Reduction in disease progression by inhibition of transforming growth factor α-CCL2 signaling in experimental
C Thomas G Appleton1, Shirine E Usmani1, Michael A Pest1
1Western University Schulich School of Medicine and Dentistry, London, Ontario, Canada.
Objective:
Transforming growth factor α (TGFα) is increased in osteoarthritic (OA) cartilage in rats and humans and modifies chondrocyte phenotype. CCL2 is increased in OA cartilage and stimulates proteoglycan loss. This study was undertaken to test whether TGFα and CCL2 cooperate to promote cartilage degradation and whether inhibiting either reduces disease progression in a rat model of posttraumatic OA.
Methods:
Microarray analysis was used to profile expression of messenger RNA (mRNA) for Tgfa, Ccl2, and related genes in a rat model of posttraumatic OA. Rat primary chondrocytes and articular cartilage explants were treated with TGFα in the presence or absence of MEK-1/2, p38, phosphatidylinositol 3-kinase, Rho-associated protein kinase, or CCR2 inhibitors and immunostained for markers of cartilage degradation. The rat model was used to administer pharmacologic inhibitors of TGFα (AG1478) and CCL2 (RS504393) signaling for up to 10 weeks and assess histopathology and serum biomarkers of cartilage synthesis (C-propeptide of type II collagen [CPII]) and breakdown (C2C).
Results:
Tgfa and Ccl2 mRNA were simultaneously up-regulated in articular cartilage in the rat model of posttraumatic OA. TGFα induced expression of CCL2, Mmp3, and Tnf in primary chondrocytes. Cleavage of type II collagen and aggrecan (by matrix metalloproteinases and ADAMTS-4/5, respectively) induced by TGFα was blocked by pharmacologic inhibition of CCL2 in cartilage explants. In vivo pharmacologic inhibition of TGFα or CCL2 signaling reduced Osteoarthritis Research Society International cartilage histopathology scores and increased serum CPII levels, but only TGFα inhibition reduced C2C levels intreated versus untreated rat OA cartilage.
Conclusion:
TGFα signaling stimulates cartilage degradation via a CCL2-dependent mechanism, but pharmacologic inhibition of the TGFα-CCL2 axis reduces experimental posttraumatic OA progression in vivo.
Insights
Transforming growth factor alpha (TGFα) and CCL2 signaling drive osteoarthritis cartilage degradation. Inhibiting this TGFα-CCL2 axis effectively reduces experimental posttraumatic OA progression in rats.
Area of Science:
- Biochemistry and Molecular Biology
- Immunology
- Orthopedics
Background:
- Transforming growth factor alpha (TGFα) and CCL2 are elevated in osteoarthritic (OA) cartilage, impacting chondrocyte function and promoting proteoglycan loss.
- Understanding the interplay between TGFα and CCL2 is crucial for developing targeted OA therapies.
Purpose of the Study:
- To investigate the cooperative effect of TGFα and CCL2 in promoting cartilage degradation in a rat model of posttraumatic OA.
- To evaluate the efficacy of inhibiting TGFα or CCL2 signaling in reducing OA progression.
Main Methods:
- Gene expression profiling (microarray) of Tgfa, Ccl2, and related genes in OA cartilage.
- In vitro studies using primary chondrocytes and cartilage explants treated with TGFα and various inhibitors (MEK-1/2, p38, PI3K, ROCK, CCR2).
- In vivo administration of pharmacologic inhibitors for TGFα (AG1478) and CCL2 (RS504393) in a rat OA model, followed by histopathological and serum biomarker analysis (CPII, C2C).
Main Results:
- Simultaneous upregulation of Tgfa and Ccl2 mRNA in OA cartilage.
- TGFα induced CCL2, MMP3, and TNF expression in chondrocytes; TGFα-induced collagen and aggrecan cleavage was blocked by CCL2 inhibition.
- Inhibition of TGFα or CCL2 signaling reduced OA histopathology and increased serum CPII. Only TGFα inhibition lowered serum C2C levels.
Conclusions:
- TGFα signaling contributes to cartilage degradation through a CCL2-dependent pathway.
- Pharmacologic inhibition of the TGFα-CCL2 axis demonstrates therapeutic potential by reducing experimental posttraumatic OA progression.
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