Experimental Study On The Role Of Schwann Cells In Macrophages Activation After Peripheral Nerve Injury

Objective:To study the role of Schwann cells in macrophages activation after peripheral nerve injury. Methods:(Din the study,we employed the secretion of IL-lp as an activation index of macrophages. Two kinds of infant rats' Schwann cells(which had come from intact and injured nerves respectively) conditioned media were treated on purified cultured macrophages for 8 hours,then measured the IL-lp contents in the cultured macrophages suspension media by an enzyme-linked immunoadsordent assay (ELISA). (2)Two kinds of infant rats' Schwann cells(which had come from intact and injured nerves respectively) were cultured in 10% BCS DMEM/F12 medium for 72 hours. Then the level of macrophage migration inhibitory factor (MIF) in the conditioned media was determined by ELISA. As control,the MIF level was also determined in the 10% BCS DMEM/F12 medium without any cell. Fifty SD rats were divided into 10 groups. One group served as normal control. The rest were anesthetized with 3% sodium pentobarbital (30-60mg/kg,i.p.) and sciatic nerves were transected just distal to the obturator tendon respectively Ih,12h,Id,3d,Id,lOd,14d,17d and 2Id just before killed. Sciatic nerves were resected and connective tissues excised. Schwann cells were gotten by digesting the nerve tissues with trypsin and collagenase. The RNA was isolated and relative quantitative reverse-transcription-polymerase chain reaction (RT-PCR) was carried out. The cDNA was analyzed by automatic system and the parameters were assessed to define the status of MIF mRNA expression in different groups. Results:The conditioned media of Schwann cells comefrom injured nerves enhanced IL-lp secreting in macrophages more obviously than that come from intact nerves. The concentration of MIF in the conditioned medium of Schwann cells come from injured nerves was higher significantly than that of control samples (P<0.05),while the concentration of MIF in the conditioned medium of Schwann cells come from intact nerves was not elevated. (3)The level of MIF mRNA started to increase 12h 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 slowly decreased to the pre-transection level. Conclusion:After peripheral nerve injury,Schwann cells can secrete MIF which may play a pivotal role as an immunomodulatory cytokine for macrophage activation and inflammatory reactions.