title: Evaluation of the Wharton׳s jelly poroelastic parameters through compressive tests on placental and foetal ends of human umbilical cords.
abstract: The umbilical cord is a conduit between the developing foetus and the placenta. In physiological conditions it contains two arteries and one vein immersed in a mucoid tissue called Wharton׳s jelly. Although the extreme importance of such a structure is fully recognized, the umbilical cord and its components have been scarcely studied. A deep investigation on the biomechanics of the umbilical cord could help to understand if the pregnancy outcome is influenced by umbilical cord mechanical properties, however, detailed biomechanical data are still lacking. In the present study, the mechanical properties during compression of the human Wharton׳s jelly have been evaluated using a poroelastic approach. Multi-ramp stress-relaxation tests in both confined and unconfined configurations were performed on Wharton׳s jelly samples extracted from foetal and placental sides of twenty human umbilical cords. The Young modulus and Aggregate modulus were calculated at three strain levels and the hydraulic permeability was found by fitting the confined stress-relaxation data to the analytical solution and minimizing the stress least square differences. The Wharton׳s jelly exhibits a highly non linear and viscoelastic behaviour showing a dependence on the applied strain values and a ~90% and ~85% relaxation in unconfined and confined configuration, respectively. Moreover, equilibrium Young and Aggregate moduli resulted significantly higher and the permeability significantly lower at the foetal than the placental site, showing a dependence of the three material parameters on the location (foetal or placental) and, consequently, a non-homogeneity in the Wharton׳s jelly mechanical properties.
authors.affiliation: Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy. Electronic address: francesca.gervaso@unisalento.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Gervaso
authors.affiliation: Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy; IRCCS Istituto Ortopedico Galeazzi, Milano, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Boschetti
authors.affiliation: Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy.
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Pennati
mesh_terms: D001696:Biomechanical Phenomena; D019245:Compressive Strength; D055119:Elastic Modulus; D005260:Female; D006801:Humans; D006868:Hydrolysis; D010539:Permeability; D010920:Placenta / Q000502:physiology; D016062:Porosity; D011247:Pregnancy; D011312:Pressure; D013314:Stress, Mechanical; D014470:Umbilical Cord / Q000502:physiology*; D014783:Viscosity; D059631:Wharton Jelly / Q000737:chemistry*
keywords: Mechanical test; Permeability; Poroelastic model; Umbilical cord