Biomimetic core-shell GelMA microspheres co-delivering ANXA1, NGF, and fibronectin enable phase-matched immunomodulation and neurorepair after spinal cord injury.

Abstract

Spinal cord injury (SCI) leads to permanent sensory and motor function loss, characterized by inflammation and neuronal loss. A promising therapeutic strategy involves delivering anti-inflammatory and neuroregenerative agents tailored to these phases.GelMA-AFN hydrogel microspheres were prepared by a UV-crosslinked microfluidic chip. Immunofluorescence was performed to assess the effect of GelMA-AFN on apoptosis, axonal growth in dorsal root ganglion (DRG) neurons. Immunohistochemistry, flow cytometry, electrophysiology, RNA-seq, and behavioral testing were used to evaluate histological and functional recovery in a rat SCI model.In this study, we developed GelMA-AFN with a dual-layer structure and an mean diameter of 50 µm. The outer layer, containing low-concentration gelatin methacryloyl (GelMA, 5%) and annexin A1 (ANXA1), provided sustained ANXA1 released for up to 7 days, while the inner layer, with high-concentration GelMA (10%), nanoclay, fibronectin (FN), and nerve growth factor (NGF), releases FN and NGF over 6 weeks., GelMA-AFN inhibits neuronal apoptosis, promoted axonal growth, and enhances survival under oxidative stress., it reduced early inflammation by limiting neutrophil recruitment and promoting macrophage M2 polarization. Eight weeks post-SCI in a rat model, GelMA-AFN enhanced axonal extension, myelin regeneration, beneficial ECM deposition, and reduced glial scar formation, leading to significant neural electrical signal conduction and motor function recovery. mRNA-seq analysis confirmed GelMA-AFN upregulates genes associated with anti-inflammatory responses and axonal extension while downregulating pro-inflammatory genes.These results suggest GelMA-AFN as a promising therapeutic approach for SCI by providing spatiotemporal delivery aligned with the injury's dynamic stages.