Development, characterization and application of a new fibroblastic-like cell line from kidney of a freshwater air breathing fish Channa striatus (Bloch, 1793)

Establishment and characterization of a kidney cell line from hybrid snakehead (male Channa argus × female Channa maculata) and its susceptibility to hybrid snakehead rhabdovirus (HSHRV)

Hybrid snakehead (male Channa argus × female Channa maculata) is an emerging fish breed with increasing production levels. However, infection with hybrid snakehead rhabdovirus (HSHRV) critically affects hybrid snakehead farming. In this study, a fish cell line called CAMK, derived from the kidneys of hybrid snakehead, was established and characterized. CAMK cells exhibited the maximum growth rate at 28 °C in Leibovitz's-15 medium supplemented with 10% fetal bovine serum(FBS). Karyotyping revealed diploid chromosomes in 54% of the cells at the 50th passage (2n = 66), and 16S rRNA sequencing validated that CAMK cells originated fromhybrid snakehead, and the detection of kidney-specific antibodies suggested that it originated from kidney. .The culture was free from mycoplasma contamination, and the green fluorescent protein gene was effectively transfected into CAMK cells, indicating their potential use for in vitro gene expression investigations. Furthermore, qRT-PCR and immunofluorescence analysis revealed that HSHRV could replicate in CAMK cells, indicating that the cells were susceptible to the virus. Transmission electron microscopy revealed that the viral particles had bullet-like morphology. The replication efficiency of HSHRV was 107.33 TCID50/mL. Altogether, we successfully established and characterized a kidney cell line susceptible to the virus. These findings provide a valuable reference for further genetic and virological studies.

Fish cell line: depositories, web resources and future applications

Cell lines are important bioresources to study the key biological processes in the areas like virology, pathology, immunology, toxicology, biotechnology, endocrinology and developmental biology. Cell lines developed from fish organs are utilized as a model in vitro system in disease surveillance programs, pharmacology, drug screening and resolving cases of metabolic abnormalities. During last decade, there were consistent efforts made globally to develop new fish cell lines from different organs like brain, eye muscles, fin, gill, heart, kidney, liver, skin, spleen, swim bladder, testes, vertebra etc. This increased use and development of cell lines necessitated the establishment of cell line depositories to store/preserve them and assure their availability to the researchers. These depositories are a source of authenticated and characterized cell lines with set protocols for material transfer agreements, maintenance and shipping as well as logistics enabling cellular research. Hence, it is important to cryopreserve and maintain cell lines in depositories and make them available to the research community. The present article reviews the current status of the fish cell lines available in different depositories across the world, along with the prominent role of cell lines in conservation of life on land or below water.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-023-00601-2.

Cell line derived from muscle of Gymnocypris przewalskii, a species of Schizothoracinae in Qinghai Lake, Qinghai-Tibet Plateau

Gymnocypris przewalskii (naked carp), a native teleost, plays an important role in the ecosystem of Qinghai Lake (altitude, 3.2 km) on the Qinghai-Tibet Plateau in China. We developed a new cell line from the muscle of G. przewalskii using the explant technique and named the cell line GPM. This cell line was maintained in DMEM medium (high glucose) supplemented with 15% fetal bovine serum (FBS). The cell line was successfully subcultured up to 32 passages and was authenticated by immunofluorescence assay, sequencing the mitochondrial cytochrome C oxidase subunit I (COI) and 16S rRNA genes, and by chromosome analysis. In the medium containing 15% FBS, the cell line could be passaged stably at 25 °C. The GPM cell line could express green fluorescent protein (GFP) with a CMV promoter with about 5% transfection efficiency. MTT tests showed that Clostridium botulinum toxin (BTX) was toxic to the cell line. The cell line could be successfully cryopreserved in liquid nitrogen with a revival efficiency of over 70%. This study demonstrated that the GPM cell line can be used as an important tool for understanding the physiological characteristics of G. przewalskii, and it can provide a resource for studying gene function and toxicological reactions in vitro.

