Spotlight on Three Rs Progress

Human Study Sheds Insight into Dopamine’s Role in Learning

The hypothesis that dopamine neurons encode information about errors in an organism’s expectations about rewarding outcomes (referred to as reward prediction errors), which promote learning and guide behaviour, has limited human data.

To gather human data to determine whether dopamine release encodes only reward prediction errors, or whether it may also encode adaptive punishment learning signals, a study enrolled patients undergoing deep brain stimulation surgery.¹ The volunteers were asked to perform a probabilistic reward and punishment learning task (where participants’ actions were reinforced or punished with monetary gains or losses), during which time subsecond measurements of dopamine release in the striatum were taken. This approach allowed the team to detect rapid changes in dopamine levels, while participants learnt from rewarding as well as punishing feedback. Their results suggest that extracellular dopamine levels can encode both reward and punishment prediction errors within distinct time intervals — early (0 to 300 ms) dopamine responses signalled reward prediction errors and later (400 to 700 ms) responses signalled punishment prediction errors. The authors concluded that: “these kinds of data are invaluable for investigating and understanding how neuromodulators like dopamine affect human behavior, human decision-making, and human subjective experience.”

Reference

1. Sands LP, Jiang A, Liebenow B, et al. Subsecond fluctuations in extracellular dopamine encode reward and punishment prediction errors in humans. Sci Adv 2023; 9: eadi4927. DOI: 10.1126/sciadv.adi4927.

Multi-chamber In Vitro Heart Model

Congenital heart disease is the leading cause of human embryonic and fetal death. However, research into the biology of embryonic cardiac development and the effects of xenobiotics is hampered by the lack of human-relevance of current in vitro models. Schmidt et al.¹ attempted to overcome these challenges by creating a multi-chamber cardioid platform based on human 3-D cell cultures. Embryonic heart structures are mainly derived from three progenitor populations that give rise to specific cardiomyocyte lineages. The interactions between these cell lineages during the initial stages of heart development (e.g. cardiac mesoderm specification, morphogenesis and functional differentiation) are difficult to analyse and are inaccessible in human embryos. This in vitro platform includes interconnected heart structures, and thus it permits research on how the chambers interact and coordinate contractions. In addition, studies to assess how genetic mutations, environmental factors and drugs affect specific regions of the developing human heart can also be performed. The authors remark that: “A significant advance of our work is the deep and comprehensive phenotyping that we used to explore the ontology of contraction signal propagation, differentiation speed, specification direction, efficiency, and morphogenesis through the early stages of cardiogenesis. This is particularly important to understand cases of embryonic cardiac failure that have been attributed to faulty specification and morphogenesis but where defects in early contraction signal propagation between chambers might have been the culprit.”¹

Reference

1. Schmidt C, Deyett A, Ilmer T, et al. Multi-chamber cardioids unravel human heart development and cardiac defects. Cell 2023; 186: 5587–5605.e27.

Human Tissue Confirms COVID-19 Microvascular Damage

A transversal observational study involving lung samples from human COVID patients corroborates that viral infection can lead to endothelial alveolar microvascular damage.¹ Infection with SARS-CoV-2 (and direct viral infection of endothelial cells) has been associated with endothelial dysfunction and secondary inflammation mainly affecting the microvascular circulation. However, the subcellular consequences of the infection and the associated thrombotic events remain poorly studied.

To study the pathophysiology of microvascular thrombosis at the cellular level, the team obtained lung tissue from COVID-19 patients who died due to acute respiratory failure and had signs of microvascular thrombosis upon histology. They then performed transmission and scanning electron microscopy to explain the pathophysiology of the respiratory failure. The microscopy findings revealed areas of endothelial damage, with basal lamina disruption and viral infection. Furthermore, in the capillary lumens, thrombi were detected, with red blood cell stacking, dysmorphism and haemolysis, fibrin meshworks and extracellular traps. Their observations indicate that microvascular thrombosis at the cellular level could lead to some of the peculiar characteristics of severe COVID-19.

Reference

1. Negri EM, Benchimol M, Mauad T, et al. Ultrastructural characterization of alveolar microvascular damage in severe COVID-19 respiratory failure. J Appl Physiol (1985) 2023; 135: 950–955.

