Supported by the National Natural Science Foundation of China 81171387,the Project of Medical Research of Chongqing 2011-2-259 and the Project of Science and Technology Research of Chongqing Municipal Education Committee KJ080313;国家自然科学基金81171387;重庆市医学科研计划项目2011-2-259;重庆市教委科学技术研究项目KJ080313