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Updated: Aug 12, 2026
Investigation of Macrophage Polarization Using Bone Marrow Derived Macrophages
Published on: June 23, 2013
Differences in angiogenic potential of classically vs alternatively activated macrophages
V Kodelja1, C Müller, S Tenorio
1Klinik und Poliklinik für Dermatologie, Universitätsklinikum Bejamin Franklin, Freie Universität Berlin, Germany.
Abstract:
Macrophages (M phi) are important for angiogenesis during inflammation, wound repair, and tumor growth. However, well-characterized M phi subsets such as IFN-gamma-induced, classically activated (ca) M phi or IL-4/glucocorticoid-induced, alternatively activated (aa) M phi have not been thoroughly examined for a positive or negative association with angiogenesis. While caM phi populate early inflammatory reactions and high-turnover granulomas, aaM phi occur in healing wounds and chronic inflammation. In contrast to caM phi-dominated lesions, aaM phi-rich lesions are highly vascularized. In order to determine their angiogenic potential in vitro, these M phi subsets as well as unstimulated control macrophages (coM phi) were analyzed by RT-PCR for mRNA expression of 10 angiogenic factors after 3 and 6 days of culture. Early during activation, caM phi and coM phi expressed equal levels of 8 of 10 angiogenic factors (PDGF-A, MK, TNF-alpha, TGF-beta 1, PDGF-B, HGF, TGF-alpha, IGF-1), while aaM phi showed expression of only 4 of these factors (TGF-beta 1, PDGF-B, HGF, GF-1). After maturation, TGF-alpha and IGF-1 showed a shift in mRNA expression from caM phi to aaM phi resulting in a considerably enhanced expression of these factors in day-6 aaM phi as compared to day-6 caM phi and coM phi while PDGF-A, MK, and TNF-alpha remained suppressed in day 6 aaM phi. In all M phi subsets including controls, mRNA expression of aFGF and bFGF was minimal or absent while TGFG-beta 1, HGF, and ODGF-B were constitutively expressed. In order to functionally integrate angiogenic factor mRNA expression profiles, mitogenic activity of M phi subsets towards microvascular endothelium was assessed by cocultivation. Coculture experiments revealed that endothelial proliferation induced by aaM phi was 3.0-3.5x higher than induced by caM phi. In conclusion, mature aaM phi are well equipped to play an important role in protracted M phi-associated angiogenic processes. Presumably due to expression of predominantly angio-inhibitory cytokines such as TNF-alpha by caM phi but much less by aaM phi, caM phi exhibit only a low angiogenic potential in vitro and in vivo despite considerable expression of angiogenic factor mRNA.
Insights
Alternatively activated macrophages (aaM phi) significantly promote angiogenesis compared to classically activated macrophages (caM phi). Mature aaM phi are crucial for sustained macrophage-associated angiogenic processes, unlike caM phi which exhibit low angiogenic potential.
Area of Science:
- Immunology
- Cell Biology
- Vascular Biology
Background:
- Macrophages (M phi) are key players in angiogenesis, a process vital for inflammation, wound repair, and tumor growth.
- Distinct macrophage subsets, classically activated (caM phi) and alternatively activated (aaM phi), have differing roles in physiological and pathological processes.
- While aaM phi are found in healing wounds and chronic inflammation, caM phi are associated with early inflammatory reactions.
Purpose of the Study:
- To investigate and compare the angiogenic potential of different macrophage subsets (caM phi, aaM phi, and control M phi).
- To analyze the mRNA expression of angiogenic factors in these M phi subsets.
- To assess the functional impact of M phi subsets on endothelial cell proliferation.
Main Methods:
- Macrophage subsets (caM phi, aaM phi, coM phi) were cultured for 3 and 6 days.
- RT-PCR was used to quantify mRNA expression of 10 angiogenic factors.
- Co-cultivation assays were performed to assess the mitogenic activity of M phi subsets on microvascular endothelium.
Main Results:
- Early activation showed similar expression of 8/10 angiogenic factors in caM phi and coM phi, with aaM phi expressing only 4.
- Mature aaM phi exhibited significantly enhanced expression of TGF-alpha and IGF-1 compared to caM phi and coM phi.
- Endothelial cell proliferation was 3.0-3.5 times higher when co-cultured with aaM phi compared to caM phi.
Conclusions:
- Mature alternatively activated macrophages (aaM phi) are potent inducers of angiogenesis.
- Classically activated macrophages (caM phi) possess low angiogenic potential, potentially due to the expression of inhibitory cytokines.
- aaM phi play a significant role in protracted macrophage-associated angiogenic processes.
