Self-healing hydrogels loaded with Spatholobi Caulis alleviate disc degeneration by promoting autophagy in nucelus pulposus

Intervertebral disc degeneration (IDD) is a common degenerative disease of the spine that has a significant impact on both society and human health. Many studies have confirmed that there is a close relationship between IDD and senescence and apoptosis, and autophagy can combat apoptosis and senescence. Spatholobi caulis (SC) is an herb that contains various active compounds that are effective in tissue repair and regeneration, but it has not been explored in field of IDD. In this study, it was first found that SC can boost autophagy and reduce the apoptosis and senescence of Nucleus pulposus cell (NPCs). However, our animal studies revealed limited absorption of SC. To improve the bioavailability and efficacy of SC, we developed a hydrogel incorporating quaternary ammonium chitosan (QCS) and oxidized starch (OST) as carriers for SC. The QCS-OST/SC hydrogel exhibits excellent compatibility with cells, can be easily injected, and can release SC durably. At the cellular level, the QCS-OST/SC hydrogel enhances cell viability, initiates autophagy and release of the extracellular matrix (ECM), and inhibits cellular senescence and apoptosis. The injection of the QCS-OST/SC hydrogel via microneedles (MNs) into discs had successfully diminished disc degeneration in rats, which shows that this hydrogel has broad potential in the treatment of IDD.