Nucleus pulposus stem cells (NPSCs) senescence plays a critical role in the progression of intervertebral disc degeneration (IDD). Stem cell-derived extracellular vesicles (EV) alleviate cellular senescence. Whereas, the underlying mechanism remains unclear. Low stability largely limited the administration of EV in vivo. RGD, an arginine-glycine-aspartic acid tripeptide, strongly binds integrins expressed on the EV membranes, allowing RGD to anchor EV and prolong their bioavailability. Researchers at Huazhong University of Science and Technology have developed an RGD-complexed nucleus pulposus matrix hydrogel (RGD-DNP) to enhance the therapeutic effects of small EV (sEV). RGD-DNP prolonged sEV retention in vitro and ex vivo. sEV-RGD-DNP promoted NPSCs migration, decreased the number of SA-β-gal-positive cells, alleviated cell cycle arrest, and reduced p16, p21, and p53 activation. Small RNA-seq showed that miR-3594-5p is enriched in sEV, and targets the homeodomain-interacting protein kinase 2 (HIPK2)/p53 pathway. The HIPK2 knockdown rescues the impaired therapeutic effects of sEV with downregulated miR-3594-5p. RGD-DNP conjugate with lower amounts of sEV achieved similar disc regeneration with free sEV of higher concentrations in DNP. In conclusion, sEV-RGD-DNP increases sEV bioavailability and relieves NPSCs senescence by targeting the HIPK2/p53 pathway, thereby alleviating IDD. This work achieves better regenerative effects with fewer sEV and consolidates the theoretical basis for sEV application for IDD treatment.
Schematic overview of the construction and application of
sEV-RGD-DNP hydrogel on disc regeneration
The hydrogel was prepared by RGD conjugated with decellularized nucleus pulposus hydrogel (DNP) and the loading of MSCs-derived sEV. sEV-RGD-DNP was injectable and applied to degenerated discs. sEV-RGD-DNP prolonged sEV retention to facilitate endogenous stem cell recruitment, alleviate the senescent phenotype of NPSCs, and inhibit the progression of IDD.