title: Engineering the periodontal ligament in hyaluronan-gelatin-type I collagen constructs: upregulation of apoptosis and alterations in gene expression by cyclic compressive strain.
abstract: To engineer constructs of the periodontal ligament (PDL), human PDL cells were incorporated into a matrix of hyaluronan, gelatin, and type I collagen (COLI) in sample holders (13×1 mm) of six-well Biopress culture plates. The loading dynamics of the PDL were mimicked by applying a cyclic compressive strain of 33.4 kPa (340.6 gm/cm(2)) to the constructs for 1.0 s every 60 s, for 6, 12, and 24 h in a Flexercell FX-4000C Strain Unit. Compression significantly increased the number of nonviable cells and increased the expression of several apoptosis-related genes, including initiator and executioner caspases. Of the 15 extracellular matrix genes screened, most were upregulated at some point after 6-12 h deformation, but all were downregulated at 24 h, except for MMPs1-3 and CTGF. In culture supernatants, matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinases-1 (TIMP-1) protein levels were upregulated at 24 h; receptor activator of nuclear kappa factor B (RANKL), osteoprotegerin (OPG) and fibroblast growth factor-2 (FGF-2) were unchanged; and connective tissue growth factor (CTGF) not detected. The low modulus of elasticity of the constructs was a disadvantage-future mechanobiology studies and tissue engineering applications will require constructs with much higher stiffness. Since the major structural protein of the PDL is COLI, a more rational approach would be to permeabilize preformed COLI scaffolds with PDL-populated matrices.
authors.affiliation: 1 Faculty of Dentistry, National University of Singapore , Singapore, Singapore .
authors.forename: Aarthi
authors.initials: A
authors.lastname: Saminathan
authors.forename: Gopu
authors.initials: G
authors.lastname: Sriram
authors.forename: Jayasaleen Kumar
authors.initials: JK
authors.lastname: Vinoth
authors.forename: Tong
authors.initials: T
authors.lastname: Cao
authors.forename: Murray C
authors.initials: MC
authors.lastname: Meikle
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D001672:Biocompatible Materials / Q000138:chemical synthesis; D002478:Cells, Cultured; D024042:Collagen Type I / Q000737:chemistry*; D019245:Compressive Strength / Q000502:physiology; D055119:Elastic Modulus / Q000502:physiology; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005780:Gelatin / Q000737:chemistry; D005786:Gene Expression Regulation / Q000502:physiology; D016557:Guided Tissue Regeneration, Periodontal / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D006820:Hyaluronic Acid / Q000737:chemistry*; D008422:Materials Testing; D040542:Mechanotransduction, Cellular / Q000502:physiology; D010513:Periodontal Ligament / Q000166:cytology* / Q000502:physiology*; D013314:Stress, Mechanical; D023822:Tissue Engineering / Q000295:instrumentation / Q000379:methods
chemical_list: D001672:Biocompatible Materials; D024042:Collagen Type I; D005780:Gelatin; D006820:Hyaluronic Acid