Afsaneh Gaillard

The online version contains supplementary material available at 10.1038/s41598-026-41741-7.

Precise quantification of fine motor behaviour is essential for understanding neural circuit function and for evaluating therapeutic interventions in neurological disorders. While markerless pose estimation frameworks such as DeepLabCut (DLC) have transformed behavioural phenotyping, the choice of convolutional neural network (CNN) backbone has a critical impact on tracking performance, particularly in tasks involving small distal joints and frequent occlusions. In this study, we present the first systematic comparison of nine CNN architectures implemented in DLC for lateral-view analysis of skilled reaching movements in the Montoya Staircase test, a gold-standard assay for forelimb dexterity in rodent models of stroke and neurodegenerative disease. Using a dataset comprising both control and primary motor cortex (M1)–lesioned mice, we evaluated model performance across six key dimensions: spatial accuracy (RMSE, PCK@5 px), mean average precision (mAP), robustness to occlusions, inference speed, and GPU memory usage. Our results demonstrate that multi-scale DLCRNet architectures substantially outperform conventional backbones. DLCRNet_ms5 achieved the highest overall accuracy, while DLCRNet_stride16_ms5 provided the most favourable balance between precision and computational efficiency. These findings provide practical methodological guidance for neuroscience laboratories and highlight the importance of CNN architecture selection for the reliable quantification of fine motor behaviour in preclinical research.

Parkinson’s disease (PD) is a complex neurological disorder characterized by the progressive degeneration of midbrain dopaminergic (mDA) neurons in the substantia nigra (SN). This degeneration disrupts the basal ganglia loops, leading to both motor and non-motor dysfunctions. Cell therapy for PD aims to replace lost mDA neurons to restore the DA neurotransmission in the denervated forebrain targets. In clinical trials for PD, mDA neurons are implanted into the target area, the striatum, and not in the SN where they are normally located. This ectopic localisation of cells may affect the functionality of transplanted neurons due to the absence of appropriate host afferent regulation. We recently demonstrated that human induced pluripotent stem cells (hiPSCs) derived mDA progenitors grafted into the substantia nigra pars compacta (SNpc) in a mouse model of PD, differentiated into mature mDA neurons, restored the degenerated nigrostriatal pathway, and induced motor recovery. The objective of the present study was to evaluate the long-term functionality of these intranigral-grafted mDA neurons by assessing their electrophysiological properties. We performed intranigral transplantation of hiPSC-derived mDA progenitors in a 6-hydroxydopamine RAG2-KO mouse model of PD. We recorded in vivo unit extracellular activity of grafted mDA neurons in anesthetised mice from 9 to 12 months post-transplantation. Their electrophysiological properties, including firing rates, patterns and spike characteristics, were analysed and compared with those of native nigral dopaminergic neurons from control mice. We demonstrated that these grafted mDA neurons exhibited functional characteristics similar to those of native nigral dopaminergic neurons, such as large bi- or triphasic spike waveforms, low firing rates, pacemaker-like properties, and two single-spike firing patterns. Although grafted mDA neurons also displayed low discharge frequencies below 10 Hz, their mean frequency was significantly lower than that of nigral mDA neurons, with a differential pattern distribution. Our findings indicate that grafted mDA neurons exhibit dopaminergic-like functional properties, including intrinsic membrane potential oscillations leading to regular firing patterns. Additionally, they demonstrated irregular and burst firing patterns, suggesting they receive modulatory inputs. However, grafted mDA neurons displayed distinct properties, potentially related to their human origin or the incomplete maturation one year after transplantation.

Export Background. Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and by the accumulation of misfolded α-synuclein (α-syn) in Lewy bodies. Ectopic transplantation of human fetal ventral mesencephalic DA neurons into the striatum of PD patients have provided proof-of-principle for the cell replacement strategy in this disorder. However, 10 to 22 years after transplantation, 1% to 27% of grafted neurons contained α-syn aggregates similar to those observed in the host brain. We hypothesized that intrastriatal grafts are more vulnerable to α-syn propagation because the striatum is not the ontogenic site of nigral DA neurons and represents an unfavorable environment for transplanted neurons. Here, we compared the long-term host-to-graft propagation of α-syn in 2 transplantation sites: the SNpc and the striatum. Methods. Two mouse models of PD were developed by injecting adeno-associated-virus2/9-human α-syn A53T into either the SNpc or the striatum of C57BL/6 mice. Mouse fetal ventral mesencephalic DA progenitors were grafted into the SNpc or into the striatum of SNpc or striatum of α-syn injected mice, respectively. Results. First, we have shown a degeneration of the nigrostriatal pathway associated with motor deficits after nigral but not striatal adeno-associated-virus-hαsyn A53T injection. Second, human α-syn preferentially accumulates in striatal grafts compared to nigral grafts. However, no differences were observed for phosphorylated α-syn, a marker of pathological α-syn aggregates. Conclusions. Taken together, our results suggest that the ectopic site of the transplantation impacts the host-to-graft transmission of α-syn.

