Macrophages maintain tissue homeostasis by removing old, damaged and apoptotic cells. During metamorphosis, holometabolous insects, including fruit flies, go through dramatic transformation — the larval fat body undergoes cell death and is eventually replaced by the adult fat body. Although it has been shown that macrophages infiltrate the dying larval adipose tissue, their role in metamorphosis is not well understood.
In the article published in Development, Adam Bajgar and colleagues show that macrophages convert engulfed larval adipocytes into suitable nutrients to be utilised by other tissues during post-metamorphic development. The authors first characterized the ultrastructure of the fat body over the course of metamorphosis and they observed that macrophages participate in adipose tissue remodelling, by engulfing lipid droplets, RNA-protein granules and other cellular debris from the adipocytes. Then, using lipidomics analysis and transcriptomic profiling, the authors found that the macrophages from newly emerged flies transiently adopt adipocyte-like metabolic features to mobilise nutritionally rich substances from larval adipocytes.
Finally, the authors genetically removed the ability of macrophages to produce lipoproteins, such that the macrophages cannot redistribute nutrients from larval adipocytes and they observed delayed ovarian maturation in those flies. Overall, the findings uncover a metabolic role of macrophages during post-metamorphic development.
The article was also selected as a Research Highlight, with Companion article and was made an interview with the authors by The people behind the papers.
Reconstructed 3D model of uCT analysis of virgin fly at 0 hours post-eclosion, available here.
Gabriela Krejčová, Adéla Danielová, Hana Sehadová, Filip Dyčka, Jiří Kubásek, Martin Moos, and Adam Bajgar. (2024) Macrophages play a nutritive role in post-metamorphic maturation in Drosophila. Development, 151 (7): dev202492. Available from: https://doi.org/10.1242/dev.202492
Contact: Mgr. Adam Bajgar, Ph.D. (bajgaa00 at prf.jcu.cz)
Image: Confocal image depicting macrophages (magenta) interacting with larval adipocytes (green) in Drosophila pupa, credit: Gabriela Krejčová, Adam Bajgar
