Liu X, Yao D L, Bondy C A, Brenner M, Hudson L D, Zhou J, Webster H D
Laboratory of Experimental Neuropathology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Mol Cell Neurosci. 1994 Oct;5(5):418-30. doi: 10.1006/mcne.1994.1052.
To assess the distribution of insulin-like growth-factor-related proteins during autoimmune CNS demyelination and remyelination, experimental autoimmune encephalomyelitis was produced by injecting Lewis rats with an emulsion containing guinea pig spinal cord and complete Freund's adjuvant. Tail weakness appeared at 10-12 days and was followed by hind and forelimb weakness. Paraplegia and incontinence were observed in some animals. From 8-40 days postinoculation (dpi), spinal cord sections were used to correlate lesion location and severity with mRNA distributions of insulin-like growth factor I (IGF-I), IGF-binding protein 2 (IGFBP-2), IGF-I-receptor (IGFR-I), glial fibrillary acidic protein (GFAP), and myelin basic protein (MBP). These were determined semiquantitatively by in situ hybridization. Fourteen dpi, there were inflammatory infiltrates and demyelination in both white matter (WM) and grey matter (GM). IGF-I and GFAP mRNAs were increased in these lesions and transcripts encoding myelin basic protein (MBP) were greatly reduced. Large lesions with extensive demyelination were evident in both WM and GM when mRNA levels of GFAP and IGF-I peaked 26 dpi. MBP mRNA levels began increasing 21 dpi and peaked 26 dpi, when a few thin regenerating myelin sheaths were found morphologically. Astrocytes, identified by their morphology and GFAP immunoreactivity, expressed very low levels of IGFBP-2 mRNA and peptide in normal controls; their levels were significantly higher 14 dpi, peaked 26 dpi, and then gradually decreased. Some neurons, as well as oligodendroglia in areas undergoing remyelination, expressed IGFR-I. Although levels of IGF-I, IGFBP-2, and GFAP mRNAs were highest in lesion areas, levels were also elevated around lesions and in some normal-appearing areas of WM and GM 14-40 dpi. The gene expression of both IGF-I and IGFBP-2 by hypertrophic GFAP-positive astrocytes was demonstrated 14-40 dpi by combined in situ hybridization and immunocytochemistry as well as by double immunostaining. Coexpression of IGF-I and IGFBP-2 in the same astrocyte was a frequent finding. Relative increases in both IGF-I, GFAP, IGFBP-2, IGFR-I, and MBP mRNAs peaked at about the same time. This suggests that during lesion progression and recovery, astrocytic expression of IGF-I-related peptides may reduce immune-mediated myelin injury. We also suggest that astrocytic IGFBP-2 in lesions may help target IGF-I to IGFR-I-expressing oligodendrocytes and promote remyelination of demyelinated axons.
为评估胰岛素样生长因子相关蛋白在自身免疫性中枢神经系统脱髓鞘和再髓鞘化过程中的分布情况，通过给Lewis大鼠注射含有豚鼠脊髓和完全弗氏佐剂的乳剂来诱发实验性自身免疫性脑脊髓炎。在10 - 12天时出现尾部无力，随后出现后肢和前肢无力。部分动物出现截瘫和尿失禁。在接种后8 - 40天（dpi），使用脊髓切片将病变位置和严重程度与胰岛素样生长因子I（IGF - I）、IGF结合蛋白2（IGFBP - 2）、IGF - I受体（IGFR - I）、胶质纤维酸性蛋白（GFAP）和髓磷脂碱性蛋白（MBP）的mRNA分布进行关联。通过原位杂交对这些进行半定量测定。接种后14天，白质（WM）和灰质（GM）均出现炎性浸润和脱髓鞘。这些病变中IGF - I和GFAP mRNA增加，而编码髓磷脂碱性蛋白（MBP）的转录本大幅减少。当GFAP和IGF - I的mRNA水平在26 dpi达到峰值时，WM和GM中均出现伴有广泛脱髓鞘的大病变。MBP mRNA水平在21 dpi开始升高并在26 dpi达到峰值，此时在形态学上发现了一些薄的再生髓鞘。通过形态学和GFAP免疫反应性鉴定的星形胶质细胞在正常对照中表达非常低水平的IGFBP - 2 mRNA和肽；其水平在14 dpi时显著升高，在26 dpi达到峰值，然后逐渐下降。一些神经元以及正在进行再髓鞘化区域的少突胶质细胞表达IGFR - I。虽然IGF - I、IGFBP - 2和GFAP mRNA水平在病变区域最高，但在14 - 40 dpi时，病变周围以及WM和GM的一些外观正常区域的水平也有所升高。在14 - 40 dpi，通过联合原位杂交和免疫细胞化学以及双重免疫染色证明肥大的GFAP阳性星形胶质细胞同时表达IGF - I和IGFBP - 2。在同一星形胶质细胞中同时表达IGF - I和IGFBP - 2是常见现象。IGF - I、GFAP、IGFBP - 2、IGFR - I和MBP mRNA的相对增加在大约同一时间达到峰值。这表明在病变进展和恢复过程中，星形胶质细胞表达的IGF - I相关肽可能减少免疫介导的髓鞘损伤。我们还认为病变中的星形胶质细胞IGFBP - 2可能有助于将IGF - I靶向表达IGFR - I的少突胶质细胞，并促进脱髓鞘轴突的再髓鞘化。
