Osteoarthritic chondrocytes undergo a glycolysis-related metabolic switch upon exposure to IL-1b or TNF

TGF-β2 enhances glycolysis in chondrocytes via TβRI/p-Smad3 signaling pathway

Chondrocytes rely heavily on glycolysis to maintain the metabolic homeostasis and cartilage matrix turnover. Glycolysis in chondrocytes is remodeled by diverse biochemical and biomechanical factors due to the sporty joint microenvironment. Transforming growth factor-β2 (TGF-β2), one of the most abundant TGF-β superfamily members in chondrocytes, has increasingly attracted attention in cartilage physiology and pathology. Although previous studies have emphasized the importance of TGF-β superfamily members on cell metabolism, whether and how TGF-β2 modulates glycolysis in chondrocytes remains elusive. In the current study, we investigated the effects of TGF-β2 on glycolysis in chondrocytes and explored the underlying biomechanisms. The results showed that TGF-β2 could enhance glycolysis in chondrocytes by increasing glucose consumption, up-regulating liver-type ATP-dependent 6-phosphofructokinase (Pfkl) expression, and boosting lactate production. The TGF-β2 signal entered chondrocytes via TGF-β receptor type I (TβRI), and activated p-Smad3 signaling to regulate the glycolytic pathway. Subsequent experiments employing specific inhibitors of TβRI and p-Smad3 further substantiated the role of TGF-β2 in enhancement of glycolysis via TβRI/p-Smad3 axis in chondrocytes. The results provide new understanding of the metabolic homeostasis in chondrocytes induced by TGF-β superfamily and might shed light on the prevention and treatment of related osteoarticular diseases.

Tisochrysis lutea Fucoxanthin Suppresses NF-κB, JNK, and p38-Associated MMP Expression in Arthritis Pathogenesis via Antioxidant Activity

Tisochrysis lutea is a highly nutritious marine microalga that has various applications in aquaculture and biotechnology. However, the effects of T. lutea extract (TLE) on osteoarthritis (OA) pathogenesis remain unexplored. In this study, we aimed to determine the effects of TLE on OA development. We found that TLE inhibits the expression of matrix metalloproteinases (MMPs) and reactive oxygen species (ROS) activity in an OA mouse model generated by the destabilization of the medial meniscus (DMM) surgery. In vivo assays of the OA model mice demonstrated that TLE has a protective effect against cartilage destruction by inhibiting MMP3 and MMP13 expression. To enable the medical use of TLE, the components of TLE were characterized using high-performance liquid chromatography (HPLC) analysis. Interestingly, we found that Fucoxanthin accounts for 41.2% of TLE and showed anti-catabolic and antioxidant effects under IL-1β-treated in vitro conditions. RNA sequencing analysis showed that fucoxanthin decreased p38, NF-κB, and JNK signaling pathway gene expression, all of which are activated by IL-1β. Furthermore, in vivo analysis showed that fucoxanthin inhibited the IL-1β-stimulated phosphorylation of p65, JNK, and p38. These results highlight new possibilities for the use of TLE as a source of fucoxanthin, an antioxidant, for OA treatment.

Therapeutic Potential of Olfactory Ensheathing Cells and Adipose-Derived Stem Cells in Osteoarthritis: Insights from Preclinical Studies

