Barker R A, Dunnett S B, Faissner A, Fawcett J W
MRC Cambridge Centre for Brain Repair, University of Cambridge, United Kingdom.
Exp Neurol. 1996 Sep;141(1):79-93. doi: 10.1006/exnr.1996.0141.
Grafts of embryonic ventral mesencephalic tissue placed in the striatum of 6-hydroxydopamine-lesioned rats survive, and make and receive connections to and from the host brain. The dopaminergic neurons of the graft can grow processes into the host brain, and thereby alleviate many of the behavioral deficits of this form of experimental Parkinson's disease. However, when examined some weeks after implantation, grafted substantia nigra only contains about 5% of the expected complement of dopaminergic neurons. We have examined the time course of loss of grafted neurons. We find that the majority die during the first 7 days after transplantation. However, we have shown previously that three-dimensional cultures with the same dimensions as a graft, made of identical cell suspensions, have much better dopaminergic neuronal survival. There must, therefore, be features in the environment surrounding a graft that are toxic to dopaminergic neurons. A limiting factor in the efficacy of dopaminergic grafts is the small distance over which the neurons are able to grow neurites and form connections in the host brain. We find that the growth of neurites from dopaminergic neurons into the host striatum occurs in two phases. Neurites reach their maximum length within 7 days of transplantation, and this is followed by a much slower process of branch and terminal formation. Since axon growth in the adult brain may be inhibited by a number of factors associated with reactive gliosis, we have immunostained various ages of graft for vimentin, tenascin, chondroitin sulfate proteoglycan (CS-PG) using the CS56 antibody, the DSD-1 proteoglycan, and microglia using the OX-42 antibody. We have compared this staining with that surrounding a simple stab wound. Vimentin staining was initially seen in the graft and in astrocytes immediately surrounding it. By 7 weeks staining was restricted to a ring of astrocytes surrounding the graft. Tenascin, DSD-1, and CS-PG were initially seen in and around the grafts. By 7 weeks they had disappeared from grafts, but CS-PG and tenascin persisted in small amounts around stab wounds. In general, immunostaining of these molecules persisted longer around a stab lesion than around a graft. There was also an intense local microglial reaction surrounding both grafts and stab wounds which had largely resolved by 7 weeks.
将胚胎腹侧中脑组织移植到经6-羟基多巴胺损伤的大鼠纹状体中后，移植组织能够存活，并与宿主脑建立双向连接。移植组织中的多巴胺能神经元可以长出神经突进入宿主脑，从而缓解这种实验性帕金森病形式的许多行为缺陷。然而，在植入几周后检查时，移植的黑质中仅含有约5%预期数量的多巴胺能神经元。我们研究了移植神经元损失的时间进程。我们发现，大多数神经元在移植后的头7天内死亡。然而，我们之前已经表明，由相同细胞悬液制成的、与移植组织尺寸相同的三维培养物中，多巴胺能神经元的存活率要高得多。因此，移植组织周围的环境中一定存在对多巴胺能神经元有毒性的特征。多巴胺能移植组织功效的一个限制因素是神经元能够在宿主脑中生长神经突并形成连接的距离较短。我们发现，多巴胺能神经元的神经突向宿主纹状体的生长分为两个阶段。神经突在移植后7天内达到最大长度，随后是一个慢得多的分支和终末形成过程。由于成体脑中的轴突生长可能受到与反应性胶质增生相关的多种因素的抑制，我们使用CS56抗体对不同年龄的移植组织进行波形蛋白、腱生蛋白、硫酸软骨素蛋白聚糖（CS-PG）免疫染色，使用OX-42抗体对DSD-1蛋白聚糖和小胶质细胞进行免疫染色。我们将这种染色与简单刺伤周围的染色进行了比较。波形蛋白染色最初出现在移植组织及其紧邻的星形胶质细胞中。到7周时，染色局限于移植组织周围的一层星形胶质细胞。腱生蛋白、DSD-1和CS-PG最初出现在移植组织内部及其周围。到7周时，它们已从移植组织中消失，但CS-PG和腱生蛋白在刺伤周围仍有少量残留。一般来说，这些分子的免疫染色在刺伤周围比在移植组织周围持续的时间更长。移植组织和刺伤周围还存在强烈的局部小胶质细胞反应，到7周时这种反应已基本消退。
