Macrophages are mainly divided into two subtypes: pro-inflammatory M1 and anti-inflammatory M2. During early acute inflammatory reaction, macrophages can secrete vascular endothelial growth factor, basic fibroblast growth factor, transforming growth factor-β1, interleukin, platelet-derived growth factor, matrix metalloproteinase, and numerous other substances. The seproteins can promote angiogenesis and structural reconstruction of defects. Macrophages coordinate with each other to promote the regeneration of blood vesselsand improve the efficiency of tissue regeneration. This coordination is not a simple antagonistic effect between anti-inflammatory and pro-inflammatory effects. In tissue engineering, scaffold, mesenchymal stem cells(MSC), and several types of cytokines can regulate macrophage phenotype conversion, which can promote angiogenesis by secreting cytokines and angiogenic growth factors at variousstages. MSC can secrete various cytokines to improve the hematopoietic microenvironment and promote the reconstruction of hematopoietic function after transplantation.
