Accelerated and increased joint damage in young mice with global inactivation of mitogen-inducible gene 6 after ligament and meniscus injury.

INTRODUCTION

Ligament and meniscal damage can cause joint disease. Arthritic joints contain increased amounts of epidermal growth factor receptor (EGFR) protein, and polymorphisms in EGFR are associated with arthritis risk. The role of endogenous EGFR regulation during joint disease due to ligament and meniscal trauma is unknown. Mitogen-inducible gene 6 (MIG-6) can reduce EGFR phosphorylation and downstream signaling. We examined the effect of EGFR modulation by MIG-6 on joint disease development after ligament and meniscus injury.

METHODS

Knee ligament transection and meniscus removal were performed surgically on mice homozygous for a global inactivating mutation in MIG-6 (Mig-6⁻/⁻) and in wild-type (WT) animals.

RESULTS

Two weeks after surgery, Mig-6⁻/⁻mice had bone erosion as well as greater fibrous tissue area and serum RANKL concentration than WT mice. Four weeks after surgery, Mig-6⁻/⁻mice had less cartilage and increased cell proliferation relative to contralateral control and WT knees. Increased apoptotic cells and growth outside the articulating region occurred in Mig-6⁻/⁻mice. Tibia trabecular bone mineral density (BMD) and the number of trabeculae were lower in surgically treated knees relative to the respective control knees for both groups. BMD, as well as trabecular thickness and number, were lower in surgically treated knees from Mig-6⁻/⁻mice relative to WT surgically treated knees. Phosphorylated EGFR staining in surgically treated knees decreased for WT mice and increased for Mig-6⁻/⁻mice. Fewer inflammatory cells were present in the knees of WT mice.

CONCLUSION

Mig-6⁻/⁻mice have rapid and increased joint damage after ligament and meniscal trauma. Mig-6 modification could lessen degenerative disease development after this type of injury.