Abstract: BACKGROUND: Aortic dissection is a rare life-threatening disease with high mortality. At present, the pathogenesis of aortic dissection is still not fully understood; therefore, research on its pathogenesis will have important clinical significance.
OBJECTIVE: To investigate the pathological basis of arterial dissection in mice with connective tissue disease through constructing an aortic dissection model by bleomycin combined with angiotensin II.
METHODS: Twenty-four female BALB/c mice were randomly divided into control group and experimental group, with twelve mice in each group. Mice in the experimental group were subcutaneously treated with bleomycin to establish a systemic sclerosis model, while those in the control group were treated with phosphate buffered saline. Administration in each group lasted for 3 weeks. Mice in the two groups were examined for urine hydroxyproline level, back skin thickness and body mass to verify whether the model was successfully established. Mice were intraperitoneally injected angiotensin II beginning at 7 days after modeling for 14 continuous days. The histopathological changes in the aortic media of the two groups were analyzed and semi-quantitative grading was performed after modeling.
RESULTS AND CONCLUSION: There were significant increases in the urine hydroxyproline level and back skin thickness and a significant reduction in body mass in the experimental group compared with the control group (P < 0.05). There were no significant differences in systolic pressure, diastolic stage and mean arterial pressure between the two groups at 30 minutes after intraperitoneal injection of angiotensin II (P > 0.05). Compared with the control group, mice in the experimental group presented with significantly severer non-inflammatory degenerative lesions of the aortic media (P < 0.05). All findings indicate that non-inflammatory degeneration of the aortic media is more serious in the experimental mice then the control mice, that is, experimental mice are more prone to arterial dissection pathologically.

Key words: bleomycin, angiotensin II, systemic sclerosis, non-inflammatory degeneration of the aortic media, aortic dissection, connective tissue disease