Olfactory-ensheathing cells (OECs) are known for their role in neuronal regeneration and potential to promote tissue repair. Adipose-derived stem cells (ADSCs), characterized by mesenchymal stem cell (MSC) traits, display a fibroblast-like morphology and express MSC surface markers, making them suitable for regenerative therapies for osteoarthritis (OA). In this study, OECs and ADSCs were derived from tissues and characterized for their morphology, surface marker expression, and differentiation capabilities. Collagenase-induced OA was created in 10-week-old C57BL/6 mice, followed by intra-articular injections of ADSCs (1 × 105), OECs (1 × 105), or a higher dose of OECs (5 × 105). Therapeutic efficacy was evaluated using rotarod performance tests, MRI, histology, and immunohistochemistry. Both cell types exhibited typical MSC characteristics and successfully differentiated into adipocytes, osteoblasts, and chondrocytes, confirmed by gene expression and staining. Transplantation significantly improved rotarod performance and preserved cartilage integrity, as seen in MRI and histology, with reduced cartilage destruction and increased chondrocytes. Immunohistochemistry showed elevated type II collagen and aggrecan in treated joints, indicating hyaline cartilage formation, and reduced MMP13 and IL-1β expression, suggesting decreased inflammation and catabolic activity. These findings highlight the regenerative potential of OECs and ADSCs in treating OA by preserving cartilage, promoting chondrocyte proliferation, and reducing inflammation. Further research is needed to optimize delivery methods and evaluate long-term clinical outcomes.

Molecular portrait of chronic joint diseases: Defining endotypes toward personalized medicine

Joint diseases affect hundreds of millions of people worldwide, and their prevalence is constantly increasing. To date, despite recent advances in the development of therapeutic options for most rheumatic conditions, a significant proportion of patients still lack efficient disease management, considerably impacting their quality of life. Through the spectrum of rheumatoid arthritis (RA), psoriatic arthritis (PsA), and osteoarthritis (OA) as quintessential and common rheumatic diseases, this review first provides an overview of their epidemiological and clinical features before exploring how the better definition of clinical phenotypes has helped their clinical management. It then discusses the recent progress in understanding the diversity of endotypes underlying disease phenotypes. Finally, this review highlights the current challenges of implementing molecular endotypes towards the personalized management of RA, PsA and OA patients in the future.

Skeletal interoception in osteoarthritis

The interoception maintains proper physiological conditions and metabolic homeostasis by releasing regulatory signals after perceving changes in the internal state of the organism. Among its various forms, skeletal interoception specifically regulates the metabolic homeostasis of bones. Osteoarthritis (OA) is a complex joint disorder involving cartilage, subchondral bone, and synovium. The subchondral bone undergoes continuous remodeling to adapt to dynamic joint loads. Recent findings highlight that skeletal interoception mediated by aberrant mechanical loads contributes to pathological remodeling of the subchondral bone, resulting in subchondral bone sclerosis in OA. The skeletal interoception is also a potential mechanism for chronic synovial inflammation in OA. In this review, we offer a general overview of interoception, specifically skeletal interoception, subchondral bone microenviroment and the aberrant subchondral remedeling. We also discuss the role of skeletal interoception in abnormal subchondral bone remodeling and synovial inflammation in OA, as well as the potential prospects and challenges in exploring novel OA therapies that target skeletal interoception.

Bioenergetic dysfunction in the pathogenesis of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is a frequent cause of low back pain and is the most common cause of disability. Treatments for symptomatic IVD degeneration, including conservative treatments such as analgesics, physical therapy, anti-inflammatories and surgeries, are aimed at alleviating neurological symptoms. However, there are no effective treatments to prevent or delay IVD degeneration. Previous studies have identified risk factors for IVD degeneration such as aging, inflammation, genetic factors, mechanical overload, nutrient deprivation and smoking, but metabolic dysfunction has not been highlighted. IVDs are the largest avascular structures in the human body and determine the hypoxic and glycolytic features of nucleus pulposus (NP) cells. Accumulating evidence has demonstrated that intracellular metabolic dysfunction is associated with IVD degeneration, but a comprehensive review is lacking. Here, by reviewing the physiological features of IVDs, pathological processes and metabolic changes associated with IVD degeneration and the functions of metabolic genes in IVDs, we highlight that glycolytic pathway and intact mitochondrial function are essential for IVD homeostasis. In degenerated NPs, glycolysis and mitochondrial function are downregulated. Boosting glycolysis such as HIF1α overexpression protects against IVD degeneration. Moreover, the correlations between metabolic diseases such as diabetes, obesity and IVD degeneration and their underlying molecular mechanisms are discussed. Hyperglycemia in diabetic diseases leads to cell senescence, the senescence-associated phenotype (SASP), apoptosis and catabolism of extracellualr matrix in IVDs. Correcting the global metabolic disorders such as insulin or GLP-1 receptor agonist administration is beneficial for diabetes associated IVD degeneration. Overall, we summarized the recent progress of investigations on metabolic contributions to IVD degeneration and provide a new perspective that correcting metabolic dysfunction may be beneficial for treating IVD degeneration.

