Expression of integrinα5β1, focal adhesion kinase and integrin-linked kinase in rat condylar cartilage during mandibular lateral displacement

Integrins are cell-surface mechanochemical sensors and transducers involved in various cellular processes in combination with extracellular ligands. The aim of this study was to investigate the effect of mechanical stress on the expression of integrinα5β1 and its downstream kinases, focal adhesion kinase (FAK) and integrin-linked kinase (ILK), in condylar cartilage during mandible lateral shift in young rats. Sixty 4-week-old male Wistar rats were divided at random into five control groups and five experimental groups. All rats in the experimental groups were fitted with a resin plate to functionally displace the mandible 2 mm to the left (ipsilateral side). The rats were killed 1, 3, 7, 14 and 28 days after attachment of the appliance. Serial 6-μm sagittal sections were cut through the condylar head and processed for immunostaining of integrinα5β1, FAK and ILK. The results were quantified using an image analysing system. Integrinα5β1 expression in the superior–posterior region of the condylar cartilage on the ipsilateral side increased from 3 to 14 days compared with the contralateral side, with an intermediate level of expression in the control groups. Expression of FAK and ILK was similar to integrinα5β1 expression, and they were also upregulated on the ipsilateral side compared with the contralateral side at the early stages of the experiment. The different mechanical loading on the two sides of the condylar cartilage led to different expression patterns of integrinα5β1, FAK and ILK, which may correlate with the different morphological and histological changes seen between sides during mandibular lateral shift.