Roger A Barker

In 2011, the UK medical research charity Cure Parkinson’s set up the international Linked Clinical Trials (iLCT) committee to help expedite the clinical testing of potentially disease modifying therapies for Parkinson’s disease (PD). The first committee meeting was held at the Van Andel Institute in Grand Rapids, Michigan in 2012. This group of PD experts has subsequently met annually to assess and prioritize agents that may slow the progression of this neurodegenerative condition, using a systematic approach based on preclinical, epidemiological and, where possible, clinical data. Over the last 12 years, 171 unique agents have been evaluated by the iLCT committee, and there have been 21 completed clinical studies and 20 ongoing trials associated with the initiative. In this review, we briefly outline the iLCT process as well as the clinical development and outcomes of some of the top prioritized agents. We also …

In recent years there has been a renewed interest in the basal forebrain (BF) cholinergic system as a target for the treatment of cognitive impairments in patients with Parkinson´s disease (PD), due in part to the need to explore novel approaches to treat the cognitive symptoms of the disease, and in part to the development of more refined imaging tools that have made it possible to monitor the progressive changes in the structure and function of the BF system as they evolve over time. In parallel, emerging technologies allowing the derivation of authentic BF cholinergic neurons from human pluripotent stem cells are providing new powerful tools for the exploration of cholinergic neuron replacement in animal models of PD-like cognitive decline. In this review, we discuss the rationale for cholinergic cell replacement as a potential therapeutic strategy in PD and how this approach can be explored in rodent …

Noradrenaline is a powerful modulator of cognitive processes, including action-decisions underlying saccadic control. Changes in saccadic eye movements are common across neurodegenerative diseases of ageing, including Parkinson’s disease. With growing interest in noradrenergic treatment potential for non-motor symptoms in Parkinson’s disease, the temporal precision of oculomotor function is advantageous to assess the effects of this modulation. Here we studied the effect of 40 mg atomoxetine, a noradrenaline reuptake inhibitor, in nineteen people with idiopathic Parkinson’s disease using a single dose, randomised double-blind crossover placebo-controlled design. Twenty-five healthy adult participants completed the assessments to provide normative data. Participants performed prosaccade and antisaccade tasks. The latency, velocity and accuracy of saccades, and resting pupil diameter, were measured. Increased pupil diameter on the drug confirmed its expected effect on the locus coeruleus ascending arousal system. Atomoxetine improved key aspects of saccade performance: prosaccade latencies were faster and the saccadic main sequence was normalised. These improvements were accompanied by increased antisaccade error rates on the drug. Together these findings suggest a shift in the speed-accuracy trade-off for visuo-motor decisions in response to noradrenergic treatment. Our results provide new evidence to substantiate a role for noradrenergic modulation of saccades, and based on known circuitry we advance the hypothesis that this reflects modulation at the level of the locus coeruleus–superior colliculus …

Background: Due to the progressive nature of Parkinson’s disease (PD), many individuals will develop complications such as falls, dementia, institutionalisation, and even death. Understanding the factors that contribute to these ‘milestones’ may lead to new therapeutic avenues. Sleep disturbances are amongst the commonest non-motor symptoms in PD. The aim of this study was to investigate the prevalence and prognostic significance of sleep disturbances in PD.Methods: We utilised data from the ‘Parkinsonism: Incidence and Cognitive and Non-motor heterogeneity In CambridgeShire’study. This is a prospective incident cohort that originally recruited 280 individuals with newly-diagnosed PD between 2008-2013 and undertook repeated clinical evaluations every 18 months.Results: At baseline, 47% of participants reported poor self-reported sleep quality (PSQI> 5), while 15% reported excessive daytime …

Huntington’s disease (HD) is a fatal, progressive neurodegenerative disorder that affects approximately 80,000 people globally, with an additional 300,000 individuals at-risk of carrying the disease-causing gene. In HD, the presence of the mutant huntingtin protein triggers a range of detrimental changes in the brain including the activation of inflammatory pathways which contributes to neurodegeneration, particularly in the striatum and cerebral cortex [1]. While neuronal injury and death are hallmark features of HD, inflammation and astrocytic dysfunction have been frequently described in post-mortem studies of HD brains [2, 3], following closely the onset of the neurodegeneration process [4]. Furthermore, in vitro and in vivo models of HD have shown that mutant huntingtin accumulation leads to astrocytic dysfunction and worsening of neurodegeneration, pointing to the importance of astrocytes to the disease …

