MSX2 serves as a chondroprotective factor in osteoarthritis: insights from expression analysis and functional validation studies
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Shuai Wu1, Bin Li2, Fulin Tao3
1Department of Joint Surgery, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, 250012, China.
Objective:
Despite the high prevalence of osteoarthritis (OA), molecular mechanisms underlying cartilage destruction remain incompletely understood. This study investigated the expression pattern and functional role of muscle segment homeobox 2 (MSX2) in osteoarthritis pathogenesis.
Methods:
Differential gene expression analysis was performed using three independent Gene Expression Omnibus (GEO) datasets (GSE55457, GSE12021, and GSE114007) to examine MSX2 expression in osteoarthritic versus normal cartilage. Expression patterns were validated in primary chondrocytes from human osteoarthritis patients and mouse osteoarthritis models using Western blot and quantitative reverse transcription polymerase chain reaction (RT-PCR). Functional studies employed both loss-of-function and gain-of-function approaches through intra-articular injection of adeno-associated virus expressing MSX2-specific short hairpin ribonucleic acid (shRNA) or MSX2 overexpression constructs. Cartilage morphology, proteoglycan content, chondrocyte apoptosis, matrix markers, and inflammatory responses were assessed through histological analysis, immunohistochemistry, and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) staining.
Results:
MSX2 was consistently downregulated in osteoarthritic samples across all datasets, with validation confirming reduced MSX2 protein and messenger ribonucleic acid (mRNA) levels in both human patients and mouse models (p < 0.05). MSX2 knockdown significantly exacerbated cartilage degeneration, increased chondrocyte apoptosis, and disrupted matrix homeostasis by reducing anabolic markers type II collagen (COL2) and aggrecan (ACAN) while upregulating matrix metalloproteinase 13 (MMP13). Additionally, MSX2 knockdown enhanced inflammatory responses, evidenced by increased macrophage infiltration and tumor necrosis factor-alpha (TNFα) expression. Conversely, MSX2 overexpression demonstrated chondroprotective effects with improved cartilage morphology and reduced apoptosis.
Conclusion:
MSX2 serves as a critical chondroprotective factor maintaining cartilage homeostasis. Its downregulation contributes to osteoarthritis pathogenesis through disruption of matrix homeostasis, promotion of chondrocyte apoptosis, and enhancement of inflammatory responses. These findings identify MSX2 as a potential therapeutic target for osteoarthritis treatment.
Insights
Muscle segment homeobox 2 (MSX2) is downregulated in osteoarthritis, worsening cartilage destruction and inflammation. Restoring MSX2 levels may offer a new therapeutic strategy for osteoarthritis.
Area of Science:
- Biochemistry
- Molecular Biology
- Orthopedics
Background:
- Osteoarthritis (OA) is a prevalent degenerative joint disease with incompletely understood mechanisms of cartilage destruction.
- Muscle segment homeobox 2 (MSX2) is a transcription factor with potential roles in skeletal development and disease.
Purpose of the Study:
- To investigate the expression pattern of MSX2 in osteoarthritis.
- To elucidate the functional role of MSX2 in the pathogenesis of osteoarthritis.
Main Methods:
- Differential gene expression analysis of three GEO datasets (GSE55457, GSE12021, GSE114007) to assess MSX2 levels in OA vs. normal cartilage.
- Validation of MSX2 expression in human and mouse OA models using Western blot and RT-PCR.
- Functional studies involving MSX2 knockdown and overexpression via adeno-associated virus (AAV) vectors.
- Assessment of cartilage integrity, chondrocyte apoptosis, matrix markers (COL2, ACAN, MMP13), and inflammation (macrophage infiltration, TNFα).
Main Results:
- MSX2 was significantly downregulated in osteoarthritic cartilage from human patients and mouse models.
- MSX2 knockdown exacerbated cartilage degeneration, increased chondrocyte apoptosis, and disrupted matrix homeostasis by decreasing COL2 and ACAN while increasing MMP13.
- MSX2 knockdown enhanced inflammatory responses, indicated by increased macrophage infiltration and TNFα expression.
- MSX2 overexpression exhibited chondroprotective effects, improving cartilage morphology and reducing apoptosis.
Conclusions:
- MSX2 is a critical chondroprotective factor that maintains cartilage homeostasis.
- Downregulation of MSX2 contributes to OA pathogenesis by disrupting matrix homeostasis, promoting chondrocyte apoptosis, and enhancing inflammation.
- MSX2 represents a potential therapeutic target for osteoarthritis treatment.
