Demyelination initiated by oligodendrocyte apoptosis through enhancing endoplasmic reticulum-mitochondria interactions and Id2 expression after compressed spinal cord injury in rats.
BACKGROUND
Demyelination is one of the most important pathological factors of spinal cord injury. Oligodendrocyte apoptosis is involved in triggering demyelination. However, fewer reports on pathological changes and mechanism of demyelination have been presented from compressed spinal cord injury (CSCI). The relative effect of oligodendrocyte apoptosis on CSCI-induced demyelination and the mechanism of apoptosis remain unclear.


OBJECTIVE
In this study, a custom-designed model of CSCI was used to determine whether or not demyelination and oligodendrocyte apoptosis occur after CSCI. The pathological changes in axonal myelinated fibers were investigated by osmic acid staining and transmission electron microscopy. Myelin basic protein (MBP), which is used in myelin formation in the central nervous system, was detected by immunofluorescence and Western blot assays. Oligodendrocyte apoptosis was revealed by in situ terminal-deoxytransferase-mediated dUTP nick-end labeling. To analyze the mechanism of oligodendrocyte apoptosis, we detected caspase-12 [a representative of endoplasmic reticulum (ER) stress], cytochrome c (an apoptotic factor and hallmark of mitochondria), and inhibitor of DNA binding 2 (Id2, an oligodendrocyte lineage gene) by immunofluorescence and Western blot assays.


RESULTS
The custom-designed model of CSCI was successfully established. The rats were spastic, paralyzed, and incontinent. The Basso, Beattie, and Bresnahan (BBB) locomotor rating scale scores were decreased as time passed. The compressed spinal cord slices were ischemic. Myelin sheaths became swollen and degenerative; these sheaths were broken down as time passed after CSCI. MBP expression was downregulated after CSCI and consistent with the degree of demyelination. Oligodendrocyte apoptosis occurred at 1 day after CSCI and increased as caspase-12 expression was enhanced and cytochrome c was released. Id2 was distributed widely in the white matter. Id2 expression increased with time after CSCI.


CONCLUSIONS
Demyelination occurred after CSCI and might be partly caused by oligodendrocyte apoptosis, which was positively correlated with ER-mitochondria interactions and enhanced Id2 expression after CSCI in rats.
Traditional Chinese Medicine College, Chongqing Medical University, Chongqing, China; Institute of Neuroscience, Chongqing Medical University, Chongqing, China.
Si-Qin
SQ
Huang
Cheng-Lin
CL
Tang
Shan-Quan
SQ
Sun
Cheng
C
Yang
Jin
J
Xu
Ke-Jian
KJ
Wang
Wei-Tian
WT
Lu
Juan
J
Huang
Fei
F
Zhuo
Guo-Ping
GP
Qiu
Xiu-Yu
XY
Wu
Wei
W
Qi
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001369:Axons / Q000502:physiology / Q000648:ultrastructure; D015153:Blotting, Western; D053454:Caspase 12 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003711:Demyelinating Diseases / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D004721:Endoplasmic Reticulum / Q000502:physiology / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D020287:In Situ Nick-End Labeling; D051797:Inhibitor of Differentiation Protein 2 / Q000378:metabolism*; D007511:Ischemia / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D008159:Lumbar Vertebrae; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000502:physiology / Q000648:ultrastructure; D004676:Myelin Basic Protein / Q000378:metabolism; D009836:Oligodendroglia / Q000502:physiology* / Q000648:ultrastructure; D015388:Organelles / Q000502:physiology* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013117:Spinal Cord Compression / Q000150:complications / Q000473:pathology / Q000503:physiopathology*
C497451:Id2 protein, rat; D051797:Inhibitor of Differentiation Protein 2; C436006:Mbp protein, rat; D004676:Myelin Basic Protein; D045304:Cytochromes c; C506443:Casp12 protein, rat; D053454:Caspase 12
Compressed spinal cord injury; Demyelination; Oligodendrocyte apoptosis