Neuronal Reprogramming for Brain Repair: Challenges and Perspectives

Evolving Therapeutic Landscape of Intracerebral Hemorrhage: Emerging Cutting-Edge Advancements in Surgical Robots, Regenerative Medicine, and Neurorehabilitation Techniques

Intracerebral hemorrhage (ICH) is the most serious form of stroke and has limited available therapeutic options. As knowledge on ICH rapidly develops, cutting-edge techniques in the fields of surgical robots, regenerative medicine, and neurorehabilitation may revolutionize ICH treatment. However, these new advances still must be translated into clinical practice. In this review, we examined several emerging therapeutic strategies and their major challenges in managing ICH, with a particular focus on innovative therapies involving robot-assisted minimally invasive surgery, stem cell transplantation, in situ neuronal reprogramming, and brain-computer interfaces. Despite the limited expansion of the drug armamentarium for ICH over the past few decades, the judicious selection of more efficacious therapeutic modalities and the exploration of multimodal combination therapies represent opportunities to improve patient prognoses after ICH.

Challenges and Efficacy of Astrocyte-to-Neuron Reprogramming in Spinal Cord Injury: In Vitro Insights and In Vivo Outcomes

Traumatic spinal cord injury (SCI) leads to the disruption of neural pathways, causing loss of neural cells, with subsequent reactive gliosis and tissue scarring that limit endogenous repair. One potential therapeutic strategy to address this is to target reactive scar-forming astrocytes with direct cellular reprogramming to convert them into neurons, by overexpression of neurogenic transcription factors. Here we used lentiviral constructs to overexpress Ascl1 or a combination of microRNAs (miRs) miR124, miR9/9*and NeuroD1 transfected into cultured and in vivo astrocytes. In vitro experiments revealed cortically-derived astrocytes display a higher efficiency (70%) of reprogramming to neurons than spinal cord-derived astrocytes. In a rat cervical SCI model, the same strategy induced only limited reprogramming of astrocytes. Delivery of reprogramming factors did not significantly affect patterns of breathing under baseline and hypoxic conditions, but significant differences in average diaphragm amplitude were seen in the reprogrammed groups during eupneic breathing, hypoxic, and hypercapnic challenges. These results show that while cellular reprogramming can be readily achieved in carefully controlled in vitro conditions, achieving a similar degree of successful reprogramming in vivo is challenging and may require additional steps.

Cell-to-Cell Interactions Mediating Functional Recovery after Stroke

Ischemic damage in brain tissue triggers a cascade of molecular and structural plastic changes, thus influencing a wide range of cell-to-cell interactions. Understanding and manipulating this scenario of intercellular connections is the Holy Grail for post-stroke neurorehabilitation. Here, we discuss the main findings in the literature related to post-stroke alterations in cell-to-cell interactions, which may be either detrimental or supportive for functional recovery. We consider both neural and non-neural cells, starting from astrocytes and reactive astrogliosis and moving to the roles of the oligodendrocytes in the support of vulnerable neurons and sprouting inhibition. We discuss the controversial role of microglia in neural inflammation after injury and we conclude with the description of post-stroke alterations in pyramidal and GABAergic cells interactions. For all of these sections, we review not only the spontaneous evolution in cellular interactions after ischemic injury, but also the experimental strategies which have targeted these interactions and that are inspiring novel therapeutic strategies for clinical application.

Neuronal replacement: Concepts, achievements, and call for caution

Regenerative approaches have made such a great progress, now aiming toward replacing the exact neurons lost upon injury or neurodegeneration. Transplantation and direct reprogramming approaches benefit from identification of molecular programs for neuronal subtype specification, allowing engineering of more precise neuronal subtypes. Disentangling subtype diversity from dynamic transcriptional states presents a challenge now. Adequate identity and connectivity is a prerequisite to restore neuronal network function, which is achieved by transplanted neurons generating the correct output and input, depending on the location and injury condition. Direct neuronal reprogramming of local glial cells has also made great progress in achieving high efficiency of conversion, with adequate output connectivity now aiming toward the goal of replacing neurons in a noninvasive approach.