MRI molecular imaging targeting P selectin in severity grading of acute pancreatitis in rats

Abstract

Objective To investigate the application of MRI targeting contrast agent (P-Gd-Probe) for P selectin in evaluating the severity grades of acute pancreatitis(AP). Methods L-arginine solution (100mg/100kg) were intraperitoneally injected for 3 times once an hour to establish AP model in SD rats. Control group was injected with normal saline in a equal volume. All rats were divided into acute edematous pancreatitis (AEP) group (6 h and 12 h after model establishment)and acute necrotizing pancreatitis (ANP) group (24 h and 48 h after model establishment) based on the pathology. The rats were examined by T1WI plain and enhanced scanning at 6 h, 12 h, 24 h and 48 h after injection, and P-Gd-probe was as the enhanced contrast agent. The signal noise ratio (SNR) of the pancreas were measured before and after enhancement. Then the pancreas tissues were harvested for pathological examination and P selectin expression in pancreatic tissue was detected using immunohistochemical analysis. Results Inflammation was observed in pancreatic tissue at 6h after establishment, and became more serious as the modeling time extended. P selectin expression was increased as pancreatitis inflammation became more serious. The SNR of control group was stable before and after enhancement. The SNR before and after enhancement was 17.22±1.35 and 37.38±1.66 in AEP group, and 16.29±1.39 and 58.18±1.03 in ANP group. The SNR after enhancement was higher than that before enhancement, and the differences were significantly different (t=-49.59 and -86.09, P<0.001). Conclusions Monoclonal antibody MRI contrast agent targeting P selectin is helpful in evaluating the severity of AP. Key words: Pancreatitis, acute necrotizing; P-selection; Targeted contrast agent; Magnetic resonance imaging