B9 - Role of macrophages in adipocyte degradation - a live-imaging approach

Innate immune cells, such as macrophages, degrade dying cells or cell debris, a process called efferocytosis. Efficient efferocytosis licenses anti-inflammatory removal of aged or damaged cells and is crucial to maintain tissues homeostasis. In adipose tissue (AT), clearing of dead adipocytes seems to be challenging, because hypertrophic adipocytes in obesity can exceed more than 150 µm in diameter, a dimension about 10-fold bigger than regular phagocytes. To investigate the molecular and cellular events following adipocyte death, we have recently established a live-imaging approach allowing us to study adipocyte - macrophage interaction after adipocyte death in living tissue. Hence, we are aiming at determining mechanisms for efficient and inefficient efferocytosis of adipocytes using our live-imaging approach combined with subsequent post-hoc super-resolution microscopy or electron microscopy. The combination of these techniques can further determine the molecular interaction between macrophages and dying adipocytes in an unprecedented spatio-temporal resolution.

This project is designed to i) unravel the molecular decision process in macrophages leading to recognition and engulfment of adipocyte remnants and, ii) study if a critical size is a natural limit for efficient, non-inflammatory removal of large particles, such as hypertrophic adipocytes in obesity. Our working hypothesis is that inefficient efferocytosis of hypertrophic adipocytes leads to a pro-inflammatory microenvironment and type 2 diabetes. Therefore, increasing scavenger function of macrophages could be a new pharmacological target to treat metabolic disease.

Figure 1: Two time-lapse movies unravel fundamentally different clearing behaviour of macrophages in adipose tissue (AT). AT explants showing macrophages (red) and adipocytes (green). Upper row: One macrophage detects, internalizes and digests a small adipocyte remnant (star), a process leading to efficient removal of the adipocyte remnant within ~36 h. Lower row: After initial contact between macrophages and a hypertrophic adipocyte (star), more macrophages become attracted, resulting in a CLS formation with now signs of efficient degradation after 4 days. Scale bar represents 50 µm.

 

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Schopow N, Kallendrusch S, Gong S, Rapp F, Körfer J, Gericke M, Spindler N, Josten C, Langer S, Bechmann I. Examination of Ex-Vivo Viability of Human Adipose Tissue Slice Culture. PLoS One. 2020 May 26;15(5):e0233152.


Massier L, Chakaroun R, Tabei S, Crane A, Didt KD, Fallmann J, von Bergen M, Haange SB, Heyne H, Stumvoll M, Gericke M, Dietrich A, Blüher M, Musat N, Kovacs P. Adipose tissue derived bacteria are associated with inflammation in obesity and type 2 diabetes. Gut. 2020 Apr 21. pii: gutjnl-2019-320118.


Piotrowska A, Winter K, Carare RO, Bechmann I. Vital Functions Contribute to the Spread of Extracellular Fluids in the Brain: Comparison Between Life and Death. Front Aging Neurosci. 2020 Feb 11;12:15.


Zhao S, Todorov MI, Cai R, -Maskari RA, Steinke H, Kemter E, Mai H, Rong Z, Warmer M, Stanic K, Schoppe O, Paetzold JC, Gesierich B, Wong MN, Huber TB, Duering M, Bruns OT, Menze B, Lipfert J, Puelles VG, Wolf E, Bechmann I, Ertürk A. Cellular and Molecular Probing of Intact Human Organs. Cell. 2020 Feb 20;180(4):796-812.e19.


Streit WJ, Khoshbouei H, Bechmann I. Dystrophic microglia in late-onset Alzheimer's disease. Glia. 2020 Apr;68(4):845-854.


Hadadi-Bechor S, Haim Y, Pecht T, Gat R, Tarnovsky T, Gericke M, Rudich A. Autophagy differentially regulates macrophage lipid handling depending on the lipid substrate (oleic acid vs. acetylated-LDL) and inflammatory activation state. Biochim Biophys Acta Mol Cell Biol Lipids. 2019 Sep 11:158527


García-Cáceres C, Balland E, Prevot V, Luquet S, Woods SC, Koch M, Horvath TL, Yi CX, Chowen JA, Verkhratsky A, Araque A, Bechmann I, Tschöp MH. Role of astrocytes, microglia, and tanycytes in brain control of systemic metabolism. Nat Neurosci. 2019 Jan;22(1):7-14.


