AIP and aortic aneurysm: However, this AIP in VSMCs during development of aortic aneurysms was not sufficient to compensate the loss of VSMCs elicited by apoptosis, as evidenced by fact that the number of apoptotic VSMCs was much higher than that of proliferating cells in AD and AAA tissues, thus contributing to aortic wall thinning and the development of aortic aneurysms.