title: Three-dimensional hypoxic culture of human mesenchymal stem cells encapsulated in a photocurable, biodegradable polymer hydrogel: a potential injectable cellular product for nucleus pulposus regeneration.
abstract: Nucleus pulposus (NP) tissue damage can induce detrimental mechanical stresses and strains on the intervertebral disc, leading to disc degeneration. This study demonstrates the potential of a novel, photo-curable, injectable, synthetic polymer hydrogel (pHEMA-co-APMA grafted with polyamidoamine (PAA)) to encapsulate and differentiate human mesenchymal stem cells (hMSC) towards a NP phenotype under hypoxic conditions which could be used to restore NP tissue function and mechanical properties. Encapsulated hMSC cultured in media (hMSC and chondrogenic) displayed good cell viability up to day 14. The genotoxicity effects of ultraviolet (UV) on hMSC activity confirmed the acceptability of 2.5min of UV light exposure to cells. Cytotoxicity investigations revealed that hMSC cultured in media containing p(HEMA-co-APMA) grafted with PAA degradation product (10% and 20%v/v concentration) for 14days significantly decreased the initial hMSC adhesion ability and proliferation rate from 24hrs to day 14. Successful differentiation of encapsulated hMSC within hydrogels towards chondrogenesis was observed with elevated expression levels of aggrecan and collagen II when cultured in chondrogenic media under hypoxic conditions, in comparison with culture in hMSC media for 14days. Characterization of the mechanical properties revealed a significant decrease in stiffness and modulus values of cellular hydrogels in comparison with acellular hydrogels at both day 7 and day 14. These results demonstrate the potential use of an in vivo photo-curable injectable, synthetic hydrogel with encapsulated hMSC for application in the repair and regeneration of NP tissue.
authors.affiliation: Loughborough University, Wolfson Building, School of Manufacturing and Engineering, Loughborough, Leicestershire LE11 3TU, UK; Guy Hilton Research Centre, Institute of Science and Technology in Medicine, University of Keele, Thornburrow Drive, Stoke-on-Trent, Staffordshire ST4 7QB, UK.
authors.forename: Deepak
authors.initials: D
authors.lastname: Kumar
authors.affiliation: Fondazione Filarete, Viale Ortles 22/4, 20139 Milan, Italy.
authors.forename: Irini
authors.initials: I
authors.lastname: Gerges
authors.affiliation: Fondazione Filarete, Viale Ortles 22/4, 20139 Milan, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Tamplenizza
authors.affiliation: Fondazione Filarete, Viale Ortles 22/4, 20139 Milan, Italy; CIMAINA, Dipartimento di Fisica, Via Celoria 16, 20133 Milan, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Lenardi
authors.affiliation: Guy Hilton Research Centre, Institute of Science and Technology in Medicine, University of Keele, Thornburrow Drive, Stoke-on-Trent, Staffordshire ST4 7QB, UK. Electronic address: n.r.forsyth@keele.ac.uk.
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Forsyth
authors.affiliation: Loughborough University, Wolfson Building, School of Manufacturing and Engineering, Loughborough, Leicestershire LE11 3TU, UK. Electronic address: Y.Liu3@lboro.ac.uk.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
mesh_terms: D020341:Absorbable Implants; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured; D004867:Equipment Design; D019544:Equipment Failure Analysis; D048091:Guided Tissue Regeneration / Q000295:instrumentation; D006801:Humans; D020100:Hydrogels / Q000737:chemistry* / Q000528:radiation effects; D007267:Injections; D007403:Intervertebral Disc / Q000166:cytology / Q000254:growth & development*; D008422:Materials Testing; D045164:Mesenchymal Stem Cell Transplantation / Q000295:instrumentation*; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000502:physiology*; D010777:Photochemistry / Q000379:methods; D011474:Prosthesis Design; D012038:Regeneration / Q000502:physiology*; D014466:Ultraviolet Rays
chemical_list: D020100:Hydrogels
keywords: Chondrogenic differentiation; Encapsulation; Hypoxia; Mesenchymal stem cells; Photocurable hydrogels