REVIEW: Direct Neural Reprogramming in situ: Existing Approaches and Their Optimization

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Nikita V. Dokukin¹, Daria A. Chudakova^1,2, Matvey O. Shkap¹, Anna M. Kovalchuk¹, Pavel D. Kibirsky¹, Vladimir P. Baklaushev^1,3,4,5,a*

¹Federal Center for Brain and Neurotechnology, Federal Medical and Biological Agency of Russia, 117513 Moscow, Russia

²National Medical Research Center of Children’s Health, Ministry of Health of the Russian Federation, 119991 Moscow, Russia

³Federal Scientific and Clinical Center for Specialized Types of Medical Care and Medical Technologies, Federal Medical and Biological Agency of Russia, 115682 Moscow, Russia

⁴Research Institute of Pulmonology, Federal Medical and Biological Agency of Russia, 115682 Moscow, Russia

⁵Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991 Moscow, Russia

^* To whom correspondence should be addressed.

Received: November 25, 2024; Revised: January 28, 2025; Accepted: January 31, 2025

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Direct in situ neuronal reprogramming (transdifferentiation) of glial cells (astrocytes and microglia) has attracted a significant interest as a potential approach for the treatment of a wide range of neurodegenerative diseases and damages of the central nervous system (CNS). The nervous system of higher mammals has a very limited capacity for repair. Disruption of CNS functioning due to traumatic injuries or neurodegenerative processes can significantly affect the quality of patients’ life, lead to motor and cognitive impairments, and result in disability and, in some cases, death. Restoration of lost neurons in situ via direct reprogramming of glial cells without the intermediate stage of pluripotency seems to be the most attractive approach from the viewpoint of translational biomedicine. The ability of astroglia to actively proliferate in response to the damage of neural tissue supports the idea that these neuron-like cells, which are already present at the lesion site, are good candidates for transdifferentiation into neurons, considering that the possibility of direct neuronal reprogramming of astrocytes both in vitro and in vivo have demonstrated in many independent studies. Overexpression of proneuronal transcription factors, e.g., neurogenic differentiation factors 1-4 (NeuroD1-4), Neurogenin 2 (NeuroG2), Ascl1 (Achaete-Scute homolog 1), and Dlx2 (distal-less homeobox 2), including pioneer transcription factors that recognize target sequences in the compacted chromatin and activate transcription of silent genes, has already been proven as a potential therapeutic strategy. Other strategies, such as microRNA-mediated suppression of activity of PTB and REST transcription factors and application of small molecules or various biomaterials, are also utilized in neuronal reprogramming. However, the efficiency of direct in situ reprogramming is limited by a number of factors, including cell specificity of transgene delivery systems and promoters, brain regions in which transdifferentiation occurs, factors affecting cell metabolism, microenvironment, etc. Reprogramming in situ, which takes place in the presence of a large number of different cell types, requires monitoring and precise phenotypic characterization of subpopulations of cells undergoing transdifferentiation in order to confirm the reprogramming of the astroglia into neurons and subsequent integration of these neurons into the CNS. Here, we discussed the most efficient strategies of neuronal reprogramming and technologies used to visualize the transdifferentiation process, with special focus on the obstacles to efficient neuronal conversion, as well as approaches to overcome them.

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KEY WORDS: direct reprogramming in situ, neurons, astrocytes, transcription factors, regeneration, efficiency

DOI: 10.1134/S000629792460426X

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