Human Atherosclerosis Cell Atlas

An atlas of human atherosclerosis, that shows the cell types and specific mechanisms involved, has been published.¹ The pathological characteristic of coronary artery disease is atherosclerosis — a build-up of plaque inside arterial walls — that can lead to stroke and heart attacks. It a disease that is challenging to replicate in animal models and in vitro, and thus human-based studies are crucial to improve prevention and treatments. Several cell types, including vascular and immune cells, are known to play a part in disease progression, but the cell phenotypes remain controversial. The team analysed the data from single-cell sequencing (scRNA-seq) studies of human atherosclerosis (including early and advanced lesions, and normal samples) to generate an atlas of human atherosclerosis with 118,578 cells. This permitted the identification of previously missed vascular and immune cell types, and confirmed markers for immune cells known to play a part in the disease (e.g. foamy macrophages). Further analyses, including genome-wide association data, revealed an important role for modulated smooth muscle cell phenotypes in coronary artery disease and identified fibromyocyte/fibrochondrogenic smooth muscle cell markers as proxies of atherosclerosis. Thus, this atlas provides a human-relevant reference tool for atherosclerotic disease, providing a critical step toward translating cell-specific mechanistic knowledge and developing more-targeted interventions.

Reference

1. Mosquera JV, Auguste G, Wong D, et al. Integrative single-cell meta-analysis reveals disease-relevant vascular cell states and markers in human atherosclerosis. Cell Rep 2023; 42: 113380.

In Vitro Model for the Study of Alzheimer’s Disease

The development of a human cell-based 3-D model that can be used for the study of Alzheimer’s disease has recently been published.¹ The pathology of Alzheimer’s disease is believed to be a consequence of the interaction between multiple cell types, namely resident brain cells and infiltrating peripheral immune cells. To generate an in vitro model where these interactions can be closely scrutinised, the team employed stem cell-derived neurons, astrocytes and microglia, as well as peripheral immune cells. They found that more T-cells and monocytes infiltrated into Alzheimer’s cultures, as compared to the control cultures. Furthermore, infiltration of CD8⁺ T-cells into the Alzheimer’s cultures led to increased microglial activation, neuroinflammation and neurodegeneration. Interestingly, the team identified a pathway involving a chemokine (CXCL10) and chemokine receptor (CXCR3) that plays a key role in regulating T-cell infiltration. Blocking this pathway largely prevented T-cell infiltration and neurodegeneration in the Alzheimer’s cultures. These mechanistic findings could help in identifying new therapeutic targets to impede the infiltration of T-cells into the brain, and potentially reduce the cognitive impact of the disease.²

References

1. Jorfi M, Park J, Hall CK, et al. Infiltrating CD8⁺ T cells exacerbate Alzheimer’s disease pathology in a 3D human neuroimmune axis model. Nat Neurosci 2023; 26: 1489–1504.

2. Inside Precision Medicine. New 3D cellular model for Alzheimer’s shows brain immune interaction, https://www.insideprecisionmedicine.com/news-and-features/new-3d-cellular-model-for-alzheimers-shows-brain-immune-interaction/ (accessed 18 December 2023).

The 2024 CRACK IT Challenge

The CRACK IT Challenge is a particular funding competition run by the UK National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) that focuses on developing and commercialising new technologies into Three Rs products and services that are directly targeted to meet end-user needs.¹ The programme funds collaborations between industry, SMEs and academia to tackle specific challenges involving the use of animals. Ideas for a Challenge can come from industry, academia or the charity sector, and are pitched to the bioscience sector to develop new technologies which deliver Three Rs, scientific and business benefits. A Challenge should be a call for a product, technology or process that:

— Will have a significant impact on the Three Rs.

If you have a research question for a CRACK IT Challenge to solve, please visit the NC3Rs website for further information on how to submit your idea, the process and the role of a Sponsor, or contact the CRACK IT team directly at crackitenquiries@nc3rs.org.uk. Submissions for the 2024 Challenge are open until 16 February 2024.

Reference

1. NC3Rs. Call open for 2024 CRACK IT Challenges, https://nc3rs.org.uk/crackit/news/call-open-2024-crack-it-challenges (accessed 11 December 2023).

FRAME Training Resource Survey

The Fund for the Replacement of Animals in Medical Experiments (FRAME) wants to create resources to help researchers and other stakeholders find, access and implement alternatives to animals. To ensure that the tools created are useful to the community, FRAME is currently conducting a short survey. FRAME is interested in learning the views and perspectives of all those associated with the use of animals in the biosciences, including animal care staff, students and early-career researchers. The survey is aimed at evaluating Three Rs training — specifically replacement — across research institutions, and the data will be used to help develop new resources. The closing date is 1 March 2024, and any questions can be sent to ellie@frame.org.uk. Please share the link with anyone who might be interested: https://forms.office.com/e/KkUcnVCLkP