Regulation of the inflammatory cycle by a controllable release hydrogel for eliminating postoperative inflammation after discectomy

Surgery is the final choice for most patients with intervertebral disc degeneration(IDD).Operation-caused trauma will cause inflammation in the intervertebral disc.Serious inflammation will cause tissue defects and induce tissue degeneration,IDD recurrence and the occurrence of other diseases.Therefore,we proposed a scheme to treat recurrence after discectomy by inhibiting inflammation with an aspirin(ASP)-loaded hydrogel to restore the mechanical stability of the spine and relieve local inflammation.ASP-liposomes(ASP-Lips)were incorporated into a photocrosslinkable gelatin-methacryloyl(GelMA)via mixing.This material can effectively alleviate inflammation by inhibiting the release of high mobility group box 1(HMGB1)from the nucleus to the cytoplasm.We further assessed the expression of inflammatory cytokines,such as interleukin 6(IL-6)and tumor necrosis factor-α(TNF-α),and degeneration-related factors,such as type II collagen(COL-2),Aggrecan,matrix metallopeptidases-3(MMP-3),MMP-13,a disintegrin and metalloproteinase with thrombospondin motifs-4(ADAMTS-4)and ADAMTS-5 in rat nucleus pulpous cells.The level of IDD was analyzed through H&E,safranin-O staining and immunohistochemistry in rabbit samples.In vitro,we found that ASP-Lip@GelMA treatment significantly decreased inflammatory cytokines,MMP-3 and-13,and ADAMTS-4 and-5 and up-regulated COL-2 and Aggrecan via the inhibited release of HMGB-1 from the nucleus.In vivo,ASP-Lip@GelMA can effectively inhibit inflammation of local tissue after disc surgery and fill local tissue defects.This composite hydrogel system is a promising way to treat the recurrence of IDD after surgery without persistent complications.