Ceramic hydroxyapatite coating on titanium implants drives selective bone marrow stromal cell adhesion

: The aim of this study was to determine the cell characteristics that regulate implant osseointegration. The heterogeneity of bone marrow stromal cells obtained from 11 donors was assessed by measuring the expression of a large panel of adhesion molecules. Large differences in expression of adhesion molecules were detected depending on the culture conditions used. Cells cultured in fetal bovine serum induced the expression of different adhesion molecules from cells cultured in human serum. Donor‐to‐donor variation was determined by measuring the expression of adhesion molecules for stromal cells obtained from different donors that were processed identically. Fat adherent cells but also loose bone marrow cells showed large differences in expression of some but not all adhesion molecules. The flow cytometric data demonstrated large heterogeneity in expression of adhesion molecules, and this heterogeneity was influenced by culture conditions and varied from donor to donor. This demonstrates that the implant encounters different cell types, which could lead to different levels of integration. Surprisingly, in vitro only a subfraction of bone marrow stromal cells attached to titanium coated with ceramic hydroxyapatite. Adaptation of all cell types present in heterogeneous bone marrow to a coated surface is apparently not possible. Differential binding was not caused by aberrant staining of the stromal cells as the results were confirmed with bone marrow cells obtained from transgenic GFP mice. These results demonstrate that hydroxyapatite ceramics are selective in cell recruitment from the bone marrow, explaining the differences found in vivo for these coatings compared with titanium. Résumé Le but de cette étude a été de trouver les caractéristiques cellulaires qui régulent l'ostéoïntégration implantaire. Les cellules du stroma de la moeëlle osseuse prélevée chez onze donneurs ont étéétudiées en mesurant l'expression d'un large éventail de molécules d'adhésion. De grandes différences dans l'expression des molécules d'adhésion ont été dues aux conditions de culture utilisées. Les cellules cultivées dans le sérum bovin foetal produisaient l'expression d'autres molécules d'adhésion que les cellules mises en culture dans le sérum humain. Une variation de donneur à donneur a été déterminée en mesurant l'expression des molécules d'adhésion des cellules obtenues de différents donneurs qui ont été analysées de manière identique. Les cellules adhérentes de la graisse