Peripheral nerve injury (PNI) regeneration involves complex immunoregulatory mechanisms, particularly M2 macrophage‑mediated immunomodulation. Promoting macrophage polarization toward the M2 phenotype represents a potential therapeutic strategy. Exosomes can create favorable microenvironments for tissue regeneration, but their clinical application is often limited by low concentration and purity. Three‑dimensional‑bioprinted exosomes (3D‑Exos) have recently gained attention due to their enhanced concentration and purity. In this study, 3D‑Exos were applied to treat PNI. The regenerative effects of 3D‑Exos were compared with conventionally produced exosomes (2D‑Exos) in vivo. In vitro experiments, RNA sequencing, and miRNA microarray analyses were performed to investigate the underlying mechanisms. The mechanism was further validated in vitro and in vivo. 3D‑Exos significantly enhanced nerve regeneration after PNI and outperformed 2D‑Exos. In vitro studies revealed that 3D‑Exos promoted macrophages polarization toward the M2 macrophages. RNA sequencing indicated that the PI3K/AKT pathway was activated by 3D‑Exos, and miRNA microarray analysis identified miR‑26b‑5p within 3D‑Exos as the key mediator targeting PTEN to activate PI3K/AKT signaling. Subsequently, M2 macrophages facilitated Schwann cell migration, elongation, and myelination, thereby accelerating nerve regeneration. Inhibition of the PI3K/AKT signaling pathway abolished the therapeutic effects of 3D-Exos on nerve regeneration after PNI. This study elucidates a novel mechanism by which 3D‑Exos promote nerve regeneration through reprogramming macrophages polarization via the PI3K/AKT pathway. The work establishes a paradigm‑shifting therapeutic framework that integrates 3D-Exos with immunomodulatory strategies for the treatment of PNI. First demonstration of 3D-Exos as a high-concentration, high-purity therapeutic way to overcome limitations of conventional exosomes applications for PNI. Mechanistic insight into macrophages reprogramming: 3D-Exos drives macrophages polarize into M2 phenotype via PI3K/AKT signaling pathway, fostering an conducive microenvironment critical for SCs myelination, and nerve regeneration. Paradigm-shifting therapeutic framework: Integrates 3D-Exos technology with immunomodulation, establishing a novel crosstalk axis between extracellular vesicles, macrophages, and SCs for functional PNI rehabilitation.
Sun et al. (Wed,) studied this question.