Induction of functional dopamine neurons from human astrocytes in vitro and mouse astrocytes in a Parkinson's disease model

Abstract

Cell replacement therapies for neurodegenerative disease have focused on transplantation of the cell types affected by the pathological process. Here we describe an alternative strategy for Parkinson's disease in which dopamine neurons are generated by direct conversion of astrocytes. Using three transcription factors, NEUROD1, ASCL1 and LMX1A, and the microRNA miR218, collectively designated NeAL218, we reprogram human astrocytes in vitro, and mouse astrocytes in vivo, into induced dopamine neurons (iDANs). Reprogramming efficiency in vitro is improved by small molecules that promote chromatin remodeling and activate the TGFβ, Shh and Wnt signaling pathways. The reprogramming efficiency of human astrocytes reaches up to 16%, resulting in iDANs with appropriate midbrain markers and excitability. In a mouse model of Parkinson's disease, NeAL218 alone reprograms adult striatal astrocytes into iDANs that are excitable and correct some aspects of motor behavior in vivo, including gait impairments. With further optimization, this approach may enable clinical therapies for Parkinson's disease by delivery of genes rather than cells.

Diversification of molecularly defined myenteric neuron classes revealed by single cell RNA-sequencing

“…We also present the generic neurogenic transcriptional core, knowledge needed in efforts to convert enteric glia to neurons. With further functional interrogation of the herein identified transcription factors, selective production of NOS1 + neurons is likely conceivable following the same principle used to make various types of brain neurons 43,44 .…”

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

“…Here we demonstrated that NeuroD1-mediated astrocyte reprogramming results in the production of mature, active and regionally appropriate neurons that survive long term and correlate with motor improvement following cortical stroke. Previous studies have demonstrated the feasibility of direct cellular conversion in vivo [7,9,[12][13][14][22][23][24][25] but few have demonstrated improved behavioural outcomes following injury [12,17]. Using a foot fault task and gait analysis, we demonstrate that astrocyte-to-neuron reprogramming leads to functional improvement as early as three weeks post-reprogramming, and sustained long-term recovery.…”

“…Of particular interest in the context of CNS injury is the application of direct lineage reprogramming in vivo. Recent work by a number of groups have validated the feasibility of astrocyte-to-neuron conversion in pre-clinical models of Alzheimer's Disease, Parkinson's Disease, stab wound injury and most recently, stroke [12][13][14][15][16][17]. Typically, these studies have used single neural-specific bHLH TFs including Ascl1, Neurog2 and Neurod1, with varying degrees of reprogramming efficiency reported [13,14,16].…”

“…However, a considerable gap exists in terms of understanding the behavioural outcomes of astrocyte-to-neuron reprogramming. One study demonstrated that astrocyte conversion to dopaminergic neurons improves some aspects of motor behavior in a mouse model of Parkinson's Disease [12], and more recently, a report demonstrating improved functional outcomes following astrocyte-to-neuron conversion following ischemia has highlighted the promising potential of cellular reprogramming for functional recovery [17].…”

Concepts toward directing human astroplasticity to promote neuroregeneration

“…This approach includes the potential for in vivo reprogramming of astrocytes directly into neurons to replace those lost in neurodegenerative disorders or with the goal of removing reactive astrocytes (Chen et al, ; Boda et al, ; Gascon et al, ; Chouchane and Costa, ). For example, astrocytes have been exploited as a source for dopamine neurons in a Parkinson's disease model by using neurod1, ascl1, and lmx1A together with a microRNA, miR218 (Rivetti di Val Cervo et al, ). We should keep in mind that some states of reactivity described above may be beneficial to neuroregeneration, and thus it would be detrimental to completely remove these astrocytes from the environment.…”