Summary: Tissue repair is a complex process that involves a delicate temporal balance between inflammatory and regenerative mechanisms. In health, initial inflammatory events are replaced by regenerative processes in a coordinated manner. This sequence is disrupted in diseased states and complex injuries. The goal of regenerative medicine is to reestablish this balance by preventing chronic/aberrant inflammation and promoting repair and regeneration in a tissue-specific manner. While stem cell and growth factor therapies have been explored for this purpose traditionally, recent studies highlight the immunomodulatory and protective functions of mesenchymal stem cell derived extracellular vesicles (MSC EVs). Although MSC EVs possess versatile properties, to engage tissue-specific pathways and fit the goals of precision medicine with translational relevance, MSC EVs have to be engineered for enhanced pathway-specific functionality and delivered on site in a spatially and temporally controlled manner. In this proposal, leveraging our preliminary results and our expertise in EV biology, immunology and bone biology, we hypothesize that: Spatiotemporal control of immunomodulatory and regenerative pathways can be achieved by selective incorporation of Functionally Engineered EVs (FEEs)in 3D printed scaffolds. Using bone regeneration as a model system, we will test this hypothesis in three specific aims. In aim 1, we will generate functionally engineered EVs (FEEs) that target specific osteoinductive and immunomodulatory pathways. In aim 2, we will develop a photocrosslinkable alginate-based delivery system with EV carrier and release motifs for spatial localization and temporally controlled delivery of the FEEs developed in aim 1. In aim 3, we will utilize 3D printing technology to print defined structures encapsulating the FEEs for spatially and temporally controlled biphasic delivery in vivo. This system will be tested in a rat calvarial defect model. From the proposed studies, we will develop a platform technology that can impact the field of regenerative medicine beyond the craniofacial and musculoskeletal systems.

Narrative: Effective tissue repair requires the delivery of immunomodulatory and reparative cues in a spatially and temporally controlled manner. Using bone regeneration as a model, this proposal aims to develop functionally engineered extracellular vesicles (FEEs) and deliver them in a spatially and temporally controlled manner using 3D printing technology. Successful completion of this work will result in the development of a technique that can be used to control inflammation and enhance tissue repair bone as well as other organ systems.