Advances in Animal Models and Cutting-Edge Research in Alternatives: Proceedings of the Third International Conference on 3Rs Research and Progress, Vishakhapatnam, 2022.

Animal experimentation has been integral to drug discovery and development and safety assessment for many years, since it provides insights into the mechanisms of drug efficacy and toxicity (e.g. pharmacology, pharmacokinetics and pharmacodynamics).

A human kidney and liver organoid-based multi-organ-on-a-chip model to study the therapeutic effects and biodistribution of mesenchymal stromal cell-derived extracellular vesicles.

Mesenchymal stromal cell (MSC)-derived small extracellular vesicles (sEVs) show therapeutic potential in multiple disease models, including kidney injury. Clinical translation of sEVs requires further preclinical and regulatory developments, including elucidation of the biodistribution and mode of action (MoA). Biodistribution can be determined using labelled sEVs in animal models which come with ethical concerns, are time-consuming and expensive, and may not well represent human physiology.

Organ-on-a-chip: Determine feasibility of a human liver microphysiological model to assess long-term steroid metabolites in sports drug testing.

A fundamental challenge in preventive doping research is the study of metabolic pathways of substances banned in sport. However, the pharmacological predictions obtained by conventional in vitro or in vivo animal studies are occasionally of limited transferability to humans according to an inability of in vitro models to mimic higher order system physiology or due to various species-specific differences using animal models. A more recently established technology for simulating human physiology is the "organ-on-a-chip" principle.

Validation of Bioreactor and Human-on-a-Chip Devices for Chemical Safety Assessment.

Equipment and device qualification and test assay validation in the field of tissue engineered human organs for substance assessment remain formidable tasks with only a few successful examples so far. The hurdles seem to increase with the growing complexity of the biological systems, emulated by the respective models. Controlled single tissue or organ culture in bioreactors improves the organ-specific functions and maintains their phenotypic stability for longer periods of time.

The multi-organ chip--a microfluidic platform for long-term multi-tissue coculture.

The ever growing amount of new substances released onto the market and the limited predictability of current in vitro test systems has led to a high need for new solutions for substance testing. Many drugs that have been removed from the market due to drug-induced liver injury released their toxic potential only after several doses of chronic testing in humans. However, a controlled microenvironment is pivotal for long-term multiple dosing experiments, as even minor alterations in extracellular conditions may greatly influence the cell physiology.

Integrating biological vasculature into a multi-organ-chip microsystem.

A chip-based system mimicking the transport function of the human cardiovascular system has been established at minute but standardized microsystem scale. A peristaltic on-chip micropump generates pulsatile shear stress in a widely adjustable physiological range within a microchannel circuit entirely covered on all fluid contact surfaces with human dermal microvascular endothelial cells. This microvascular transport system can be reproducibly established within four days, independently of the individual endothelial cell donor background.

Skin and hair on-a-chip: in vitro skin models versus ex vivo tissue maintenance with dynamic perfusion.

Substantial progress has been achieved over the last few decades in the development of skin equivalents to model the skin as an organ. However, their static culture still limits the emulation of essential physiological properties crucial for toxicity testing and compound screening. Here, we describe a dynamically perfused chip-based bioreactor platform capable of applying variable mechanical shear stress and extending culture periods.

'Human-on-a-chip' developments: a translational cutting-edge alternative to systemic safety assessment and efficiency evaluation of substances in laboratory animals and man?

Various factors, including the phylogenetic distance between laboratory animals and humans, the discrepancy between current in vitro systems and the human body, and the restrictions of in silico modelling, have generated the need for new solutions to the ever-increasing worldwide dilemma of substance testing. This review provides a historical sketch on the accentuation of this dilemma, and highlights fundamental limitations to the countermeasures taken so far. It describes the potential of recently-introduced microsystems to emulate human organs in 'organ-on-a-chip' devices.

Cartilage oligomeric matrix protein (COMP) forms part of the connective tissue of normal human hair follicles.

Hair follicle cycling is driven by epithelial-mesenchymal interactions (EMI), which require extracellular matrix (ECM) modifications to control the crosstalk between key epithelial- and mesenchymal-derived growth factors and cytokines. The exact roles of these ECM modifications in hair cycle-associated EMI are still unknown. Here, we used differential microarray analysis of laser capture-microdissected human scalp hair follicles (HF) to identify new ECM components that distinguish fibroblasts from the connective tissue sheath (CTS) from those of the follicular dermal papilla (DP).

De novo formation and ultra-structural characterization of a fiber-producing human hair follicle equivalent in vitro.

Across many tissues and organs, the ability to create an organoid, the smallest functional unit of an organ, in vitro is the key both to tissue engineering and preclinical testing regimes. The hair follicle is an organoid that has been much studied based on its ability to grow quickly and to regenerate after trauma. But hair follicle formation in vitro has been elusive.

Design and prototyping of a chip-based multi-micro-organoid culture system for substance testing, predictive to human (substance) exposure.

Dynamic miniaturized human multi-micro-organ bioreactor systems are envisaged as a possible solution for the embarrassing gap of predictive substance testing prior to human exposure. A rational approach was applied to simulate and design dynamic long-term cultures of the smallest possible functional human organ units, human "micro-organoids", on a chip the shape of a microscope slide. Each chip contains six identical dynamic micro-bioreactors with three different micro-organoid culture segments each, a feed supply and waste reservoirs.