title: Age- and region-related changes in the biomechanical properties and composition of the human ureter.
abstract: The ureter has been largely overlooked heretofore in the study of the biomechanics of soft biological tissues, although there has been significant motivation to use its biomechanical properties as inputs to mathematical models of ureteral function. Herein, we used histological analysis for quantification of collagen contents and thickness/area of ureteral layers, with concomitant geometrical analysis of zero-stress and no-load states, and inflation/extension testing to biomechanically characterize with the Fung-type model the ureters from cadavers. The effects of age and gender on the regional distribution of those properties were examined. Tissue properties did not differ (p>0.05) between the left and right ureter. Regional heterogeneity was established that was profoundly age-related but seldom gender-related, based on the following evidence: 1) In younger subjects, the axial stress-circumferential strain curves of upper ureter were shifted to smaller stresses and model parameter a2representing axial stiffness was smallest (p<0.05), i.e. upper ureter was the least stiff region axially; 2) upper ureter underwent axial stiffening with advanced age, evidenced by the increasing (p<0.05) parameter a2, and the stress-strain curves were uniformly exhibited along the ureter, evidenced by the non-varying (p>0.05) parameters C,a1,a2,anda4; 3) aging raised (p<0.05) the collagen content of upper ureter to favor a near-uniform regional distribution; 4) wall thickness increased with age, unlike the opening angle and residual strains, reflecting the thickening of outer (muscular) vs. inner (mucosal) layers in aged subjects, with significant differences (p<0.05) in some regions; and 5) gender affected little (p>0.05) the opening angle and morphometry of no-load and zero-stress states.
authors.affiliation: Laboratory of Biomechanics, Center of Clinical, Experimental Surgery, and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, Greece. Electronic address: DimitrisSokolis@ath.forthnet.gr.
authors.forename: Dimitrios P
authors.initials: DP
authors.lastname: Sokolis
authors.affiliation: Department of Mechanics, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Athens, Greece.
authors.forename: Despoina C
authors.initials: DC
authors.lastname: Petsepe
authors.affiliation: Department of Forensic Medicine and Toxicology, Medical School, University of Athens, Athens, Greece.
authors.forename: Stavroula A
authors.initials: SA
authors.lastname: Papadodima
authors.affiliation: Department of Mechanics, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Athens, Greece.
authors.forename: Stavros K
authors.initials: SK
authors.lastname: Kourkoulis
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena; D003094:Collagen / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D013314:Stress, Mechanical; D014513:Ureter / Q000033:anatomy & histology / Q000378:metabolism / Q000502:physiology*
chemical_list: D003094:Collagen
keywords: Aging; Collagen; Fung-type model; Gender; Human ureter; Inflation/extension; Opening angle; Residual strain distribution