From organotypic culture to body-on-a-chip: A neuroendocrine perspective

Organ-on-a-Chip Models-New Possibilities in Experimental Science and Disease Modeling

'Organ-on-a-chip' technology is a promising and rapidly evolving model in biological research. This innovative microfluidic cell culture device was created using a microchip with continuously perfused chambers, populated by living cells arranged to replicate physiological processes at the tissue and organ levels. By consolidating multicellular structures, tissue-tissue interfaces, and physicochemical microenvironments, these microchips can replicate key organ functions. They also enable the high-resolution, real-time imaging and analysis of the biochemical, genetic, and metabolic activities of living cells in the functional tissue and organ contexts. This technology can accelerate research into tissue development, organ physiology and disease etiology, therapeutic approaches, and drug testing. It enables the replication of entire organ functions (e.g., liver-on-a-chip, hypothalamus-pituitary-on-a-chip) or the creation of disease models (e.g., amyotrophic lateral sclerosis-on-a-chip, Parkinson's disease-on-a-chip) using specialized microchips and combining them into an integrated functional system. This technology allows for a significant reduction in the number of animals used in experiments, high reproducibility of results, and the possibility of simultaneous use of multiple cell types in a single model. However, its application requires specialized equipment, advanced expertise, and currently incurs high costs. Additionally, achieving the level of standardization needed for commercialization remains a challenge at this stage of development.

How to use an in vitro approach to characterize the toxicity of airborne compounds

As part of the development of new approach methodologies (NAMs), numerous in vitro methods are being developed to characterize the potential toxicity of inhalable xenobiotics (gases, volatile organic compounds, polycyclic aromatic hydrocarbons, particulate matter, nanoparticles). However, the materials and methods employed are extremely diverse, and no single method is currently in use. Method standardization and validation would raise trust in the results and enable them to be compared. This four-part review lists and compares biological models and exposure methodologies before describing measurable biomarkers of exposure or effect. The first section emphasizes the importance of developing alternative methods to reduce, if not replace, animal testing (3R principle). The biological models presented are mostly to cultures of epithelial cells from the respiratory system, as the lungs are the first organ to come into contact with air pollutants. Monocultures or cocultures of primary cells or cell lines, as well as 3D organotypic cultures such as organoids, spheroids and reconstituted tissues, but also the organ(s) model on a chip are examples. The exposure methods for these biological models applicable to airborne compounds are submerged, intermittent, continuous either static or dynamic. Finally, within the restrictions of these models (i.e. relative tiny quantities, adhering cells), the mechanisms of toxicity and the phenotypic markers most commonly examined in models exposed at the air-liquid interface (ALI) are outlined.

Organ-on-a-chip technologies for biomedical research and drug development: A focus on the vasculature

Current biomedical models fail to replicate the complexity of human biology. Consequently, almost 90% of drug candidates fail during clinical trials after decades of research and billions of investments in drug development. Despite their physiological similarities, animal models often misrepresent human responses, and instead, trigger ethical and societal debates regarding their use. The overall aim across regulatory entities worldwide is to replace, reduce, and refine the use of animal experimentation, a concept known as the Three Rs principle. In response, researchers develop experimental alternatives to improve the biological relevance of in vitro models through interdisciplinary approaches. This article highlights the emerging organ-on-a-chip technologies, also known as microphysiological systems, with a focus on models of the vasculature. The cardiovascular system transports all necessary substances, including drugs, throughout the body while in charge of thermal regulation and communication between other organ systems. In addition, we discuss the benefits, limitations, and challenges in the widespread use of new biomedical models. Coupled with patient-derived induced pluripotent stem cells, organ-on-a-chip technologies are the future of drug discovery, development, and personalized medicine.

Functional bioengineered models of the central nervous system

The functional complexity of the central nervous system (CNS) is unparalleled in living organisms. Its nested cells, circuits and networks encode memories, move bodies and generate experiences. Neural tissues can be engineered to assemble model systems that recapitulate essential features of the CNS and to investigate neurodevelopment, delineate pathophysiology, improve regeneration and accelerate drug discovery. In this Review, we discuss essential structure-function relationships of the CNS and examine materials and design considerations, including composition, scale, complexity and maturation, of cell biology-based and engineering-based CNS models. We highlight region-specific CNS models that can emulate functions of the cerebral cortex, hippocampus, spinal cord, neural-X interfaces and other regions, and investigate a range of applications for CNS models, including fundamental and clinical research. We conclude with an outlook to future possibilities of CNS models, highlighting the engineering challenges that remain to be overcome.

