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

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

Bladder

Trachea

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

Induce osteogenic differentiation

Transplant cells back to defect site

Isolate MSCs from patient

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

500 nm

TitaniumSubstrate

CaP

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

SubstratesGlass: 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

Surface Roughness

Sample Average Ra (nm)

Glass 3 ± 0.5

Ti 17 ± 2

Ti/CaP 22 ± 2

AFM images showing 3D analysis of substrates

MSCs cultured in osteogenic media

DAY 7DAY 21DAY 14DAY 28

NORMAL MEDIAMagnification 40x

OSTEOGENIC MEDIAMagnification 40x

Alizarin Red Staining

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