Light-Responsive Oxygen Generation from Chlorella Hydrogels for Facial Nerve Injury Recovery: Crosstalk between M1/M2 Macrophages and Schwann Cells

Facial nerve injury (FNI), hindered by hypoxic microenvironments limiting Schwann cell (SCs) repair potential, remains a therapeutic challenge. We developed light-responsive Chlorella hydrogels (C-Gel) to modulate oxygen release and inflammation. In vitro, light-activated C-Gel enhanced RSC96 SC proliferation, migration, and secretion while reducing reactive oxygen species (ROS), hypoxia-inducible factor-1a (HIF-1a), tumor necrosis factor-alpha (TNF-a), and interleukin-6 (IL-6). It also shifted macrophage polarization from pro-inflammatory M1 (inducible nitric oxide synthase (iNOS)+/TNF-a+) to anti-inflammatory M2 (arginase-1 (Arg-1)+/IL-10+), with M2-conditioned mediumboosting SCs production of neurotrophic factors (nerve growth factor, NGF; glial cell line-derived neurotrophic factor, GDNF), adhesion molecules (neural cell adhesion molecule-1, NCAM-1), regeneration-associated proteins (c-JUN), and myelin components (myelin basic protein, MBP; myelin-associated glycoprotein, MAG). In vivo, C-Gel-light therapy improved behavioral recovery in FNI rats, suppressed inflammation (ROS/HIF-1a/TNF-a), and enhanced SC-mediated remyelination (S100 calcium-binding protein, S100; neurofilament 200, NF200). RNA sequencing identified upregulated phosphoinositide 3-kinase-protein kinase (PI3K-Akt) and calcium ion (Ca²+) signaling pathways. This oxygen-regulating, immunomodulatory biomaterial offers a dual-action strategy to advance FNI rehabilitation by synergistically optimizing the regenerative microenvironment. Overall design: Transcriptomic profiling of rat facial nerve tissue at day 14 post-injury, comparing the injury model (FNI) with a C-Gel-light treatment group to elucidate repair mechanisms. To elucidate the molecular mechanism by which C-Gel-light promotes facial nerve repair, a comparative transcriptomic analysis was conducted. Facial nerve tissues were harvested on day 14 post-injury from two groups: the facial nerve injury (FNI) model group and the C-Gel-light treatment group. Total RNA was extracted from the tissues using TRIzol reagent (Invitrogen). After quality assessment, sequencing libraries were prepared, and paired-end (150 bp) sequencing was performed on an Illumina NovaSeq 6000 platform (Illumina, USA) by Heyuan Biotechnology Co., Ltd. (Shanghai, China). Differential gene expression analysis identified 682 upregulated and 803 downregulated genes in the C-Gel-light group compared to the FNI group. Subsequent bioinformatic analyses, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, were performed to interpret the functional implications of the differentially expressed genes in the context of nerve regeneration.