Mitochondrial dysfunction activates ADAMTS-5 expression via mt-dsRNA-PKR-Spi-1 axis in osteoarthritic chondrocytes

Area of Science:

• Biochemistry
• Molecular Biology
• Orthopedics

Background:

• Osteoarthritis (OA) is characterized by cartilage degradation, primarily mediated by ADAMTS-5.
• The precise mechanisms activating ADAMTS-5 expression, particularly in response to mitochondrial dysfunction, remain incompletely understood.
• Previous research implicated mitochondrial double-stranded RNA (mt-dsRNA) leakage and protein kinase R (PKR) activation in OA progression.

Purpose of the Study:

• To elucidate the molecular mechanisms by which mt-dsRNAs and PKR signaling activate ADAMTS-5 expression in chondrocytes experiencing mitochondrial dysfunction.
• To investigate the role of the mt-dsRNA-PKR axis in OA pathogenesis.
• To evaluate the therapeutic potential of targeting this pathway for OA treatment.

Main Methods:

• Induction of mitochondrial dysfunction in chondrocytes to trigger mt-dsRNA release.
• Assessment of PKR activation and its downstream effects on ADAMTS-5 transcription.
• Analysis of mt-dsRNA and PKR levels in cartilage from OA patients and mouse models.
• Conditional knockout of PKR in articular chondrocytes to assess its role in OA phenotypes.

Main Results:

• Mitochondrial dysfunction was confirmed to induce mt-dsRNA leakage into the cytosol.
• Activated PKR was found to initiate Spi-1-dependent ADAMTS-5 transcription.
• Elevated levels of mt-dsRNAs and PKR activation were observed in OA cartilage.
• Conditional knockout of PKR in chondrocytes significantly alleviated OA pathological phenotypes in mice.

Conclusions:

• Mitochondrial dysfunction in chondrocytes leads to mt-dsRNA release, activating PKR and subsequently ADAMTS-5 expression, thereby driving OA.
• The mt-dsRNA-PKR signaling pathway represents a critical mechanism in OA pathogenesis.
• Targeting the mt-dsRNA-PKR pathway holds promise for developing novel OA therapeutics.