Tessler A, Himes B T, Houle J, Reier P J
Department of Anatomy, Medical College of Pennsylvania, Philadelphia 19129.
J Comp Neurol. 1988 Apr 22;270(4):537-48. doi: 10.1002/cne.902700407.
Transplants of the embryonic rat spinal cord survive and differentiate in the spinal cords of adult and newborn host rats. Very little is known about the extent to which these homotopic transplants can provide an environment for regeneration of adult host axons that normally terminate in the spinal cord. We have used horseradish peroxidase injury filling and transganglionic transport methods to determine whether transected dorsal roots regenerate into fetal spinal cord tissue grafted into the spinal cords of adult rats. Additional transplants were examined for the presence of calcitonin gene-related peptide-like immunoreactivity, which in the normal dorsal horn is derived exclusively from primary afferent axons. Host animals had one side of the L4-5 spinal cord resected and replaced by a transplant of E14 or E15 spinal cord. Adjacent dorsal roots were sectioned and juxtaposed to the graft. The dorsal roots and their projections into the transplants were then labeled 2-9 months later. The tracing methods that used transport or diffusion of horseradish peroxidase demonstrated that severed host dorsal root axons had regenerated and grown into the transplants. In addition, some donor and host neurons had extended their axons into the periphery to at least the midthigh level as indicated by retrograde labeling following application of tracer to the sciatic nerve. Primary afferent axons immunoreactive for calcitonin gene-related peptide were among those that regenerated into transplants, and the projections shown by this immunocytochemical method exceeded those demonstrated by the horseradish peroxidase tracing techniques. Growth of the host dorsal roots into transplants indicates that fetal spinal cord tissue permits regeneration of adult axotomized neurons that would otherwise be aborted at the dorsal root/spinal cord junction. This transplantation model should therefore prove useful in studying the enhancement and specificity of the regrowth of axons that normally terminate in the spinal cord.
胚胎大鼠脊髓移植在成年和新生宿主大鼠的脊髓中能够存活并分化。对于这些同位移植能在多大程度上为正常终止于脊髓的成年宿主轴突再生提供环境，人们了解甚少。我们采用辣根过氧化物酶损伤填充和跨神经节运输方法，来确定横断的背根是否能再生进入移植到成年大鼠脊髓中的胎儿脊髓组织。还对其他移植组织进行了降钙素基因相关肽样免疫反应性检测，在正常背角中，这种免疫反应性仅来自初级传入轴突。宿主动物一侧的L4 - 5脊髓被切除，并用E14或E15脊髓移植替代。相邻的背根被切断并与移植物并列。然后在2 - 9个月后对背根及其向移植物中的投射进行标记。使用辣根过氧化物酶运输或扩散的追踪方法表明，切断的宿主背根轴突已经再生并长入移植物中。此外，一些供体和宿主神经元将其轴突延伸到了外周，至少达到了大腿中部水平，这是在将示踪剂应用于坐骨神经后通过逆行标记显示的。对降钙素基因相关肽呈免疫反应性的初级传入轴突是再生进入移植物的轴突之一，这种免疫细胞化学方法显示的投射超过了辣根过氧化物酶追踪技术所显示的。宿主背根向移植物的生长表明，胎儿脊髓组织允许成年轴突切断的神经元再生，否则这些神经元会在背根/脊髓交界处停止生长。因此，这个移植模型在研究正常终止于脊髓的轴突再生的增强和特异性方面应该会被证明是有用的。
