Direct reprogramming of astrocytes to neurons leads to functional recovery after stroke

Abstract

Stroke is the leading cause of adult disability with few treatment options for stroke survivors. Astrocyte reprogramming to neurons enables the targeted in vivo generation of new cells at the site of injury and represents a novel approach for brain repair. A number of studies have demonstrated successful conversion of astrocytes to neurons in various models of brain injury and disease; however, the impact of this strategy on tissue and functional outcome following stroke is not well established. Using AAV delivery of the transcription factor NeuroD1, we reprogrammed astrocytes 7 days after endothelin-1 induced cortical stroke, and studied the long-term cellular and functional outcomes. We found that by 63 days post-stroke, 20% of neurons in the perilesional cortex were reprogrammed. Furthermore, reprogrammed neurons had matured into regionally appropriate neuronal subtypes. Importantly, this treatment was associated with improved functional outcome using the foot fault test and gait analysis. Together, our findings indicate that in vivo reprogramming is a promising regenerative approach for stroke repair.

Enhancing NeuroD1 Expression to Convert Lineage-Traced Astrocytes into Neurons

“…While precise mechanisms behind such high barrier in lineage-traced astrocytes warrant further study, one possibility is that lineage-traced astrocytes require Cre-LoxP-mediated DNA recombination, which involves DNA cutting and annealing. For any healthy cell, DNA cutting and annealing is a kind of DNA damage which may trigger massive cellular responses including DNA methylation and other epigenetic modifications (Karakaidos et al, 2020; Livingston et al, 2020; Loonstra et al, 2001). Given the fact that the lineage-traced astrocytes behave very differently from WT astrocytes in terms of conversion, we strongly advise the entire AtN conversion field to be extra cautious when using lineage-traced astrocytes for reprogramming purpose.…”

Astrocyte-Derived Neuronal Transdifferentiation as a Therapy for Ischemic Stroke: Advances and Challenges

“…Some studies revealed considerable structural [ 32 ] and functional repair [ 29 , 46 ] in mice after transplanting newborn neurons into the cranium of an ischemia mouse model. NeuroD1-induced astrocyte introduction into the mouse cranium resulted in a 35% lesser reduction in motor cortex volume over 2 months compared to the control group [ 29 ].…”

“…NeuroD1-induced astrocyte introduction into the mouse cranium resulted in a 35% lesser reduction in motor cortex volume over 2 months compared to the control group [ 29 ]. By analyzing the forelimb fine movements in mice, NeuroD1 treatment was found to be beneficial in the recovery of motor deficits after ischemic stroke [ 46 ]. NeuroD1 was introduced into the rat amygdala, and auditory fear regulation showed that NeuroD1 was able to rescue the defect of fear memory [ 29 ].…”

Direct Neuronal Reprogramming: Bridging the Gap Between Basic Science and Clinical Application

“…Neurod1 -induced lineage conversion of reactive astrocytes has also been applied to the treatment of a focal stroke model in mice induced using endothelin-1, a vasoconstrictor ( Chen et al, 2020 ; Livingston et al, 2020 ). In both of these studies, Neurod1 -induced the effective transdifferentiation of astrocytes to functional iNs in vivo , and provided a significant enhancement of motor behavior ( Chen et al, 2020 ; Livingston et al, 2020 ). These studies provide important proof-of-concept evidence that a neuronal reprogramming strategy could be applied to the treatment of brain injury.…”