Severe asthma is associated with a remodeling of the pulmonary arteries in horses.

This study explores the occurrence and effects of remodeling in the pulmonary arteries of horses with severe asthma, its locations, and possibilities for its reversal through avoidance of allergens or the use of inhaled steroids.

Introduction

• The research was sparked by complications associated with severe equine asthma, namely pulmonary hypertension and cor pulmonale brought on by pulmonary hypoxic vasoconstriction.
• These conditions are only partially treatable with oxygen, suggesting other etiological factors are at play.
• The study posits that, as in human chronic obstructive pulmonary disease, changes to the structure of pulmonary arteries may contribute to pulmonary hypertension.
• Earlier research on rodent models also found remodeling in pulmonary vessels as a result of allergic inflammation in airways.

Methodology

• The study focused on identifying whether remodeling of pulmonary arteries occurs in horses experiencing severe asthma, the locations of this remodelling within the lung, and the potential of reversing these vascular changes via long-term antigen avoidance strategies and administration of inhaled corticosteroids.
• The researchers measured the total area of the pulmonary artery walls taken from various areas of the lungs in both asthmatic horses and a control group through histomorphometry.
• Estimations of smooth muscle mass in pulmonary arteries were also taken using lung sections stained for α-smooth muscle actin.

Results

• The research showed that, both during asthma exacerbation and remission, there was an increase in the wall area of pulmonary arteries in the apical and caudodorsal regions of the asthmatic horses’ lungs.
• Correspondingly, the smooth muscle mass in the pulmonary arteries was found to be increased.
• Both the antigen avoidance and the administration of inhaled fluticasone reversed the enlargement of the artery wall area.
• However, only the antigen avoidance strategy showed potential for causing the vascular smooth muscle to return to normal size, while fluticasone treatment did not.

Conclusion

• The study found that severe equine asthma is accompanied by the remodeling of pulmonary arteries, specifically the enlargement of smooth muscle mass.
• This change narrows the artery lumen, potentially enhancing hypoxic vasoconstriction and contributing to pulmonary hypertension.
• The research indicates that avoiding antigens could be more effective than inhaling corticosteroids for managing vascular remodeling, but fulther study is necessary to confirm the potential reversibility of vascular smooth muscle mass remodeling after asthma treatment.