Investigations to extend viability of a rainbow trout primary gill cell culture

Establishment and validation of a 2D primary gill cell culture of the sevenband grouper (Hyporthodus septemfasciatus)

A 2D primary gill cell culture system of the sevenband grouper (Hyporthodus septemfasciatus) was established to validate the pathogenesis of nervous necrosis virus (NNV) as observed in previous studies. This system, developed using the double-seeded insert (DSI) technique, yielded confluent cell layers. Upon challenge with NNV in a setup containing both autoclaved salt water and L15 media in the apical compartment, viral replication akin to that anticipated based on previous studies was observed. Consequently, we advocate for the utilization of primary gill cell culture as a viable alternative to conventional methodologies for investigating host pathogen interactions.

Profiling the Physiological Roles in Fish Primary Cell Culture

Fish primary cell culture has emerged as a valuable tool for investigating the physiological roles and responses of various cell types found in fish species. This review aims to provide an overview of the advancements and applications of fish primary cell culture techniques, focusing on the profiling of physiological roles exhibited by fish cells in vitro. Fish primary cell culture involves the isolation and cultivation of cells directly derived from fish tissues, maintaining their functional characteristics and enabling researchers to study their behavior and responses under controlled conditions. Over the years, significant progress has been made in optimizing the culture conditions, establishing standardized protocols, and improving the characterization techniques for fish primary cell cultures. The review highlights the diverse cell types that have been successfully cultured from different fish species, including gonad cells, pituitary cells, muscle cells, hepatocytes, kidney and immune cells, adipocyte cells and myeloid cells, brain cells, primary fin cells, gill cells, and other cells. Each cell type exhibits distinct physiological functions, contributing to vital processes such as metabolism, tissue regeneration, immune response, and toxin metabolism. Furthermore, this paper explores the pivotal role of fish primary cell culture in elucidating the mechanisms underlying various physiological processes. Researchers have utilized fish primary cell cultures to study the effects of environmental factors, toxins, pathogens, and pharmaceutical compounds on cellular functions, providing valuable insights into fish health, disease pathogenesis, and drug development. The paper also discusses the application of fish primary cell cultures in aquaculture research, particularly in investigating fish growth, nutrition, reproduction, and stress responses. By mimicking the in vivo conditions in vitro, primary cell culture has proven instrumental in identifying key factors influencing fish health and performance, thereby contributing to the development of sustainable aquaculture practices.

Live-Cell Systems in Real-Time Biomonitoring of Water Pollution: Practical Considerations and Future Perspectives

Continuous monitoring and early warning of potential water contamination with toxic chemicals is of paramount importance for human health and sustainable food production. During the last few decades there have been noteworthy advances in technologies for the automated sensing of physicochemical parameters of water. These do not translate well into online monitoring of chemical pollutants since most of them are either incapable of real-time detection or unable to detect impacts on biological organisms. As a result, biological early warning systems have been proposed to supplement conventional water quality test strategies. Such systems can continuously evaluate physiological parameters of suitable aquatic species and alert the user to the presence of toxicants. In this regard, single cellular organisms, such as bacteria, cyanobacteria, micro-algae and vertebrate cell lines, offer promising avenues for development of water biosensors. Historically, only a handful of systems utilising single-cell organisms have been deployed as established online water biomonitoring tools. Recent advances in recombinant microorganisms, cell immobilisation techniques, live-cell microarrays and microfluidic Lab-on-a-Chip technologies open new avenues to develop miniaturised systems capable of detecting a broad range of water contaminants. In experimental settings, they have been shown as sensitive and rapid biosensors with capabilities to detect traces of contaminants. In this work, we critically review the recent advances and practical prospects of biological early warning systems based on live-cell biosensors. We demonstrate historical deployment successes, technological innovations, as well as current challenges for the broader deployment of live-cell biosensors in the monitoring of water quality.

Copper and cadmium impair sperm performance, fertilization and hatching of oocytes from Amazonian fish Colossoma macropomum

The contamination of aquatic environments by transition metals can have a direct influence on the reproductive process of several organisms in the aquatic biota. This study aimed to evaluate the effect of cadmium and copper on the sperm of tambaqui (Colossoma macropomum). Male (n = 4) and female (n = 4) specimens of C. macropomum were induced to spermiation and ovulation, with sperm being activated in the following media: 0; 0.6; 1.2 and 1.8 mg/L of cadmium (CdCl₂) and 0; 0.4; 0.8 and 1.2 mg/L of copper (CuCl₂). Sperm quality was assessed through time (s) and motility rate (%), superoxide dismutase (SOD) and glutathione S-transferase (GST) activities, lipoperoxidation levels (LPO), and morphological characteristics. In parallel, the effects of these metals on the rate of fertilization and hatching of the oocytes were evaluated. The duration and motility rate of sperm were longer in the control treatment, 85.67 ± 11.01 s; 90 ± 0.01%, and progressively decreased to 44.67 ± 4.16 s and 60 ± 5%, respectively, in concentrations of 1.8 mg/L (44.67 ± 4.16 s; 60 ± 5%) of CdCl₂ and to 65.67 ± 3.30 s; 70 ± 5%, respectively, in concentrations of 0.8 mg/L of CuCl₂. We observed an increase in the activity of the SOD enzyme in sperm cells exposed to 1.2 mg/L of CdCl₂. The LPO levels were increased significantly in sperm cells exposed to 1.2 and 1.8 mg/L of CdCl₂ and 0.8 mg/L of CuCl₂. Fertilization and hatching were severely impaired in the presence of Cd and Cu. These data indicate that environments contaminated with cadmium and copper harm the gametes of C. macropomum.

