Cells communicate with extracellular matrix (ECM) through the some essential components of mechano-biological factors. Integrin and fibronectin are known as a connecting organizer between ECM and the cells. Moreover, these are also known as a sensor of mechanical cues. In this study, we focus the function of this sensor of mechanical cue to elucidate the mechanism of anterior cruciate ligaments.

All experiment used 10-week-old male Wistar rats after more than 2 weeks of acclimatization. Initially, 4 rats had their ACL transected, which were divided into 2 groups: ACL transection (ACL-T) groups and ACL transection and controlled abnormal tibial translation (CATT) groups. These rats were then used for a microarray analysis. Next, 40 rats were distributed across the 4 groups based on two factors for comparing controlled abnormal tibial translation and treadmill exercise (sedentary and exercise): ACL transection sedentary or exercise groups (ACLT-Sed or ACLT-Ex), or the controlled abnormal tibia translation sedentary or exercise groups (CATT-Sed or CATT-Ex). Contralateral knees (intact ACL [IN]) of ACLT-Sed rats were used as controls. These rats were used in RT-qPCR.

The relative expression of ACL remnants had no remarkable changes between groups. However, the relative mRNA expression of infra-patellar fat pad in the both CATT groups had an increasing trend compared to the both non-exercise group.

Integrin and fibronectin have a key role in ACL spontaneous healing as a sensor of mechanical cues. These protein works at the infra-patellar fad pad, not at ACL remnants. These results suggest that infra-patellar fad pad works mechanosensor in knee joint, and in detail, these functions may support by the integrin and fibronectin.