Multi-lineage MSC differentiation via engineered morphogen fields

Tissue loss due to oral diseases requires the healing and regeneration of tissues of multiple lineages. While stem cells are native to oral tissues, a current major limitation to regeneration is the ability to direct their lineage-specific differentiation. This work utilizes polymeric scaffold systems with spatiotemporally controlled morphogen cues to develop precise morphogen fields to direct mesenchymal stem cell differentiation. First, a simple three-layer scaffold design was developed that presented two spatially segregated, lineage-specific cues (Dentinogenic TGF-β1 and Osteogenic BMP4). However, this system resulted in diffuse morphogen fields, as assessed by the in vitro imaging of cell-signaling pathways triggered by the morphogens. Mathematical modeling was then exploited, in combination with incorporation of specific inhibitors (neutralizing antibodies or a small molecule kinase inhibitor) into each morphogen in an opposing spatial pattern as the respective morphogen, to design a five-layer scaffold that was predicted to yield distinct, spatially segregated zones of morphogen signaling. To validate this system, undifferentiated MSCs were uniformly seeded in these scaffold systems, and distinct mineralized tissue differentiation were noted within these morphogen zones. Finally, to demonstrate temporal control over morphogen signaling, latent TGF-β1 was incorporated into one region of a concentric scaffold design, and laser treatment was used to activate the morphogen on-demand and to induce dentin differentiation solely within that specific spatial zone. This study demonstrates a significant advance in scaffold design to generate precise morphogen fields that can be used to develop in situ models to explore tissue differentiation and may ultimately be useful in engineering multi-lineage tissues in clinical dentistry.