Sustained Exosome‐Guided Macrophage Polarization Using Hydrolytically Degradable PEG Hydrogels for Cutaneous Wound Healing: Identification of Key Proteins and MiRNAs, and Sustained Release Formulation

Macrophages (Mφs) are characterized by remarkable plasticity, an essential component of chronic inflammation. Thus, an appropriate and timely transition from proinflammatory (M1) to anti‐inflammatory (M2) Mφs during wound healing is vital to promoting resolution of acute inflammation and enhancing tissue repair. Herein, exosomes derived from M2‐Mφs (M2‐Exos), which contain putative key regulators driving Mφ polarization, are used as local microenvironmental cues to induce reprogramming of M1‐Mφs toward M2‐Mφs for effective wound management. As an injectable controlled release depot for exosomes, hydrolytically degradable poly(ethylene glycol) (PEG) hydrogels (Exogels) are designed and employed for encapsulating M2‐Exos to maximize their therapeutic effects in cutaneous wound healing. The degradation time of the hydrogels is adjustable from 6 days or up to 27 days by controlling the crosslinking density and tightness. The localization of M2‐Exos leads to a successful local transition from M1‐Mφs to M2‐Mφs within the lesion for more than 6 days, followed by enhanced therapeutic effects including rapid wound closure and increased healing quality in an animal model for cutaneous wound healing. Collectively, the hydrolytically degradable PEG hydrogel‐based exosome delivery system may serve as a potential tool in regulating local polarization state of Mφs, which is crucial for tissue homeostasis and wound repair. An exosome‐encapsulated hydrogel system to reprogramming M1 into M2 Mφs is designed for maximizing their therapeutic effects in cutaneous wound healing. By controlling the crosslinking density and tightness, the degradation time of the hydrogel can be adjusted, and the localization and sustained release of exosomes leads to rapid wound closure and improvement of healing quality.