Nucleus Pulposus-Targeting Nanocarriers Facilitate Mirna-Based Therapeutics for Intervertebral Disc Degeneration

Nanotechnology-Enhanced Pharmacotherapy for Intervertebral Disc Degeneration Treatment

Intervertebral disc degeneration (IDD) is a primary contributor to chronic back pain and disability globally, with current therapeutic approaches often proving inadequate due to the complex nature of its pathophysiology. This review assesses the potential of nanoparticle-driven pharmacotherapies to address the intricate challenges presented by IDD. We initially analyze the primary mechanisms driving IDD, with particular emphasis on mitochondrial dysfunction, oxidative stress, and the inflammatory microenvironment, all of which play pivotal roles in disc degeneration. Then, we evaluate the application of metal-phenolic and catalytic nanodots in targeting mitochondrial defects and alleviating oxidative stress within the degenerative disc environment. Additionally, multifunctional and stimuli-responsive nanoparticles are explored for their capacity to provide precise targeting and controlled therapeutic release, offering improved localization and sustained delivery. Finally, we outline future research directions and identify emerging trends in nanoparticle-based therapies, highlighting their potential to significantly advance IDD treatment by overcoming the limitations of conventional therapeutic modalities and enabling more effective, targeted management strategies.

Cartilage Endplate-Targeted Engineered Exosome Releasing and Acid Neutralizing Hydrogel Reverses Intervertebral Disc Degeneration

Cartilage endplate cell (CEPC) and nucleus pulposus cell (NPC) inflammation are critical factors that contribute to intervertebral disc degeneration (IVDD). Recent evidence indicated that iron ion influx, reactive oxygen species (ROS), and the cGAS-STING pathway are involved in CEPC inflammatory degeneration. Moreover, cytokines produced by degenerating CEPCs and lactic acid accumulation within the microenvironment significantly contribute to NPC inflammation. Consequently, simultaneous alleviation of CEPC inflammation and correction of the acidic microenvironment are anticipated to reverse IVDD. Herein, CEPC-targeted engineered exosomes loaded with salvianolic acid A are incorporated into a CaCO3/chitosan hydrogel, forming a composite gel, CAP-sEXOs@Gel. Notably, CAP-sEXOs@Gel shows long local retention, realizes the slow release of CAP-sEXOs and specific uptake by CEPCs. After uptake by CEPCs, CAP-sEXOs reduce intracellular iron ion and ROS by inhibiting hypoxia-inducible factor-2α (HIF-2α)/TfR1 expression. Iron ion influx and ROS inhibition contribute to the maintenance of normal mitochondrial function and reduced mtDNA leakage, suppresing the cGAS-STING pathway. Additionally, the CaCO3 component of CAP-sEXOs@Gel neutralizes H+, thereby alleviating NPC inflammation. Collectively, this novel composite hydrogel demonstrates the ability to concurrently inhibit CEPC and NPC inflammation, thereby presenting a promising therapeutic approach for IVDD.

The role of sirtuins in intervertebral disc degeneration: Mechanisms and therapeutic potential

Intervertebral disc degeneration (IDD) is one of the main causes of low back pain, which affects the patients' quality of life and health and imposes a significant socioeconomic burden. Despite great efforts made by researchers to understand the pathogenesis of IDD, effective strategies for preventing and treating this disease remain very limited. Sirtuins are a highly conserved family of (NAD+)-dependent deacetylases in mammals that are involved in a variety of metabolic processes in vivo. In recent years, sirtuins have attracted much attention owing to their regulatory roles in IDD on physiological activities such as inflammation, apoptosis, autophagy, aging, oxidative stress, and mitochondrial function. At the same time, many studies have explored the therapeutic effects of sirtuins-targeting activators or micro-RNA in IDD. This review summarizes the molecular pathways of sirtuins involved in IDD, and summarizes the therapeutic role of activators or micro-RNA targeting Sirtuins in IDD, as well as the current limitations and challenges, with a view to provide possible solutions for the treatment of IDD.

Effective delivery of miR-150-5p with nucleus pulposus cell-specific nanoparticles attenuates intervertebral disc degeneration

BACKGROUND

The use of gene therapy to deliver microRNAs (miRNAs) has gradually translated to preclinical application for the treatment of intervertebral disc degeneration (IDD). However, the effects of miRNAs are hindered by the short half-life time and the poor cellular uptake, owing to the lack of efficient delivery systems. Here, we investigated nucleus pulposus cell (NPC) specific aptamer-decorated polymeric nanoparticles that can load miR-150-5p for IDD treatment.

METHODS

The role of miR-150-5p during disc development and degeneration was examined by miR-150-5p knockout (KO) mice. Histological analysis was undertaken in disc specimens. The functional mechanism of miR-150-5p in IDD development was investigated by qRT-PCR assay, Western blot, coimmunoprecipitation and immunofluorescence. NPC specific aptamer-decorated nanoparticles was designed, and its penetration, stability and safety were evaluated. IDD progression was assessed by radiological analysis including X-ray and MRI, after the annulus fibrosus needle puncture surgery with miR-150-5p manipulation by intradiscal injection of nanoparticles. The investigations into the interaction between aptamer and receptor were conducted using mass spectrometry, molecular docking and molecular dynamics simulations.