Joost E, Jordão MJC, Mages B, Prinz M, Bechmann I, Krueger M. Microglia contribute to the glia limitans around arteries, capillaries and veins under physiological conditions, in a model of neuroinflammation and in human brain tissue. Brain Struct Funct. 2019 Jan 31.


Streit WJ, Braak H, Del Tredici K, Leyh J, Lier J, Khoshbouei H, Eisenlöffel C, Müller W, Bechmann I. Microglial activation occurs late during preclinical Alzheimer's disease. Glia. 2018 Nov 11.


Haimon Z, Volaski A, Orthgiess J, Boura-Halfon S, Varol D, Shemer A, Yona S, Zuckerman B, David E, Chappell-Maor L, Bechmann IGericke M, Ulitsky I, Jung S., Re-evaluating microglia expression profiles using RiboTag and cell isolation strategies. Nat Immunol. 2018 May 18.


Zieger K, Weiner J, Kunath A, Gericke M, Krause K, Kern M, Stumvoll M, Klöting N, Blüher M, Heiker JT. Ablation of kallikrein 7 (KLK7) in adipose tissue ameliorates metabolic consequences of high-fat diet induced obesity by counteracting adipose tissue inflammation in vivo. Cell Mol Life Sci. 2017; Epub ahead of print.


Braune J, Weyer U, Hobusch C, Mauer J, Brüning J, Bechmann IGericke M. IL-6 regulates M2 polarization and local proliferation of adipose tissue macrophes in obesity. J Immunol. 2017;198:2927-34.


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Orthgiess J, Gericke M, Immig K, Schulz A, Hirrlinger J, Bechmann I, Eilers J. Neurons exhibit Lyz2 promotor activity in vivo: Implications for using LysM-Cre mice in myeloid cell research. Eur J Immunol. 2016;46:1529-32.


Haim Y, Blüher M, Slutsky N, Goldstein N, Klöting N, Harman-Boehm I, Kirshstein B, Ginsberg D, Gericke M, Guiu Jurado E, Kovsan J, Tarnovscki T, Kachko L, Bashan N, Gepner Y, Shai I, Rudich A. Elevated autophagy gene expression in adipose tissue of humans: A potential non-cell-cycle-dependent function of E2F1. Autophagy. 2015;11:2074-88.


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Gericke M, Weyer U, Braune J, Bechmann I, Eilers J. A method for long-term live-imaging of tissue macrophages in adipose tissue explants. Am J Physiol Endocrinol Metab. 2015;308:E1023-33.


Kosacka J, Kern M, Klöting N, Paeschke S, Rudich A, Haim Y, Gericke M, Serke H, Stumvoll M, Bechmann I, Nowicki M, Blüher M. Autophagy in adipose tissue of patients with obesity and type 2 diabetes. Mol Cell Endocrinol. 2015;409:21-32.


Immig K, Gericke M, Menzel F, Merz F, Krueger M, Schiefenhövel F, Lösche A, Jäger K, Hanisch UK, Biber K, Bechmann I. CD11c-positive cells from brain, spleen, lung and liver exhibit site-specific immune phenotypes and plastically adapt to new environments. Glia. 2015;63:11-25.


Haase J, Weyer U, Immig K, Klöting N, Blüher M, Eilers J, Bechmann I, Gericke M. Local proliferation of macrophages in adipose tissue during obesity-induced inflammation. Diabetologia. 2014;57:562-71.


Gericke M, Schröder T, Kosacka J, Nowicki M, Klöting N, Spanel-Borowski K. Neuropeptide Y impairs insulin-stimulated translocation of glucose transporter 4 in 3T3-L1 adipocytes through the Y1 receptor. Mol Cell Endocrinol. 2012;348:27-32.


Prodinger C, Bunse J, Krüger M, Schiefenhövel F, Brandt C, Laman JD, Greter M, Immig K, Heppner F, Becher B, Bechmann I. CD11c-expressing cells reside in juxtavascular parenchyma and extend processes into the glia limitans of the mouse nervous system. Acta Neuropathol. 2011;121:445-58.


Gericke M, Kosacka J, Koch D, Nowicki M, Schröder T, Ricken AM, Nieber K, Spanel-Borowski K. Receptors for NPY and PACAP differ in expression and activity during adipogenesis in the murine 3T3-L1 fibroblast cell line. Br J Pharmacol. 2009;157:620-32.

 

PROJECT TEAM

Andreas Lindhorst, PhD student