Mesenchymal Stem Cells Decrease M1/M2 Ratio and Alleviate Inflammation to Improve Limb Ischemia in Mice
Ye Song1, Tian-Jie Zhang2, Yuan Li3
1Department of Ultrasound Medicine, The Affiliated Zhoupu Hospital, Shanghai University of Medicine and Health Sciences, Shanghai, China (mainland).
Abstract:
BACKGROUND Limb ischemia (LI) is the underlying pathology of peripheral artery disease (PAD). Macrophages play a critical role in inflammation and can contribute to the exacerbation or reduction of inflammation. Transplantation of mesenchymal stem cells (MSCs) is an emerging therapeutic strategy for PAD. However, the mechanism by which human placenta-derived mesenchymal stem cells (PMSCs) regulate macrophage differentiation in ischemic tissue remains unclear. MATERIAL AND METHODS Placentas were obtained from healthy donors with normal 38- to 40-week gestation, and PMSCs were isolated from the placentas and cultured. A mouse model of hind-limb ischemia was established. Ischemic limbs were injected intramuscularly with about 5×10⁶ PMSCs in the PMSCs group or a placebo solution (phosphate-buffered saline) in the control group at 4 different sites 1 day after the procedure. The blood perfusion of hind-limbs and the histological morphology were observed at day 1, 7, and 14 after the surgical procedure. Macrophages were detected by flow cytometry. The expression of serum tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, and IL-10 were detected by enzyme-linked immunosorbent assay (ELISA). The expression of CD31 and smooth muscle alpha-actin (alpha-SMA) in frozen muscle samples were detected by immunofluorescence staining. RESULTS In the PMSCs group, blood perfusion was gradually recovered and ischemic injury was markedly alleviated. The percentage of M2-like macrophages was increased dramatically, while the M1/M2 macrophage ratio was reduced. The expression of TNF-alpha and IL-6 was reduced, while the IL-10 level was elevated. The expression and density of CD31- and alpha-SMA-positive vessels were both significantly increased. CONCLUSIONS Transplanted PMSCs alleviated inflammation, promoted neovascularization, and improved hind limb ischemia through regulating macrophage differentiation toward the M2 phenotype and cytokine secretion. Cytokine manipulation of macrophage phenotypes may have potential therapeutic benefits in injured ischemic limbs.
Insights
Transplanted placenta-derived mesenchymal stem cells (PMSCs) improved hind limb ischemia by shifting macrophages to an anti-inflammatory M2 phenotype. This promoted blood vessel growth and reduced inflammation in ischemic tissues.
Area of Science:
- Regenerative Medicine
- Immunology
- Vascular Biology
Background:
- Limb ischemia (LI), a key feature of peripheral artery disease (PAD), involves complex inflammatory processes mediated by macrophages.
- Mesenchymal stem cell (MSC) transplantation is a promising therapy for PAD, but the precise mechanisms of human placenta-derived MSCs (PMSCs) in regulating macrophage differentiation in ischemic environments are not fully understood.
Purpose of the Study:
- To investigate the therapeutic effects of PMSCs on hind limb ischemia in a mouse model.
- To elucidate the role of PMSCs in modulating macrophage polarization and promoting neovascularization in ischemic tissue.
Main Methods:
- Establishment of a mouse model of hind-limb ischemia.
- Intramuscular injection of PMSCs or placebo into ischemic limbs.
- Assessment of blood perfusion, histological changes, macrophage populations (flow cytometry), cytokine levels (ELISA), and neovascularization markers (immunofluorescence).
Main Results:
- PMSCs significantly improved blood perfusion and alleviated ischemic injury.
- Transplantation of PMSCs led to a marked increase in M2-like macrophages and a decrease in the M1/M2 macrophage ratio.
- Reduced levels of pro-inflammatory cytokines (TNF-alpha, IL-6) and increased levels of anti-inflammatory cytokine (IL-10) were observed.
- Significant increases in CD31 and alpha-SMA expression indicated enhanced neovascularization.
Conclusions:
- PMSCs effectively alleviate inflammation and promote neovascularization in ischemic limbs by reprogramming macrophage differentiation towards an M2 phenotype.
- The therapeutic benefits of PMSCs in hind limb ischemia are mediated by modulating cytokine secretion and macrophage polarization.
- Targeting macrophage phenotypes holds potential for treating ischemic limb injuries.
