Combinatorial presentation of cartilage-inspired peptides on nanopatterned surfaces enables directed differentiation of human mesenchymal stem cells towards distinct articular chondrogenic phenotypes

Human articular cartilage is a complex multi-zonal tissue in which cells displaying three chondrocyte phenotypes (persistent, transient and hypertrophic) are supported and maintained by distinctly different (zonal) combinations of extracellular matrix (ECM) molecules. Articular cartilage has limited regenerative capacity, even though adjacent to the medullary cavity, an easily accessible reservoir of multipotent progenitor cells capable of eliciting repair, (human) mesenchymal stromal/stem cells (hMSCs). A greater understanding of the impacts of the extracellular cues provided in each zone of articular cartilage on hMSCs thus offers the potential to develop new scaffolds that can effect multi-zonal cartilage generation. In this work, we have systematically surveyed combinatorial mixtures of peptide sequences derived from ECM and cell adhesion molecules (CAMs) found to be present in cartilage and bone tissues, at a range of concentrations and ratios, to assess their ability to modulate hMSC fate. We show that directed differentiation of hMSCs towards persistent, transient and hypertrophic chondrogenic phenotypes is possible via the controlled presentation of specific peptide combinations on self-assembled polymeric coatings displaying hexagonally-packed nanodomains. These biomimetic substrates highlight that a high level of spatial and compositional control over biochemical cues is required by hMSCs in order to specify different cellular sub-phenotypes.