The overall goal of this REVISED proposal is to design and fabricate biomimetic scaffolds that mimic how certain embryonic tissues induce whole organ formation in the embryo, and ultimately, to use these developmentally-inspired materials to engineer artificial tissues and organs in adult animals. As a proof-of- principle, we propose to fabricate multifunctional scaffolds that induce formation of differentiated tooth starting with adult mesenchymal stem cells (aMSCs) and adult oral epithelial cells (aOECs). Our approach is based our past work which shows that during embryogenesis, the dental epithelium transfers its inductive capabilities to undifferentiated dental mesenchyme by stimulating a mesenchymal condensation response, and that the resulting physical compaction of cells is sufficient to trigger this developmental switch in vitro as well as subsequent tooth differentiatio in vivo. In addition, we now include new preliminary results that show we can fabricate thermosensitive polymer scaffolds that shrink and artificially induce mesenchymal condensation when placed at body temperature, and that tooth differentiation can be stimulated both by warming in vitro and by combining these materials with embryonic dental mesenchymal cells and implanting them under the kidney capsule in mice in vivo. Based on analysis of the embryonic tooth induction process, we believe that we can enhance the efficiency of this artificial induction process by including other key extracellular matrix (ECM) molecules and morphogens in these scaffolds that contribute to normal tooth development;we also plan to optimize the design and fabrication of the mechano-inductive scaffolds. Thus, the long-term goal of this proposal is to fabricate biomimetic polymer scaffolds that can reprogram aMSCs to differentiate into inductive mesenchyme that instructs normal aOECs to form a differentiated tooth in vivo.
The Specific Aims of this proposal include: 1) to fabricate a mechanically actuatable biomimetic polymer scaffold that induces aMSCs to undergo odontogenic differentiation in vitro by producing cell compaction, 2) to identify molecules that mediate tooth formation during embryogenesis that can enhance compaction-induced tooth differentiation in vitro, and 3) to bioengineer a differentiated tooth in vivo using an optimized biomimetic scaffold in combination with aMSCs and aOECs in a mouse model.
A major goal of the fields of Tissue Engineering and Regenerative Medicine is to stimulate new tissue formation, with the ultimate challenge being able to induce regeneration of whole organs. Past approaches focused on use of tissue scaffolds that were fabricated to resemble the ECM of the relevant adult organs, or on use of stem cells that can undergo specific lineage switching and drive tissue formation. In this proposal, we focus on an alternative approach: we seek to understand how embryonic tissues induce organ formation using whole tooth as a model system, and to leverage this knowledge to fabricate biomimetic scaffolds that can reprogram adult mesenchymal stem cells (aMSCs) so that they can induce adult oral epithelial cells (aOECs) to form new teeth in vivo. Thus, the overall objective of this proposal is to explore how embryonic tissues induce whole organ formation using tooth as a model system, and to use this knowledge to fabricate synthetic scaffolds with the appropriate set of mechanical, adhesive and chemical cues necessary to induce adult cells to 'reboot'and regenerate new teeth in a living animal.