Cells embedded within tissues respond to mechanical, chemical and biological signals. However, the detail of how mechanical forces are transmitted to cells is poorly understood at present and represents a key missing link in Tissue Engineering. As cells attach to the fibrils in fibroblast-seeded 3D collagen scaffolds they generate contractile forces to levels, which depend on cell type, attachment, density, growth factors and matrix stiffness. The aim of this study was to use external applied strain to increase matrix stiffness in collagen constructs. Embedded resident cells (from three different sites) were then subjected to specific mechanical loading regimes in scaffolds of increasing stiffness and matrix remodelling genes quantified as markers of mechanoregulatory cellular response. Mechanical responses of cells were also quantified as contraction profiles over time. Our findings indicated that collagen got stiffer with application of high strains and visco-elastic properties resulted in minimal transfer of applied loads as recorded by movement of indwelling markers. The mechanical and molecular responses of three different cell lineages: human dermal (HDF), neonatal foreskin fibroblasts (HNFF) and human bone marrow stem (hBMSC) cells seeded in constructs of increased stiffness was tested. Results indicated that in HNFFs contraction was predominantly attachment-dependent while in HDFs it was predominantly stiffness-dependent. hBMSCs showed differential response to serum levels. Molecular responses in progressively stiffer constructs investigated were MMP-2, MMP-3, MMP-9, TIMP- 2,COL-l,COL-3 and IGF-1. Different cell types expressed specific variations in gene regulation. The effect of specific mechanical loading (slow and fast ramp) regimes on regulation of matrix remodelling genes also showed a lineage dependent response. The major impact of this project has been the identification of a strong co-relation between substrate stiffness, mechanical loading and regulation of key ECM turnover genes. This knowledge is crucial to successful tissue engineering outcomes. The differential lineage dependent response is a key finding and will have to be tailored depending on cell source and specific outcomes desired. regimes on regulation of matrix remodelling genes also showed a lineage dependent response. The major impact of this project has been the identification of a strong co-relation between substrate stiffness, mechanical loading and regulation of key ECM turnover genes. This knowledge is crucial to successful tissue engineering outcomes. The differential lineage dependent response is a key finding and will have to be tailored depending on cell source and specific outcomes desired.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:486332 |
| Date | January 2007 |
| Creators | Karamichos, Dimitrios |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1445416/ |
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