Ultrastructural findings in horses with chronic obstructive pulmonary disease (COPD). II: Pathomorphological changes of the terminal airways and the alveolar region.

This study examines the structural abnormalities in the lungs and airways of horses with chronic obstructive pulmonary disease (COPD) and correlates these changes to the severity of their condition. The results demonstrate that as COPD progresses in horses, significant alterations occur in cell structure, granulation, and functional transformation in the bronchial and alveolar areas of the lungs.

Research Methodologies

• The researchers used extensive light and electron microscope studies, involving both transmission and scanning electron microscopy to study the bronchioles and alveolar region of the lungs.
• The subjects comprised 28 horses with COPD and eight healthy horses used as control samples.

Findings and Interpretation

• A key finding was noticeable changes in the bronchiolar epithelium, especially in the non-ciliated bronchiolar epithelial (Clara) cells. These cells exhibited signs of degeneration and a lack of differentiation, even in the early stages of COPD.
• Concurrent with the degradation of Clara cells, the study also recorded loss of granulation and metaplasia (abnormal change in tissue structure) in the goblet cells.
• One interesting observation was the presence of unusual intracytoplasmic lamellar inclusions within these cells; the number of these inclusions increased markedly with the severity of the disease.
• In the alveolar region, which is responsible for gas exchange, the researchers identified necrosis (cell death) in type I epithelial cells, varying degrees of fibrosis (tissue thickening and scarring), and transformation of type II epithelial cells along with emphysema or hyperinflation conditions.
• The study also noticed an increase in Kohn’s pores, small holes that allow for the flow of air between alveoli, which is typical of emphysema conditions.
• Some horses also showed signs of issues with the surfactant system, the compound which reduces surface tension in the alveoli, as evidenced by marked cysts with a lamellar structure.

Limitations and Conclusion

• Most of the changes observed were found in the region around the bronchiolar tubes, and are thus interpreted as reactive processes – the body’s response to harmful stimuli such as disease or injury.
• Despite the detailed morphological studies, the research does not draw any conclusions about the causes of equine COPD, emphasizing the need for further research.