Parkinsons Disease involves the progressive loss of dopaminergic neurons (DAn), prompting clinical trials replacing cell loss with neural grafts. This includes the transplantation of pluripotent stem cell-derived DAn progenitor cells (NPC) currently under investigation in the STEM-PD trial. To determine the likelihood of immune rejection post-grafting, we characterised the immunogenicity of the STEM-PD product (RC17-hESC-derived NPCs), comparing them to human foetal ventral mesencephalic tissue (hfVM) previously tested in trials, including our own TRANSEURO trial. Despite MHC-Class I expression, upregulated by proinflammatory cytokines, no immune response to NPCs was detected in vitro. Instead, they were immunosuppressive. Transcriptomic analysis revealed similarities between RC17-NPCs and hfVM, both strongly upregulating antigen processing and presentation pathways in response to IFNgamma. Furthermore, immunosuppressant mycophenolate mofetil detrimentally affected NPC survival and differentiation in vitro. Overall, our data suggest that aggressive immunosuppression is not required following hESC-NPC transplantation and that caution should be exercised when selecting the immunosuppressive regimen.

The human brain develops through a tightly organized cascade of patterning events, induced by transcription factor expression and changes in chromatin accessibility. Although gene expression across the developing brain has been described at single-cell resolution, similar atlases of chromatin accessibility have been primarily focused on the forebrain, –. Here we describe chromatin accessibility and paired gene expression across the entire developing human brain during the first trimester (6–13 weeks after conception). We defined 135 clusters and used multiomic measurements to link candidate cis-regulatory elements to gene expression. The number of accessible regions increased both with age and along neuronal differentiation. Using a convolutional neural network, we identified putative functional transcription factor-binding sites in enhancers characterizing neuronal subtypes. We applied this model to cis …

ObjectiveTo determine if any association between previously identified alleles that confer risk for Parkinson disease and variables measuring disease progression.

Outer radial glia (oRG) emerge as cortical progenitor cells that support the development of an enlarged outer subventricular zone (oSVZ) and the expansion of the neocortex. The in vitro generation of oRG is essential to investigate the underlying mechanisms of human neocortical development and expansion. By activating the STAT3 signaling pathway using leukemia inhibitory factor (LIF), which is not expressed in guided cortical organoids, we define a cortical organoid differentiation method from human pluripotent stem cells (hPSCs) that recapitulates the expansion of a progenitor pool into the oSVZ. The oSVZ comprises progenitor cells expressing specific oRG markers such as GFAP, LIFR, and HOPX, closely matching human fetal oRG. Finally, incorporating neural crest-derived LIF-producing cortical pericytes into cortical organoids recapitulates the effects of LIF treatment. These data indicate that increasing …

The final United Kingdom Regenerative Medicine Platform (UKRMP) conference held in Edinburgh's iconic McEwan Hall between 8th and November 10, 2023 saw a gathering of nearly 200 international delegates presenting exceptional science and celebrating a decade of this initiative. The UKRMP had the core mission to break down the major barriers to clinical translation of regenerative medicine products. UKRMP2 was established as three hubs that worked closely with industry and regulators: 1) Pluripotent Stem Cells and Engineered Cells, 2) Engineered Cell Environments, and 3) Smart Materials. In this meeting report, we outline the original aims of UKRMP, examine how it achieved critical mass, summarise the major developments that the UKRMP hubs delivered, and examine some unresolved challenges that still lie ahead in the field of regenerative medicine.

Positron emission tomography of proteinopathies with high-affinity and selective radioligands has played a vital role in expanding our knowledge of neurodegenerative diseases such as Parkinson’s and Alzheimer’s disease. The pathogenesis of Huntington’s disease, a CAG trinucleotide repeat disorder, is similarly linked to the presence of protein fibrils formed from mutant huntingtin (mHTT). Development of mHTT fibril-specific radioligands has been limited by the lack of structural knowledge around mHTT and a dearth of available hit compounds for medicinal chemistry refinement. Over the past decade, the Cure Huntington’s Disease Initiative (CHDI), a non-for-profit scientific management organisation has orchestrated a large-scale screen of small molecules to identify high affinity ligands of mHTT, with lead compounds now reaching clinical maturity. Here we describe the mHTT radioligands developed to date and opportunities for further improvement of this radiotracer class.

