BackgroundIn　secondary　spinal　cord　injury　(SCI),　the　immune　microenvironment　of　the　injured　spinal　cord　plays　an　important　role　in　spinal　regeneration.　Among　the　immune　microenvironment　components,　macrophages/microglia　play　a　dual　role　of　pro-inflammation　and　anti-inflammation　in　the　subacute　stage　of　SCI.　Therefore,　discovering　the　immune　hub　genes　and　targeted　therapeutic　drugs　of　macrophages/microglia　after　SCI　has　crucial　implications　in　neuroregeneration.　This　study　aimed　to　identify　immune　hub　genes　and　targeted　therapeutic　drugs　for　the　subacute　phase　of　SCI.　MethodsBulk　RNA　sequencing　(bulk-RNA　seq)　datasets　(GSE5296　and　GSE47681)　and　single-cell　RNA　sequencing　(scRNA-seq)　dataset　(GSE189070)　were　obtained　from　the　Gene　Expression　Omnibus　database.　In　the　bulk　RNA-seq,　the　R　package　＇limma,＇　＇WGCNA,＇　and　＇CIBERSORT＇　were　used　to　jointly　screen　key　immune　genes.　Subsequently,　the　R　package　＇Seurat＇　and　the　R　package　＇celldex＇　were　used　to　divide　and　annotate　the　cell　clusters,　respectively.　After　using　the　Autodock　software　to　dock　immune　hub　genes　and　drugs　that　may　be　combined,　the　effectiveness　of　the　drug　was　verified　using　an　in　vivo　experiment　with　the　T9　SCI　mouse　model.　ResultsIn　the　bulk-RNA　seq,　B2m,　Itgb5,　and　Vav1　were　identified　as　immune　hub　genes.　Ten　cell　clusters　were　identified　in　scRNA-seq,　and　B2m　and　Itgb5　were　mainly　located　in　the　microglia,　while　Vav1　was　mainly　located　in　macrophages.　Molecular　docking　results　showed　that　the　proteins　corresponding　to　these　immune　genes　could　accurately　bind　to　decitabine.　In　decitabine-treated　mice,　the　pro-inflammatory　factor　(TNF-alpha,　IL-1　beta)　levels　were　decreased　while　anti-inflammatory　factor　(IL-4,　IL-10)　levels　were　increased　at　2　weeks　post-SCI,　and　macrophages/microglia　transformed　from　M1　to　M2.　At　6　weeks　post-SCI,　the　neurological　function　score　and　electromyography　of　the　decitabine　treatment　group　were　also　improved.　ConclusionIn　the　subacute　phase　of　SCI,　B2m,　Itgb5,　and　Vav1　in　macrophages/microglia　may　be　key　therapeutic　targets　to　promote　nerve　regeneration.　In　addition,　low-dose　decitabine　may　promote　spinal　cord　regeneration　by　regulating　the　polarization　state　of　macrophages/microglia.