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An In vitro Model to Study Heterogeneity of Human Macrophage Differentiation and Polarization
Published on: June 12, 2013
Traffic and functional polarization of macrophages in the areas of programmed interdigital cell death in the
G Moran1, C Duarte-Olivenza1, J M Hurle1
1Departamento de Anatomía y Biología Celular and IDIVAL, Facultad de Medicina, Universidad de Cantabria, Av. Cardenal Herrera Oria s/n, Santander, 39011, Spain.
Abstract:
In this study, we show that during digit development, the embryonic limb contains an abundant and widespread population of "resident macrophages" that precede the onset of interdigital cell death responsible for the separation of digit primordia. The use of cultures of interdigital mesoderm at different remodeling stages, and GFP+ transgenic embryos in which the distal part of the autopodium has been surgically replaced by a fragment with identical characteristics from wild-type embryos, indicate that "transient macrophages" are also recruited at the beginning of interdigital death. The expression of the Pu.1 gene in coincidence with the onset of interdigital death suggests that primary yolk-sac macrophages are later complemented by macrophages of hematopoietic origin. Q-PCR analysis revealed a predominant M2/anti-inflammatory gene signature in the interdigits during the whole remodeling process that correlated with an interdigital transcriptome including Csf1, Il-34, Igf1, Igfbp5, Tgfβ4 (Tgfβ1 in mammals), P75NTR/ Tnfrsf16, Hgf, Vegfa, that presumably stabilizes the macrophage M2 phenotype. However, M1-proinflammatory genes, including Tnfα and Tlr4, are expressed at very low levels prior to the onset of cell death but become up-regulated at the end of tissue remodeling. Together, our findings support the existence of "Tissue-Resident" and "Passenger/Transitory" macrophage populations of distinct origin and molecular profile participating in tissue remodeling processes associated with embryonic morphogenesis.
Insights
Embryonic limb development involves resident macrophages and recruited transient macrophages. These cells, with distinct M2/anti-inflammatory and M1-proinflammatory profiles, are crucial for interdigital tissue remodeling and digit separation.
Area of Science:
- Developmental Biology
- Immunology
- Cell Biology
Background:
- Embryonic limb development requires precise tissue remodeling.
- Macrophages play critical roles in tissue homeostasis and development.
Purpose of the Study:
- To investigate the origin, identity, and function of macrophages during embryonic digit development.
- To characterize the molecular profiles of macrophages involved in interdigital tissue remodeling.
Main Methods:
- Analysis of GFP+ transgenic embryos and surgical limb fragment replacement.
- In vitro culture of interdigital mesoderm.
- Quantitative PCR (Q-PCR) for gene expression analysis.
- Transcriptome analysis.
Main Results:
- Identified abundant resident macrophages preceding interdigital cell death.
- Demonstrated recruitment of transient macrophages during interdigital death.
- Revealed a predominant M2/anti-inflammatory gene signature in interdigital macrophages.
- Observed upregulation of M1-proinflammatory genes at the end of tissue remodeling.
- Identified key genes (e.g., Csf1, Il-34, Igf1, Tgfβ4, Vegfa) stabilizing the M2 phenotype.
Conclusions:
- Two distinct macrophage populations, tissue-resident and transient, participate in embryonic morphogenesis.
- Macrophages exhibit dynamic M1/M2 polarization during digit development.
- These findings elucidate the role of macrophages in embryonic tissue remodeling and digit formation.
