Rest is a common treatment for overuse injuries, but its effectiveness on gene expression has not been systematically evaluated
under controlled experimental conditions. We asked whether genes regulated in the supraspinatus tendon as a result of overuse
would return to normal levels after 2 or 4 weeks of rest. We used a rat model of tendon overuse that generates reproducible
changes in the histology, geometry, gene expression, and mechanical properties consistent with an overuse injury. Animals
were subjected to the overuse protocol for 2 or 4 weeks followed by either 2 or 4 weeks of rest. Microarray analysis was used
to measure global changes in gene expression after the overuse plus rest protocol. Genes upregulated as a result of the overuse
returned to near normal levels after rest in most animals. The biochemical composition of the tendon was similar to normal
after the imposed rest period, except for slightly lower collagen content. These results suggest as little as 2 weeks of rest
is often sufficient to recover from the molecular and biochemical effects of 2 and 4 weeks of overuse in this rat model.
One or more of the authors (SPL, LJS) have received funding from the National Institutes of Health, Wyeth Research, and the
National Science Foundation. Two of the authors (SAJ, JMA) are employed by Wyeth Research.
Each author certifies that his or her institution has approved the animal protocol for this investigation and that all investigations
were conducted in conformity with ethical principles of research.