Anterior cruciate ligament (ACL)
rupture is a common
knee injury for athletes. Although surgical reconstruction is recommended for the treatment of ACL
ruptures, 100% functional recovery is unlikely. Therefore, the discovery of risk factors for ACL
ruptures may prevent injury. Several studies have reported an association between polymorphisms of the
collagen XII gene COL12A1 and ACL
rupture.
Collagen XII is highly expressed in tendons and ligaments and regulates tissue structure and mechanical property. Therefore, we hypothesized that
collagen XII deficiency may cause
ACL injury. To elucidate the influence of
collagen XII deficiency on ACL, we analyzed a mouse model deficient for Col12a1. Four- to 19-week-old male Col12a1-/- and wild-type control mice were used for gait analysis; histological and immunofluorescent analysis of
collagen XII, and real-time RT-PCR evaluation of Col12a1
mRNA expression. The Col12a1-/- mice showed an abnormal gait with an approximately 2.7-fold increase in step angle, suggesting altered step alignment. Col12a1-/- mice displayed 20-60% ACL discontinuities, but 0% discontinuity in the posterior cruciate ligament. No discontinuities in knee ligaments were found in wild-type mice.
Collagen XII
mRNA expression in the ACL tended to decrease with aging. Our study demonstrates for the first time that
collagen XII deficiency increases the risk of
ACL injury.