Engineering the Periodontal Ligament in Hyaluronan–Gelatin–Type I Collagen Constructs: Upregulation of Apoptosis and Alterations in Gene Expression by Cyclic Compressive Strain

• Published in: Tissue engineering. Part A 2015-02, Vol.21 (3-4), p.518-529
• Main Authors: Saminathan, Aarthi, Sriram, Gopu, Vinoth, Jayasaleen Kumar, Cao, Tong, Meikle, Murray C.
• Format: Article
• Language: English
• Subjects: Apoptosis; Apoptosis - physiology; Biocompatible Materials - chemical synthesis; Cells, Cultured; Cellular biology; Collagen Type I - chemistry; Compressive Strength - physiology; Elastic Modulus - physiology; Equipment Design; Equipment Failure Analysis; Gelatin - chemistry; Gene expression; Gene Expression Regulation - physiology; Guided Tissue Regeneration, Periodontal - instrumentation; Guided Tissue Regeneration, Periodontal - methods; Humans; Hyaluronic Acid - chemistry; Materials Testing; Mechanotransduction, Cellular - physiology; Original Articles; Periodontal Ligament - cytology; Periodontal Ligament - physiology; Stress, Mechanical; Studies; Tissue engineering; Tissue Engineering - instrumentation; Tissue Engineering - methods
• ISSN: 1937-3341; 1937-335X
• DOI: 10.1089/ten.tea.2014.0221

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.