School of Biomedical Engineering, Sciences and Health Systems, Drexel University, Philadelphia, PA, USA.
Department of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa, Israel.
Biomaterials. 2023 May;296:122095. doi: 10.1016/j.biomaterials.2023.122095. Epub 2023 Mar 23.
Macrophages are major regulators of angiogenesis in response to injury, but the mechanisms behind their diverse and phenotypically specific functions are still poorly understood. In particular, the effects of interleukin-4 (IL-4) on macrophage behavior have been well studied in vitro, but it remains unclear whether the release of IL-4 from biomaterials can be used to control macrophage phenotype and subsequent effects on angiogenesis in vivo. We used the murine hindlimb ischemia model to investigate the effects of IL-4-releasing poly(lactic-co-glycolic acid) microparticles co-delivered with IL-4-polarized macrophages on host macrophage phenotype and angiogenesis in vivo. We established a minimum dose of IL-4 required to modulate macrophage phenotype in vivo and evaluated effects on macrophage subpopulation diversity using multidimensional flow cytometry and pseudotime analysis. The delivery of IL-4-releasing microparticles did not affect the density or size of blood vessels as measured by immunohistochemical (IHC) analysis, but it did increase perfused tissue volume as measured by 3D microcomputed tomography (microCT). In contrast, the co-delivery of IL-4-releasing microparticles and exogenously IL-4-polarized macrophages increased the size of blood vessels as measured by IHC, but without effects on perfused tissue volume via microCT. These effects occurred in spite of low recovery of adoptively transferred macrophages at 4 days after administration. Spatial analysis of macrophage-blood vessel interactions via IHC showed that macrophages closely interacted with blood vessels, which was slightly influenced by treatment, and that blood vessel size was positively correlated with number of macrophages in close proximity. Altogether, these findings indicate that delivery of IL-4-releasing microparticles and exogenously IL-4-polarized macrophages can be beneficial for angiogenesis, but further mechanistic investigations are required.
巨噬细胞是损伤后血管生成的主要调节者，但它们多样化和表型特异性功能的背后机制仍知之甚少。特别是，白细胞介素-4（IL-4）对巨噬细胞行为的影响在体外已经得到了很好的研究，但仍不清楚生物材料中 IL-4 的释放是否可以用于控制巨噬细胞表型以及随后对体内血管生成的影响。我们使用鼠后肢缺血模型来研究共递送 IL-4 极化巨噬细胞的 IL-4 释放聚（乳酸-共-乙醇酸）微球对宿主巨噬细胞表型和体内血管生成的影响。我们确定了体内调节巨噬细胞表型所需的最小剂量 IL-4，并使用多维流式细胞术和伪时间分析评估了对巨噬细胞亚群多样性的影响。IL-4 释放微球的递送并不影响血管的密度或大小，如免疫组化（IHC）分析所示，但确实增加了灌注组织体积，如 3D 微计算机断层扫描（microCT）所示。相比之下，共递送 IL-4 释放微球和外源性 IL-4 极化巨噬细胞增加了 IHC 测量的血管大小，但通过 microCT 对灌注组织体积没有影响。这些影响发生在给药后 4 天转移的巨噬细胞回收量低的情况下。通过 IHC 进行的巨噬细胞-血管相互作用的空间分析表明，巨噬细胞与血管密切相互作用，这受到治疗的轻微影响，并且血管大小与靠近的巨噬细胞数量呈正相关。总的来说，这些发现表明，IL-4 释放微球和外源性 IL-4 极化巨噬细胞的递送有利于血管生成，但需要进一步的机制研究。
