[Pathological changes of ultrastructures of oligodendrocytes following ischemic brain injury in 3-day-old premature rats].
OBJECTIVE
The oligodendrocyte is a key cell component of brain white matter. It is important to understand the pathology of oligodendrocyte injury to better understand the mechanisms leading to white matter injury in the premature brain. This study investigated the ultrastructural changes of oligodendrocytes following ischemic brain injury in 3-day-old premature rats.


METHODS
One hundred and eight 3-day-old Sprague-Dawley (SD) premature rats were randomly divided into experimental and control groups. Ischemic brain injury was induced by ligation of bilateral carotid arteries. The control group underwent a sham operation without carotid ligation. At 6, 12 and 24 hrs after operation, 8 rats were randomly selected from surviving rats of both groups. The brain tissues were sampled for transmission electron microscopy.


RESULTS
The survival rate of the control and the experimental groups was 100% and 51%, respectively. At 6 hrs of ischemia, swollen oligodendrocytes were observed in all 8 experimental rats. Organelles, including mitochondria, endoplasmic reticulum, and the Golgi apparatus, were swollen and the number of organelles in all 8 rats decreased noticeably compared with control animals. The swollen and decreased mitochondria were the most frequent change. Vacuolated mitochondria were seen in one rat and degranulated rough endoplasmic reticulum was seen in another rat from the experimental group. At 12 hrs of ischemia, oligodendrocyte swelling and decreased number of organelles became more severe in the experimental group. The oligodendrocyte nuclear chromatin was unevenly distributed and karyopycnosis began to appear in experimental animals. At 24 hrs of ischemia, oligodendrocytes generally displayed karyopycnosis and karyolysis, and organelles disappeared in experimental animals.


CONCLUSIONS
Progressive oligodendrocyte damage occurred in 3-day-old premature rats subjected to permanent cerebral ischemia. The organelles injury was observed at 6 hrs of ischemia and evolved to oligodendrocyte apoptosis at 24 hrs of ischemia.
Hu
Lan
L
Department of Neonatology, Children's Hospital, Fudan University, Shanghai 200032, China.
Chen
Chao
C
D000818:Animals; D000831:Animals, Newborn; D001835:Body Weight; D002545:Brain Ischemia / Q000473:pathology*; D005260:Female; D008297:Male; D008855:Microscopy, Electron, Scanning; D009836:Oligodendroglia / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley