Moffatt, Sarah; (2003) Integrin expression and function in osteoblasts. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Communication between osteoblasts and the surrounding milieu is important in the regulation of osteoblast behaviour and function. Evidence suggests that the β1 family of integrins is important in the regulation of this relationship. Although trends in integrin expression and function are beginning to emerge, there is little functional evidence using human osteoblasts. In this thesis I have shown, using FACS analysis, that both MG63 cells and mandibular primary human osteoblasts (HOBs) express α2, α3, α4, α5, α6 and β1 integrins. HOBs were also shown to express αv integrin but had low or negative expression of αvβ3. Integrin expression was confirmed by immunocytochemistry. Adhesion assays showed that MG63s and HOBs were adherent to ECM substrates, including plasma fibronectin, type I collagen and the 120kDa plasma fibronectin fragment. Adhesion to plasma fibronectin and type I collagen was reduced by the β1 integrin blocking antibody. RGD blocking peptide reduced adhesion to plasma fibronectin. Boyden chamber migration assays showed that MG63s were highly migratory after 2 hours on plasma fibronectin, type I collagen and the 120kDa plasma fibronectin fragment. HOBs were also migratory but with lower cell numbers migrating. Addition of the α2β1 and α5β1 blocking antibodies resulted in the partial inhibition of MG63 cell and HOB migration on type 1 collagen and plasma fibronectin respectively. Incubation of cells with the MAPKK inhibitor, U0126, also reduced migration of MG63 cells on plasma fibronectin. Preliminary studies into the function of integrins in the differentiation of the C2C12 stromal cell-line was also carried out. This study provides the first evidence for the involvement of integrins and ECM interaction in osteoblast migration. In addition further evidence for the role of integrins in osteoblast behaviour is reported.

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