Modeling the effect of blunt impact on mitochondrial function in cartilage: implications for development of osteoarthritis

Nanomaterial-based Reactive Oxygen Species Scavengers for Osteoarthritis Therapy

Reactive oxygen species (ROS) play distinct but important roles in physiological and pathophysiological processes. Recent studies on osteoarthritis (OA) have suggested that ROS plays a crucial role in its development and progression, serving as key mediators in the degradation of the extracellular matrix, mitochondrial dysfunction, chondrocyte apoptosis, and OA progression. With the continuous development of nanomaterial technology, the ROS-scavenging ability and antioxidant effects of nanomaterials are being explored, with promising results already achieved in OA treatment. However, current research on nanomaterials as ROS scavengers for OA is relatively non-uniform and includes both inorganic and functionalized organic nanomaterials. Although the therapeutic efficacy of nanomaterials has been reported to be conclusive, there is still no uniformity in the timing and potential of their use in clinical practice. This paper reviews the nanomaterials currently used as ROS scavengers for OA treatment, along with their mechanisms of action, with the aim of providing a reference and direction for similar studies, and ultimately promoting the early clinical use of nanomaterials for OA treatment. STATEMENT OF SIGNIFICANCE: Reactive oxygen species (ROS) play an important role in the pathogenesis of osteoarthritis (OA). Nanomaterials serving as promising ROS scavengers have gained increasing attention in recent years. This review provides a comprehensive overview of ROS production and regulation, as well as their role in OA pathogenesis. Furthermore, this review highlights the applications of various types of nanomaterials as ROS scavengers in OA treatment and their mechanisms of action. Finally, the challenges and future prospects of nanomaterial-based ROS scavengers in OA therapy are discussed.

Circular RNA CCDC66 Regulates Osteoarthritis Progression by Targeting miR-3622b-5p

OBJECTIVE

CircCCDC66 is involved in cancer progression, but its role in osteoarthritis (OA) remains unknown. This study was carried out to explore the biological role of circCCDC66 in OA and its underlying mechanism.

METHODS

The expression levels of miR-3622b-5p and circCCDC66 in OA cartilage tissues were detected by qRT-PCR. Cell Counting Kit-8 (CCK8) and flow cytometry were used to detect the chondrocyte viability and apoptosis. The expression of chondrocyte inflammatory factors (IL-6 and TNF-α) was measured by ELISA. The target genes of circCCDC66 and miR-3622b-5p were analyzed by bioinformatics analysis and luciferase reporter gene assay. The relationship between circCCDC66 and miR-3622b-5p was analyzed by bioinformatics analysis and luciferase reporter gene assay.

RESULTS

It was found that circCCDC66 expression in OA cartilage tissues was upregulated. CircCCDC66 overexpression inhibited proliferation and promoted apoptosis of chondrocytes and increased IL-6 and TNF-α levels in chondrocytes. miR-3622b-5p was predicted to be a downstream target gene of circCCDC66, and circCCDC66 overexpression inhibited miR-3622b-5p expression in chondrocytes. Moreover, miR-3622b-5p expression was downregulated in OA cartilage tissues. miR-3622b-5p overexpression increased chondrocyte proliferation, inhibited chondrocyte apoptosis, and enhanced the expression of IL-6 and TNF-α in chondrocytes. In addition, circCCDC66 overexpression enhanced SIRT3 expression in chondrocytes, while miR-3622b-5p overexpression inhibited SIRT3 expression in chondrocytes.

CONCLUSION

CircCCDC66 promoted OA chondrocyte apoptosis by regulating the miR-3622b-5p/SIRT3 axis. CircCCDC66 may be a new therapeutic target of OA.

