Integrin Expression is Upregulated During Early Healing in a Canine Intrasynovial Flexor Tendon Repair and Controlled Passive Motion Model

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Abstract
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 α5, αv and α6, along with the common β1 subunit. The two techniques revealed increasing expression of the four subunits over the two week post-repair period. Immunohistochemistry revealed that β1 and α5 expression was concentrated in the epitenon layer near the repair site and interiorly within the wound area, while α6 was associated with capillary-forming endothelial cells near the wound. RT-PCR and quantitation by NIH image analysis demonstrated peak messenger RNA expression of β1 and α5 at ten days post-repair and peak expression of α6 and av 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.