Sequentially assembled co-delivery nanoplatform of SIRT1 protein and SOX9-expressing plasmid for multipronged therapy of intervertebral disc degeneration.

Nucleus pulposus cells (NPCs) undergo metabolic disorders and matrix pathological remodeling under the influence of various adverse factors during intervertebral disc degeneration (IVDD), whereas post-translational modifications (PTMs) can confer cells with the capacity to respond quickly and adapt to complex environmental changes. Here, SIRT1 protein, a key regulator within PTMs framework, was applied against the hostile degenerative microenvironment. Then, it was sequentially assembled with SOX9-expressing plasmid, an essential transcription factor to promote extracellular matrix (ECM) biosynthesis, onto a phenylboronic acid-functionalized G5-dendrimer to construct a multifunctional nanoplatform for IVDD therapy. In vitro, the nanoplatforms showed antioxidant capacity, and the ability to restore mitochondrial homeostasis and normal ECM metabolism, as well as to maintain cellular phenotypes. RNA sequencing suggested that inhibition of the Nod-like receptor signaling might be the mechanism behind their therapeutic effects. The nanoplatforms were then wrapped in a designed dynamic hydrogel, not only prolonging the retention time of the loaded cargoes, but also well maintaining the disc structure, height, and water content in vivo. Overall, this study presents a convenient assembled strategy to inhibit the multiple adverse factors, and hold promise for the IVDD treatment.