title: Inflammatory cell response to ultra-thin amorphous and crystalline hydroxyapatite surfaces.
abstract: It has been suggested that surface modification with a thin hydroxyapatite (HA) coating enhances the osseointegration of titanium implants. However, there is insufficient information about the biological processes involved in the HA-induced response. This study aimed to investigate the inflammatory cell response to titanium implants with either amorphous or crystalline thin HA. Human mononuclear cells were cultured on titanium discs with a machined surface or with a thin, 0.1 μm, amorphous or crystalline HA coating. Cells were cultured for 24 and 96 h, with and without lipopolysaccharide (LPS) stimulation. The surfaces were characterized with respect to chemistry, phase composition, wettability and topography. Biological analyses included the percentage of implant-adherent cells and the secretion of pro-inflammatory cytokine (TNF-α) and growth factors (BMP-2 and TGF-β1). Crystalline HA revealed a smooth surface, whereas the amorphous HA displayed a porous structure, at nano-scale, and a hydrophobic surface. Higher TNF-α secretion and a higher ratio of adherent cells were demonstrated for the amorphous HA compared with the crystalline HA. TGF-β1 secretion was detected in all groups, but without any difference. No BMP-2 secretion was detected in any of the groups. The addition of LPS resulted in a significant increase in TNF-α in all groups, whereas TGF-β1 was not affected. Taken together, the results show that thin HA coatings with similar micro-roughness but a different phase composition, nano-scale roughness and wettability are associated with different monocyte responses. In the absence of strong inflammatory stimuli, crystalline hydroxyapatite elicits a lower inflammatory response compared with amorphous hydroxyapatite.
authors.affiliation: Department of Biomaterials, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Box 412, Gothenburg, SE-405 30, Sweden.
authors.forename: Louise
authors.initials: L
authors.lastname: Rydén
authors.affiliation: Department of Biomaterials, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Box 412, Gothenburg, SE-405 30, Sweden. omar.omar@biomaterials.gu.se.|BIOMATCELL, VINN Excellence Center of Biomaterials and Cell Therapy, Gothenburg, Sweden. omar.omar@biomaterials.gu.se.
authors.forename: Omar
authors.identifier: http://orcid.org/0000-0002-2610-1294
authors.initials: O
authors.lastname: Omar
authors.affiliation: Department of Biomaterials, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Box 412, Gothenburg, SE-405 30, Sweden.|BIOMATCELL, VINN Excellence Center of Biomaterials and Cell Therapy, Gothenburg, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Johansson
authors.affiliation: Department of Oral and Maxillofacial Surgery and Oral Medicine, Faculty of Odontology, Malmö University, Malmö, Sweden.
authors.forename: Ryo
authors.initials: R
authors.lastname: Jimbo
authors.affiliation: Department of Biomaterials, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Box 412, Gothenburg, SE-405 30, Sweden.|BIOMATCELL, VINN Excellence Center of Biomaterials and Cell Therapy, Gothenburg, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Palmquist
authors.affiliation: Department of Biomaterials, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Box 412, Gothenburg, SE-405 30, Sweden.|BIOMATCELL, VINN Excellence Center of Biomaterials and Cell Therapy, Gothenburg, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Thomsen
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism; D002460:Cell Line; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D003460:Crystallization; D016207:Cytokines / Q000378:metabolism; D015921:Dental Implants; D017886:Durapatite / Q000737:chemistry*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007249:Inflammation; D007963:Leukocytes, Mononuclear / Q000166:cytology; D008070:Lipopolysaccharides / Q000737:chemistry*; D008422:Materials Testing; D051379:Mice; D009000:Monocytes / Q000166:cytology; D016348:Osseointegration / Q000187:drug effects; D000067996:RAW 264.7 Cells; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D020099:Coated Materials, Biocompatible; D016207:Cytokines; D015921:Dental Implants; D008070:Lipopolysaccharides; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; D017886:Durapatite; D014025:Titanium