Insulin-like growth factor I accelerates functional recovery from Achillestendon injury in a rat model

We studied the effects of insulin-like growth factor I on Achilles tendon h ealing in a rat model. Rats were randomized into groups of six each: sham s urgery, transection alone, and transection plus growth factor. Postoperativ ely, rats treated with growth factor had a significantly smaller maximum fu nctional deficit and a decreased time to functional recovery than rats in t he untreated groups. Biomechanical testing revealed no significant differen ces in the measured parameters between the treated and the untreated groups after transection. To study the mechanism of action, six additional animal s received an Achilles tendon injection of the inflammatory agent carrageen an alone and six received carrageenan plus growth factor. Rats treated with growth factor did not show the inflammation-induced functional deficit exp erienced by the control rats. Spectrometric myeloperoxidase assays on the r emaining eight rats after Achilles tendon transection demonstrated no signi ficant difference between the untreated and the growth factor-treated group s, indicating a mechanism other than neutrophil recruitment by which the gr owth factor limits inflammation. Histologic studies were performed on carra geenan-injected rats at postinjection day 2 and on surgically treated rats at postoperative day 15. No gross histologic differences were seen between untreated and growth factor-treated groups. This study demonstrated that vi a a possible antiinflammatory mechanism, insulin-like growth factor I reduc es maximum functional deficit and accelerates recovery after Achilles tendo n injury.