Influence of ischaemia–reperfusion injury on CD44 expression in rat small intestine

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Abstract
Background: CD44 is an adhesion molecule expressed by neutrophils and lymphocytes which is involved in cell–cell and cell–matrix binding. In this study, the effect of ischaemia–reperfusion injury on CD44 messenger RNA (mRNA) and cell surface immunohistochemical expression of CD44 in the rat small intestine was evaluated. Methods: Wistar rats (n = 16) were randomized to either serve as controls (sham surgery) or to be subjected to a standardized ischaemia–reperfusion injury (suprarenal aorta occluded for 1 h followed by 1 h of reperfusion). Standardized segments of jejunum were harvested after ischaemia–reperfusion injury (ischaemic and reperfused samples) to measure the mucosal protein and DNA content, mRNA expression of CD44 and the immunohistochemical expression of CD44. Results: Reperfusion significantly damaged the jejunal mucosa, e.g. mucosal protein content was lower after reperfusion compared with that in the control group (z = −2·31, P = 0·02) and the ischaemic samples (z = −2·52, P = 0·01). The expression of cell surface CD44 protein was also significantly decreased after ischaemic injury (z = −1·99, P = 0·04); this coincided with a decrease in the amount of cytoplasmic CD44 mRNA within isolated enterocytes (z = −2·31, P = 0·02). Conclusion: Ischaemia–reperfusion injury decreases the expression of CD44 within the jejunal mucosa. This may contribute to the failure of the gut barrier after such injury.