Injectable hybrid hydrogels enhance macrophage communication via second messenger amplification

Macrophages play a pivotal role in tissue regeneration and immune regulation through efferocytosis and other mechanisms, with their intracellular communication largely dependent on second messengers (e.g., cyclic adenosine monophosphate, cAMP). However, the broad-spectrum nature of these second messengers renders related interventions susceptible to uncontrollable systemic and off-target effects. Here, we developed an injectable apoptosis-mimicking hybrid hydrogel (PAS@Gel) that enables specific and coordinated macrophage intervention of both first and second messengers involved in efferocytosis, thereby optimizing macrophage communication and promoting tissue regeneration. First, the hybrid hydrogel forms an ECM-mimicking 3D structure through a thermosensitive copolymer and incorporates apoptosis-mimicking vesicles (PAS), enabling the first messenger regulation of macrophage efferocytosis Find-me/Eat-me processes specifically. Subsequently, Rolipram delivered by PAS inhibits cAMP phosphodiesterase (PDE4), synergistically enhancing the second messenger-mediated pathway to amplify intracellular signaling. In vitro experiments demonstrated that PAS@Gel synergistically activates macrophage Tyro3-Axl-Mer receptors, RAC1, and cAMP-related signaling pathways, significantly enhancing efferocytosis-related macrophage communication. In vivo studies using a myocardial ischemia/reperfusion (MI/R) injury model further confirmed that in-situ injection of PAS@Gel effectively alleviated inflammation via second messenger amplification, and significantly promoted myocardial tissue repair. This study presents a novel strategy for guiding tissue regeneration by enhancing macrophage second messenger regulation.