title: The region-dependent biomechanical and biochemical properties of bovine cartilaginous endplate.
abstract: Regional biomechanical and biochemical properties of bovine cartilaginous endplate (CEP) and its role in disc mechanics and nutrition were determined. The equilibrium aggregate modulus and hydraulic permeability between the central and lateral regions were examined by confined compression testing. Biochemical assays were conducted to quantify the amount of water, collagen, and glycosaminoglycan (GAG). The equilibrium aggregate modulus of the CEP in the central region (0.23 ± 0.15 MPa) was significantly lower than for the lateral region (0.83 ± 0. 26 MPa). No significant regional difference was found for the permeability of the CEP (central region: 0.13 ± 0.07×10(-15)m(4)/Ns and lateral region: 0.09 ± 0.03 × 10(-15)m(4)/Ns). CEPs were an average of 75.6% water by wet weight, 41.1% collagen, and 20.4% GAG by dry weight in the central region, as well as an average of 70.2% water by wet weight, 73.8% collagen, and 11.7% GAG by dry weight in the lateral region. Regional differences observed for the equilibrium aggregate modulus were likely due to the regional variation in biochemical composition. The lateral bovine endplate is much stiffer and may share a greater portion of the load. Compared with the nucleus pulposus (NP) and annulus fibrosus (AF), a smaller hydraulic permeability was found for the CEP in both the central and lateral regions, which could be due to its lower water content and higher collagen content. Our results suggest that the CEP may block rapid fluid exchange and solute convection, allow pressurization of the interstitial fluid, and play a significant role in nutrient supply in response to loading.
authors.affiliation: Department of Bioengineering, Clemson University, Clemson, SC, United States; Department of Orthopaedics, Medical University of South Carolina (MUSC), Charleston, SC, United States.
authors.forename: Yongren
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Bioengineering, Clemson University, Clemson, SC, United States.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Cisewski
authors.affiliation: Department of Orthopaedics, Medical University of South Carolina (MUSC), Charleston, SC, United States.
authors.forename: Barton L
authors.initials: BL
authors.lastname: Sachs
authors.affiliation: Department of Orthopaedics, Medical University of South Carolina (MUSC), Charleston, SC, United States.
authors.forename: Vincent D
authors.initials: VD
authors.lastname: Pellegrini
authors.affiliation: Department of Regenerative Medicine and Cell Biology, MUSC, Charleston, SC, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kern
authors.affiliation: Department of Statistics, Florida State University, Tallahassee, FL, United States.
authors.forename: Elizabeth H
authors.initials: EH
authors.lastname: Slate
authors.affiliation: Department of Bioengineering, Clemson University, Clemson, SC, United States; Department of Orthopaedics, Medical University of South Carolina (MUSC), Charleston, SC, United States. Electronic address: haiyao@clemson.edu.
authors.forename: Hai
authors.initials: H
authors.lastname: Yao
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002417:Cattle; D003094:Collagen / Q000737:chemistry; D055119:Elastic Modulus; D006025:Glycosaminoglycans / Q000737:chemistry; D007403:Intervertebral Disc / Q000033:anatomy & histology / Q000502:physiology*; D008297:Male; D010539:Permeability; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D006025:Glycosaminoglycans; D014867:Water; D003094:Collagen
keywords: Aggregate modulus; Cartilaginous endplate; Hydraulic permeability; Intervertebral disc; Soft tissue mechanics