Differential temporal expression of mRNAs for ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), interleukin-6 (IL-6), and their receptors (CNTFR alpha, LIFR beta, IL-6R alpha and gp130) in injured peripheral nerves.

The mRNA expression of the neuropoietic cytokines, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), interleukin-6 (IL-6), and their receptor components (CNTFRalpha, LIFRbeta, IL-6Ralpha and gp130) was examined in peripheral nerves after two different types of injury, crush and transection. The CNTF mRNA expression levels decreased after injury and remained low in the transected model, but recovered in 4 weeks in the crushed model. The LIF mRNA rapidly increased after damage and returned gradually to control levels. The IL-6 mRNA expression increased rapidly within 1 day after injury but dramatically decreased soon after. The CNTFRalpha mRNA levels gradually increased after nerve injury. LIFRbeta was expressed in the intact nerve and decreased slightly after injury. The IL-6Ralpha expression was observed faintly in the intact nerve and increased significantly soon after injury. There was also an increase in the expression of gp130. Although the temporal expression of these neuropoietic cytokines and receptors was extremely different, their pattern was similar between the crushed and transected models, except for CNTF. These results suggest that the expression of the ligands and receptors are differentially regulated after peripheral nerve injury, implying that each cytokine and signal transduction system has entirely distinctive functions in neuronal regeneration and repair.