Exosomes from normal cartilage endplate stem cells ameliorate intervertebral disc degeneration more effectively than exosomes from degenerated cartilage endplate stem cell by activating the AKT/autophagy pathway

Abstract

Background Nucleus pulposus cells (NPCs) apoptosis is an important factor in exacerbating intervertebral disc degeneration (IVDD) that can be effectively suppressed by exosomes. The aim of this study was to reaearch whether normal cartilage endplate stem cells (CESCs) derived exosomes (N-Exos) were more conducive to activation of autophagy and inhibition of NPCs apoptosis and IVDD than degenerated CESCs derived exosomes (D-Exos) or not. Methods Rat CESCs were isolated and identified, and the exosomes produced by normal CESCs and degenerated CESCs were extracted. The bioinformatics differences between normal CESCs derived exosomes (N-Exos) and degenerated CESCs derived exosome (D-Exos) were analyzed by mass spectrometry, heat map and KEGG enrichment analysis biology. The effects of N-Exos and D-Exos on the inhibition of NPCs apoptosis were examined by TUNEL staining, flow cytometry and western blotting. The involvement of the AKT and autophagy signaling pathways was investigated using the signaling inhibitor LY294002. Magnetic resonance imaging, western blotting and immunofluorescence staining were used to evaluate the therapeutic effects of N-Exos in vivo. Results CESCs in the cartilage endplate (CEP) could secrete a large amount of exosomes. N-Exos were more conducive to activation of autophagy than D-Exos. The apoptotic rate of NPCs was decreased obviously after treatment with N-Exos than after D-Exos treatment. N-Exos inhibited NPCs apoptosis or attenuated IVDD in a rat tail model by activating the AKT and autophagy signaling pathways. Conclusions It was the first to confirm that CEP could delay the progression of IVDD through exosomes secreted by normal CESCs. The therapeutic effects of N-Exos on inhibiting NPCs apoptosis and slowing IVDD progression was more effective than D-Exos by activating the PI3K/AKT/autophagy pathway, which explained the reason that the incidence of IVDD was increased after inflammation of the CEP.