Tissue Engineered Rostral Migratory Stream for Directed Neuronal Replacement - PROJECT SUMMARY Chronic disability due to traumatic brain injury (TBI) affects 2% of the total population, and neuronal loss is generally considered permanent, owing to limited capacity for neuroregeneration in the adult mammalian brain. There are currently no approved treatments for improving recovery after TBI, and innovative approaches to enhance neuroregeneration are desperately needed. Intriguingly, new neurons are generated in the subventricular zone (SVZ) and then guided to the olfactory bulb/tract (and possibly striatum) via the rostral migratory stream (RMS) for integration into existing circuitry. Recent publications have demonstrated that SVZ neuroblasts can be redirected into lesions, differentiate into region-specific neuronal cell types, integrate into circuitry, and improve functional recovery in adult rodents, but a translational strategy to direct and enhance neuroblast migration into lesions has yet to be established. To address this challenge, we have assembled a multi-disciplinary team of stem cell specialists, neurobiologists, clinicians, and tissue engineers to develop the first anatomically-inspired microtissue designed to structurally and functionally emulate the glial tube of the RMS. In an exciting breakthrough, our team developed novel microtissue engineering techniques that promote the self-assembly of astrocytes into longitudinally aligned bundles that recapitulate the organization of the glial tube of the RMS. To date, we have biofabricated this Tissue Engineered Rostral Migratory Stream (TE-RMS) using rodent derived astrocytes as well as human stem cell derived astrocytes and, importantly, we have shown that the TE-RMS directly facilitates the alignment and migration of immature neurons in vitro and in vivo. In the current proposal, we will first validate the TE-RMS as an in vitro test bed to elucidate mechanisms of neuronal progenitor migration and cell fate determination (Aim 1). We will then test the ability of the TE-RMS to divert endogenous neuronal progenitors in vivo and repair damaged cerebral cortex following experimental TBI in rats (Aim 2). In this Aim, the TE-RMS will be stereotaxically microinjected after the acute injury period to span from the SVZ into lesioned tissue, and the redirection of migrating neurons to repopulate cortical areas, functional integration with residual circuitry, and facilitation of behavioral recovery will be assessed. Finally, as a first step towards clinical translation, we will perform in vitro and in vivo studies to validate the TE-RMS built using astrocytes derived from stem cells harvested from adult human gingiva to develop methods for the eventual creation of autologous, patient-derived implants from an easily accessible cell source (Aim 3). The TE-RMS recapitulates the brain's own method for delivery and integration of new neurons. Thus, the execution of these Aims will significantly advance a translational bioengineering approach capable of providing targeted and sustained cell replacement following neurotrauma and/or degeneration. Our team is uniquely positioned to provide a feasible, yet highly innovative neuroregenerative approach that can have a significant impact on patients suffering from the otherwise intractable consequences of TBI.
