AMA pregnancies.

Keywords:  SIRT1; advanced maternal age; epithelial−mesenchymal transition; placenta; senescence; trophoblast

DOI:  https://doi.org/10.1111/acel.13491
Nat Commun. 2021 Oct 08. 12(1): 5899

High-spatial and colourimetric imaging of histone modifications in single senescent cells using plasmonic nanoprobes.

Hyun Ji An, Yun Kim, Soojeong Chang, Hakchun Kim, Jihwan Song, Hyunsung Park, Inhee Choi.

Histones are closely related to the state of chromatin, and epigenetic modification of their tail results in regulation in cells. Therefore, developing various analytical tools to map the changes in position and distribution of histone modifications is helpful in studying underlying mechanisms. Herein, we propose a high-spatial and colourimetric imaging method using plasmonic nanoparticles as probes to visualize heterochromatin histone markers in a single nucleus. We visualized the reorganization between repressive histone markers, H3K9me3 and H3K27me3, caused by oncogene-induced senescence based on the scattering colours and spectral shift of plasmonic nanoprobes to longer wavelengths using their distance-dependent coupling effect. The measured scattering profiles were correlated with the computation results simulating the scattering spectra according to the arrangements and distances among the plasmonic nanoprobes. The plasmonic nanoprobe-based high-spatial hyperspectral imaging provides an advanced way to study the dynamics of histone modifications for predicting the progression of diseases or senescence.

DOI: https://doi.org/10.1038/s41467-021-26224-9
Nat Med. 2021 Oct 04.

Obesity and hyperinsulinemia drive adipocytes to activate a cell cycle program and senesce.

Qian Li, Carolina E Hagberg, Helena Silva Cascales, Shuai Lang, Mervi T Hyvönen, Firoozeh Salehzadeh, Ping Chen, Ida Alexandersson, Eleni Terezaki, Matthew J Harms, Maria Kutschke, Nahida Arifen, Niels Krämer, Myriam Aouadi, Carole Knibbe, Jeremie Boucher, Anders Thorell, Kirsty L Spalding.

Obesity is considered an important factor for many chronic diseases, including diabetes, cardiovascular disease and cancer. The expansion of adipose tissue in obesity is due to an increase in both adipocyte progenitor differentiation and mature adipocyte cell size. Adipocytes, however, are thought to be unable to divide or enter the cell cycle. We demonstrate that mature human adipocytes unexpectedly display a gene and protein signature indicative of an active cell cycle program. Adipocyte cell cycle progression associates with obesity and hyperinsulinemia, with a concomitant increase in cell size, nuclear size and nuclear DNA content. Chronic hyperinsulinemia in vitro or in humans, however, is associated with subsequent cell cycle exit, leading to a premature senescent transcriptomic and secretory profile in adipocytes. Premature senescence is rapidly becoming recognized as an important mediator of stress-induced tissue dysfunction. By demonstrating that adipocytes can activate a cell cycle program, we define a mechanism whereby mature human adipocytes senesce. We further show that by targeting the adipocyte cell cycle program using metformin, it is possible to influence adipocyte senescence and obesity-associated adipose tissue inflammation.

DOI: https://doi.org/10.1038/s41591-021-01501-8
Front Immunol. 2021 ;12 738511

The Impact of Ageing on the CNS Immune Response in Alzheimer's Disease.

Stephan En Jie Chee, Egle Solito.

  Alzheimer's Disease (AD) is a progressive neurodegenerative disease strongly associated with increasing age. Neuroinflammation and the accumulation of amyloid protein are amongst the hallmarks of this disease and most translational research to date has focused on targeting these two processes. However, the exact etiology of AD remains to be fully elucidated. When compared alongside, the immune response in AD closely resembles the central nervous system (CNS) immune changes seen in elderly individuals. It is possible that AD is a pathological consequence of an aged immune system secondary to chronic stimulation by a previous or ongoing insult. Pathological changes like amyloid accumulation and neuronal cell death may reflect this process of immunosenescence as the CNS immune system fails to maintain homeostasis in the CNS. It is likely that future treatments designed to modulate the aged immune system may prove beneficial in altering the disease course. The development of new tests for appropriate biomarkers would also be essential in screening for patients most likely to benefit from such treatments.

Keywords:  Alzheimer; aging; biomarker; immunosenescence; neuroinflammation; screening

DOI:  https://doi.org/10.3389/fimmu.2021.738511
Aging Cell. 2021 Oct 06. e13494

Aging impairs human bone marrow function and cardiac repair following myocardial infarction in a humanized chimeric mouse.

Tina B Marvasti, Faisal J Alibhai, Lukasz Wlodarek, Anne Fu, Shu-Hong Li, Jun Wu, Richard D Weisel, Robert J Cusimano, Maral Ouzounian, Terrence Yau, Ren-Ke Li.

  Ventricular remodeling following myocardial infarction (MI) is a major cause of heart failure, a condition prevalent in older individuals. Following MI, immune cells are mobilized to the myocardium from peripheral lymphoid organs and play an active role in orchestrating repair. While the effect of aging on mouse bone marrow (BM) has been studied, less is known about how aging affects human BM cells and their ability to regulate repair processes. In this study, we investigate the effect aging has on human BM cell responses post-MI using a humanized chimeric mouse model. BM samples were collected from middle aged (mean age 56.4 ± 0.97) and old (mean age 72.7 ± 0.59) patients undergoing cardiac surgery, CD34+/- cells were isolated, and NOD-scid-IL2rγnull (NSG) mice were reconstituted. Three months following reconstitution, the animals were examined at baseline or subjected to coronary artery ligation (MI). Younger patient cells exhibited greater repopulation capacity in the BM, blood, and spleen as well as greater lymphoid cell production. Following MI, CD34+ cell age impacted donor and host cellular responses. Mice reconstituted with younger CD34+ cells exhibited greater human CD45+ recruitment to the heart compared to mice reconstituted with old cells. Increased cellular responses were primarily driven by T-cell recruitment, and these changes corresponded with greater human IFNy levels and reduced mouse IL-1β in the heart. Age-dependent changes in BM function led to significantly lower survival, increased infarct expansion, impaired host cell responses, and reduced function by 4w post-MI. In contrast, younger CD34+ cells helped to limit remodeling and preserve function post-MI.

Keywords:  aging; bone marrow transplant; humanized mice; myocardial infarction

DOI:  https://doi.org/10.1111/acel.13494