Astrocyte reactivity in spinal cord and functional impairment after tendon injury in rats

Abstract

Astrocyte reactivity in the spinal cord may occur after peripheral neural damage. However, there is no data to report such reactivity after Achilles tendon injury. We investigate whether changes occur in the spinal cord, mechanical sensitivity and gait in two phases of repair after Achilles tendon injury. Wistar rats were divided into groups: control (CTRL, without rupture), 2 days post-injury (RUP2) and 21 days post-injury (RUP21). Functional and mechanical sensitivity tests were performed at 2 and 21 days post-injury (dpi). The spinal cords were processed, cryosectioned and activated astrocytes were immunostained by GFAP at 21 dpi. Astrocyte reactivity was observed in the L5 segment of the spinal cord with predominance in the white matter regions and decrease in the mechanical threshold of the ipsilateral paw only in RUP2. However, there was gait impairment in both RUP2 and RUP21. We conclude that during the acute phase of Achilles tendon repairment, there was astrocyte reactivity in the spinal cord and impairment of mechanical sensitivity and gait, whereas in the chronic phase only gait remains compromised.

Total rupture of Achilles tendon induces inflammatory response and glial activation on the spinal cord of mice

“…The tibia region of the right paw was manually trichotomized and a longitudinal skin incision (about 0.5 cm) was made to access the Achilles tendon. This step was followed by the complete transversal section of the tendon as previously described ( 12 ). The animals (n=6 per group) were separated into control group (CG), which was not submitted to the surgical procedure, and ruptured group (RG), which had the Achilles tendon transected at 0.5 cm from its calcaneal insertion.…”

“…Different studies show that localized pain and changes in gait pattern are symptoms commonly described in injured subjects ( 8 , 9 ). In fact, the biochemical and histological alterations in the area of the ruptured Achilles tendon are well documented, but there are few studies describing the impact of this injury on the central nervous system (CNS) ( 10 - 12 ).…”

“…Neuronal cells that process information from the Achilles tendon are localized in the lumbar intumescence of the L5 segment ( 18 ). Few studies have evaluated how the spinal cord responds to injury in the Achilles tendon ( 19 , 20 , 21 ). Furthermore, it remains unclear if Achilles tendon injuries are able to trigger an inflammatory response in the spinal cord of injured patients.…”

“…The Achilles tendon is connected to the gastrocnemius and soleus muscles (13), and under normal conditions, the tendon tissue is poorly innervated. In fact, anatomical and histological studies show that the tendon is located in an adjacent structure (paratenon) that forms nerve plexuses, from which small branches penetrate into the tendon sheath (epitenon) (12)(13)(14)(15)(16)(17). Notably, in pathological conditions there is intense nerve fiber growth (sensory and autonomic fibers) that inserts into collagen fibers.…”