Identification of Key Genes and Potential Mechanisms Based on the Autophagy Regulatory Network in Osteoclasts Using a Murine Osteoarthritis Model

Autophagy enhances the differentiation of insulin-producing cells from Wharton's jelly-derived mesenchymal stem cells

Autophagy disruption suppresses insulin production and induces diabetes. The role of autophagy in the differentiation of Wharton's jelly (WJ)-derived mesenchymal stem cells (WJSCs) into insulin-producing cells (IPCs) was investigated in this experimental study. The WJSCs were incubated in a differentiation medium (DM) with or without an autophagy inhibitor (3-methyladenine: 3MA). The differentiation of IPCs was confirmed by flow cytometry analysis of PDX-1 and insulin-positive cells, insulin secretion, and the high expression of β cell-specific genes, Glucose transporter 2 (GLUT-2), and INSULIN. Autophagy has been assessed by calculating the percentage of Acridine orange (AO)-positive cells, expression of autophagy-related genes, and the LC3B/LC3A ratio. β cell-specific genes were up-regulated in the DM group, and 3MA decreased their expression. In the DM+3MA-treated cells, the expression of GLUT-2 and INSULIN genes and insulin secretion decreased compared to the DM group. In cells treated with 3MA, there was a significant decrease in the percentage of PDX-1 and insulin-positive cells compared to 3MA-untreated cells. Additionally, in the group receiving both DM and 3MA treatment, the expression of autophagy-related genes, the LC3B/LC3A protein ratio, and the percentage of AO-stained cells were significantly reduced compared to the group receiving only DM treatment. These findings suggest autophagy is essential for β cell differentiation and insulin secretion.

Osteoclasts and osteoarthritis: Novel intervention targets and therapeutic potentials during aging

Osteoarthritis (OA), a chronic degenerative joint disease, is highly prevalent among the aging population, and often leads to joint pain, disability, and a diminished quality of life. Although considerable research has been conducted, the precise molecular mechanisms propelling OA pathogenesis continue to be elusive, thereby impeding the development of effective therapeutics. Notably, recent studies have revealed subchondral bone lesions precede cartilage degeneration in the early stage of OA. This development is marked by escalated osteoclast-mediated bone resorption, subsequent imbalances in bone metabolism, accelerated bone turnover, and a decrease in bone volume, thereby contributing significantly to the pathological changes. While the role of aging hallmarks in OA has been extensively elucidated from the perspective of chondrocytes, their connection with osteoclasts is not yet fully understood. There is compelling evidence to suggest that age-related abnormalities such as epigenetic alterations, proteostasis network disruption, cellular senescence, and mitochondrial dysfunction, can stimulate osteoclast activity. This review intends to systematically discuss how aging hallmarks contribute to OA pathogenesis, placing particular emphasis on the age-induced shifts in osteoclast activity. It also aims to stimulate future studies probing into the pathological mechanisms and therapeutic approaches targeting osteoclasts in OA during aging.

Bioinformatics identification and integrative analysis of ferroptosis-related key lncRNAs in patients with osteoarthritis

BACKGROUND

Ferroptosis and dysregulation of long non-coding RNA (lncRNA) have been described to be strictly relevant to the pathogenesis of osteoarthritis (OA). However, the connection between ferroptosis and lncRNA in OA is poorly appreciated. Herein, we investigated the functional contribution of lncRNA markers correlated with the progression of human OA by comprehensive bioinformatics analysis of a panoramic network of competing endogenous RNA (ceRNA) based on ferroptosis-related genes (FRGs).

METHODS

FRGs-related competing endogenous RNA (ceRNA) networks were generated using differentially expressed genes based on OA-related whole transcriptome data from the Gene Expression Omnibus (GEO) database via starBase, miRTarBase, and miRWalk databases. The pivotal lncRNAs were ascertained by topological features (degree, betweenness, and closeness) and subceRNA networks were re-visualized. The expression difference of pivotal lncRNAs was verified by quantitative real-time polymerase chain reaction (qRT-PCR). The latent molecular mechanisms of the global ceRNA and subceRNA networks were uncovered by the R package clusterProfiler-based enrichment analysis.

RESULTS

A total of 98 dysregulated lncRNA-miRNA-mRNA regulatory relationships were attained in the FRGs-related panoramic ceRNA network of OA, covering 26 mRNAs, 20 miRNAs, and 20 lncRNAs. Three lncRNAs (AC011511.5, AL358072.1, and C9orf139) were ascertained as the central lncRNAs in the panoramic ceRNA network. Functional ensemble analysis illustrated that both the panoramic ceRNA network and the subceRNA network were integrally affiliated with the immune-inflammatory response, oxygen homeostasis, and cell death (apoptosis, autophagy, and ferroptosis).

CONCLUSION

Comprehensive bioinformatics analysis of the FRGs-related ceRNA network determined three molecular biomarkers of lncRNAs that might be affiliated with OA progression.

Mitophagy—A New Target of Bone Disease

Bone diseases are usually caused by abnormal metabolism and death of cells in bones, including osteoblasts, osteoclasts, osteocytes, chondrocytes, and bone marrow mesenchymal stem cells. Mitochondrial dysfunction, as an important cause of abnormal cell metabolism, is widely involved in the occurrence and progression of multiple bone diseases, including osteoarthritis, intervertebral disc degeneration, osteoporosis, and osteosarcoma. As selective mitochondrial autophagy for damaged or dysfunctional mitochondria, mitophagy is closely related to mitochondrial quality control and homeostasis. Accumulating evidence suggests that mitophagy plays an important regulatory role in bone disease, indicating that regulating the level of mitophagy may be a new strategy for bone-related diseases. Therefore, by reviewing the relevant literature in recent years, this paper reviews the potential mechanism of mitophagy in bone-related diseases, including osteoarthritis, intervertebral disc degeneration, osteoporosis, and osteosarcoma, to provide a theoretical basis for the related research of mitophagy in bone diseases.