Anti-DKK1 Enhances the Early Osteogenic Differentiation of Human Adipose-Derived Stem/Stromal Cells

Adipose-derived stem/stromal cells (ASCs) have been previously used for bone repair. However, significant cell heterogeneity exists within the ASC population, which has the potential to result in unreliable bone tissue formation and/or low efficacy. Although the use of cell sorting to lower cell heterogeneity is one method to improve bone formation, this is a technically sophisticated and costly process. In this study, we tried to find a simpler and more deployable solution-blocking antiosteogenic molecule Dickkopf-1 (DKK1) to improve osteogenic differentiation. Human adipose-derived stem cells were derived from = 5 samples of human lipoaspirate. In vitro, anti-DKK1 treatment, but not anti-sclerostin (SOST), promoted ASC osteogenic differentiation, assessed by alizarin red staining and real-time polymerase chain reaction (qPCR). Increased canonical Wnt signaling was confirmed after anti-DKK1 treatment. Expression levels of DKK1 peaked during early osteogenic differentiation (day 3). Concordantly, anti-DKK1 supplemented early (day 3 or before), but not later (day 7) during osteogenic differentiation positively regulated osteoblast formation. Finally, anti-DKK1 led to increased transcript abundance of the Wnt inhibitor SOST, potentially representing a compensatory cellular mechanism. In sum, DKK1 represents a targetable "molecular brake"on the osteogenic differentiation of human ASC. Moreover, release of this brake by neutralizing anti-DKK1 antibody treatment at least partially rescues the poor bone-forming efficacy of ASC.