Mitoprotective therapy prevents rapid, strain-dependent mitochondrial dysfunction after articular cartilage injury

Posttraumatic osteoarthritis (PTOA) involves the mechanical and biological deterioration of articular cartilage that occurs following joint injury. PTOA is a growing problem in health care due to the lack of effective therapies combined with an aging population with high activity levels. Recently, acute mitochondrial dysfunction and altered cellular respiration have been associated with cartilage degeneration after injury. This finding is particularly important because recently developed mitoprotective drugs, including SS peptides, can preserve mitochondrial structure and function after acute injury in other tissues. It is not known, however, if cartilage injury induces rapid structural changes in mitochondria, to what degree mitochondrial dysfunction in cartilage depends on the mechanics of injury or the time frame over which such dysfunction develops. Similarly, it is unknown if SS-peptide treatment can preserve mitochondrial structure and function after cartilage injury. Here, we combined fast camera elastography, longitudinal fluorescence assays, and computer vision techniques to track the fates of thousands of individual cells. Our results show that impact induces mechanically dependent mitochondrial depolarization within a few minutes after injury. Electron microscopy revealed that impact causes rapid structural changes in mitochondria that are related to reduced mitochondrial function, namely, fission and loss of cristae structure. We found that SS-peptide treatment prior to impact protects the mitochondrial structure and preserves mitochondrial function at levels comparable with that of unimpacted control samples. Overall, this study reveals the vital role of mitochondria in mediating cartilage's peracute (within minutes) response to traumatic injury and demonstrates mitoprotection as a promising therapeutic strategy for injury-induced cartilage damage.

MicroRNA-495 enhances chondrocyte apoptosis, senescence and promotes the progression of osteoarthritis by targeting AKT1

Osteoarthritis (OA) is a common multifactorial degenerative articular disease among the aging population. The current investigation aimed to elucidate the function of microRNA-495 (miR-495) in the development of OA. We found that miR-495 was upregulated in the cartilage of OA patients. Transfection of a miR-495 mimic into rat primary chondrocytes, human chondrocytes (HC) and SW1353 chondrosarcoma cells inhibited AKT1 expression, proliferation and scratch wound closure and induced apoptosis. Transfection of a miR-495 inhibitor produced an opposite effect. Furthermore, the production of cartilage degeneration-related substances was modified by miR-495. Luciferase reporter gene assay revealed that AKT1 is directly repressed by miR-495. Moreover, the levels of AKT1, p-S6 and p-mTOR diminished in chondrocytes overexpressing miR-495. AKT1 overexpression amplified p-S6 and p-mTOR levels as well as abolished miR-495 mimic-induced apoptosis and inhibition of proliferation. In the surgically induced rat OA model, apoptosis of chondrocytes and cartilage degeneration were remedied by the administration of a miR-495 antagomir. Moreover, there was an increased expression of AKT1. These findings indicate that miR-495 induces OA by targeting AKT1 and regulating the AKT/mTOR pathway. Therefore, miR-495 may be a prospective target for OA treatment.

Articular cartilage gene expression patterns in the tissue surrounding the impact site following applications of shear and axial loads

BACKGROUND

Osteoarthritis is a degradative joint disease found in humans and commercial swine which can develop from a number of factors, including prior joint trauma. An impact injury model was developed to deliver in vitro loads to disease-free porcine patellae in a model of OA.

METHODS

Axial impactions (2000 N normal) and shear impactions (500 N normal with induced shear forces) were delivered to 48 randomly assigned patellae. The patellae were then cultured for 0, 3, 7, or 14 days following the impact. Specimens in the tissue surrounding the loading site were harvested and expression of 18 OA related genes was studied via quantitative PCR. The selected genes were previously identified from published work and fell into four categories: cartilage matrix, degradative enzymes, inflammatory response, and apoptosis.

RESULTS

Type II collagen (Col2a1) showed significantly lower expression in shear vs. axial adjacent tissue at day 0 and 7 (fold changes of 0.40 & 0.19, respectively). In addition, higher expression of degradative enzymes and Fas, an apoptosis gene, was observed in the shear specimens.

CONCLUSIONS

The results suggest that a more physiologically valid shear load may induce more damage to surrounding articular cartilage than a normal load alone.