Rapamycin-nanoliposomes target the mTORC1-mediated autophagy-lysosomal and NLRP3/Caspase-1 pathways to inhibit nucleus pulposus cell senescence in intervertebral discs.

Nucleus pulposus (NP) cell quiescence maintains intervertebral disc homeostasis, while mTORC1 regulates autophagy-lysosomal function and inflammatory secretion to preserve quiescence-rapamycin specifically targets mTORC1. Herein, we fabricated rapamycin-nanoliposomes (rapa-lipos) via ultrasonic dispersion, thin-film dispersion, and filtration to improve rapamycin bioavailability, investigating their role in inhibiting the senescence phenotype of NP cells through β-gal staining, lysosomal staining, transmission electron microscopy, ELISA, and cell cycle inhibitors. The mechanistic effects of rapa-lipos on mTORC1, NLRP3/Caspase-1 pathway (NCP) and autophagy-lysosomal pathway (ALP) were also analyzed by western blotting, immunofluorescence (IF), Si-RNA (raptor), and PCR. In vivo, rapa-lipos were injected into rat intervertebral disc with IL-1β-induced degeneration, assessed via HE staining, x-ray, MRI, and IF. Rapa-lipos exhibited high encapsulation efficiency, favorable drug loading, uniform particle size, and controlled release, suppressing NP cell senescence-related phenotypes (morphological changes, elevated IL-1β/TNF-α secretion, increased β-gal activity, lysosomal dysfunction, upregulated P21/P16 and reduced P27 expression). Mechanistically, rapa-lipos targeted-inhibited mTORC1, then blocked NCP and activated ALP to maintain NP cell quiescence. In vivo, x-ray, MRI and histological evaluation confirmed rapa-lipos mitigated intervertebral disc degeneration. Collectively, rapa-lipos target mTORC1-mediated NCP and ALP to inhibit NP cell senescence, offering a promising strategy for intervertebral disc degeneration prevention.