RESEARCH ARTICLE Focal Experimental Injury Leads to Widespread Gene Expression and Histologic

It is not known how extensively a localised flexor tendon injury affects the entire tendon. This study examined the extent of and relationship between histopathologic and gene ex-pression changes in equine superficial digital flexor tendon after a surgical injury. One fore-limb tendon was hemi-transected in six horses, and in three other horses, one tendon underwent a sham operation. After euthanasia at six weeks, transected and control (sham and non-operated contralateral) tendons were regionally sampled (medial and lateral halves each divided into six 3cm regions) for histologic (scoring and immunohistochemistry) and gene expression (real time PCR) analysis of extracellular matrix changes. The histopa-thology score was significantly higher in transected tendons compared to control tendons in all regions except for the most distal (P 0.03) with no differences between overstressed (medial) and stress-deprived (lateral) tendon halves. Proteoglycan scores were increased by transection in all but the most proximal region (P< 0.02), with increased immunostaining for aggrecan, biglycan and versican. After correcting for location within the tendon, gene ex-pression for aggrecan, versican, biglycan, lumican, collagen types I, II and III,MMP14 an