Traumatic brain injury (TBI) causes cell death mainly in the cerebral cortex. We have previously reported that transplantation of embryonic cortical neurons immediately after cortical injury allows the anatomical reconstruction of injured pathways and that a delay between cortical injury and cell transplantation can partially improve transplantation efficiency. Biomaterials supporting repair processes in combination with cell transplantation are in development. Hyaluronic acid (HA) hydrogel has attracted increasing interest in the field of tissue engineering due to its attractive biological properties. However, before combining the cell with the HA hydrogel for transplantation, it is important to know the effects of the implanted hydrogel alone. Here, we investigated the therapeutic effect of HA on host tissue after a cortical trauma. For this, we implanted HA hydrogel into the lesioned motor cortex of adult mice immediately or one week after a lesion. Our results show the vascularization of the implanted hydrogel. At one month after HA implantation, we observed a reduction in the glial scar around the lesion and the presence of the newly generated oligodendrocytes, immature and mature neurons within the hydrogel. Implanted hydrogel provides favorable environments for the survival and maturation of the newly generated neurons. Collectively, these results suggest a beneficial effect of biomaterial after a cortical traumatic injury.

: Neuropeptide Y (NPY), a 36 amino acid peptide, is widely expressed in the mammalian brain. Changes in NPY levels in different brain regions and plasma have been described in several neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, Amyotrophic Lateral Sclerosis, and Machado-Joseph disease. The changes in NPY levels may reflect the attempt to set up an endogenous neuroprotective mechanism to counteract the degenerative process. Accumulating evidence indicates that NPY can function as an anti-apoptotic, anti-inflammatory, and pro-phagocytic agent, which may be used effectively to halt or to slow down the progression of the disease. In this review, we will focus on the neuroprotective roles of NPY in several neuropathological conditions, with a particular focus on the anti-inflammatory properties of NPY.

Parkinson’s disease (PD) is a neurodegenerative disorder associated with loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc). One strategy for treating PD is transplantation of DA neuroblasts. Significant advances have been made in generating midbrain DA neurons from human pluripotent stem cells. Before these cells can be routinely used in clinical trials, extensive preclinical safety studies are required. One of the main issues to be addressed is the long-term therapeutic effectiveness of these cells. In most transplantation studies using human cells, the maturation of DA neurons has been analyzed over a relatively short period not exceeding 6 months. In present study, we generated midbrain DA neurons from human induced pluripotent stem cells (hiPSCs) and grafted these neurons into the SNpc in an animal model of PD. Graft survival and maturation were analyzed from 1 to 12 months post-transplantation (mpt). We observed long-term survival and functionality of the grafted neurons. However, at 12 mpt, we observed a decrease in the proportion of SNpc DA neuron subtype compared with that at 6 mpt. In addition, at 12 mpt, grafts still contained immature neurons. Our results suggest that longer-term evaluation of the maturation of neurons derived from human stem cells is mandatory for the safe application of cell therapy for PD.

Age-related macular degeneration (AMD) is partially characterized by retinal pigment epithelial (RPE) cell dysfunction. This study focused on phagocytosis activity and its involvement in AMD. Phagocytic activity was analyzed by flow cytometry using porcine photoreceptor outer segment (POS) and fluorescent beads in basal and under oxidative stress condition induced by Fe-NTA in fifteen hiPSC-RPE cell lines (six controls, six atrophic AMD and three exudative AMD). Oxidative stress exposure inhibited phagocytosis in the same manner for control, atrophic AMD (AMDa) and exudative AMD (AMDe) cell lines. However, altered phagocytosis in basal condition in hiPSC-RPE AMDa/e was observed compared to control cell lines. Gene expression after 3 or 24 h of POS incubation was analyzed by RNA-Seq based transcriptomic profiling. Differential gene expression was observed by RNA seq after 3 and 24 h POS exposure. We have focused on the genes involved in mTOR/PI3K-AKT/MEK-ERK pathway. We investigated differences in gene expression by analyzing the expression levels and activity of the corresponding proteins by Western blot. We showed the involvement of three proteins essential for phagocytosis activity: fak, tuberin and rictor. These findings demonstrate that hiPSC-RPE AMDa/e cells have a typical disease phenotype characterized by alteration of the main function of RPE cells, phagocytosis activity.

Intrastriatal embryonic ventral mesencephalon grafts have been shown to integrate, survive, and reinnervate the host striatum in clinical settings and in animal models of Parkinson’s disease. However, this ectopic location does not restore the physiological loops of the nigrostriatal pathway and promotes only moderate behavioral benefits. Here, we performed a direct comparison of the potential benefits of intranigral versus intrastriatal grafts in animal models of Parkinson’s disease. We report that intranigral grafts promoted better survival of dopaminergic neurons and that only intranigral grafts induced recovery of fine motor skills and normalized cortico-striatal responses. The increase in the number of toxic activated glial cells in host tissue surrounding the intrastriatal graft, as well as within the graft, may be one of the causes of the increased cell death observed in the intrastriatal graft. Homotopic localization of the graft and the subsequent physiological cell rewiring of the basal ganglia may be a key factor in successful and beneficial cell transplantation procedures.

In the article titled “Cathepsin B pH-dependent activity is involved in lysosomal dysregulation in atrophic age-related macular degeneration” [1], an affiliation was omitted in error. This affiliation has been added to the affiliation list above as number “8,” and the author affiliations have been corrected.