Visualization of OPN-Targeted Self-Assembled Micelles Encapsulated With an SIRT6 Activator and Doped Indocyanine Green for Attenuating Vascular Aging.

Objectives: Sirtuin 6 (SIRT6) is a longevity-associated gene with recognized therapeutic potential for vascular aging through the regulation of vascular smooth muscle cells (VSMCs) senescence. This study aims to develop a visualized nanodelivery system for a SIRT6 activator to attenuate vascular aging in a mouse model. Methods: The expression of the vascular aging marker, osteopontin (OPN), was detected by Western blot and histological staining in the aortas of naturally aging C57BL/6 mice. The SIRT6 activator MDL800 and the near-infrared (NIR) agent indocyanine green (ICG) were encapsulated by poly(caprolactone)-poly(ethylene glycol) (PCL-PEG), which was modified with OPN-targeting peptides, to construct OPN-targeting micelles loaded with MDL800 and ICG (OPN-MI). Particle size and zeta potential were assessed using transmission electron microscopy (TEM) and dynamic light scattering (DLS). The biocompatibility and in vitro NIR signals were evaluated in senescent VSMCs. NIR fluorescence imaging was then performed to visualize the temporal variation and biodistribution of OPN-MI micelles in aging vessels. After 8 weeks of intravenous injection into naturally aging mice, bioinformatics analysis, pulse wave velocity (PWV) measurement, pathological staining, and molecular biological experiments were conducted to explore the anti-aging mechanism of OPN-MI micelles. Results: The expression of OPN in the aortas of naturally aging mice was significantly higher than that in control mice (p < 0.001), confirming OPN as a target for vascular aging. The OPN-MI micelles exhibited a particle size of 107.008 ± 9.572 nm and a zeta potential of -7.293 ± 2.291 mV. These micelles demonstrated excellent biocompatibility, and their strength of NIR fluorescence signals increased proportionally with the concentration of OPN-MI micelles. In vivo and ex vivo NIR fluorescence imaging revealed that OPN-MI micelles accumulated significantly in the arterial walls of aged mice compared to MI micelles (p < 0.001). Bioinformatics analysis and validation showed that MDL800 reduced MMP9 expression by activating SIRT6 to deacetylate H3K9ac and H3K56ac. After 8 weeks of injection, the PWV of abdominal aortas in the OPN-MI micelles group decreased (p = 0.031), the number of elastin breaks in the OPN-MI micelles group was reduced (p = 0.016), and the intimal-medial thickness in the OPN-MI micelles group was alleviated (p = 0.048) compared to the aged group. Mechanistically, OPN-MI micelles reduced MMP9 expression (p = 0.001) through SIRT6 deacetylation. Conclusions: The visualized OPN-targeted micelles encapsulating MDL800 and ICG effectively attenuate vascular aging in a naturally aging mouse model. This delivery system holds promise as a therapeutic strategy for delaying vascular aging in the future.