Morphological Characteristics of Lungs in Laboratory Balb/C Mice

Abstract

Substantiation. Comparing the course of experimental pathological conditions in mice with human pathology requires deep knowledge of the morphology of the lungs of mice. Although it is advisable to obtain pathomorphological conclusions from an experienced pathologist, in reality, this is not always possible. Therefore, many scientists have to conduct such an analysis by themselves. The aim of the research was to study and describe the normal lung morphology of BALB/c mice for the improved characterization of phenotypes of experimentally induced lesions. Materials and methods. The study included 10 healthy male BALB/c mice, 8 weeks old, housed in individual conditions with unlimited access to food and water. Animals were euthanized by inhalation of ethyl ether. The lung necropsy was performed by tracheal infusion with 10% neutral buffered formalin. The research was carried out on paraffin sections of 3 μm, part of the left lung or one of the right lobes. Sections were stained with hematoxylin-eosin, Schiff-iodic acid, and according to Mallory. Morphology was analyzed using a light microscope. Results. The applied method of euthanasia by inhalation with ethyl ether does not cause agonal changes in the lungs. Fixation by tracheal formalin infusion prevents lung collapse and ensures optimal morphology. For the study of experimental human pathology, it is optimal to examine the left lobe of the lungs, with its longitudinal orientation for obtaining sections, which is of great importance. A blinded way of describing microspecimens does not always provide the best result. Collagen deposits in the outer layer are observed around the large arteries of the lungs; goblet cells are rare, and only in large bronchi. Bronchus-associated lymphoid tissue (BALT) is barely visible in healthy lungs of mice. Natural mouse pathogens can alter the physiology of the host, making it unsuitable for many experimental purposes, and although the number and prevalence of these pathogens have decreased significantly, many of them can be found in laboratory animals and are undesirable in research. Conclusion. Laboratory BALB/c mice may suffer from background diseases, regardless of satisfactory housing conditions, nutrition, and experimental pathology, which should be considered in the design and description of studies.