Ainhoa Arcas-Marquez

As the global population continues to age, the incidence of neurodegenerative diseases and neural injuries is increasing, presenting major challenges for healthcare systems. Due to the brain’s limited regenerative capacity, there is an urgent need for strategies that promote neuronal repair and functional integration. Brain-derived neurotrophic factor (BDNF) is a key regulator of synaptic plasticity and neuronal development. In this study, we investigated whether constitutive BDNF expression in human induced pluripotent stem cell (iPSC)-derived neural progenitor cells (NPCs) enhances their neurogenic and integrative potential in vitro. We found that NPCs engineered to overexpress BDNF produced neuronal cultures with increased numbers of mature and spontaneously active neurons, without altering the overall structure or organization of functional networks. Furthermore, BDNF-expressing neurons exhibited significantly greater axonal outgrowth, including directed axon extension in a compartmentalized microfluidic system, suggesting a chemoattractive effect of localized BDNF secretion. These effects were comparable to those observed with the early supplementation of recombinant BDNF. Our results demonstrate that sustained BDNF expression enhances neuronal maturation and axonal projection without disrupting network integrity. These findings support the use of BDNF not only as a therapeutic agent to improve cell therapy outcomes but also as a tool to accelerate the development of functional neural networks in vitro.

Cell therapy has proven to be a promising treatment for a range of neurological disorders, including Parkinson Disease, drug-resistant epilepsy, and stroke, by restoring function after brain damage. Nevertheless, evaluating the true effectiveness of these therapeutic interventions requires a deep understanding of the functional integration of grafted cells into existing neural networks. This review explores a powerful arsenal of molecular techniques revolutionizing our ability to unveil functional integration of grafted cells within the host brain. From precise manipulation of neuronal activity to pinpoint the functional contribution of transplanted cells by using opto- and chemo-genetics, to real-time monitoring of neuronal dynamics shedding light on functional connectivity within the reconstructed circuits by using genetically encoded (calcium) indicators in vivo. Finally, structural reconstruction and mapping communication pathways between grafted and host neurons can be achieved by monosynaptic tracing with viral vectors. The cutting-edge toolbox presented here holds immense promise for elucidating the impact of cell therapy on neural circuitry and guiding the development of more effective treatments for neurological disorders.