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Title: Developing synthetic polymer substrates for stem cell
Author: Glennon-Alty, Laurence Jerome
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2012
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Stem cells hold great promise for use in regenerative therapies. However, current obstacles to their use include the ability to culture them under defined conditions, and the ability to differentiate them cost effectively. Over recent years there has been a great deal of interest in designing artificial substrates that are able to regulate stem cell behaviour, and there is now much evidence to suggest that the chemical composition of the substrate plays an important role in this regulation. The use of chemically defined substrates represents simple and cheap solutions to the effective culturing of stem cells. -----.. - In this study, the surface properties of poly-acrylate substrates were altered to enact control over the self-renewal and differentiation of stem cells. Specifically, chemically defined substrates were designed and tested for their ability to support mouse embryonic stem cell (mESC) self-renewal and direct the differentiation of mouse and human mesenchymal stem cells (MSCs) to chondrocytes. Poly-acrylate substrates were designed with Biomer Technology Limited (BTL), which has developed novel synthetic accelerate ™ polymeric coatings for use as biomaterials. The surface of these poly-acrylate substrates presented a combination of amine, carboxylic acid and hydroxyl functional groups at controllable density and proportion. These functionalities are known to influence stem cell behaviour and differentiation; however their combined influence is less studied. Substrates were further developed by modelling the functional group composition and distribution found at common integrin binding sites of key extracellular matrix proteins. The poly-acrylate substrates were able to modulate stem cell behaviour through alterations in surface chemistry. Results of the mESC studies indicated that while some of the poly-acrylate substrates could support the expansion of undifferentiated mESC colonies in defined serum-free culture medium over the short-term, population expansion was significantly reduced compared with control substrates. Further investigation demonstrated that this was likely due to deficient attachment of cells to the poly-acrylate substrates. The MSC studies indicated that poly-acrylate substrates modelled on the functional composition and distribution of the RGD integrin-binding motif of fibronectin were able to promote chondrogenesis in mouse and human MSCs, without need of additional stimuli. MSCs began to aggregate following seeding onto substrates, with QPCR and immunostaining confirming the presence of chondrocyte markers within aggregates, reminiscent of limb-bud formation. The mechanism of chondrogenesis induction was thought to occur directly via an RGD-integrin-like interaction. This work is the first to show that biomaterials designed to mimic specific sites of ECM molecules have the potential to direct MSC chondrogenesis without need of additional stimuli. More broadly, this thesis demonstrates that the surface properties of biomaterials can be tailored to regulate the self-renewal or differentiation of stem cells cultured in contact with them.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available