Effect of cytosine arabinofuranoside (AraC) on reactive gliosis in vivo. An immunohistochemical and morphometric study

Glial reactivity is believed to contribute to the lack of functional recovery after injury to the mammalian central nervous system. The role of glial mitosis in the progression of events associated with reactive gliosis has received little attention. In the present study, the expression of reactive gliosis distal to the site of crush in rat optic nerves was assessed in the presence and absence of a chronically administered mitotic inhibitor, cytosine arabinofuranoside (AraC). Right optic nerves were crushed and animals sacrificed 1, 2 or 3 weeks later. Parameters assessed were (1) glial hypertrophy, (2) degradation of myelin sheaths and (3) ability of tissue to stain with antisera raised against glial filament protein (GFA), actin and vimentin. In saline treated animals, greater than 90% of the myelin sheaths distal to the site of axonal injury had degraded within 7 days post-operatively. Glial hypertrophy was evident by the second week after after crush and increased progressively. The number of GFA-positive profiles (i.e., cells) increased between 1 and 3 weeks postoperatively. Vimentin staining increased 4-fold between 1 and 2 weeks after injury and subsequently showed no change. Actin staining rose 3-fold between 1 and 2 weeks after injury, but decreased by the third postoperative week. In AraC treated animals, almost 50% of the myelin sheaths distal to the injury site were preserved a week after surgery. A delay in myelin degradation continued until the second postoperative week. Glial hypertrophy was evident at the 2 and 3 week time points. However, the extent of hypertrophy was substantially lower in drug (vs saline) treated animals. Vimentin staining never rose above minimal levels in AraC treated animals. Actin staining in AraC rats at 2 weeks postoperatively was equivalent to that in saline injected animals, but in contrast to the results in the latter group, increased (3-fold) between 2 and 3 weeks after crush. Results indicate a delay in the expression of reactive gliosis with chronic administration of AraC. It is proposed that this might be due to a delay in the appearance of ‘signals’ (e.g., myelin debris) which initiate the process of reactive gliosis.

胶质细胞反应性被认为是哺乳动物中枢神经系统损伤后功能恢复缺失的原因之一。胶质细胞有丝分裂在与反应性胶质增生相关事件进展中的作用很少受到关注。在本研究中，在有和没有长期施用有丝分裂抑制剂阿糖胞苷（AraC）的情况下，评估了大鼠视神经挤压部位远端反应性胶质增生的表达。右侧视神经被挤压，动物在1、2或3周后处死。评估的参数包括：（1）胶质细胞肥大，（2）髓鞘降解，（3）组织与抗胶质纤维酸性蛋白（GFA）、肌动蛋白和波形蛋白的抗血清染色的能力。 在生理盐水处理的动物中，轴突损伤部位远端超过90%的髓鞘在术后7天内降解。挤压后第二周胶质细胞肥大明显，并逐渐加重。术后1到3周，GFA阳性轮廓（即细胞）数量增加。损伤后1到2周，波形蛋白染色增加4倍，随后无变化。损伤后1到2周，肌动蛋白染色增加3倍，但在术后第三周下降。 在AraC处理的动物中，术后一周，损伤部位远端近50%的髓鞘得以保留。髓鞘降解的延迟一直持续到术后第二周。在2周和3周时，胶质细胞肥大明显。然而，药物（与生理盐水相比）处理的动物中肥大程度明显较低。在AraC处理的动物中，波形蛋白染色从未超过最低水平。术后2周，AraC处理大鼠的肌动蛋白染色与生理盐水注射动物相同，但与后者不同的是，挤压后2到3周之间增加了（3倍）。 结果表明，长期施用AraC会延迟反应性胶质增生的表达。据推测，这可能是由于引发反应性胶质增生过程的“信号”（例如髓鞘碎片）出现延迟所致。