Rescuing Nucleus Pulposus Cells From Senescence via Dual-Functional Greigite Nanozyme to Alleviate Intervertebral Disc Degeneration

The potential use of nanozyme in aging and age-related diseases

The effects of an increasingly elderly population are among the most far-reaching in 21st-century society. The growing healthcare expense is mainly attributable to the increased incidence of chronic illnesses that accompany longer life expectancies. Different ideas have been put up to explain aging, but it is widely accepted that oxidative damage to proteins, lipids, and nucleic acids contributes to the aging process. Increases in life expectancy in all contemporary industrialized cultures are accompanied by sharp increases in the prevalence of age-related diseases such as cardiovascular and neurological conditions, type 2 diabetes, osteoporosis, and cancer. Therefore, academic and public health authorities should prioritize the development of therapies to increase health span. Nanozyme (NZ)-like activity in nanomaterials has been identified as promising anti-aging nanomedicines. More than that, nanomaterials displaying catalytic activities have evolved as artificial enzymes with high structural stability, variable catalytic activity, and functional diversity for use in a wide range of biological settings, including those dealing with age-related disorders. Due to their inherent enzyme-mimicking qualities, enzymes have attracted significant interest in treating diseases associated with reactive oxygen species (ROS). The effects of NZs on aging and age-related disorders are summarized in this article. Finally, prospects and threats to enzyme research and use in aging and age-related disorders are offered.

Catalytic Nanodots-Driven Pyroptosis Suppression in Nucleus Pulposus for Antioxidant Intervention of Intervertebral Disc Degeneration

Low back pain resulting from intervertebral disc degeneration (IVDD) is a prevalent global concern; however, its underlying mechanism remains elusive. Single-cell sequencing analyses revealed the critical involvement of pyroptosis in IVDD. Considering the involvement of reactive oxygen species (ROS) as the primary instigator of pyroptosis and the lack of an efficient intervention approach, this study developed carbonized Mn-containing nanodots (MCDs) as ROS-scavenging catalytic biomaterials to suppress pyroptosis of nucleus pulposus (NP) cells to efficiently alleviate IVDD. Catalytic MCDs have superior efficacy in scavenging intracellular ROS and rescuing homeostasis in the NP microenvironment compared with N-acetylcysteine, a classical antioxidant. The data validates that pyroptosis plays a vital role in mediating the protective effects of catalytic MCDs against oxidative stress. Systematic in vivo assessments substantiate the effectiveness of MCDs in rescuing a puncture-induced IVDD rat model, further demonstrating their ability to suppress pyroptosis. This study highlights the potential of antioxidant catalytic nanomedicine as a pyroptosis inhibitor and mechanistically unveils an efficient strategy for the treatment of IVDD.

Progress in regulating inflammatory biomaterials for intervertebral disc regeneration

Intervertebral disc degeneration (IVDD) is rising worldwide and leading to significant health issues and financial strain for patients. Traditional treatments for IVDD can alleviate pain but do not reverse disease progression, and surgical removal of the damaged disc may be required for advanced disease. The inflammatory microenvironment is a key driver in the development of disc degeneration. Suitable anti-inflammatory substances are critical for controlling inflammation in IVDD. Several treatment options, including glucocorticoids, non-steroidal anti-inflammatory drugs, and biotherapy, are being studied for their potential to reduce inflammation. However, anti-inflammatories often have a short half-life when applied directly and are quickly excreted, thus limiting their therapeutic effects. Biomaterial-based platforms are being explored as anti-inflammation therapeutic strategies for IVDD treatment. This review introduces the pathophysiology of IVDD and discusses anti-inflammatory therapeutics and the components of these unique biomaterial platforms as comprehensive treatment systems. We discuss the strengths, shortcomings, and development prospects for various biomaterials platforms used to modulate the inflammatory microenvironment, thus providing guidance for future breakthroughs in IVDD treatment.

