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In Situ Exploration of Murine Megakaryopoiesis using Transmission Electron Microscopy
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In Situ Exploration of Murine Megakaryopoiesis using Transmission Electron Microscopy

Published on: September 8, 2021

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Megapinosomes and homologous structures in hematopoietic cells

Andrea Bauer1, Giada Frascaroli2, Paul Walther3

  • 1Central Facility for Electron Microscopy, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.

Histochemistry and Cell Biology
|July 13, 2022
PubMed

Insights

Megapinosomes, large endocytic organelles in macrophages, possess a complex internal trabecular meshwork. Similar structures in platelets suggest a conserved role in membrane dynamics across hematopoietic cells.

Area of Science:

  • Cell Biology
  • Macrophage Biology
  • Endocytosis

Background:

  • Megapinosomes are large endocytic organelles observed in M-CSF monocyte-derived macrophages.
  • These organelles exhibit a complex internal structure termed the trabecular meshwork.

Purpose of the Study:

  • To investigate the ultrastructure of megapinosomes.
  • To explore potential homologous structures in other hematopoietic cells.

Main Methods:

  • Scanning electron tomography was employed for high-resolution imaging.
  • High-pressure freezing and freeze substitution were used for sample preparation.

Main Results:

  • Megapinosomes feature a complex, interconnected trabecular meshwork (approx. 100 nm) linked to the cytosol.
  • Luminal tubules and cisterns form a megapinosome complex.
  • Homologous structures were identified in peritoneal macrophages, megakaryocytes, and platelets.

Conclusions:

  • The trabecular meshwork represents a novel ultrastructural feature of megapinosomes.
  • The presence of similar structures in platelets suggests a conserved function in membrane storage and cellular dynamics.
Keywords:
Blood plateletsElectron microscopyHigh-pressure freezingM macrophagesMegakaryocytesMegapinosomesSTEM tomography

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