OBJECTIVESTo investigate the expression of macrophage migration inhibitory factor (MIF) mRNA in Schwann cells after peripheral nerve injury and roles of Schwann cells and MIF in macrophages activation and nerve regeneration.

METHODSFifty SD rats were divided into 10 groups. One group served as normal control. The rest were anesthetized with 3% sodium pentobarbital (30 - 60 mg/kg, i.p) and sciatic nerves were transected distal to the obturator tendon respectively 1 h, 12 h, 1 d, 3 d, 7 d, 10 d, 14 d, 17 d and 21 d before being killed. Sciatic nerves were resected and connective tissues excised. Schwann cells were obtained by digesting the nerve tissues with trypsin and collagenase. RNA was isolated and reverse-transcription-polymerase chain reaction (RT-PCR) was carried out. cDNA was analyzed by automatic system and the parameters were assessed to define the status of MIF mRNA expression in different groups.

RESULTSThe level of MIF mRNA started to increase 12 h after the nerve transection. The level remained high from day 7 up to 10 after the injury. During the period from days 10 to 21, MIF mRNA decreased slowly to the pre-transection level.

CONCLUSIONAfter peripheral nerve injury, Schwann cells can secrete MIF which may play a pivotal role as an immunomodulatory cytokine in macrophage activation and inflammatory reaction.