Synergistic Enhancement of Adeno-Associated Virus-Mediated In Vivo Direct Neuronal Reprogramming by Spatially Aligned Fibrous Matrices in Spinal Cord Injury Models

Abstract

In vivo direct neuronal reprogramming approaches, which convert host glial cells into neurons without using exogenous cellular supplies, have become a powerful strategy for neuronal regeneration. However, their effectiveness in severe spinal cord injury (SCI) models with a physical gap between the injured sites is unclear. This study highlights the important role of physical guidance in increasing the therapeutic efficacy of in vivo reprogramming technologies in SCI hemisection models. Reactive astrocytes are selected as host targets for conversion into neurons. An astrocyte-tropic adeno-associated viral (AAV) vector, AAVShH19, is used to deliver the neuronal transcription factor NeuroD1 to reactive astrocytes. The infusion of AAVShH19-NeuroD1 induces astrocyte-to-neuron conversion, but improvement of locomotive function is not observed due to the physical distance between the rostral and caudal sides, which impedes axonal extension. To address this issue, electrospun fibrous matrices with adhesive and aligned structural features are implanted into the hemisection cavity and designed to release AAVShH19-NeuroD1. The combination of the AAV-mediated reprogramming approach and the matrices promoted astrocyte-to-neuron conversion and coordinated the elongation of neuronal axons along the fibers, leading to improved synaptic connections and motor function. This study demonstrates the potential of physical support to enhance the efficacy of direct neuronal reprogramming.