Rescuing Nucleus Pulposus Cells from ROS Toxic Microenvironment via Mitochondria-Targeted Carbon Dot-Supported Prussian Blue to Alleviate Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is invariably accompanied by excessive accumulation of reactive oxygen species (ROS), resulting in progressive deterioration of mitochondrial function and senescence in nucleus pulposus cells (NPCs). Significantly, the main ROS production site in non-immune cells is mitochondria, suggesting mitochondria is a feasible therapeutic target to reverse IVDD. Triphenylphosphine (TPP), which is known as mitochondrial-tropic ligands, is utilized to modify carbon dot-supported Prussian blue (CD-PB) to scavenge superfluous intro-cellular ROS and maintain NPCs at normal redox levels. CD-PB-TPP can effectively escape from lysosomal phagocytosis, permitting efficient mitochondrial targeting. After strikingly lessening the ROS in mitochondria via exerting antioxidant enzyme-like activities, such as superoxide dismutase, and catalase, CD-PB-TPP rescues damaged mitochondrial function and NPCs from senescence, catabolism, and inflammatory reaction in vitro. Imaging evaluation and tissue morphology assessment in vivo suggest that disc height index, mean grey values of nucleus pulposus tissue, and histological morphology are significantly improved in the IVDD model after CD-PB-TPP is locally performed. In conclusion, this study demonstrates that ROS-induced mitochondrial dysfunction and senescence of NPCs leads to IVDD and the CD-PB-TPP possesses enormous potential to rescue this pathological process through efficient removal of ROS via targeting mitochondria, supplying a neoteric strategy for IVDD treatment.

Beyond Traditional Medicine: EVs-Loaded Hydrogels as a Game Changer in Disease Therapeutics

Extracellular vesicles (EVs), especially exosomes, have shown great therapeutic potential in the treatment of diseases, as they can target cells or tissues. However, the therapeutic effect of EVs is limited due to the susceptibility of EVs to immune system clearance during transport in vivo. Hydrogels have become an ideal delivery platform for EVs due to their good biocompatibility and porous structure. This article reviews the preparation and application of EVs-loaded hydrogels as a cell-free therapy strategy in the treatment of diseases. The article also discusses the challenges and future outlook of EVs-loaded hydrogels.

SYNJ2BP ameliorates intervertebral disc degeneration by facilitating mitochondria-associated endoplasmic reticulum membrane formation and mitochondrial Zn2+ homeostasis

Nucleus pulposus (NP) cell function-loss is one main contributor during intervertebral disc degeneration (IDD) progression. Both mitochondria and endoplasmic reticulum (ER) play vital roles in sustaining NP cell homeostasis, while the precise function of ER-mitochondria tethering and cross talk in IDD remain to be clarified. Here, we demonstrated that a notable disruption of mitochondria-associated ER membrane (MAM) was identified in degenerated discs and TBHP-induced NP cells, accompanied by mitochondrial Zn2+ overload and NP cell senescence. Importantly, experimental coupling of MAM contacts by MFN2, a critical regulator of MAM formation, could enhance NLRX1-SLC39A7 complex formation and mitochondrial Zn2+ homeostasis. Further using the sequencing data from TBHP-induced degenerative model of NP cells, combining the reported MAM proteomes, we demonstrated that SYNJ2BP loss was one critical pathological characteristic of NP cell senescence and IDD progression, which showed close relationship with MAM disruption. Overexpression of SYNJ2BP could facilitate MAM contact organization and NLRX1-SLC39A7 complex formation, thus promoted mitochondrial Zn2+ homeostasis, NP cell proliferation and intervertebral disc rejuvenation. Collectively, our present study revealed a critical role of SYNJ2BP in maintaining mitochondrial Zn2+ homeostasis in NP cells during IDD progression, partially via sustaining MAM contact and NLRX1-SLC39A7 complex formation.

Fisetin suppresses ferroptosis through Nrf2 and attenuates intervertebral disc degeneration in rats

Low back pain, primarily caused by intervertebral disc degeneration (IVDD), lacks effective pharmacological treatments. Oxidative stress has been identified as a significant contributor to IVDD. This study aims to establish an in vitro model of IVDD induced by oxidative stress and identify potential therapeutic agents and their underlying mechanisms. By screening the natural product library, fisetin emerged as the most promising compound in suppressing cell death induced by oxidative stress in nucleus pulposus cells (NPCs). Furthermore, our investigation revealed that the cell death induced by oxidative stress was predominantly associated with ferroptosis, and fisetin demonstrated the ability to inhibit ferroptosis in NPCs. Mechanistic exploration suggested that the impact of fisetin on ferroptosis may be mediated through the Nrf2/HO-1 (Nuclear factor erythroid 2-related factor 2/heme oxygenase-1) axis. Notably, the in vivo study demonstrated that fisetin could alleviate IVDD in rats. These findings highlight fisetin as a potential therapeutic option for IVDD and implicate the involvement of the Nrf2/HO-1 pathway in its mechanism of action.