Comparison of cryoprotective methods for histological examination of rat and porcine lung tissue

Proper histological evaluation of lung tissue and accurate antigen detection by immunodetection techniques require histological tissue processing to preserve tissue reactivity and open alveolar spaces. In this study, we focused on testing and comparing different procedures of tissue cryopreservation. Sucrose or Tissue Tek were used with several methods of freezing samples by supercooled liquids and liquid nitrogen. Changes in tissue caused during the freezing of samples and the effect of cryoprotectants on the tissue were recorded. Rat and porcine pulmonary tissues were used in this experiment. This study aimed to optimize the process of lung cryopreservation with emphasis on enabling proper anatomical evaluation and preserving a high tissue immunoreactivity. The best results were obtained by inflating pulmonary parenchyma with a 1 : 1 mixture of O.C.T. with phosphate buffered saline (PBS) frozen in supercooled n-heptane placed on dry ice. Pulmonary tissue prepared in this way enables to perform proper histological evaluation and to detect target molecules by immunohistochemical analysis.