title: In situ longitudinal pre-stretch in the human femoropopliteal artery.
abstract: In situ longitudinal (axial) pre-stretch (LPS) plays a fundamental role in the mechanics of the femoropopliteal artery (FPA). It conserves energy during pulsation and prevents buckling of the artery during limb movement. We investigated how LPS is affected by demographics and risk factors, and how these patient characteristics associate with the structural and physiologic features of the FPA. LPS was measured in n=148 fresh human FPAs (14-80 years old). Mechanical properties were characterized with biaxial extension and histopathological characteristics were quantified with Verhoeff-Van Gieson Staining. Constitutive modeling was used to calculate physiological stresses and stretches which were then analyzed in the context of demographics, risk factors and structural characteristics. Age had the strongest negative effect (r=-0.812, p<0.01) on LPS and could alone explain 66% of LPS variability. Male gender, higher body mass index, hypertension, diabetes, coronary artery disease, dyslipidemia and tobacco use had negative effects on LPS, but only the effect of tobacco was not associated with aging. FPAs with less pre-stretch had thicker medial layers, but thinner intramural elastic fibers with less dense and more fragmented external elastic laminae. Elastin degradation was associated with decreased physiological tethering force and longitudinal stress, while circumferential stress remained constant. FPA wall pathology was negatively associated with LPS (r=-0.553, p<0.01), but the effect was due primarily to aging. LPS in the FPA may serve as an energy reserve for adaptive remodeling. Reduction of LPS due to degradation and fragmentation of intramural longitudinal elastin during aging can be accelerated in tobacco users.
  
  
  CONCLUSIONS
  This work studies in situ longitudinal pre-stretch (LPS) in the human femoropopliteal artery. LPS has a fundamental role in arterial mechanics, but is rather poorly studied due to lack of direct in vivo measurement method. We have investigated LPS in the n=148 human femoropopliteal arteries in the context of subject demographics and risk factors, and structural and physiologic characteristics of the artery. Our results demonstrate that LPS reduces with age due to degradation and fragmentation of intramural elastin. LPS may serve as an energy reserve for adaptive remodeling, and reduction of LPS can be accelerated in tobacco users.
authors.affiliation: Dept of Surgery, University of Nebraska Medical Center, Omaha, NE, United States. Electronic address: Alexey.Kamenskiy@unmc.edu.
authors.forename: Alexey
authors.initials: A
authors.lastname: Kamenskiy
authors.affiliation: Dept of Chemical Engineering, University of Maryland, Baltimore County, MD, United States.
authors.forename: Andreas
authors.initials: A
authors.lastname: Seas
authors.affiliation: Dept of Surgery, University of Nebraska Medical Center, Omaha, NE, United States.
authors.forename: Grant
authors.initials: G
authors.lastname: Bowen
authors.affiliation: Dept of Surgery, University of Nebraska Medical Center, Omaha, NE, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Deegan
authors.affiliation: Dept of Surgery, University of Nebraska Medical Center, Omaha, NE, United States; Dept of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE, United States.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Desyatova
authors.affiliation: Dept of Surgery, University of Nebraska Medical Center, Omaha, NE, United States.
authors.forename: Nick
authors.initials: N
authors.lastname: Bohlim
authors.affiliation: Dept of Surgery, University of Nebraska Medical Center, Omaha, NE, United States.
authors.forename: William
authors.initials: W
authors.lastname: Poulson
authors.affiliation: Dept of Surgery, University of Nebraska Medical Center, Omaha, NE, United States. Electronic address: JMacTaggart@unmc.edu.
authors.forename: Jason
authors.initials: J
authors.lastname: MacTaggart
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005263:Femoral Artery / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011150:Popliteal Artery / Q000502:physiology*; D012307:Risk Factors; D013314:Stress, Mechanical; D017539:Tunica Intima / Q000473:pathology; D017540:Tunica Media / Q000473:pathology; D055815:Young Adult
keywords: Adaptation; Femoropopliteal artery; Human; Longitudinal (axial) pre-stretch; Peripheral artery disease