Characterization and internalization of small extracellular vesicles released by human primary macrophages derived from circulating monocytes

PLoS One. 2020 Aug 24;15(8):e0237795. doi: 10.1371/journal.pone.0237795. eCollection 2020.

Abstract

Extracellular vesicles (EVs) are small membrane-limited structures derived from outward budding of the plasma membrane or endosomal system that participate in cellular communication processes through the transport of bioactive molecules to recipient cells. To date, there are no published methodological works showing step-by-step the isolation, characterization and internalization of small EVs secreted by human primary macrophages derived from circulating monocytes (MDM-derived sEVs). Thus, here we aimed to provide an alternative protocol based on differential ultracentrifugation (dUC) to describe small EVs (sEVs) from these cells. Monocyte-derived macrophages were cultured in EV-free medium during 24, 48 or 72 h and, then, EVs were isolated from culture supernatants by (dUC). Macrophages secreted a large amount of sEVs in the first 24 h, with size ranging from 40-150 nm, peaking at 105 nm, as evaluated by nanoparticle tracking analysis and scanning electron microscopy. The markers Alix, CD63 and CD81 were detected by immunoblotting in EV samples, and the co-localization of CD63 and CD81 after sucrose density gradient ultracentrifugation (S-DGUC) indicated the presence of sEVs from late endosomal origin. Confocal fluorescence revealed that the sEVs were internalized by primary macrophages after three hours of co-culture. The methodology here applied aims to contribute for enhancing reproducibility between the limited number of available protocols for the isolation and characterization of MDM-derived sEVs, thus providing basic knowledge in the area of EV methods that can be useful for those investigators working with sEVs released by human primary macrophages derived from circulating monocytes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blood Buffy Coat / cytology
  • Cell Communication*
  • Cell Differentiation
  • Cell Fractionation / methods
  • Centrifugation, Density Gradient / methods
  • Coculture Techniques
  • Extracellular Vesicles / metabolism*
  • Healthy Volunteers
  • Humans
  • Intravital Microscopy
  • Macrophages / cytology
  • Macrophages / metabolism*
  • Macrophages / ultrastructure
  • Microscopy, Confocal
  • Microscopy, Electron, Scanning
  • Microscopy, Fluorescence
  • Monocytes / physiology
  • Primary Cell Culture

Grants and funding

This work was supported by Brazilian National Research Council (CNPq; www.cnpq.br), grant # 475958/2011-0 (DCBH); Carlos Chagas Filho Rio de Janeiro Research Foundation (FAPERJ; www.faperj.br) grant # E-26/102.972/2011 (DCBH); Oswaldo Cruz Foundation (INOVA-Fiocruz; www.fiocruz.br), grant # 3440295262; DCBH). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.