窒息死亡原因分析和死亡时间推断一直是法医学研究的重点和难点。近年来，利用荧光定量RT-PCR检测管家基因mRNA水平来分析死因和进行死亡时间推断已逐渐成为研究热点。我们前期利用建立的大鼠断颈处死模型获得了推测死亡时间的样条函数方程，但发现其精确性很大程度上依赖于稳定的内参指标；同时，发现不同死因的管家基因mRNA的水平差异很大。MicroRNA作为短链小分子，性质稳定，不易降解。本课题拟利用miRNA表达谱芯片，以人体样本为研究材料，将机械性窒息作为实验组，颅脑损伤、失血性休克和猝死作为不同死因的对照组，通过检测对缺氧敏感的大脑组织，分别筛选出差异明显的miRNA作为窒息死亡原因推测的指标，并通过靶基因的确定和验证，明确缺氧与miRNA表达变化之间的机制，最终将之应用于窒息死亡原因推测；同时，筛选出表达稳定的miRNA作为死亡时间推断的内参指标，用于进一步优化已有的推测死亡时间的样条函数。

The estimation of asphyxia and the postmortem interval are the difficult and hotspot areas all the time. Currently, more and more published papers mentioned that the methods of using fluorescence quantitative PCR detection of the housekeeping gene mRNA levels to estimate postmortem interval. In the previous study, we had used sacrificed rat model to build up the spline function. However, the accuracy of this method largely depends on the stability of the internal reference genes. Meanwhile, we found that the mRNA levels of housekeeping genes vary widely in different causes of death. MicroRNA is a short-chain molecules, having considerable stability from degradation after death. In this study, using miRNA microarray, we will focus on human samples, detecting the hypoxia-sensitive brain tissues, to identify microRNA markers of asphyxia and reference marker of postmortem interval. We set up the mechanical asphyxia as the experimental group, traumatic brain injury, hemorrhagic shock and sudden death as different death caused control groups. The purpose of this study are screening the special changes of miRNA (such as extraordinarily high or low levels of miRNA) as indicators of asphyxia to speculate the cause of death and screening stable miRNA as the internal reference marker in the estimating of postmortem interval, these parameters will ultimately be used on the optimizing of our previous buildup postmortem interval spline function. The target genes of these miRNA will be identified and validated,to elucidate the mechanisms of the miRNA expression changes in hypoxia caused asphyxia and death. Our study will provide new insight for analysis the cause of death of mechanical asphyxia and the estimating of postmortem interval.