HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 296/6/H1898    most recent 01173.2008v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Aldous, I. G. Articles by Lee, J. M. PubMed PubMed Citation Articles by Aldous, I. G. Articles by Lee, J. M.

Differences in collagen cross-linking between the four valves of the bovine heart: a possible role in adaptation to mechanical fatigue

School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada

Submitted 10 November 2008 ; accepted in final form 25 March 2009

Hydrothermal isometric tension (HIT) testing and high-performance liquid chromatography were used to assess the molecular stability and cross-link population of collagen in the four valves of the adult bovine heart. Untreated and NaBH₄-treated tissues under isometric tension were heated in a water bath to a 90°C isotherm that was sustained for 5 h. The denaturation temperature (T_d), associated with hydrogen bond rupture and molecular stability, and the half-time of load decay (t_1/2), associated with peptide bond hydrolysis and intermolecular cross-linking, were calculated from acquired load/temperature/time data. An unpaired group of samples of the same population was biochemically assayed for the types and quantities of enzymatic cross-links present. Tissues known to endure higher in vivo transvalvular pressures had lower T_d values, suggesting that molecular stability is inversely related to in vivo loading. The treated inflow valves (mitral and tricuspid) had significantly lower t_1/2 values than did treated outflow valves (aortic and pulmonary), suggesting lower overall cross-linking in the inflow valves. Inflow valves were also found to fail during HIT testing significantly more often than outflow valves, also suggestive of a decreased cross-link population. Inflow valves may be remodeling at a faster rate and may be at an earlier state of molecular "maturity" than outflow valves. At the molecular level, the thermal stability of collagen is associated with in vivo loading and may be influenced by the mature, aldimine-derived cross-link, histidinohydroxylysinonorleucine. We conclude that the valves of the heart utilize differing, location-specific strategies to resist biomechanical fatigue loading.

collagen; cross-linking; remodeling; hydrothermal isometric tension