Kraft, David Christian Evar5; Melsen, Birte6; Bindslev, Dorthe Arenholt7
1 Department of Orthodontics, Faculty of Health Sciences, Aarhus University, Aarhus University2 Department of Dentistry and Oral Health - Dentistry, Department of Dentistry and Oral Health, Health, Aarhus University3 Department of Dentistry and Oral Health - Department of Orthodontics, Department of Dentistry and Oral Health, Health, Aarhus University4 Department of Forensic Medicine - Retspatologisk, Department of Forensic Medicine, Health, Aarhus University5 Department of Dentistry and Oral Health - Dentistry, Department of Dentistry and Oral Health, Health, Aarhus University6 Department of Dentistry and Oral Health - Department of Orthodontics, Department of Dentistry and Oral Health, Health, Aarhus University7 Department of Forensic Medicine - Retspatologisk, Department of Forensic Medicine, Health, Aarhus University
Recent studies have shown that dental pulp cells possess stem cell like potential and thus may be potential candidates for tissue engineering purposes particularly in the oro-facial region. Successful tissue engineering ideally requires that newly formed bone adapts its mass, shape, and trabecular architecture to the prevailing mechanical load and should be able to conduct bone cell-specific functions, such as bone remodeling. In vitro investigation of the responsiveness of different cell types to mechanical loading is so far a relative new research field. The aim of this study was to establish and characterize cell lines from human 3rd molar dental pulp tissue to determine whether human dental pulp-derived cells (DPCs) are osteogenic and responsive to mechanical loading by pulsating fluid flow (PFF) in vitro. Methods: Human DPCs used for this study were characterized by measuring proliferation, osteogenic potential in vitro and expression of mesenchymal stem cells (MSC) surface markers. DPCs were subjected to 1-h PFF (0.7 +/- 0.3Pa, 5Hz) and the response was quantified by measuring nitric oxide (NO) and prostaglandin E 2 (PGE(2)) production, and gene expression of cyclooxygenase (COX)-1 and COX-2. We also assessed bone formation by DPCs on hydroxyapatite-tricalcium phosphate granules after subcutaneous implantation in mice. Results: We found that DPCs are intrinsically mechanosensitive and, like osteogenic cells, respond to PFF-induced fluid shear stress. Implantation of DPCs resulted in formation of woven mineralized tissue, and lamellar bone-like structures. DPCs showed potent osteogenic potential in vitro high proliferation capacity, with 0.5 population doublings per day and high population doublings before reaching senescence. More than 90% of the DPCs expressed MSC surface markers CD44, CD105, CD73, CD146 and CD166. Conclusions: This study is the first to show that human DPCs can form bone, and like osteogenic cells derived from e.g. bone marrow, are responsive to pulsating fluid shear stress. DPCs might thus be able to perform bone-like functions during mineralized tissue remodeling in vivo, and therefore provide a promising new tool for regenerative dentistry, for example mineralized tissue engineering to restore bone defects in relation to periodontitis, periimplantatis and orofacial surgery. Experiments in progress have proven that DPCSs are also useful for assessing the surface characteristics and biocompatibility of e.g. implant surfaces.