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RhoA deficiency in chondrocyte inhibits cartilage fibrosis and ameliorates osteoarthritis progression via SOX4/MMP2
Yizhou Xu1,2, Shuyi Xu2, Jiayi Li1,2
1Department of Spinal Surgery, Orthopedic Medical Center, Zhujiang Hospital, Southern Medical University, Guangzhou, 510280, China.
Background:
Cartilage fibrosis plays a critical role in the onset and progression of osteoarthritis (OA), and although RhoA is a well-known small GTPase that regulates cytoskeletal reorganization, its role in OA progression remains inadequately explored.
Methods:
In this study, we first screened public scRNA-seq datasets for genes enriched in fibrocartilage chondrocytes and found that RHOA is significantly upregulated in fibrocartilage chondrocytes within OA cartilage obtained from patients undergoing total knee arthroplasty. Then, we induced post-traumatic OA in 8-week-old male C57BL/6J mice by destabilization of the medial meniscus and generated chondrocyte-specific Rhoa deletion using Col2a1-CreERT-Rhoa-flox/flox mice. After that, cartilage damage was graded by Safranin-O/Fast Green, Toluidine blue, and Micro-CT, and molecular changes were validated by Immunofluorescence and Western blot, leading to the identification-by integrated single-cell and bulk RNA-seq-of a β-catenin/SOX4/MMP2 axis downstream of RhoA. Finally, we injected AAV-Sox4 or AAV-Mmp2 intra-articularly to rescue the loss of RhoA function.
Results:
The results showed that conditional knockout of Rhoa in chondrocytes resulted in a marked reduction in cartilage fibrosis and a concurrent decrease in extracellular matrix degradation in OA mice. Mechanistically, the integrated single-cell and bulk tissue transcriptomic analyses indicated that RhoA promotes the chondrocyte transition to a fibrotic phenotype through the novel β-catenin/SOX4/MMP2 pathway, while notably, intra-articular delivery of adeno-associated viral vectors overexpressing Sox4 or Mmp2 reversed the phenotypes of Rhoa-deficient mice.
Conclusion:
These findings position RHOA as a central regulator of chondrocyte fibrosis and as a promising therapeutic target for OA treatment.
The Translational Potential Of This Article:
These findings highlight that RhoA may represent a therapeutic target for ameliorating cartilage fibrosis and the OA process via targeted gene intervention.
Insights
RhoA is a key regulator of cartilage fibrosis in osteoarthritis (OA). Targeting RhoA may offer a new therapeutic strategy for OA by reducing fibrosis and extracellular matrix degradation.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Cartilage fibrosis is a key factor in osteoarthritis (OA) development and progression.
- The role of RhoA, a small GTPase regulating the cytoskeleton, in OA progression is not well understood.
Purpose of the Study:
- To investigate the role of RhoA in chondrocyte fibrosis and OA progression.
- To identify downstream molecular pathways regulated by RhoA in OA chondrocytes.
Main Methods:
- Screened scRNA-seq datasets for genes in OA fibrocartilage chondrocytes, identifying RhoA upregulation.
- Generated chondrocyte-specific RhoA knockout mice (Col2a1-CreERT-Rhoa-flox/flox) to model post-traumatic OA.
- Analyzed cartilage damage and molecular changes using histology, Micro-CT, immunofluorescence, Western blot, and integrated single-cell and bulk RNA-seq.
Main Results:
- Conditional knockout of RhoA in chondrocytes significantly reduced cartilage fibrosis and extracellular matrix degradation in OA mice.
- RhoA was found to promote chondrocyte fibrotic transition via a novel β-catenin/SOX4/MMP2 pathway.
- Overexpression of SOX4 or MMP2 via AAV vectors reversed the fibrotic phenotypes in RhoA-deficient mice.
Conclusions:
- RhoA is a central regulator of chondrocyte fibrosis in OA.
- The RhoA/β-catenin/SOX4/MMP2 axis represents a potential therapeutic target for OA treatment.
