Ependymal cell proliferation and apoptosis following acute spinal cord injury in the adult rat

BACKGROUND: Studies have reported that spinal cord injury can induce the reactive proliferation of ependymal cells and secondarily cause the apoptosis of nerve cells. However, there is no generally accepted theory on the apoptotic characteristics of ependymal cells in the injured spinal cord.OBJECTIVE: To observe the reactive proliferation and apoptosis of ependymal cells in adult rats following acute spinal cord injury.DESIGN, TIME AND SETTING: A randomized control study based on neuropathology was performed in the Third Military Medical University of Chinese PLA between 2005 and 2007.MATERIALS: Forty healthy, adult, Wistar rats were included in the present study.METHODS: Moderate spinal cord injury was established in twenty rats using Feeney's method, while the remaining 20 rats served as controls and were only treated with laminectomy. All rats were injected intraperitoneally with 1.25 mL of BrdU solution (10 mg BrdU/mL saline) 3 times at 4 hours intervals during the 12 hours prior to sacrifice.MAIN OUTCOME MEASURES: Ependymal cell proliferation and apoptosis in the rat spinal cord were determined by BrdU and nestin immunofluorescence double-labeling, as well as the TUNEL method, at 1, 3, 7, and 14 days after operation.RESULTS: In the moderate spinal cord injury rats, nestin expression was observed in the cytoplasm of ependymal cells. One day immediately following surgery, ependymal cells were BrdU-labeled. The number of BrdU-positive cells increased at 3 days, reached a peak at 7 days, and gradually reduced thereafter. The ependyma developed ti'om a constitutive monolayer cells to a multi-layer cell complex. Some BrdU/Nestin double-positive ependymal cells migrated out from the ependyma. TUNEL-positive cells were also detected in the ependyma in the central region, as well as ischemic regions of the injured spinal cord. In addition, TUNEL-positive cells were visible in the ependyma. No TUNEL-positive ependymal cells were observed in the normal spinal cord.CONCLUSION: Proliferating ependymal cells induced apoptosis in the central and surrounding region following spinal cord injury.