Revisiting prostaglandin E2: A promising therapeutic target for osteoarthritis

Osteoarthritis (OA) is a complex disease characterized by cartilage degeneration and persistent pain. Prostaglandin E2 (PGE2) plays a significant role in OA inflammation and pain. Recent studies have revealed the significant role of PGE2-mediated skeletal interoception in the progression of OA, providing new insights into the pathogenesis and treatment of OA. This aspect also deserves special attention in this review. Additionally, PGE2 is directly involved in pathologic processes including aberrant subchondral bone remodeling, cartilage degeneration, and synovial inflammation. Therefore, celecoxib, a commonly used drug to alleviate inflammatory pain through inhibiting PGE2, serves not only as an analgesic for OA but also as a potential disease-modifying drug. This review provides a comprehensive overview of the discovery history, synthesis and release pathways, and common physiological roles of PGE2. We discuss the roles of PGE2 and celecoxib in OA and pain from skeletal interoception and multiple perspectives. The purpose of this review is to highlight PGE2-mediated skeletal interoception and refresh our understanding of celecoxib in the pathogenesis and treatment of OA.

Glycolysis: an emerging regulator of osteoarthritis

Osteoarthritis (OA) has been a leading cause of disability in the elderly and there remains a lack of effective therapeutic approaches as the mechanisms of pathogenesis and progression have yet to be elucidated. As OA progresses, cellular metabolic profiles and energy production are altered, and emerging metabolic reprogramming highlights the importance of specific metabolic pathways in disease progression. As a crucial part of glucose metabolism, glycolysis bridges metabolic and inflammatory dysfunctions. Moreover, the glycolytic pathway is involved in different areas of metabolism and inflammation, and is associated with a variety of transcription factors. To date, it has not been fully elucidated whether the changes in the glycolytic pathway and its associated key enzymes are associated with the onset or progression of OA. This review summarizes the important role of glycolysis in mediating cellular metabolic reprogramming in OA and its role in inducing tissue inflammation and injury, with the aim of providing further insights into its pathological functions and proposing new targets for the treatment of OA.

Mucopolysaccharidosis IVA: Current Disease Models and Drawbacks

Mucopolysaccharidosis IVA (MPS IVA) is a rare disorder caused by mutations in the N-acetylgalactosamine-6-sulfate-sulfatase (GALNS) encoding gene. GALNS leads to the lysosomal degradation of the glycosaminoglyccreasans keratan sulfate and chondroitin 6-sulfate. Impaired GALNS enzymes result in skeletal and non-skeletal complications in patients. For years, the MPS IVA pathogenesis and the assessment of promising drugs have been evaluated using in vitro (primarily fibroblasts) and in vivo (mainly mouse) models. Even though value information has been raised from those studies, these models have several limitations. For instance, chondrocytes have been well recognized as primary cells affected in MPS IVA and responsible for displaying bone development impairment in MPS IVA patients; nonetheless, only a few investigations have used those cells to evaluate basic and applied concepts. Likewise, current animal models are extensively represented by mice lacking GALNS expression; however, it is well known that MPS IVA mice do not recapitulate the skeletal dysplasia observed in humans, making some comparisons difficult. This manuscript reviews the current in vitro and in vivo MPS IVA models and their drawbacks.