Keirstead H S, Hughes H C, Blakemore W F
Department of Clinical Veterinary Medicine, University of Cambridge, Robinson Way, Cambridge, CB2 2PY , United Kingdom.
Exp Neurol. 1998 Jun;151(2):303-13. doi: 10.1006/exnr.1998.6806.
Strategies to increase the extent of axonal regeneration in the adult CNS must address an array of intrinsic and environmental factors which influence neuritic outgrowth. In order to develop an in vivo model of axonal regeneration in which potential therapies may be assessed, we have quantified growth cones within demyelinated regions in the dorsal funiculus of the spinal cord, following a discrete axotomy. Demyelinated lesions were produced by the intraspinal injection of galactocerebroside antibodies plus serum complement proteins. Axonal integrity was not compromised by the demyelination protocol. Axonal injury was induced at the caudal extent of the demyelinated region using a micromanipulator-controlled Scouten knife. The severity of axonal injury was varied in different animals at the time of surgery and was quantified 8 days later by counting degenerate axons in transverse 1-microm resin sections. Evidence of axonal regeneration within these animals was assessed by an electron microscopic analysis of growth cone frequency and position relative to the site of axotomy. Growth cones were identified within the region of demyelination only; no growth cones were identified within the dorsal column white matter adjacent to the demyelinated region, or rostral or caudal to the region of demyelination, or in animals with an injury but no demyelination. Quantification of growth cones within regions of demyelination indicated a strong linear relationship (P < 0.001) between the number of growth cones and the number of axons severed. These findings indicate that demyelination facilitates axonal regeneration in the adult rat CNS and illustrate a quantifiable method of assessing axonal regeneration.
提高成年中枢神经系统轴突再生程度的策略必须应对一系列影响神经突生长的内在和环境因素。为了建立一种可评估潜在治疗方法的轴突再生体内模型，我们在脊髓背索脱髓鞘区域进行离散轴突切断后，对生长锥进行了定量分析。通过脊髓内注射半乳糖脑苷脂抗体加血清补体蛋白来产生脱髓鞘病变。脱髓鞘方案并未损害轴突的完整性。使用显微操作器控制的斯考滕刀在脱髓鞘区域的尾端诱导轴突损伤。在手术时，不同动物的轴突损伤严重程度各不相同，并在8天后通过计数1微米厚的横向树脂切片中的变性轴突进行定量。通过对生长锥频率以及相对于轴突切断部位的位置进行电子显微镜分析，评估这些动物体内轴突再生的证据。仅在脱髓鞘区域内发现了生长锥；在与脱髓鞘区域相邻的背柱白质内、脱髓鞘区域的头端或尾端，或在有损伤但无脱髓鞘的动物中均未发现生长锥。对脱髓鞘区域内生长锥的定量分析表明，生长锥数量与切断的轴突数量之间存在很强的线性关系（P < 0.001）。这些发现表明，脱髓鞘促进成年大鼠中枢神经系统的轴突再生，并说明了一种评估轴突再生的可量化方法。