The Contribution of Cell Imaging to the Study of Anterior Pituitary Function and Its Regulation

Advances in the knowledge of the neuroendocrine system are closely related to the development of cellular imaging and labeling techniques. This synergy ranges from the staining techniques that allowed the first characterizations of the anterior pituitary gland, its relationship with the hypothalamus, and the birth of neuroendocrinology; through the development of fluorescence microscopy applications, specific labeling strategies, transgenic systems, and intracellular calcium sensors that enabled the study of processes and dynamics at the cellular and tissue level; until the advent of super-resolution microscopy, miniscopes, optogenetics, fiber photometry, and other imaging methods that allowed high spatiotemporal resolution and long-term three-dimensional cellular activity recordings in living systems in a conscious and freely moving condition. In this review, we briefly summarize the main contributions of cellular imaging techniques that have allowed relevant advances in the field of neuroendocrinology and paradigm shifts that have improved our understanding of the function of the hypothalamic-pituitary axes. The development of these methods and equipment is the result of the integration of knowledge achieved by the integration of several disciplines and effort to solve scientific questions and problems of high impact on health and society that this system entails.

Multiorgan-on-a-Chip: A Systemic Approach To Model and Decipher Inter-Organ Communication

Multiorgan-on-a-chip (multi-OoC) platforms have great potential to redefine the way in which human health research is conducted. After briefly reviewing the need for comprehensive multiorgan models with a systemic dimension, we highlight scenarios in which multiorgan models are advantageous. We next overview existing multi-OoC platforms, including integrated body-on-a-chip devices and modular approaches involving interconnected organ-specific modules. We highlight how multi-OoC models can provide unique information that is not accessible using single-OoC models. Finally, we discuss remaining challenges for the realization of multi-OoC platforms and their worldwide adoption. We anticipate that multi-OoC technology will metamorphose research in biology and medicine by providing holistic and personalized models for understanding and treating multisystem diseases.

Optimization of Organotypic Cultures of Mouse Spleen for Staining and Functional Assays

By preserving cell viability and three-dimensional localization, organotypic culture stands out among the newest frontiers of cell culture. It has been successfully employed for the study of diseases among which neoplasias, where tumoral cells take advantage of the surrounding stroma to promote their own proliferation and survival. Organotypic culture acquires major importance in the context of the immune system, whose cells cross-talk in a complex and dynamic fashion to elicit productive responses. However, organotypic culture has been as yet poorly developed for and applied to primary and secondary lymphoid organs. Here we describe in detail the development of a protocol suitable for the efficient cutting of mouse spleen, which overcomes technical difficulties related to the peculiar organ texture, and for optimized organotypic culture of spleen slices. Moreover, we used microscopy, immunofluorescence, flow cytometry, and qRT-PCR to demonstrate that the majority of cells residing in spleen slices remain alive and maintain their original location in the organ architecture for several days after cutting. The development of this protocol represents a significant technical improvement in the study of the lymphoid microenvironment in both physiological and pathological conditions involving the immune system.

Vasoactive intestinal peptide regulates ileal goblet cell production in mice

Innervation of the intestinal mucosa has gained more attention with demonstrations of tuft and enteroendocrine cell innervation. However, the role(s) these fibers play in maintaining the epithelial and mucus barriers are still poorly understood. This study therefore examines the proximity of mouse ileal goblet cells to neuronal fibers, and the regulation of goblet cell production by vasoactive intestinal peptide (VIP). An organotypic intestinal slice model that maintains the cellular diversity of the intestinal wall ex vivo was used. An ex vivo copper-free click-reaction to label glycosaminoglycans was used to identify goblet cells. Pharmacological treatment of slices was used to assess the influence of VIP receptor antagonism on goblet cell production and neuronal fiber proximity. Goblet cells were counted and shown to have at least one peripherin immunoreactive fiber within 3 µm of the cell, 51% of the time. Treatment with a VIP receptor type I and II antagonist (VPACa) resulted in an increase in the percentage of goblet cells with peripherin fibers. Pharmacological treatments altered goblet cell counts in intestinal crypts and villi, with tetrodotoxin and VPACa substantially decreasing goblet cell counts. When cultured with 5-Ethynyl-2'-deoxyuridine (EdU) as an indicator of cell proliferation, colocalization of labeled goblet cells and EdU in ileal crypts was decreased by 77% when treated with VPACa. This study demonstrates a close relationship of intestinal goblet cells to neuronal fibers. By using organotypic slices from mouse ileum, vasoactive intestinal peptide receptor regulation of gut wall goblet cell production was revealed.

Why Study the History of Neuroscience?

The history of neuroscience is the memory of the discipline and this memory depends on the study of the present traces of the past; the things left behind: artifacts, equipment, written documents, data books, photographs, memoirs, etc. History, in all of its definitions, is an integral part of neuroscience and I have used examples from the literature and my personal experience to illustrate the importance of the different aspects of history in neuroscience. Each time we talk about the brain, do an experiment, or write a research article, we are involved in history. Each published experiment becomes a historical document; it relies on past research (the "Introduction" section), procedures developed in the past ("Methods" section) and as soon as new data are published, they become history and become embedded into the history of the discipline ("Discussion" section). In order to be transparent and able to be replicated, each experiment requires its own historical archive. Studying history means researching books, documents and objects in libraries, archives, and museums. It means looking at data books, letters and memos, talking to scientists, and reading biographies and autobiographies. History can be made relevant by integrating historical documents into classes and by using historical websites. Finally, conducting historical research can be interesting, entertaining, and can lead to travel to out-of-the-way and exotic places and meeting interesting people.