Pulmonary response to airway instillation of autologous blood in horses.

The research investigates whether injecting a horse’s own blood into their airways can cause lung fibrosis, mainly as a model for exercise-induced pulmonary hemorrhage (EIPH), a condition common in horses performing intense exercise. However, it was found that a single injection of a horse’s own blood into the lung regions did not cause lung fibrosis, suggesting that other factors contribute to the condition.

Objective and Methodology

The study’s main goal was to ascertain if instilling a horse’s own blood (autologous blood) into its airways would lead to alveolar wall fibrosis, a form of lung scarring. Additionally, the research aimed to determine if blood in the airways also results in peribronchiolar fibrosis, another type of lung scarring.

Different regions of each horse’s lungs were inoculated with either blood or saline, serving as a control group. This was done at varying times – 14 days, 7 days, 48 hours, 24 hours, and 6 hours before euthanasia. To examine the effects of the inoculations, the research team inspected the resulting lesions histologically, or at a microscopic level, and quantified the amount of collagen in the alveolar and airway wall.

Key Findings

The major pathological change observed from the histological analyses was the enlargement and excessive cellular production (hypertrophy and hyperplasia) of type II pneumocytes, 7 days post blood instillation. These cells line the alveoli in the lungs, and hyperplasia is often a response to lung injury, while hypertrophy marks an increase in volume of these cells. However, this effect was no longer present 14 days after the blood instillation.

There were no significant influences from the region of the lung inoculated or the type of treatment (saline or blood instillation) on the amount of collagen in the interstitial or peribronchial regions.

Conclusion and Implications

The overall findings indicate that a single instillation of autologous blood in lung regions does not cause fibrosis in horses’ lungs. It suggests that the pulmonary fibrosis and lung remodelling – key characteristics of EIPH – may stem from other causes rather than just the presence of blood in the airspaces, for instance, repetitive bleeding or blood presence in the pulmonary interstitium.

The conclusion underscores the need for a deeper understanding of the mechanisms leading to lung scarring in treating and preventing the onset of conditions like pulmonary fibrosis. This understanding can be particularly pivotal in designing interventions to treat EIPH in horses, a common condition impacting their endurance performance.