Photoacoustic Imaging in Evaluating Early Intestinal Ischemia and Reperfusion Injury with Rat Models

Abstract

Purpose: It is still a challenge to distinguish whether the damaged intestine is viable or not in the treatment of acute mesenteric ischemia. In this study, photoacoustic imaging (PAI) was used to observe the activity of intestinal tissue after ischemia and reperfusion injury in rats.Methods: With the approval of animal ethics committee our university, in vivo study was carried out. Forty male SD rats were randomly divided into four groups: sham operated (SO) group, 1 h ischemia group, 2 h ischemia group and ischemia-reperfusion (I/R) group. In the ischemia group, superior mesenteric artery (SMA) was isolated and clamped for 1 h (n = 10) and 2 h (n = 10), respectively. In I/R group, after ischemia for 1 hour, the clamp was removed and reperfused for 1 hour (n = 10). The same time interval of SMA was taken as SO group (n = 10). Immediately after the establishment of the animal model, PAI examination was performed. After PAI examination, the small intestine was collected for histopathology.Results: The PAI derived parameters of 2 h ischemia group were significantly different from those of SO group and I/R group (P < 0.05). The levels of Hb, HbR, map760 and map 840 were increased in different degrees in ischemia group, especially in 2 h ischemia group (compared with SO group, P < 0.01). With the prolongation of ischemia time, the injury was aggravated. In immunohistochemistry, compared with SO group, BAX increased significantly in 2 h ischemia group (P < 0.01). Similarly, Caspase-3 was significantly higher than the baseline level (P < 0.05). The level of HIF-1a increased in 2 h ischemia group and I/R group (P < 0.05). TUNEL staining showed that the number of apoptotic positive nuclei in 2 h ischemia group was significantly higher than that in SO group (P < 0.05). HE staining showed that ischemia for 2 hours was the most serious, with obvious mucosal damage, extensive epithelial injury and bleeding.Conclusions: PAI can be used as an effective tool to detect acute intestinal ischemia injury and quantitatively evaluate tissue viability.