Expression of Intermediate Filament Proteins in Rat Brain after Cryoinjury

No, Kyu Tae; Hwang, Kyu Geun; Yoo, Ki Soo

Abstract

PURPOSE: Traumatic brain injury is a multifaceted injury that involves direct mechanical damage, intraparenchymal and subarachnoid hemorrhage, breakdown of the blood-brain barrier, excitotoxicity, and ischemia. Even though much investigations were performed, acceptable mechanical informations were rare. The aim of this study was to reveal the expression pattern of intermediate filament proteins associated with gliotic scars in cerebral cortex of rats after cryoinjury.
METHODS
A total of 18 male Sprague-Dawley rats weighing 300 g, 2 months old, were used throughout the experiments. To injure the brain, rats were anesthetized for surgery with 3.5% chloral hydrate(1 mL/100 g, intraperitoneally); the frontal bones were exposed by elevating the skin; and craniectomies were performed adjacent to the central suture, midway between lambda and bregma. A cryoinjury was then created by applying a cold probe(3-mm-diameter steel rod chilled in liquid nitrogen) to the left frontal cortex(ipsilateral cortex) for 1 min. Rats were sacrificed at 1, 4, 7 and 14 days postsurgery(n=3, per time point), and three rats were sacrificed as normal controls. Serial brain cryosections were made by cryostat. For immunohistochemistry, brain tissue sections were allowed to react with mouse anti-rat GFAP antibody(1:200), mouse anti-rat vimentin antibody(1: 200), and mouse anti-rat nestin antibody(1:200).
RESULTS
Reactive astrocytes expressing GFAP, vimentin and nestin appeared for the first time at 6 hours after cryoinjury. Proliferation of GFAP and nestin positive cells started at 1 day after cryoinjury, reached its maximum on day 4, and returned to normal level after the 7th post-injured day. Proliferation of vimentin positive cells started at 1 day after cryoinjury, reached its maximum on day 4, and returned to normal level after the 14th post-injured day. Characteristic morphological changes in reactive astrocytes were seen at 4 days after cryoinjury.
CONCLUSION
The above results suggest that GFAP, vimentin and nestin positive cells attend in the formation of gliotic scars.