Cay Kielty, BSc PhD FMedSci
The cell surface microenvironment controls the ordered assembly and deposition of newly-secreted extracellular matrix (ECM) molecules into functional assemblies, the bioavailability of growth factors through storage with ECM, and ECM-dependent cell surface receptor ‘crosstalk’ that controls regulates growth factor signals. Our group is investigating these interconnected themes. focussing on elastic fibres and on mesenchymal stem cells.
The importance of microfibrils and elastic fibres is highlighted by the fact that mutations in fibrillins, elastin and associated molecules cause a range of severe connective tissue disorders. Our ECM assembly and growth factor storage studies focus on how these structures assemble and how they control the sequestration of latent TGFb (transforming growth factor-beta).
Using human mesenchymal stem cells, we are studying how ECM regulates receptor ‘crosstalk’. We are investigating how ECM molecules such as fibronectin and fibrillin-1 regulate signalling interactions between PDGF receptors (‘receptor tyrosine kinases’) and integrin receptors.
The scientific story
Fibrillin microfibrils endow connective tissues with long-range elastic recoil, and microfibrillar structures include zonular fibres which hold the lens in dynamic suspension and oxytalan fibres which dispense elasticity to skin. During elastic fibre formation, elastin is deposited on pre-formed microfibrils, in association with fibulin-4, fibulin-5 and the crosslinking enzyme lysyl oxidase. We are using recombinant elastic fibre molecules in combination with microscopy and in vitro binding studies to determine how elastic fibre molecules assemble, electron microscopy approaches to map tropoelastin binding sites on microfibrils, and biophysical approaches (analytical ultracentrifugation, laser light scattering) to study the process of multimerisation. We have also developed a comprehensive mass spectrometry database of the molecular interactions of elastic fibres. The roles of cell surface receptors in this process are being determined using knock-down, overexpression and mutagenesis, in combination with biochemical and microscopy approaches.
Our interest in human mesenchymal stem cells (MSCs) arose from vascular tissue engineering. We have focussed on the role of PDGF (platelet-deerived growth factor) receptors in regulating the recruitment and phenotypic status of MSCs. Currently, we are defining how PDGF receptors interface with integrin and neuropilin receptors, how this crosstalk regulates MSC differentiation, and the structural and signalling basis of growth factor ligand binding to PDGF receptors. Our research has important implications for regulating neovascularisation. New approaches include quantitative proteomics and glycomics of the cell-matrix ‘niche’ of MSCs, and interdisciplinary studies to exploit this cell-matrix interface to fractionate MSCs.
Recent key publications
Ball, S.G., Shutteworth, C.A. and Kielty, C.M. (2012). Inhibition of platelet-derived growth factor receptor signaling regulates Oct4 and Nanog expression, cell shape and mesenchymal stem cell potency. Stem Cells. 30, 548-60. PubMed
Veevers-Lowe, J., Ball, S.G., Shuttleworth, A. and Kielty, C.M. (2011). Mesenchymal stem cell migration is regulated by fibronectin through 51-integrin-mediated activation of PDGFR- and potentiation of growth factor signals. J. Cell Sci.124, 1288-300. PubMed
Ball, S.G., Merry, C.L.R., Canfield, Worthington, J.J. and Kielty, C.M. (2013). Mesenchymal stromal cells: inhibiting PDGF receptors or depleting fibronectin induces mesodermal progenitors with endothelial potential. Stem Cells in press.