Young Persons’ World Lecture Competition Response of human mesenchymal stem cells to modified biomaterial surfaces Mura McCafferty Young Persons’ World Lecture Competition Kuala Lumpur September 2010

Tissue Engineering Holds the promise of being able to produce functional tissue and organs for transplant Skin Trachea Bladder Ear

Stem Cells

Mesenchymal Stem Cells (MSCs) Can be sourced from the bone marrow, peripheral blood, adipose tissue, dental pulp and synovium Can be easily isolated and expanded in culture to generate large numbers of cells Multipotent - capable of producing cells of different lineages Magnification 40X

Mesenchymal Stem Cells

Bone Tissue Engineering Bone struggles to heal large defects caused by: Disease Non-union fracture Age Tumors Congential Deformations Commonly used methods to aid healing of large defects include: Intramedullary pins Plating Synamic external fixation Bone grafts

MSCs and bone tissue engineering Dexamethasone L-ascorbic acid-2-phosphatase β-glycerophosphate Expensive May cause adverse reaction to body Expand MSCs in vitro Isolate MSCs from patient Induce osteogenic differentiation Transplant cells back to defect site

MSCs and bone tissue engineering There is therefore an existing need to develop alternative methods of inducing the osteogenic differentiation of MSCs One such route: FUNCTIONAL BIOMATERIALS

Control of osteogenic differentiation through modified biomaterials The chemical and physical properties of a biomaterial has a significant effect on cell behaviour It is thought, and has been demonstrated in some studies, that surface topographical features have the potential to induce osteogenic differentiation of MSCs Dalby, M.J., et al., The control of human mesenchymal cell differentiation using nanoscale symmetry and disorder. Nat Mater, 2007. 6(12): p. 997-1003. Sjostrom, T., et al., Fabrication of pillar-like titania nanostructures on titanium and their interactions with human skeletal stem cells. Acta Biomater, 2009. 5(5): p. 1433-41. Bigi, A., et al., In vitro culture of mesenchymal cells onto nanocrystalline hydroxyapatite-coated Ti13Nb13Zr alloy. J Biomed Mater Res A, 2007. 82(1): p. 213-21. MSCs cultured on planar PMMA MSCs cultured on embossed PMMA

Sputter Deposition Previous published studies have shown that sputter deposited titanium (Ti) and calcium phosphate (CaP) thin films can promote bone cell attachment and proliferation Sputter deposition is a thin film coating process that has been used successfully to provide bioactive layers that are inherently osteoconductive Sputter deposited Ti and CaP thin films have promising potential for directing the osteogenic differentiation of MSCs 500 nm CaP Titanium Substrate

AFM images showing 3D analysis of substrates Glass: Amorphous glass substrate (control) Ti: Annealed (500°C) titanium coating on glass TiCaP: Annealed (500°C) calcium phosphate coating on Ti interlayer on glass Glass Ti Ti/CaP AFM images showing 3D analysis of substrates Surface Roughness Sample Average Ra (nm) Glass 3 ± 0.5 Ti 17 ± 2 Ti/CaP 22 ± 2

MSCs cultured in osteogenic media Alizarin Red Staining DAY 28 DAY 14 DAY 21 DAY 7 NORMAL MEDIA Magnification 40x OSTEOGENIC MEDIA Magnification 40x

Gene expression analysis - Collagen I mRNA expression of Collagen I in MSCs cultured on control, Ti and Ti/CaP substrates

Gene expression analysis - Osteopontin mRNA expression of Osteopontin in MSCs cultured on control, Ti and Ti/CaP substrates

Immunocytochemical Localisation of Osteopontin Control (Normal Media) Control (Osteogenic Media) Ti Ti/CaP

Summary While MSCs hold great promise for use in bone tissue engineering applications, there is a need for more effective in vitro expansion and differentiation methods Reduce dependence on bone graft treatment Improve healing Reduce recovery time CaP and Ti sputter deposited surfaces have utility in directing the osteogenic differentiation of MSCs While these are promising results and further research to fully understand if this is as a result of the surface topography as supplied by the Ti coating or by the potential bioactive nature of the CaP

Acknowledgements Professor Brian Meenan Dr George Burke Dr Peter O’Hare Linzi Charters Chris O’Kane Dr Fiona McKavanagh