Conference Agenda

The striatum plays a crucial role in various cognitive and motor functions and is implicated in a number of neuropsychiatric and neurodegenerative disorders. Recent advancements in single-cell RNA sequencing technologies have provided unprecedented opportunities to unravel the cellular composition and dynamics of the human striatum during embryonic development. Through the application of these technologies, we have identified distinct cell types, characterized transcriptional programs, and delineated developmental trajectories within the early phase of human striatal development. Moreover, leveraging human embryonic stem cells differentiation towards striatal fate in vitro, we have established a cell platform to model striatal development and investigate disease mechanism of Huntington Disease. These findings shed light on the molecular mechanisms underlying striatal development and highlight potential targets for therapeutic interventions.

The adult brain retains over life endogenous neural stem/precursors cells (eNPCs) within the subventricular zone (SVZ). Whether or not these cells exert physiological functions is still unclear. We recently provided evidence that GABAergic transmission between parvalbumin-expressing fast-spiking interneurons (FSIs) and medium spiny neurons (MSNs) is tuned by SVZ-eNPCs via secretion of Insulin-Like Growth Factor Binding Protein Like 1 (IGFBPL-1). Consistently, selective ablation of SVZ-eNPCs or selective abrogation of IGFBPL-1 signalling determines the impairment of striatal functionality, a higher failure rate of GABAergic transmission mediated by FSIs and striatum-related behavioural dysfunctions impairing decision making. Human validation studies revealed IGFBPL-1 expression in the SVZ as in foetal and induced-pluripotent stem cell-derived NPCs. Finally, in neurological patients, we found a significative correlation between SVZ damage, reduction of striatum volume and impairment of information processing speed. Our results highlight in mice and humans a novel non-neurogenic physiological role of adult SVZ-eNPCs in supporting cognitive functions by regulating striatal neuronal activity.

Huntington’s Disease (HD) is a motor and cognitive neurodegenerative disorder due to prominent loss of striatal medium spiny neurons (MSNs). Cell replacement using human embryonic stem cells (hESCs) derivatives may offer new therapeutic opportunities to replace degenerated neurons and repair damaged circuits. Towards this goal, we have investigated the therapeutic value of hESC-derived striatal progenitors by grafting the cells into the striatum of a preclinical model of HD. Human striatal progenitors displayed an excellent survival up to 6 months after transplantation, and cells showed features typical of human MSNs. Grafts wired in striatal circuits, and promoted a degree of functional recovery. Enhanced differentiation and integration were achieved by animal exposure to environmental enrichment. These data underscore the capability of the host damaged brain to support rewiring and integration of donor neurons, and hold promise for future development of stem cell-based therapies.

Neurotransplantation represents a promising alternative for the treatment of certain localized neurodegenerative pathologies, such as Huntington´s disease. We showed that transplantation of both rodent and human MSN progenitor cells into a toxin-based rat model of HD leads to the survival, integration and differentiation of the graft and supports a degree of recovery as measured by sensory-motor tests (Bessuso et al., 2020). However, little is known about graft functional integration. Thus, we addressed this issue by fiber-photometry mediated analysis of graft-dependent Ca2+ signals in freely behaving animals.

QA-lesioned rats were grafted with whole ganglionic eminence (WGE) embryonic cells (E15-16) transduced with AAV-hSyn1GCaMP7s or AAV-hSyn1GFP. Ca2+ activity in the graft was evaluated at 2-4MPT under two different conditions: free behavior in the open arena and anesthesia. To analyze the Ca2+ signals, we computed a number of features, used as pure formal descriptors. As result, free-behaving animals showed statistically significant higher GCaMP7s signal predictability compared to the other conditions, indicating an origin in graft’s neural activity of such non-random signal trajectory over time. Further inspection of the GCaMP7s transient, showed a well-defined oscillatory pattern which displayed low frequency and synchronous activity in a subset of animals, overall reminding of Ca2+ signals reported for striatal populations in freely behaving mice (Legaria et al., 2022). In all the conditions, the induction of anesthesia decreased the amplitude of Ca2+ transients.

Since aversive stimuli alter the activity of the striatum, we tested if footshocks would influence graft oscillatory Ca2+ activity. Preliminary results show that each footshock stimulated responses embedded in spontaneous oscillations.

These results suggest the grafted cells at 2-4MPT exhibit neuronal activity, with certain levels of evoked responses. It remains to be elucidated if the cells are fully integrated in the host circuit, and the possible maturation at extended times post transplantation.

NSC-Reconstruct H2020, GA 875758