The Last Half Century of Fish Explant and Organ Culture

Explants are three-dimensional tissue fragments maintained outside the organism. The goals of this article are to review the history of fish explant culture and discuss applications of this technique that may assist the modern zebrafish laboratory. Because most zebrafish workers do not have a background in tissue culture, the key variables of this method are deliberately explained in a general way. This is followed by a review of fish-specific explantation approaches, including presurgical husbandry, aseptic dissection technique, choice of media and additives, incubation conditions, viability assays, and imaging studies. Relevant articles since 1970 are organized in a table grouped by organ system. From these, I highlight several recent studies using explant culture to study physiological and embryological processes in teleosts, including circadian rhythms, hormonal regulation, and cardiac development.

In vitro gill cell monolayer successfully reproduces in vivo Atlantic salmon host responses to Neoparamoeba perurans infection

An in vitro model to study the host response to Neoparamoeba perurans, the causative agent of amoebic gill disease (AGD), was evaluated. The rainbow trout gill derived cell line, RTgill-W1, was seeded onto permeable cell culture supports and maintained asymmetrically with apical seawater. Cells were inoculated with either a passage attenuated or a recent wild clone of N. perurans. Amoebae, loaded with phagocytosed fluorescent beads, were observed associated with host cells within 20 min post inoculation (pi). By 6 h small foci of cytopathic effect appeared and at 72 h cytolysis was observed, with total disruption of the cell monolayer at 96 h pi. Due to cell monolayer disruption, the platform could not support proliferation of amoebae, which showed a 3-log reduction in parasite 18S rRNA mRNA after 72 h (10⁶ copies at 1 h to 10³ at 72 h pi). SEM observations showed amoebae-like cells with either short pseudopodia and a malleiform shape, or, long pseudopodia embedded within the gill cells and erosion of the cell monolayer. To study the host immune response, inoculated gill cells were harvested from triplicate inserts at 0, 1, 3, 6, 24 and 48 h pi, and expression of 12 genes involved in the Atlantic salmon response to AGD was compared between infected and uninfected cells and between amoebic clones. Both clones induced similar host inmate immune responses, with the up-regulation of proinflammatory cytokine IL1β, complement C3 and cell receptor MHC-1. The Th2 pathway was up-regulated, with increased gene expression of the transcription factor GATA3, and Th2 cytokines IL10, IL6 and IL4/13A. PCNA and AG-2 were also up-regulated. The wild clone induced significantly higher up-regulation of IL1β, MHC-1, PCNA, lysozyme and IL10 than the attenuated clone for at least some exposure times, but AG-2 gene expression was higher in cells inoculated with the attenuated one. A principal component analysis showed that AG-2 and IL10 were key genes in the in vitro host response to N. perurans. This in vitro model has proved to be a promising tool to study host responses to amoebae and may therefore reduce the requirement for in vivo studies when evaluating alternative therapeutants to AGD control.

An Ultra-Rapid Biosensory Point-of-Care (POC) Assay for Prostate-Specific Antigen (PSA) Detection in Human Serum

Prostate-specific antigen (PSA) is the established routine screening tool for the detection of early-stage prostate cancer. Given the laboratory-centric nature of the process, the development of a portable, ultra rapid high-throughput system for PSA screening is highly desirable. In this study, an advancedpoint-of-care system for PSA detection in human serum was developed based on a cellular biosensor where the cell membrane was modified by electroinserting a specific antibody against PSA. Thirty nine human serum samples were used for validation of this biosensory system for PSA detection. Samples were analyzed in parallel with a standard immunoradiometric assay (IRMA) and an established electrochemical immunoassay was used for comparison purposes. They were classified in three different PSA concentration ranges (0, <4 and ≥4 ng/mL). Cells membrane-engineered with 0.25 μg/mL anti-PSA antibody demonstrated a statistically lower response against the upper (≥4 ng/mL) PSA concentration range. In addition, the cell-based biosensor performed better than the immunosensor in terms of sensitivity and resolution against positive samples containing <4 ng/mL PSA. In spite of its preliminary, proof-of-concept stage of development, the cell-based biosensor could be used as aninitiative for the development of a fast, low-cost, and high-throughput POC screening system for PSA.

Establishment and long-term maintenance of primary intestinal epithelial cells cultured from the rainbow trout, Oncorhynchus mykiss

A novel method for the establishment and long-term maintenance of ex vivo cultures from intestinal regions of the rainbow trout, Oncorhynchus mykiss (Walbaum), is reported. Adherence of cells was observed within hours, epithelial island formation recorded at 48 h and rapid proliferation with confluence achieved between 9-14 days. In addition to metabolic characterisation, basic morphology of growing cells was characterised using histology, immunofluorescence, transmission electron microscopy (TEM) and transepithelial electrical resistance (TEER). Regional differences in intestinal ethoxyresorufin-O-deethylase (EROD) and 7-ethoxycoumarin-O-deethylation (ECOD) activities in these primary grown enterocytes were compared following exposure to model inducers [i.e. α-NF, β-NF, B(a)P] which demonstrated significant differences. Regional differences in dietary uptake and metabolism of contaminants can therefore be studied in this in vitro system to increase our understanding of fundamental processes, while concurrently providing a means to reduce the number of fish required for biological studies in line with the principles of the 3Rs (Reduce, Refine and Replace).

This article has an associated First Person interview with the first author of the paper.

Summary: Understanding chemical uptake from the diet is difficult in live fish: we developed long-term intestinal cell cultures that enables the science and provides an alternative method.