Sham surgery is often required for cell therapies adopting a randomized placebo-controlled double-blinded trial design. Using the case of dopamine neuron therapy for Parkinson's disease, we argue that alternative trial designs should be considered instead, for several reasons relating to ethics, patient burden, ease of unblinding, and cost.

Human prenatal skin is populated by innate immune cells including macrophages, and whether they act solely in immunity or have additional functions in morphogenesis is unclear. We assembled the first comprehensive multi-omic reference atlas of prenatal human skin (7-16 post-conception weeks), combining single cell and spatial transcriptomic data, to characterise the skin's microenvironmental cellular organisation. This revealed that crosstalk between non-immune and immune cells underpins formation of hair follicles, has implications for scarless wound healing, and is critical for skin angiogenesis. We benchmarked a skin organoid model, derived from human embryonic stem (ES) and induced pluripotent stem (iPS) cells, against prenatal and adult skin, demonstrating close recapitulation of the epidermal and dermal skin components during hair follicle development. Notably, the skin organoid lacked immune cells and had markedly diminished endothelial cell heterogeneity and quantity. From our in vivo skin cell atlas data, we found that macrophages and macrophage-derived growth factors play a key role in driving endothelial development prenatally. Indeed, vascular network formation was enhanced following transfer of autologous iPS-derived macrophages into both endothelial cell angiogenesis assays and skin organoid cultures. In summary, innate immune cells moonlight as key players in skin morphogenesis beyond their conventional immune roles, a function they achieve via extensive crosstalk with non-immune cells. Finally, we leveraged our human prenatal skin cell atlas to further our understanding of the pathogenesis of …

Cell therapies as potential treatments for Parkinson’s disease first gained traction in the 1980s, owing to the clinical success of trials that used transplants of foetal midbrain dopaminergic tissue. However, the poor standardization of the tissue for grafting, and constraints on its availability and ethical use, have hindered this treatment strategy. Recent advances in stem-cell technologies and in the understanding of the development of dopaminergic neurons have enabled preclinical advancements of promising stem-cell therapies. To move these therapies to the clinic, appropriate levels of safety screening, as well as optimization of the cell products and the scalability of their manufacturing, will be required. In this Review, we discuss how challenges pertaining to cell sources, functional and safety testing, manufacturing and storage, and clinical-trial design are being addressed to advance the translational and clinical …

T cells develop from circulating precursors, which enter the thymus and migrate throughout specialised sub-compartments to support maturation and selection. This process starts already in early fetal development and is highly active until the involution of the thymus in adolescence. To map the micro-anatomical underpinnings of this process in pre-vs. post-natal states, we undertook a spatially resolved analysis and established a new quantitative morphological framework for the thymus, the Cortico-Medullary Axis. Using this axis in conjunction with the curation of a multimodal single-cell, spatial transcriptomics and high-resolution multiplex imaging atlas, we show that canonical thymocyte trajectories and thymic epithelial cells are highly organised and fully established by post-conception week 12, pinpoint TEC progenitor states, find that TEC subsets and peripheral tissue genes are associated with Hassall’s …

Selective loss of discrete neuronal populations is a prominent feature of many neurodegenerative conditions, but the molecular basis of this is poorly understood. A central role of α‐synuclein in the selective neurodegeneration of Parkinson's disease has been speculated, as its level of expression critically determines the propensity of this protein to misfold. To investigate whether the propensity of neuronal cell loss is associated with the level of endogenous α‐synuclein expression, non‐transgenic rats were given a single intravenous administration of α‐synuclein pre‐formed fibrils (PFFs) reversibly complexed with the rabies virus glycoprotein peptide (RVG9R). The number of surviving cells in different neuronal populations was systematically quantified using unbiased stereology. Our data demonstrated that a non‐selective, transvascular delivery of α‐synuclein PFFs led to a time‐dependent loss of specific …

