Leveraging Viscosity to Unlock the Osteogenic Potential of BMP-2 Mimetic DWIVA.

Growth factor mimetics offer great potential for osteogenic biomaterials; yet, their use remains limited, likely due to an incomplete understanding of the effects of the microenvironment on their activity. The extracellular matrices (ECMs) where growth factors are presented in vivo are viscoelastic environments, where dynamic receptor-ligand interactions drive cellular responses. Here, supported lipid bilayers of varying viscosity are used as 2D dynamic ECM models, where the bone morphogenetic 2 (BMP-2) mimetic DWIVA is presented to mesenchymal stem cells alongside the adhesive peptide RGD. DWIVA is demonstrated to have no impact on mechanotransductive processes, including actin organisation, focal adhesion formation and YAP localisation, which are exclusively controlled by viscosity via RGD. Interestingly, DWIVA promotes osteogenic markers' expression only on a viscous bilayer, through a process that involves non-canonical BMP-2 pathways; on a mobile bilayer or on a static control, it lacks osteogenic activity. Crucially, osteogenesis is accompanied by a translocation of BMP receptor 1a to the cell edge, where it colocalises with focal adhesions. Our ECM models hence reveal that both a viscosity-enabled threshold of cell-generated forces and a dynamic environment are necessary to harness the osteogenic potential of DWIVA, uncovering key microenvironment properties for the design of DWIVA-based biomaterials.