The role of type I collagen in aortic wall strength with a homotrimeric.
OBJECTIVE
Elastin and collagen (types I and III) are the primary load-bearing elements in aortic tissue. Deficiencies and derangements in elastin and type III collagen have been associated with the development of aneurysmal disease. However, the role of type I collagen is less well defined. The purpose of this study was to define the role of type I collagen in maintaining biomechanical integrity in the thoracic aorta, with a mouse model that produces homotrimeric type I collagen [alpha1(I)]3, rather than the normally present heterotrimeric [alpha1(I)]2 alpha2(I) type I collagen isotype.


METHODS
Ascending and descending thoracic aortas from homozygous (oim/oim ), heterozygous (oim /+), and wildtype (+/+) mice were harvested. Circumferential and longitudinal load-extension curves were used as a means of determining maximum breaking strength (Fmax) and incremental elastic modulus (IEM). Histologic analyses and hydroxyproline assays were performed as a means of determining collagen organization and content.


RESULTS
Circumferentially, the ascending and descending aortas of oim /oim mice demonstrated significantly reduced Fmax, with an Fmax of only 60% and 23%, respectively, of wildtype mice aortas. Oim/oim descending aortas demonstrated significantly greater compliance (decreased IEM), and the ascending aortas also exhibited a trend toward increased compliance. Reduced breaking strength was also demonstrated with longitudinal extension of the descending aorta.


CONCLUSIONS
The presence of homotrimeric type I collagen isotype (absence of alpha2(I) collagen) significantly weakens the aorta. This study demonstrates the integral role of type I collagen in the biomechanical and functional properties of the aorta and may help to elucidate the role of collagen in the development of aneurysmal aortic disease or dissection.
Vouyouka
A G
AG
Division of Vascular Surgery, and the Department of Biochemistry, University of Missouri, Columbia 65212, USA.
Pfeiffer
B J
BJ
Liem
T K
TK
Taylor
T A
TA
Mudaliar
J
J
Phillips
C L
CL
D000704:Analysis of Variance; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000502:physiology*; D001696:Biomechanical Phenomena; D003094:Collagen / Q000378:metabolism*; D046508:Culture Techniques; D006909:Hydroxyproline / Q000032:analysis*; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D023421:Models, Animal; D011336:Probability; D012680:Sensitivity and Specificity; D013045:Species Specificity; D013718:Tensile Strength
D003094:Collagen; D006909:Hydroxyproline