The human brain is capable of highly complex functions that develops through a tightly organized cascade of patterning events, expressed transcription factors and changes in chromatin accessibility. While extensive datasets exist describing gene expression across the developing brain with single-cell resolution, similar atlases of chromatin accessibility have been primarily focused on the forebrain. Here, we focus on the chromatin landscape and paired gene expression across the developing human brain to provide a comprehensive single cell atlas during the first trimester (6 - 13 post-conceptional weeks). We identified 135 clusters across half a million nuclei and using the multiomic measurements linked candidate cis-regulatory elements (cCREs) to gene expression. We found an increase in the number of accessible regions driven both by age and neuronal differentiation. Using a convolutional neural network we identified putative functional TF-binding sites in enhancers characterizing neuronal subtypes and we applied this model to cCREs upstream of ESRRB to elucidate its activation mechanism. Finally, by linking disease-associated SNPs to cCREs we validated putative pathogenic mechanisms in several diseases and identified midbrain-derived GABAergic neurons as being the most vulnerable to major depressive disorder related mutations. Together, our findings provide a higher degree of detail to some key gene regulatory mechanisms underlying the emergence of cell types during the first trimester. We anticipate this resource to be a valuable reference for future studies related to human neurodevelopment, such as identifying cell …

The proteasome is an evolutionary conserved protease that recognizes and degrades damaged and misfolded proteins via proteolysis. 1 The 26S proteasome consists of the 19S regulatory subunit and the core proteolytic enzyme, 20S proteasome. 2 The proteasome-dependent degradation of tagged, polyubiquitinated proteins is an essential cellular pathway that regulates a wide range of cellular processes, including cell cycle, apoptosis, oxidative stress, cell proliferation and activation of transcription factors such as NF-κB. 3 In contrast to the ubiquitously expressed constitutive proteasome, which is the crucial cellular protease containing the three catalytic subunits, β1, β2 and β5, the immunoproteasome is induced via de novo assembly upon stimulation of cells by Type I and Type II interferons. The incorporation of newly synthetized catalytic subunits, β1i/LMP2, β2i/MECL-1 and β5i/LMP7, is an essential cellular strategy to eliminate intracellular bacteria and viruses. 4 The immunoproteasome exhibits an altered proteolytic function that is required for optimal generation of epitopes for presentation on major histocompatibility complex Class I (MHC-I) molecules in infected cells. It was shown that immunoproteasomes transiently replace constitutive proteasomes during an anti-bacterial (Listeria monocytogenes) and anti-viral (lymphocytic choriomeningitis virus) immune response in the liver. 5 Apart from their function in the generation of a broad pool of MHC-I ligands and in triggering effective activation of cytotoxic T lymphocytes, immunoproteasomes appear to act as a pro-inflammatory factor that is involved in tissue inflammation and damage, as …

Huntington’s disease (HD) is a dominantly inherited neurodegenerative disorder resulting from a CAG expansion in the huntingtin (HTT) gene, which leads to the production and accumulation of mutant huntingtin (mHTT). While primarily considered a disorder of the central nervous system, multiple changes have been described to occur throughout the body, including activation of the immune system. In other neurodegenerative disorders, activation of the immune system has been shown to include the production of antibodies against disease-associated pathological proteins. However, the existence of mHTT-targeted antibodies has never been reported. In this study, we assessed the presence and titer of antibodies recognizing HTT/mHTT in patients with HD (n = 66) and age- and gender-matched healthy controls (n = 66) using a combination of Western blotting and ELISA. Together, these analyses revealed …

Objective: An observational study ahead of the proof-of-concept transplant trial may reduce some of the confounding factors associated with investigating therapies in Parkinson’s disease. TRANSCEND 1 will follow a cohort of patients with Parkinson’s disease receiving a local standard of care (SoC) to monitor fluctuations in individual performance and disease characteristics over time and to facilitate a reliable baseline of disease severity before a subsequent proof-of-concept trial with a novel stem-cell based treatment in some patients from this cohort. Background: Novo Nordisk is developing a cell therapy for Parkinson’s disease in collaboration with groups at Lund University (Sweden) and the University of Cambridge (UK). The therapy comprises dopaminergic progenitor cells derived from human embryonic stem cells; the clinical development programme currently includes this observational study (TRANSCEND 1) and a planned phase 1/2, proof-of-concept transplant trial (TRANSCEND 2 …