RESULTS

We investigated NPC-specific aptamer-decorated polymeric nanoparticles that can bind to miR-150-5p for IDD treatment. Furthermore, we detected that nanoparticle-loaded miR-150-5p inhibitors alleviated NPC senescence in vitro, and the effects of the nanoparticles were sustained for more than 3 months in vivo. The microenvironment of NPCs improves the endo/lysosomal escape of miRNAs, greatly inhibiting the secretion of senescence-associated factors and the subsequent degeneration of NPCs. Importantly, nanoparticles delivering miR-150-5p inhibitors attenuated needle puncture-induced IDD in mouse models by targeting FBXW11 and inhibiting TAK1 ubiquitination, resulting in the downregulation of NF-kB signaling pathway activity.

CONCLUSIONS

NPC-targeting nanoparticles delivering miR-150-5p show favorable therapeutic efficacy and safety and may constitute a promising treatment for IDD.

MicroRNA-targeting nanomedicines for the treatment of intervertebral disc degeneration

Low back pain stands as a pervasive global health concern, afflicting almost 80% of adults at some point in their lives with nearly 40% attributable to intervertebral disc degeneration (IVDD). As only symptomatic relief can be offered to patients there is a dire need for innovative treatments.Given the accumulating evidence that multiple microRNAs (miRs) are dysregulated during IVDD, they could have a huge potential against this debilitating condition. The way miRs can profoundly modulate signaling pathways and influence several cellular processes at once is particularly exciting to tackle this multifaceted disorder. However, miR delivery encounters extracellular and intracellular biological barriers. A promising technology to address this challenge is the vectorization of miRs within nanoparticles, providing both protection and enhancing their uptake within the scarce target cells of the degenerated IVD. This comprehensive review presents the diverse spectrum of miRs' connection with IVDD and demonstrates their therapeutic potential when vectorized in nanomedicines.

Sirtuins in intervertebral disc degeneration: current understanding

BACKGROUND

Intervertebral disc degeneration (IVDD) is one of the etiologic factors of degenerative spinal diseases, which can lead to a variety of pathological spinal conditions such as disc herniation, spinal stenosis, and scoliosis. IVDD is a leading cause of lower back pain, the prevalence of which increases with age. Recently, Sirtuins/SIRTs and their related activators have received attention for their activity in the treatment of IVDD. In this paper, a comprehensive systematic review of the literature on the role of SIRTs and their activators on IVDD in recent years is presented. The molecular pathways involved in the regulation of IVDD by SIRTs are summarized, and the effects of SIRTs on senescence, inflammatory responses, oxidative stress, and mitochondrial dysfunction in myeloid cells are discussed with a view to suggesting possible solutions for the current treatment of IVDD.

PURPOSE

This paper focuses on the molecular mechanisms by which SIRTs and their activators act on IVDD.

METHODS

A literature search was conducted in Pubmed and Web of Science databases over a 13-year period from 2011 to 2024 for the terms "SIRT", "Sirtuin", "IVDD", "IDD", "IVD", "NP", "Intervertebral disc degeneration", "Intervertebral disc" and "Nucleus pulposus".

RESULTS

According to the results, SIRTs and a large number of activators showed positive effects against IVDD.SIRTs modulate autophagy, myeloid apoptosis, oxidative stress and extracellular matrix degradation. In addition, they attenuate inflammatory factor-induced disc damage and maintain homeostasis during disc degeneration. Several clinical studies have reported the protective effects of some SIRTs activators (e.g., resveratrol, melatonin, honokiol, and 1,4-dihydropyridine) against IVDD.

CONCLUSION

The fact that SIRTs and their activators play a hundred different roles in IVDD helps to better understand their potential to develop further treatments for IVDD.

NOVELTY

This review summarizes current information on the mechanisms of action of SIRTs in IVDD and the challenges and limitations of translating their basic research into therapy.

Silencing circATXN1 in Aging Nucleus Pulposus Cell Alleviates Intervertebral Disc Degeneration via Correcting Progerin Mislocalization

Circular RNAs (circRNAs) play a critical regulatory role in degenerative diseases; however, their functions and therapeutic applications in intervertebral disc degeneration (IVDD) have not been explored. Here, we identified that a novel circATXN1 highly accumulates in aging nucleus pulposus cells (NPCs) accountable for IVDD. CircATXN1 accelerates cellular senescence, disrupts extracellular matrix organization, and inhibits mitochondrial respiration. Mechanistically, circATXN1, regulated by heterogeneous nuclear ribonucleoprotein A2B1-mediated splicing circularization, promotes progerin translocation from the cell nucleus to the cytoplasm and inhibits the expression of insulin-like growth factor 1 receptor (IGF-1R). To demonstrate the therapeutic potential of circATXN1, siRNA targeting the backsplice junction of circATNX1 was screened and delivered by tetrahedral framework nucleic acids (tFNAs) due to their unique compositional and tetrahedral structural features. Our siRNA delivery system demonstrates superior abilities to transfect aging cells, clear intracellular ROS, and enhanced biological safety. Using siRNA-tFNAs to silence circATXN1, aging NPCs exhibit reduced mislocalization of progerin in the cytoplasm and up-regulation of IGF-1R, thereby demonstrating a rejuvenated cellular phenotype and improved mitochondrial function. In vivo, administering an aging cell-adapted siRNA nucleic acid framework delivery system to progerin pathologically expressed premature aging mice (zmpste24-/-) can ameliorate the cellular matrix in the nucleus pulposus tissue, effectively delaying IVDD. This study not only identified circATXN1 functioning as a cell senescence promoter in IVDD for the first time, but also successfully demonstrated its therapeutic potential via a tFNA-based siRNA delivery strategy.