The Apoptosis and Expression of p53, Bcl-2 in Graded Contusion Injury of Rat Spinal Cord

ABSTRACT

OBJECTIVE: This study is designed to investigate how apoptosis is presented and how the genes of p53 and bcl-2 are expressed depending on graded injury in experimental spinal cord injury. METHODS: Experimental spinal cord injury was made on rats with weight drop method. Two different amounts of impact were applied on rat spinal cord. Rats were categorized into three groups (control; five rats, mild injury; five rats, severe injury; five rats). Fourty eight hours following cord injury, cord specimen was harvested from injury epicenter. TUNEL staining was done for apoptotic detection and immunohistochemical staining for p53 and bcl-2 expression. Positively stained cells were counted and mean values were compared among three groups. RESULTS: TUNEL positive cells increased depending on injury severity(p=0.027). The p53 positive cells increased in both injury groups compared to control group(p=0.001). Bcl-2 positive cells decreased as injury amount increased(p=0.002). The p53 expression increased in proportion to TUNEL staining in correlation curve in white matter(correlation coefficient, 0.387). The bcl-2 expression was inversely proportional to TUNEL staining and steeper decrease was found in gray matter than in white matter (correlation coefficient, -0.875). CONCLUSION: Apoptosis increases as the injury grading elevated within 20gm-cm of impact. The p53 seems to promote apoptosis in white matter, but do not show proportional relationship with injury amount. Bcl-2 appeared to be protective to cell death due to apoptosis.