Remodeling of the pulmonary circulation - a novel response to allergic airway inflammation

Asthma is characterized, not only by inflammation but also by airway and vascular remodeling. Airway remodeling is established early in disease, structural alterations have been found in children, and is thought to contribute to asthma symptoms. Unfortunately, airway remodeling is considered difficult to reverse and it seldom resolves completely. Studies of vascular involvement in asthma have mainly focused on the tracheal and bronchial microcirculation, as these vessels are relatively easy to obtain. Some scattered studies have investigated bronchial and pulmonary arteries, using autopsy specimens. The overall aim of the project was to investigate vascular remodeling by utilizing two different animal models of allergic airway inflammation (where chicken egg albumin (OVA) or house dust mite (HDM) extract were used as allergens). More specifically the structural alterations of remodeling, the time frame of development and the resolution were investigated. The studies show that vascular remodeling is a feature of allergic airway inflammation, despite which allergen used to initialize the inflammatory response. Both the systemic tracheal microvessels as well as all parts of the pulmonary circulation undergo changes. The structural alterations of vascular remodeling induced by allergic airway inflammation, was similar to features as seen in airway remodeling. Vascular remodeling appears to be only partially reversible, as some structural alterations seem to remain even when the allergic inflammation is resolved.

In summary this thesis describes the involvement of the vasculature in airway inflammation, characterizes vascular remodeling and shows that similar structural alterations are induced by two different allergens.