Background: Gut mucosal homeostasis depends on a balance between cell proli
feration and cell death. After cutaneous burn injury, gut mucosal weight ha
s been shown to decrease. This decrease in weight was paradoxically associa
ted with an increase in gut proliferative factors. For mucosal weight to de
crease in the presence of increased proliferation, there must be an even gr
eater increase in cell death. We postulate that cutaneous burn injury cause
s an increase in gut epithelial cell death primarily by apoptosis.
Study Design: We produced a 30% full-thickness scald burn in the dorsum of
anesthetized mate C57BL6 mice and collected the proximal small bowel at 12,
24, 36, 48, and GO hours after injury. Sham burned animals served as contr
ols. Apoptosis and proliferation were measured by immunohistochemical assay
s (terminal deoxyuridine nick-end labeling for apoptosis and proliferative
cell nuclear antigen assay for proliferation). Apoptosis was also measured
by ELISA for cytoplasmic histone-associated DNA fragments. Mucosal height w
as determined on histologic sections. The two groups were compared at each
time point using Wilcoxon two-sample test and t-test with Bonferroni's corr
ection where appropriate.
Results: The percentage of apoptotic cells (number of cells stained by term
inal deoxyuridine nick-end labeling per 100 villus cells) was significantly
higher at 12, 24, and 48 hours after injury This increase was corroborated
by an increase in the ELISA at 12 hours. Proliferation as measured by immu
nostaining for proliferative cell nuclear antigen significantly increased a
t 12, 24, 48, and GO hours. Mucosal height as a gross measure of mucosal at
rophy was not different between the groups.
Conclusions: We have shown an increase in apoptosis coupled with an increas
e in proliferation after a burn injury. These results imply an increase in
cell turnover in the gut epithelial cells after a burn. Impaired bowel func
tion has been demonstrated repeatedly after burn injury, and this increase
in cell turnover may be related. (J Am Coll Surg 1999;188:10-16 (C) 1999 by
the American College of Surgeons).