Influence of reproductive status on tissue composition and biomechanical properties of ovine vagina.
OBJECTIVE
To undertake a comprehensive analysis of the biochemical tissue composition and passive biomechanical properties of ovine vagina and relate this to the histo-architecture at different reproductive stages as part of the establishment of a large preclinical animal model for evaluating regenerative medicine approaches for surgical treatment of pelvic organ prolapse.


METHODS
Vaginal tissue was collected from virgin (n = 3), parous (n = 6) and pregnant sheep (n = 6; mean gestation; 132 d; term = 145 d). Tissue histology was analyzed using H+E and Masson's Trichrome staining. Biochemical analysis of the extracellular matrix proteins used a hydroxyproline assay to quantify total collagen, SDS PAGE to measure collagen III/I+III ratios, dimethylmethylene blue to quantify glycosaminoglycans and amino acid analysis to quantify elastin. Uniaxial tensiometry was used to determine the Young's modulus, maximum stress and strain, and permanent strain following cyclic loading.


RESULTS
Vaginal tissue of virgin sheep had the lowest total collagen content and permanent strain. Parous tissue had the highest total collagen and lowest elastin content with concomitant high maximum stress. In contrast, pregnant sheep had the highest elastin and lowest collagen contents, and thickest smooth muscle layer, which was associated with low maximum stress and poor dimensional recovery following repetitive loading.


CONCLUSIONS
Pregnant ovine vagina was the most extensible, but the weakest tissue, whereas parous and virgin tissues were strong and elastic. Pregnancy had the greatest impact on tissue composition and biomechanical properties, compatible with significant tissue remodeling as demonstrated in other species. Biochemical changes in tissue protein composition coincide with these altered biomechanical properties.
The Ritchie Centre, MIMR-PHI Institute of Medical Research, Melbourne, VIC, Australia; Department of Obstetrics and Gynecology, Monash University, Melbourne, Victoria, Australia.
Daniela
D
Ulrich
CSIRO Materials Science Engineering, Melbourne, VIC, Australia.
Sharon L
SL
Edwards
CSIRO Materials Science Engineering, Melbourne, VIC, Australia.
Kai
K
Su
CSIRO Materials Science Engineering, Melbourne, VIC, Australia.
Jacinta F
JF
White
CSIRO Materials Science Engineering, Melbourne, VIC, Australia.
John A M
JA
Ramshaw
The Ritchie Centre, MIMR-PHI Institute of Medical Research, Melbourne, VIC, Australia.
Graham
G
Jenkin
Department of Obstetrics and Gynecology, University Hospitals Leuven, Leuven, Belgium.
Jan
J
Deprest
Department of Obstetrics and Gynecology, Monash University, Melbourne, Victoria, Australia.
Anna
A
Rosamilia
CSIRO Materials Science Engineering, Melbourne, VIC, Australia.
Jerome A
JA
Werkmeister
The Ritchie Centre, MIMR-PHI Institute of Medical Research, Melbourne, VIC, Australia; Department of Obstetrics and Gynecology, Monash University, Melbourne, Victoria, Australia.
Caroline E
CE
Gargett
D000818:Animals; D024043:Collagen Type II / Q000378:metabolism*; D024061:Collagen Type III / Q000378:metabolism*; D004548:Elasticity / Q000502:physiology*; D005260:Female; D011247:Pregnancy / Q000378:metabolism*; D012756:Sheep; D014621:Vagina / Q000378:metabolism*
D024043:Collagen Type II; D024061:Collagen Type III