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Title: Calcium phosphate substrate-directed osteogenic differentiation of mesenchymal stem cells
Author: Cameron, Katherine Rachel
ISNI:       0000 0004 2747 6615
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2013
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An increase in degenerative bone disease in an ageing population, combined with a rise in the number of patients suffering from bone defects caused by physical trauma, makes the repair of bone an issue of growing clinical relevance. Current treatments such as autografts and allografts have major drawbacks, including donor site morbidity, limited availability, disease transmission and immune rejection. To overcome these issues synthetic bone grafts have been developed to mimic the mineral phase of bone. Given the significant roles of silicon in bone growth and development there has been great interest in introducing silicon into synthetic bone grafts to enhance their bioactivity. Calcium phosphate based silicate containing grafts have demonstrated enhanced bioactivity, improved physical properties, enhanced protein adsorption and greater bone formation, when compared to non-silicated calcium phosphates such as hydroxyapatite. However, is not clear whether the increased bone formation associated with these materials is the result of greater osteoblast activity or a rise in numbers of osteoblasts resulting from activation and differentiation of stem/ progenitor cells. To answer this question, multipotent stem cells were cultured on silicate substituted calcium phosphate (Si-CaP) and hydroxyapatite (HA). Si-CaP promoted greater cell adhesion and enhanced proliferation when compared to HA. Cells differentiated along the osteogenic lineage on both substrates as evidenced by up regulation of osteoblast specific genes and proteins. However, cells on Si-CaP showed earlier and greater gene expression of all osteoblast genes examined, and greater protein production as detected by immunohistochemistry. Integrin gene expression analysis revealed up regulation of α an d β subunits on both substrates during differentiation. Integrins α5 and β1 expression were greater on Si-CaP than on HA, suggesting preferential binding of fibronectin. The implication of these findings for tissue engineering is clear, suggesting these substrates may be utilized to control stem cell fate in vivo and in vitro without the need for osteogenic supplementation. Furthermore, the increased rate of differentiation seen on Si-CaP may enable the development of novel substrates for osteogenic differentiation of MSC, which may have significant impact in regenerative medicine.
Supervisor: Noble, Brendon; Mann, Valerie; Travers, Paul Sponsor: Engineering and Physical Sciences Research Council (EPSRC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Bone graft substitutes ; mesenchymal stem cell ; osteogenic differentiation ; calcium phosphate