title: Role of biomolecules on annulus fibrosus micromechanics: effect of enzymatic digestion on elastic and failure properties.
abstract: Uniaxial tension was applied to selectively digested single lamellar human cadaveric annulus fibrosus specimens to investigate the role of different biomolecules in annular biomechanics. Single layered and inter-lamellar annulus fibrosus samples were obtained from 10 isolated cadaveric lumbar intervertebral discs in one of four orientations: longitudinal, transverse, radial, and circumferential. Within each orientation the samples were subjected to a selective enzymatic digestion protocol with collagenase, elastase, chondroitinase ABC, or 1× Phosphate Buffered Saline. Uniaxial tensile tests were performed to failure at a strain rate of 0.005s(-1). Failure stress and strain, and elastic moduli were compared among the digested conditions. The collagenase- and elastase-treated groups had the most significant effect on the mechanical properties among the orientation groups, decreasing the failure stress for both interlaminar and intralaminar groups. Collagenase-treated groups showed an increase in the failure strain following enzymatic digestion for the intralaminar groups and one interlaminar testing direction (circumferential). The chondroitinase ABC-treated group only had a significant impact on the single layer orientations, decreasing the failure stress and strain (intralaminar group). The digested properties described provide insights into the laminar mechanical behavior and the role of the molecular components to the annular mechanical behavior. Understanding annular mechanics may prove insightful in diagnosis, prevention and repair of debilitating intervertebral disc disorders and manufacturing of tissue-engineered annulus.
authors.affiliation: Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Isaacs
authors.affiliation: Department of Orthopedic Surgery, Milton S. Hershey Medical Center, Hershey, PA, USA.
authors.forename: Edward
authors.initials: E
authors.lastname: Vresilovic
authors.affiliation: School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, PA, USA.
authors.forename: Sumona
authors.initials: S
authors.lastname: Sarkar
authors.affiliation: Department of Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA. Electronic address: marcolms@drexel.edu.
authors.forename: Michele
authors.initials: M
authors.lastname: Marcolongo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D055119:Elastic Modulus; D006801:Humans; D006867:Hydrolases / Q000378:metabolism*; D007403:Intervertebral Disc / Q000166:cytology / Q000378:metabolism*; D046911:Macromolecular Substances / Q000378:metabolism*; D008422:Materials Testing; D008875:Middle Aged; D013314:Stress, Mechanical; D013718:Tensile Strength; D023822:Tissue Engineering
chemical_list: D046911:Macromolecular Substances; D006867:Hydrolases
keywords: Annulus fibrosus; Enzymatic digestion; Intervertebral disc; Micromechanics; Spine