Prøveforelesning
Bedømmelseskomité
Reseacher MD,PhD Lise Sofie Haug Nissen-Meyer Bioteknologisenteret, Universitetet i Oslo
Professor MD, PhD Lars Magnus Bjursten Department of Experimental Research, University of Lund, Malmø General Hospital
Professor DDS, PhD Magne Bryne Institutt for oral biologi, Det odontologiske fakultet, Universitetet i Oslo
Leder av disputas: Professor Morten Rykke
Veileder: Professor Janne Elin Reseland og Professor Ståle Petter Lyngstadaas
Sammendrag
Bone cell growth in artificial scaffolds; the importance of 3D growth, scaffold architecture and surface chemistry.
There is an increasing demand for bone repair due to bone lost cause by tumors, infections or trauma. Along the past decade a paradigm shift is taking place from using tissue autologous and allogenic bone grafts to biomaterials. Ideally, these materials should create more tissue-like multi-functional materials that are able to simultaneously provide structural support and complex biological signals that consequently restore the lost or diseased tissue. The selection of the specific material will depend on the site to be constructed. A graft material composed of titanium dioxide (solid material) and a hydrogel (inject-able material) hydroxylpropyl-methyl cellulose gel (HPMC, HISTOCARE™) were chosen as substrate candidates to evaluate their properties and characteristics for cell therapy approaches in treatment of bone defects. We have focused on testing the biocompatibility of ceramic titanium dioxide (TiO2) bone graft substitute and HPMC gel and on investigating both the proliferation of mesenchymal progenitor cells in the three dimensional environment provided by these two materials.
Recent studies have suggested that trace elements or foreign substances on the implant surface significantly affect the clinical treatment outcome. We compared six different commercial titanium dioxide powders in order to choose the most appropriate raw powder for making titanium dioxide scaffolds. The level of elemental contaminations on different titanium dioxide powders varied greatly. We found a strong correlation between aluminium and silicon and the inflammatory response and cytotoxicity measured. It is suggested that concentration of these elements should be reduced in order to enhance the scaffolds’ biocompatibility.
The TiO2 bone graft substitute show to provided appropriate conditions for enhanced cell proliferation and viability compared to three commercially available implants. These results were strongly associated with higher porosity, interconnectivity and surface area-to-volume ratio structural properties of TiO2 bone graft substitute.
The injectable HPMC gel (HISTOCARE™) provided low toxicity, high proliferation rate, and 3-dimentional cell organization compared GEltrex™ and monolayer cell culture. These characteristics make HPMC gel (HISTOCARE™) a superior substrate for expansion of stem cell and osteoprogenitor cell in vitro cultures for tissue engineering and research purposes. Due to the injectable property of HPMC gel (HISTOCARE™), it allows easy transition from 3-D culture of stem cells and osteoprogenitor cells from in vitro to in vivo for cell therapy and clinical applications in a minimal invasive manner.