Ruptura total do tendão de Aquiles induz resposta inflamatória e ativação glial na medula espinhal de camundongos

Abstract

Achilles tendon rupture is a common accident that affects both professional and recreational athletes. Acute and chronic pain are commonly seen in patients after rupture, usually associated with local inflammatory activation. The factors leading to hyperalgesia in symptomatic patients are poorly understood. Evidence suggests that Achilles tendon rupture is not restricted to tissue changes, but is able to evoke changes in the central nervous system (CNS). This study aimed to evaluate the impact of Achilles tendon rupture on the biochemical and histological profile in the spinal cord (L5) and on the nociceptive response in a murine model. The animals after Achilles tendon tenotomy surgery were divided into two groups: control (without rupture) and Rupture (tenotomized). Mechanical sensitivity test (von Frey) was assessed on the 7th and 14th day post-tenotomy (dpt). Glial reactivity was assessed by immunohistochemistry for microglia (IBA-1) and astrocytes (GFAP). Inflammatory activation was assessed by immunofluorescence for NOS-2 and COX2 at 7th and 14th dpt. We show, by the mechanical sensitivity test, an increase in the algesic response in the ipsilateral paw of the ruptured group on the 7th and 14th dpt when compared to the control group. This phenomenon was accompanied by hyperactivation of astrocytes and microglia in sensory processing areas of the L5 spinal cord, predominantly on the ipsilateral side to the tendon injury. We show inflammatory activation by expression of COX-2 and NOS-2, exclusively in the 14th dpt. These data were supported by biochemical findings that demonstrated significant nitrite levels increase in the lumbar spinal cord of animals submitted to Achilles tendon rupture at 7 and 14 dpt. The present study demonstrated for the first time that complete rupture of the Achilles tendon induces a neuroinflammatory response associated with glial activation in the spinal cord (L5) of mice.