title: A method for long-term live imaging of tissue macrophages in adipose tissue explants.
abstract: Obesity is frequently associated with a chronic low-grade inflammation within adipose tissue (AT). Although classical signs of inflammation are missing in AT inflammation, there is a significant increase in macrophages and, to a lesser extent, other immune cells, such as T cells, B cells, mast cells, and neutrophils. The spatial and temporal activation of these cells as well as their accumulation in the AT seem to be tightly linked to so-called crown-like structures (CLS). CLS are accumulations of adipose tissue macrophages (ATMs) around dead adipocytes and are thought to reflect a scavenger response. At present, data on the life cycle of CLS are missing. To better understand the cellular events underlying AT inflammation, we developed an approach that allows long-term imaging of ATMs, adipocytes, and CLS within live AT explants. We tested three putative reporter mouse lines for myeloid cells in regard to their suitability for live imaging. Thereby, we identified ATMs from CSF1R-eGFP mice to exhibit the most robust expression of eGFP. AT explants from these mice allowed stable live imaging for more than 7 days without significant phototoxicity. Long-term imaging thus revealed the accumulation of ATMs around dying adipocytes, migration of ATMs within AT, and also the degradation of the lipid remnants of perishing adipocytes. The observed behavior of ATMs in the context of AT inflammation is in line with previous studies but for the first time provides data on the specific behavior of individual ATMs and on the life cycle of CLS with unprecedented spatiotemporal resolution.
authors: Institute of Anatomy, Leipzig University, Leipzig, Germany; and martin.gericke@medizin.uni-leipzig.de.
authors: Martin
authors: M
authors: Gericke
authors: Institute of Anatomy, Leipzig University, Leipzig, Germany; and.
authors: Ulrike
authors: U
authors: Weyer
authors: Institute of Anatomy, Leipzig University, Leipzig, Germany; and.
authors: Julia
authors: J
authors: Braune
authors: Institute of Anatomy, Leipzig University, Leipzig, Germany; and.
authors: Ingo
authors: I
authors: Bechmann
authors: Carl-Ludwig Institute of Physiology, Leipzig University, Leipzig, Germany.
authors: Jens
authors: J
authors: Eilers
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism / Q000473:pathology*; D000818:Animals; D058948:Cell Tracking / Q000379:methods*; D002478:Cells, Cultured; D049452:Green Fluorescent Proteins / Q000235:genetics; D008264:Macrophages / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D008822:Mice, Transgenic; D009765:Obesity / Q000378:metabolism / Q000473:pathology; D009924:Organ Culture Techniques; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000235:genetics; D059008:Time-Lapse Imaging / Q000379:methods*
chemical_list: D049452:Green Fluorescent Proteins; D016186:Receptor, Macrophage Colony-Stimulating Factor
keywords: adipocytes; crown-like structures; inflammation; live imaging; macrophages; obesity