You can teach an old dog new tricks: angiopoietin-1 instructs Tie2(pos) myeloid cells to promote neovascularization in ischemic limbs

The Role of Macrophages in Vascular Repair and Regeneration after Ischemic Injury

Macrophage is one of the important players in immune response which perform many different functions during tissue injury, repair, and regeneration. Studies using animal models of cardiovascular diseases have provided a clear picture describing the effect of macrophages and their phenotype during injury and regeneration of various vascular beds. Many data have been generated to demonstrate that macrophages secrete many important factors including cytokines and growth factors to regulate angiogenesis and arteriogenesis, acting directly or indirectly on the vascular cells. Different subsets of macrophages may participate at different stages of vascular repair. Recent findings also suggest a direct interaction between macrophages and other cell types during the generation and repair of vasculature. In this short review, we focused our discussion on how macrophages adapt to the surrounding microenvironment and their potential interaction with other cells, in the context of vascular repair supported by evidences mostly from studies using hindlimb ischemia as a model for studying post-ischemic vascular repair.

Netrin-1 promotes mesenchymal stem cell revascularization of limb ischaemia

This study examines the effect and mechanism of action of Netrin-1 on bone marrow mesenchymal stem cells in angiogenesis. Tube formation and migration of bone marrow mesenchymal stem cells were observed in cell culture. Bone marrow mesenchymal stem cells or Netrin-1-bone marrow mesenchymal stem cells were injected into the ischaemic area of the rat hind limb on the first day after surgery. Laser Doppler perfusion imaging was performed to analyse the levels of vascular endothelial growth factor in plasma and muscles, and immunohistochemistry and immunofluorescence were used to analyse angiogenesis. Bone marrow mesenchymal stem cells in medium containing Netrin-1 markedly increased the number of tubes formed and the migration of bone marrow mesenchymal stem cells compared with the untreated control group. The function of Netrin-1 in tube formation and migration is similar to vascular endothelial growth factor, and combined with vascular endothelial growth factor, Netrin-1 has more enhanced effect than in the other three groups. The Netrin-1-bone marrow mesenchymal stem cell group had better augmented blood-perfusion scores and vessel densities, as well as improved function of the ischaemic limb than that of the group injected with bone marrow mesenchymal stem cells (treated with bone marrow mesenchymal stem cells individually) or the control group (treated with medium). These results suggest that Netrin-1 has the ability to augment the angiogenesis of bone marrow mesenchymal stem cells and improve the function of the ischaemic hind limb by increasing the level of vascular endothelial growth factor.