Treatment of the chronic inflammation in peripheral target tissue improves the crushed nerve recovery in the rat: histopathological assessment of the nerve recovery

An experimental study was performed to investigate the influence of subsidence of chronic inflammation in peripheral target tissue on the recovery of crushed nerve. Seventy-eight male Wistar rats weighing 300-370 g were used. The sciatic nerve was operatively crushed unilaterally with an aneurysm clip (250 gf) applied for 5 min. Chronic inflammation, localized to the ankle, was induced by intra-articular injection of complete Freund's adjuvant 1 week preoperatively. Prednisolone farnesylate (PNF-21) 1.4% gel was applied on the ankle as an anti-inflammatory agent for consecutive days after the operation. The Animals were divided into five groups as follows: crush injury with ipsilateral arthritis (CIA); crush injury with ipsilateral arthritis and PNF-21 gel applied on the ipsilateral ankle (CIA + IPNF); crush injury with ipsilateral arthritis and PNF-21 gel applied on the contralateral ankle (CIA + CPNF); crush injury with contralateral arthritis (CCA); crush injury without arthritis (C). Specimens for histopathological examination were taken from the nerve at a site 5 mm distal to the crush lesion at 4 weeks postoperatively. The average axon diameter was significantly larger in the CIA + IPNF group than in the CIA group (p < 0.01). No significant difference was observed between the CIA + CPNF group and the CIA group. In conclusion, chronic inflammation in peripheral target tissue suppresses recovery of the crushed nerve, and subsidence of this chronic inflammation improves this suppression histopathologically.