Study on the morphological changes of pulmonary bronchioles and the expression of PHH3 in lymph node nuclei to infer the early time of death
Objective To study the feasibility of using morphological changes of bronchioles and lymph nodes in rats for estimating the postmortem interval(PMI).Methods Thirty-five 8-week-old male SD rats were sacrificed by cervical dislocation and placed in a constant temperature and humidity box.Lung tissues of 5 rats were extracted at each time point within 24 hours after death for routine HE and PHH3 immunohistochemical staining.Image J was used to measure mucosal area,extramucosal area,luminal area of small bronchi,Then calculate the ratio of mucosal area to luminal area,extramucosal area to extramucosal,extramucosal area to mucosal area.imageJIHCprofiler was used to measure the positive degree of PHH3 immunohistochemical staining in lymph node nuclei,and the above calculation results and the positive degree of PHH3 staining were statistically analyzed by GraphPad Prism 9.5.Results The ratio of mucosal area to lumen area showed an overall downward trend with the increase of PMI(0h was statistically different compared with 18h and 24h,P<0.05).The ratio of extramucosal to lumen area and extramucosal to mucosa area showed an upward trend with the increase of PMI(0h was statistically different from other time points,P<0.05),the positive degree of PHH3 immunohistochemical staining was significantly decreased at 24 h after death(P<0.05).Conclusion The morphological changes of pulmonary bronchiole and lymph nodes showed a certain regularity within 24h after death,which was helpful to infer the early PMI,lymph node nucleus PHH3 was expected to be a critical index to distinguish early and late PMI.