Investigating the structural basis of pulmonary vascular stiffening in hypoxia induced pulmonary hypertension through quantitative analysis of collagen and elastin ultrastructure

Pulmonary Hypertension (PH) is a disease marked by abnormally high blood pressure in the pulmonary circulation. The disease often causes death from right heart failure as a result of the greatly increased cardiac load. Pulmonary vascular stiffening has been shown to contribute to up to 30-40% of the increased cardiac load seen in PH patients. Extracellular matrix proteins collagen and elastin, proven players in the pathology of pulmonary hypertension, have also been proven to contribute to the stiffness of large elastic arteries. We examined the relationship of three specific structural properties of collagen, the tortuocity locking stretch, orientation, and total locking stretch, to stiffening in bovine main pulmonary arteries. We investigated locking stretch by imaging collagen using Second Harmonic Generation (SHG ). Locking stretches and orientations of collagen fibers were measured from SHG images using a MATLAB based image processing program. We sought to validate this method by comparing its results to data from hand tracing collagen fibers. The data produced by these two methods did not match, and thus we failed to validate our MATLAB based image processing method. However we have shown the hand tracing method to be considerably flawed, casting doubt on the validity of that data. In the future we hope to validate the MATLAB based method by analyzing a series of random sine curves of known locking stretch and orientation. Once our method has been validated we can begin to examine the relationship between collagen structure and pulmonary vascular stiffening in patients with pulmonary hypertension.