2.12 | Angiotensin II-induced aortic aneurysm
Male WT and SKI mice in LDLR−/− background at 7 weeks old (18–22 g) were fed on a Western diet (21% w/w milk fat, 0.15% w/w cholesterol, Beijing Keao Xieli Feed Corporation) for 7 days and then received subcutaneous implantation of ALZET osmotic pumps (Model 2004, DURECT Corporation, USA), delivering angiotensin II (1.44 mg·kg−1·day−1, dissolved in saline)(Bhamidipati et al., 2014). Before implantation, mice were given buprenorphine (0.08 mg·kg−1, s.c.) as analgesic, and during pump implantation, they were anaesthetised with isoflurane (1.5%) inhalation. The mouse back was depilated with depilatory ointment. After disinfection with iodophor, the pump was implanted subcutaneously into the back of the mouse. The incision was sealed with sterile sutures and disinfected with iodophor. Buprenorphine (0.08 mg·kg−1, s.c., every 8 hr) was given to the mouse the first day after surgery. The mice were monitored every day in the first week after operation. Seven days after angiotensin II infusion, SKI mice were randomly given pioglitazone (15 mg·kg−1·day−1, suspended in 200 μL sterile water, n = 11) or solvent control sterile water (200 μL, n = 11), and WT mice were given sterile water (200 μL,n = 11). They were given by gavage once a day. Western diet was applied during the whole experiment. 28 days after the infusion of angiotensin II, mice were killed and perfused with ice-cold PBS, and then the connective tissue was removed to expose the whole aorta and its collateral branches and digital images were acquired for aneurysm analysis using an Olympus microscope (model SZX16). Aneurysms are defined as enlargements > 50% diameter compared to littermate controls without angiotensin II infusion. The composition of aneurysms was evaluated according to the type of aneurysm, including the ruptured aneurysm, unruptured aneurysm, and non-aneurysm. The survival rate and incidence of aneurysm were monitored and calculated. The number of aneurysms per mouse was counted. The length of aneurysm was measured according to the scale with CellSens standard software 1.12 (RRID:SCR_014551 , Olympus).