Wound Administration of M2-Polarized Macrophages Does Not Improve Murine Cutaneous Healing Responses

Macrophages play a crucial role in all stages of cutaneous wound healing responses and dysregulation of macrophage function can result in derailed wound repair. The phenotype of macrophages is influenced by the wound microenvironment and evolves during healing from a more pro-inflammatory (M1) profile in early stages, to a less inflammatory pro-healing (M2) phenotype in later stages of repair. The aim of the current study was to investigate the potential of exogenous administration of M2 macrophages to promote wound healing in an experimental mouse model of cutaneous injury. Bone marrow derived macrophages were stimulated in-vitro with IL-4 or IL-10 to obtain two different subsets of M2-polarized cells, M2a or M2c respectively. Polarized macrophages were injected into full-thickness excisional skin wounds of either C57BL/6 or diabetic db/db mice. Control groups were injected with non-polarized (M0) macrophages or saline. Our data indicate that despite M2 macrophages exhibit an anti-inflammatory phenotype in-vitro, they do not improve wound closure in wild type mice while they delay healing in diabetic mice. Examination of wounds on day 15 post-injury indicated delayed re-epithelialization and persistence of neutrophils in M2 macrophage treated diabetic wounds. Therefore, topical application of ex-vivo generated M2 macrophages is not beneficial and contraindicated for cell therapy of skin wounds.巨噬细胞（Macrophages）在皮肤伤口愈合反应的所有阶段均发挥关键作用，其功能失调可导致伤口修复紊乱。巨噬细胞的表型受伤口微环境调控，并在愈合进程中发生动态演变：修复早期以促炎表型（M1）为主，后期则转向低炎症、促修复表型（M2）。本研究旨在探究外源性输注M2型巨噬细胞对皮肤损伤实验小鼠模型伤口愈合的促进潜力。研究通过白细胞介素4（IL-4）或白细胞介素10（IL-10）体外刺激骨髓来源巨噬细胞，分别获得两种不同的M2极化细胞亚型：M2a与M2c。将极化后的巨噬细胞注射至C57BL/6野生型小鼠或糖尿病db/db小鼠的全层切除性皮肤伤口中；对照组分别注射未极化（M0）巨噬细胞或生理盐水。本研究数据显示，尽管M2巨噬细胞在体外呈现抗炎表型，但它们并未改善野生型小鼠的伤口闭合效果，反而延缓了糖尿病小鼠的伤口愈合。伤后第15天的伤口检测结果表明，经M2巨噬细胞处理的糖尿病小鼠伤口存在表皮再生延迟及中性粒细胞持续浸润现象。因此，离体培养获得的M2巨噬细胞局部应用对皮肤伤口的细胞治疗不仅无益，反而属于禁忌范畴。