Differential scanning calorimetric studies of superficial digital flexor tendon degeneration in the horse

Abstract
Differential scanning calorimetry (DSC) of equine superficial digital flexor tendons revealed the presence of a small exothermic peak at 23°C of unknown origin, and a large endothermic peak at 70°C due to denaturation of cross‐linked collagen fibres. In the central degenerated core of damaged tendons the denaturation temperature remained at 70°C but the enthalpy decreased in relation to the extent of degeneration of the tendon. We suggest that this reduction in enthalpy is due to depolymerisation and denaturation of the collagen fibres. This contention is supported by the observed increased activity of the degradative enzyme cathepsin B secreted by the fibroblasts. DSC analysis of cultured porcine tendon fibroblasts revealed a multicomponent endotherm, denaturation beginning at 46°C, a temperature capable of being achieved within the tendon during intensive exercise. DSC clearly has considerable potential in complementing morphological and biochemical studies to determine the aetiology and progress of equine tendon degeneration.