Integrin expression is upregulated during early healing in a canine intrasynovial flexor tendon repair and controlled passive motion model

To explore crucial early molecular events involved in contact healing of the intrasynovial flexor tendon, integrin expression was evaluated at the transcriptional and post-transcriptional levels during the first two weeks following injury, repair and controlled passive motion in a canine model, Specifically, immunohistochemical and reverse transcription polymerase chain reaction (RT-PCR) techniques were employed to evaluate expression of the fibronectin, vitronectin and endothelial cell binding integrin receptor subunits alpha 5, alpha v and alpha 6, along,vith the common beta 1 subunit, The two techniques revealed increasing expression of the four subunits over the two week post-repair period. Immunohistochemistry revealed that beta 1 and alpha 5 expression was concentrated in the epitenon layer near the repair site and interiorly within the wound area, while alpha 6 was associated with capillary-forming endothelial cells near the wound. RT-PCR and quantitation by NM image analysis demonstrated peak messenger RNA expression of beta 1 and alpha 5 at ten days post-repair and peak expression of alpha 6 and alpha v at 15 days. The results in this study correlate well with previous results demonstrating increased fibronectin deposition and angiogenesis during the same time period in a similar injury/repair model.