Molecular basis for the extensibility of elastin

Free Lung Desmosine: A Potential Biomarker for Elastic Fiber Injury in Pulmonary Emphysema

INTRODUCTION

Desmosine and isodesmosine (DID) are biomarkers for elastic fiber damage in pulmonary emphysema. However, current methods for measuring lung DID involve tissue hydrolysis and lack specificity for those fibers undergoing breakdown. To address this limitation, free (nonpeptide-bound) DID content in unhydrolyzed tissues was evaluated as a more accurate biomarker in an animal model of pulmonary emphysema.

METHODS

Hamsters were treated with either cigarette smoke and lipopolysaccharide (LPS), room air and LPS, or room air alone (controls). Free DID levels in fresh and formalin-fixed lungs were measured by LC-MS/MS and correlated with the mean linear intercept (MLI) measure of airspace size.

RESULTS

There was no significant difference in free DID between fresh and formalin-fixed lungs. Animals treated with smoke and LPS had significantly higher levels of free DID than the LPS only group (359 vs. 93.1 ng/g wet lung, respectively; p = 0.0012) and room air controls (undetectable levels; p = 0.0002). There was a significant positive correlation between free DID and MLI (p < 0.0001).

CONCLUSIONS

The results support the hypothesis that free lung DID is a sensitive indicator of alveolar wall injury that may be used to study the development of pulmonary emphysema in both animal models and post-mortem human lung tissue.

Energetic electron assisted synthesis of highly tunable temperature-responsive collagen/elastin gels for cyclic actuation: macroscopic switching and molecular origins

Thermoresponsive bio-only gels that yield sufficiently large strokes reversibly and without large hysteresis at a well-defined temperature in the physiological range, promise to be of value in biomedical application. Within the present work we demonstrate that electron beam modification of a blend of natural collagen and elastin gels is a route to achieve this goal, viz. to synthesize a bioresorbable gel with largely reversible volume contractions as large as 90% upon traversing a transition temperature that can be preadjusted between 36 °C and 43 °C by the applied electron dose. Employing circular dichroism and temperature depending confocal laser scanning microscopy measurements, we furthermore unravel the mechanisms underlying this macroscopic behavior on a molecular and network level, respectively and suggest a stringent picture to account for the experimental observations.

Elastic Fibers and Large Artery Mechanics in Animal Models of Development and Disease

Development of a closed circulatory system requires that large arteries adapt to the mechanical demands of high, pulsatile pressure. Elastin and collagen uniquely address these design criteria in the low and high stress regimes, resulting in a nonlinear mechanical response. Elastin is the core component of elastic fibers, which provide the artery wall with energy storage and recoil. The integrity of the elastic fiber network is affected by component insufficiency or disorganization, leading to an array of vascular pathologies and compromised mechanical behavior. In this review, we discuss how elastic fibers are formed and how they adapt in development and disease. We discuss elastic fiber contributions to arterial mechanical behavior and remodeling. We primarily present data from mouse models with elastic fiber deficiencies, but suggest that alternate small animal models may have unique experimental advantages and the potential to provide new insights. Advanced ultrastructural and biomechanical data are constantly being used to update computational models of arterial mechanics. We discuss the progression from early phenomenological models to microstructurally motivated strain energy functions for both collagen and elastic fiber networks. Although many current models individually account for arterial adaptation, complex geometries, and fluid-solid interactions (FSIs), future models will need to include an even greater number of factors and interactions in the complex system. Among these factors, we identify the need to revisit the role of time dependence and axial growth and remodeling in large artery mechanics, especially in cardiovascular diseases that affect the mechanical integrity of the elastic fibers.