The impact of culture variables on 3D human in vitro bone remodeling; a design of experiments approach

Human in vitro bone remodeling models, using osteoclast-osteoblast co-cultures, could facilitate the investigation of human healthy (i.e., balanced) and pathological (i.e., unbalanced) bone remodeling while reducing the need for animal experiments. Although current in vitro osteoclast-osteoblast co-cultures have improved our understanding of bone remodeling, they lack culture method and outcome measurement standardization, which is hampering reproducibility and translatability. Therefore, in vitro bone remodeling models could benefit from a thorough evaluation of the impact of culture variables on functional and translatable outcome measures, with the aim to reach healthy balanced osteoclast and osteoblast activity. Using a resolution III fractional factorial design, we identified the main effects of commonly used culture variables on bone turnover markers in a robust in vitro human bone remodeling model. Our model was able to capture physiological quantitative resorption - formation coupling along all conditions, whereby remodeling could be enhanced by external stimuli. Especially culture conditions of two runs showed promising results, where conditions of one run could be used as a high bone turnover system and conditions of another run as a self-regulating system as the addition of osteoclastic and osteogenic differentiation factors was not required for remodeling. The results generated with our in vitro model allow for better translation between in vitro studies and towards in vivo studies, for improved preclinical bone remodeling drug development. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=67 SRC="FIGDIR/small/516134v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@1068cc1org.highwire.dtl.DTLVardef@102d788org.highwire.dtl.DTLVardef@1942864org.highwire.dtl.DTLVardef@1e7d8b7_HPS_FORMAT_FIGEXP M_FIG C_FIG