Vitamin D Attenuates Pain and Cartilage Destruction in OA Animals via Enhancing Autophagic Flux and Attenuating Inflammatory Cell Death

Effect of vitamin D supplementation on circulating level of autophagosome protein LC3A, inflammation, and physical performance in knee osteoarthritis

Aberrant autophagic activity is observed in osteoarthritic joints. Vitamin D was shown to alleviate not only osteoarthritis severity, but also autophagy process. However, the influence of vitamin D on autophagy in knee osteoarthritis (KOA) remains ambiguous. This study aimed to determine the effect of vitamin D2 on serum levels of autophagosome protein LC3A in patients with KOA and whether LC3A levels were correlated with serum 25-hydroxyvitamin D (25(OH)D) and clinical outcomes of patients with KOA. A total of 165 patients with KOA and 25 healthy controls were recruited. Vitamin D2 (ergocalciferol) was administered to patients with KOA at a weekly dosage of 40,000 IU. Serum LC3A, knee pain and functional scores, muscle strength, physical performance, and biochemical parameters were examined before and after 6 months of vitamin D2 supplementation. Serum LC3A levels were significantly higher in patients with KOA than healthy controls. In patients with KOA, vitamin D2 supplementation significantly decreased serum LC3A levels. Furthermore, baseline levels of serum LC3A were significantly associated with radiographic severity, pain and functional scores, total cholesterol, hs-CRP, IL-6, protein carbonyl, and serum 25(OH)D. After adjusting for established confounders, independent relationships among serum LC3A and radiographic severity, pain and functional scores, total cholesterol, hs-CRP, IL-6, protein carbonyl, and serum 25(OH)D were also observed. Vitamin D2 supplementation was shown to not only decrease serum levels of LC3A, inflammatory markers, as well as oxidative stress, but also improve muscle strength and physical performance in patients with KOA.

Vitamin D and autophagy in knee osteoarthritis: A review

Knee osteoarthritis (KOA), the highly prevalent degenerative disease affecting the joint, perpetually devastates the health of the elderly. Of various mechanisms known to participate in KOA etiology, apoptosis of chondrocytes is widely regarded as the primary cause of cartilage degradation. It has been suggested that the induction of autophagy in chondrocytes could potentially prolong the progression of KOA by modulating intracellular metabolic processes, which may be helpful for ameliorating chondrocyte apoptosis and eventual cartilage degeneration. Autophagy, a physiological process characterized by intracellular self-degradation, has been reportedly implicated in various pathologic conditions including KOA. Interestingly, vitamin D has been shown to regulate autophagy in human chondrocytes through multiple pathways, specifically AMPK/mTOR signaling pathway. This observation underscores the potential of vitamin D as a novel approach for restoring the functionality and survivability of chondrocytes in KOA. Supporting vitamin D's clinical significance, previous studies have demonstrated its substantial involvement in the symptoms and irregular joint morphology observed in KOA patients, strengthening potential therapeutic efficacy of vitamin D in treatment of KOA. Herein, the purpose of this review was to determine the mechanisms underlying the multi-processes of vitamin D implicated in autophagy in several cells including chondrocytes, which would bring unique insights into KOA pathogenesis.

Targeting regulated chondrocyte death in osteoarthritis therapy

In vivo articular cartilage degeneration is an essential hallmark of osteoarthritis (OA), involving chondrocyte senescence, extracellular matrix degradation, chondrocyte death, cartilage loss, and bone erosion. Among them, chondrocyte death is one of the major factors leading to cartilage degeneration. Many studies have reported that various cell death modes, including apoptosis, ferroptosis, and autophagy, play a key role in OA chondrocyte death. Currently, there is insufficient understanding of OA pathogenesis, and there remains a lack of treatment methods to prevent OA and inhibit its progression. Studies suggest that OA prevention and treatment are mainly directed to arrest premature or excessive chondrocyte death. In this review, we a) discuss the forms of death of chondrocytes and the associations between them, b) summarize the critical factors in chondrocyte death, c) discuss the vital role of chondrocyte death in OA, d) and, explore new approaches for targeting the regulation of chondrocyte death in OA treatment.

Efficient Generation of Chondrocytes From Bone Marrow-Derived Mesenchymal Stem Cells in a 3D Culture System: Protocol for a Practical Model for Assessing Anti-Inflammatory Therapies

BACKGROUND

Chondrocytes are the primary cells responsible for maintaining cartilage integrity and function. Their role in cartilage homeostasis and response to inflammation is crucial for understanding the progression and potential therapeutic interventions for various cartilage-related disorders. Developing an accessible and cost-effective model to generate viable chondrocytes and to assess their response to different bioactive compounds can significantly advance our knowledge of cartilage biology and contribute to the discovery of novel therapeutic approaches.

OBJECTIVE

We developed a novel, streamlined protocol for generating chondrocytes from bone marrow-derived mesenchymal stem cells (BMSCs) in a 3D culture system that offers significant implications for the study of cartilage biology and the discovery of potential therapeutic interventions for cartilage-related and associated disorders.

METHODS

We developed a streamlined protocol for generating chondrocytes from BMSCs in a 3D culture system using an "in-tube" culture approach. This simple pellet-based 3D culture system allows for cell aggregation and spheroid formation, facilitating cell-cell and cell-extracellular matrix interactions that better mimic the in vivo cellular environment compared with 2D monolayer cultures. A proinflammatory chondrocyte model was created by treating the chondrocytes with lipopolysaccharide and was subsequently used to evaluate the anti-inflammatory effects of vitamin D, curcumin, and resveratrol.

RESULTS

The established protocol successfully generated a large quantity of viable chondrocytes, characterized by alcian blue and toluidine blue staining, and demonstrated versatility in assessing the anti-inflammatory effects of various bioactive compounds. The chondrocytes exhibited reduced inflammation, as evidenced by the decreased tumor necrosis factor-α levels, in response to vitamin D, curcumin, and resveratrol treatment.

CONCLUSIONS

Our novel protocol offers an accessible and cost-effective approach for generating chondrocytes from BMSCs and for evaluating potential therapeutic leads in the context of inflammatory chondrocyte-related diseases. Although our approach has several advantages, further investigation is required to address its limitations, such as the potential differences between chondrocytes generated using our protocol and those derived from other established methods, and to refine the model for broader applicability and clinical translation.

Lipid Metabolism in Cartilage Development, Degeneration, and Regeneration

Lipids affect cartilage growth, injury, and regeneration in diverse ways. Diet and metabolism have become increasingly important as the prevalence of obesity has risen. Proper lipid supplementation in the diet contributes to the preservation of cartilage function, whereas excessive lipid buildup is detrimental to cartilage. Lipid metabolic pathways can generate proinflammatory substances that are crucial to the development and management of osteoarthritis (OA). Lipid metabolism is a complicated metabolic process involving several regulatory systems, and lipid metabolites influence different features of cartilage. In this review, we examine the current knowledge about cartilage growth, degeneration, and regeneration processes, as well as the most recent research on the significance of lipids and their metabolism in cartilage, including the extracellular matrix and chondrocytes. An in-depth examination of the involvement of lipid metabolism in cartilage metabolism will provide insight into cartilage metabolism and lead to the development of new treatment techniques for metabolic cartilage damage.