Lee D A, Zurawel R H, Windebank A J
Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA.
J Neurochem. 1995 Aug;65(2):564-8. doi: 10.1046/j.1471-4159.1995.65020564.x.
In the PNS, ciliary neurotrophic factor (CNTF) is found in significant amounts in the adult sciatic nerve, localized to myelin-related Schwann cells (SCs). Levels are undetectable in newborn but high in adult animals. After crush injury, CNTF production is reduced, recovering only as the nerve regenerates; if regeneration does not occur, CNTF levels remain low. We have examined the coupling of CNTF expression to myelination in vitro and in vivo to determine if axon-SC contact without myelination is sufficient to induce CNTF expression. Embryonic day 15 (E15) rat dorsal root ganglion (DRG) neuron and SCs were cocultured. CNTF was not detected in the DRGs either at E15 or after 2 days in vitro (div) by western blotting. However, after 10 div, CNTF could be identified and remained at constant levels up to 30 div. Depriving the cultures of ascorbic acid prevents myelination but not axon-SC contact. This did not affect CNTF protein production. Using reverse transcriptase-linked PCR (RT-PCR) techniques, no CNTF message was present in DRG from day 14 or 15 fetal rats; but by 6 days in culture, message was detected in both myelinating and nonmyelinating cultures. Isolated SC cultures, without axonal contact, failed to express CNTF protein; however, mRNA was detected by RT-PCR. Embryonic SC can be induced to synthesize CNTF in culture by axonal contact. Active myelination is not required.
在周围神经系统（PNS）中，成年坐骨神经中存在大量睫状神经营养因子（CNTF），定位于与髓鞘相关的施万细胞（SCs）。新生动物中检测不到其水平，但成年动物中含量很高。挤压损伤后，CNTF的产生减少，仅在神经再生时恢复；如果不发生再生，CNTF水平则保持较低。我们已经在体外和体内研究了CNTF表达与髓鞘形成的耦合，以确定无髓鞘形成的轴突与施万细胞接触是否足以诱导CNTF表达。将胚胎第15天（E15）的大鼠背根神经节（DRG）神经元与施万细胞共培养。通过蛋白质印迹法在E15时或体外培养2天后（div）在DRG中均未检测到CNTF。然而，培养10 div后，可以鉴定出CNTF，并且其水平在30 div时保持恒定。剥夺培养物中的抗坏血酸可阻止髓鞘形成，但不影响轴突与施万细胞的接触。这并不影响CNTF蛋白的产生。使用逆转录酶联PCR（RT-PCR）技术，在第14或15天的胎鼠DRG中未检测到CNTF信息；但培养6天后，在有髓鞘形成和无髓鞘形成的培养物中均检测到了信息。没有轴突接触的分离的施万细胞培养物未能表达CNTF蛋白；然而，通过RT-PCR检测到了mRNA。胚胎施万细胞在培养中可通过轴突接触被诱导合成CNTF。不需要活跃的髓鞘形成。
