Precision mitochondrial delivery for tissue repair in intervertebral disc degeneration

This study aims to develop a pathological microenvironment-responsive hydrogel system leveraging AMP-activated protein kinase (AMPK) activation and mitochondrial delivery to regulate mitochondrial function, mitigate oxidative stress, and inhibit ferroptosis in nucleus pulposus cells (NPCs) for microenvironmental remodeling and tissue repair in intervertebral disc degeneration (IVDD). Bulk RNA Sequencing (RNA-seq) on nucleus pulposus (NP) tissues from Sham and IVDD rats, intersected with tert-butyl hydroperoxide (TBHP)-treated NPCs, identified key regulatory pathways. Treatment with AMPK modulators, A-769,662 and EX229, systematically evaluated AMPK's regulatory impact on mitochondrial function and ferroptosis. FoxO3a interference via small hairpin RNA, coupled with molecular analyses, elucidated downstream targets and mechanisms. Mitochondria-derived microvesicles loaded with A-769,662, encapsulated in phenylboronic acid-modified gelatin hydrogel (GPVA), demonstrated enhanced mitochondrial function and efficient drug release behavior. In IVDD animal models, GPVA hydrogels significantly improved tissue structure, mitochondrial function, and mitigated oxidative stress and ferroptosis, with FoxO3a knockdown confirming the significance of AMPK-FoxO3a axis. This novel ROS/pH-responsive injectable hydrogel system offers precision delivery of mitochondrial therapy, effectively enhancing NPC function, promoting tissue repair, and showing promising translational potential for IVDD treatment.