Lafarga M, Andres M A, Calle E, Berciano M T
Departamento de Anatomía y Biología Celular, Facultad de Medicina, Santander, Spain.
Anat Embryol (Berl). 1998 Aug;198(2):111-22. doi: 10.1007/s004290050169.
The morphology, organization and expression of proliferating cell nuclear antigen (PCNA) and the cytoskeletal proteins vimentin and GFAP in immature Bergmann glial cells were studied after a developmental injury induced by a single dose of the cytotoxic agent methylazoxymethanol (MAM) administered on postnatal day 5. This drug, which produces cell death of cerebellar granule cell precursors, did not induce apoptosis in Bergmann glial cells, which are in a proliferative stage. After MAM treatment, PCNA staining showed a severe depletion of PCNA-positive granule cell precursors, whereas PCNA-positive Bergmann glial nuclei in the Purkinje cell layer were preserved. Moreover, the quantitative analysis revealed an increase in the density of both Purkinje cells and PCNA-positive Bergmann glial cells per mm of Purkinje cell layer in MAM-treated rats relative to age-matched controls, but the numerical ratio between these two cell populations remains invariable after MAM treatment. Vimentin and GFAP immunocytochemistry revealed a reinforcement of the Bergmann glial palisade with overexpression of both proteins and thicker immunoreactive glial processes in MAM-treated rats. At the ultrastructural level, Bergmann glial processes closely associated with dying cells in different stages of apoptosis were observed. Frequently, these processes enclosed dying cells in extracellular compartments. Furthermore, phagosomes containing apoptotic bodies were found in Bergmann fibers of MAM-treated rats. These data indicate that the cell death of granule cell precursors triggers a reactive response in immature Bergmann glia. We suggest that this response reflects the plasticity of Bergmann glia to control the neuronal microenvironment in the maturing molecular layer, protecting healthy cells against the potentially harmful contents of dying cells. In situ labeling of cell death with the TUNEL method revealed that the cell death of granule cell precursors is of the apoptotic type. The participation of ameboid microglial cells in the phagocytosis of apoptotic cells was shown with tomato lectin histochemistry and ultrastructural analysis. Moreover, the presence of mitosis in this microglial population demonstrates its proliferative activity in regions of extensive cell death.
在出生后第5天给予单剂量细胞毒性药物甲基偶氮甲醇（MAM）诱导发育性损伤后，研究了未成熟伯格曼胶质细胞中增殖细胞核抗原（PCNA）以及细胞骨架蛋白波形蛋白和胶质纤维酸性蛋白（GFAP）的形态、组织和表达。这种药物可导致小脑颗粒细胞前体细胞死亡，但不会诱导处于增殖阶段的伯格曼胶质细胞凋亡。MAM处理后，PCNA染色显示PCNA阳性的颗粒细胞前体严重减少，而浦肯野细胞层中PCNA阳性的伯格曼胶质细胞核得以保留。此外，定量分析显示，与年龄匹配的对照组相比，MAM处理的大鼠每毫米浦肯野细胞层中浦肯野细胞和PCNA阳性伯格曼胶质细胞的密度增加，但MAM处理后这两种细胞群体之间的数量比保持不变。波形蛋白和GFAP免疫细胞化学显示，MAM处理的大鼠中伯格曼胶质栅栏增强，两种蛋白均过度表达，免疫反应性胶质突起更粗。在超微结构水平上，观察到伯格曼胶质突起与处于不同凋亡阶段的死亡细胞紧密相关。这些突起经常在细胞外区域包裹着死亡细胞。此外，在MAM处理的大鼠的伯格曼纤维中发现了含有凋亡小体的吞噬体。这些数据表明，颗粒细胞前体的细胞死亡会触发未成熟伯格曼胶质细胞的反应性反应。我们认为，这种反应反映了伯格曼胶质细胞在控制成熟分子层中神经元微环境方面的可塑性，保护健康细胞免受死亡细胞潜在有害内容物的影响。用TUNEL法对细胞死亡进行原位标记显示，颗粒细胞前体的细胞死亡为凋亡类型。用番茄凝集素组织化学和超微结构分析表明，阿米巴样小胶质细胞参与了凋亡细胞的吞噬作用。此外，该小胶质细胞群体中存在有丝分裂，表明其在广泛细胞死亡区域具有增殖活性。
