title: Influence of the mechanical environment on the engineering of mineralised tissues using human dental pulp stem cells and silk fibroin scaffolds.
abstract: Teeth constitute a promising source of stem cells that can be used for tissue engineering and regenerative medicine purposes. Bone loss in the craniofacial complex due to pathological conditions and severe injuries could be treated with new materials combined with human dental pulp stem cells (hDPSCs) that have the same embryonic origin as craniofacial bones. Optimising combinations of scaffolds, cells, growth factors and culture conditions still remains a great challenge. In the present study, we evaluate the mineralisation potential of hDPSCs seeded on porous silk fibroin scaffolds in a mechanically dynamic environment provided by spinner flask bioreactors. Cell-seeded scaffolds were cultured in either standard or osteogenic media in both static and dynamic conditions for 47 days. Histological analysis and micro-computed tomography of the samples showed low levels of mineralisation when samples were cultured in static conditions (0.16±0.1 BV/TV%), while their culture in a dynamic environment with osteogenic medium and weekly µCT scans (4.9±1.6 BV/TV%) significantly increased the formation of homogeneously mineralised structures, which was also confirmed by the elevated calcium levels (4.5±1.0 vs. 8.8±1.7 mg/mL). Molecular analysis of the samples showed that the expression of tooth correlated genes such as Dentin Sialophosphoprotein and Nestin were downregulated by a factor of 6.7 and 7.4, respectively, in hDPSCs when cultured in presence of osteogenic medium. This finding indicates that hDPSCs are able to adopt a non-dental identity by changing the culture conditions only. Also an increased expression of Osteocalcin (1.4x) and Collagen type I (1.7x) was found after culture under mechanically dynamic conditions in control medium. In conclusion, the combination of hDPSCs and silk scaffolds cultured under mechanical loading in spinner flask bioreactors could offer a novel and promising approach for bone tissue engineering where appropriate and rapid bone regeneration in mechanically loaded tissues is required.
authors.affiliation: Orofacial Development and Regeneration, Institute of Oral Biology, Centre of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Anna
authors.initials: A
authors.lastname: Woloszyk
authors.affiliation: Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Holsten Dircksen
authors.affiliation: Oral Translational Research, Institute of Oral Biology, Centre of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Nagihan
authors.initials: N
authors.lastname: Bostanci
authors.affiliation: Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
authors.forename: Ralph
authors.initials: R
authors.lastname: Müller
authors.affiliation: Institute for Biomechanics, ETH Zurich, Zurich, Switzerland; Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands; Institute for Complex Molecular Sciences, Eindhoven University of Technology, Eindhoven, the Netherlands.
authors.forename: Sandra
authors.initials: S
authors.lastname: Hofmann
authors.affiliation: Orofacial Development and Regeneration, Institute of Oral Biology, Centre of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Thimios A
authors.initials: TA
authors.lastname: Mitsiadis
mesh_terms: D000293:Adolescent; D053687:Adult Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D049109:Cell Proliferation; D003782:Dental Pulp / Q000166:cytology*; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism; D005349:Fibroins / Q000494:pharmacology*; D006801:Humans; D064231:Nestin / Q000235:genetics / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D010012:Osteogenesis; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D012795:Sialoglycoproteins / Q000235:genetics / Q000378:metabolism; D013314:Stress, Mechanical; D023822:Tissue Engineering; D054457:Tissue Scaffolds / Q000737:chemistry*; D000099311:Dentin Sialophosphoprotein
chemical_list: D016326:Extracellular Matrix Proteins; D005349:Fibroins; D064231:Nestin; D015675:Osteocalcin; D010750:Phosphoproteins; D012795:Sialoglycoproteins; D000099311:Dentin Sialophosphoprotein