A simple method for the formalin fixation of lungs in toxicological pathology studies.

Optimized lung preparation for detailed structural evaluation is required to improve consistency in preclinical safety evaluation, differences of opinion exist among regulatory agency personnel regarding the optimal methods for routine formalin fixation of lungs from rodent toxicology studies. The simple tracheal ligation fixation method emphasizes tracheal ligation before opening the thorax instead of attempting to re-inflate after lung collapse when opening the thorax. Photomicrographs of this method demonstrated an unprecedented ability to maintain the natural lung architecture, in contrast to the unavoidable changes in the alveolar environment by the intratracheal instillation and vascular perfusion methods. In addition, a comparison of fixation methods on lung morphology in a rodent model of LPS-induced acute lung injury demonstrated that the tracheal ligation fixation method may provide a standard approach for morphometry. Additionally, a TUNEL assay was used to determine the degree of autolysis, which revealed that the autolysis was insignificant in the central areas of each lobe of the lung compared to the lung periphery by tracheal ligation fixation. In conclusion, our novel modified method, which avoids the disadvantages of generating artifacts, fulfills the requirement of preserving the clear, natural morphology of the lung making it suitable and worthy of recommendation for toxicological studies in a good laboratory practice (GLP) lab.