Cloning, Characterization, and Antibacterial Properties of Endolysin LysE Against Planktonic Cells and Biofilms of Aeromonas hydrophila

Multidrug-resistant bacteria are emerging as a major global threat to public health. Bacteriophages are an important source of antimicrobial enzymes and could be developed as an alternative antibiotic candidate. This study investigates the antibacterial capacity of the endolysin LysE against Aeromonas hydrophila. The endolysin LysE gene was cloned and expressed in Escherichia coli BL21 (DE3) cells. Purified recombinant LysE protein was tested for its antimicrobial activity against A. hydrophila. The study reveals that recombinant LysE protein was highly effective against Gram-negative bacteria when combined with antimicrobials that alter the permeability of the outer membrane. Specifically, the enzyme had the highest muralytic activity at pH 4, and maintained over 50% of the activity at pH 10. Moreover, endolysin displayed more than 50% activity even after 30 min of incubation at 100 °C. Also, endolysin LysE resulted in one log reduction in CFU/mL in 30 min and demonstrated antibiofilm capabilities when combined with EDTA. Interestingly, checkerboard assay showed its synergistic effects in combination with lower concentrations of colistin against A. hydrophila. Additionally, in vitro tests with Channa striatus kidney (CSK) cell lines do not show cytotoxic effects. Taken together, these findings suggest that LysE can be employed with outer membrane permeabilizers to expand the arsenal repertoire against Gram-negative bacteria in the aquaculture, food, and medical industries.

Development and characterization of five novel cell lines from snubnose pompano, Trachinotus blochii (Lacepede, 1801), and their application in gene expression and virological studies

Five novel permanent cell lines have been established from gill, heart, kidney, eye and fin of snubnose pompano, Trachinotus blochii. They were designated as snubnose pompano gill (SPG), snubnose pompano heart (SPH), snubnose pompano kidney (SPK), snubnose pompano eye (SPE) and snubnose pompano fin (SPF), respectively. All these cell lines were characterized and cryopreserved successfully at different passage levels. Cell lines were passaged every alternate day; SPG, SPH, SPK, SPE and SPF cell lines attained passage levels of 68, 74, 82, 79 and 106, respectively, since the initiation of their development in 2019. The cell lines grew well in Leibovitz's 15 medium containing 15% foetal bovine serum at 28°C. Immunophenotyping of the cell lines revealed the presence of fibronectin and pancytokeratin. No mycoplasma contamination was found. The transfection study revealed the gene expression efficiency of these cell lines by expressing the green fluorescent protein (GFP). The authentication on origin of cell lines from T. blochii was confirmed by amplification of species-specific mitochondrial cytochrome oxidase I gene. The results showed the susceptibility of these cell lines to fish nodavirus (FNV) and tilapia lake virus (TiLV) and resistance to cyprinid herpesvirus 2 (CyHV-2). The FNV infection in the cell lines was confirmed by RT-PCR, Western blot, ELISA and immunocytochemistry, while TiLV infection was confirmed by RT-PCR assay. These results revealed that these cell lines are suitable for virological and foreign gene expression studies.

Susceptibility of betanodavirus in a newly established vertebra-derived cell line from Mosquitofish (Gambusia affinis)

In the present study, a new cell line from the vertebra of mosquitofish Gambusia affinis was successfully established and characterized. The cell line is named as bone Gambusia affinis (BGA) and subcultured for more than 55 passages in Leibovitz's/L15 medium supplemented with 15% FBS at 28°C. The cell line has a modal chromosome number of 48. Molecular characterization of the partial sequence of the coi gene confirmed the origin of the BGA cell line from mosquitofish. These cells exhibited epithelial morphology confirmed by the cytokeratin marker. The BGA cells showed mineralization of their extracellular matrix when stained with alizarin red and von Kossa stain. BGA cells were found to be susceptible to RGNNV and SJNNV strains of betanodavirus (NNV) showing cytopathic effect with multiple vacuolations in the cells. The RT-PCR confirmed the betanodavirus infections in BGA cells. The SEM micrograph showed the morphological changes observed in the cell during virus infection. The in vivo challenge experiment also showed the viral replicating efficiency in the Gambusia affinis with increasing viral titre. Thus, our present results show that the BGA cell line is a useful tool for isolating betanodavirus and could be used to investigate bone cell differentiation and extracellular matrix mineralization.

New Protocol for Cell Culture to Obtain Mitotic Chromosomes in Fishes

Cell culture is an excellent alternative for the maintenance of cell lines and to obtain quality chromosome preparations of fishes. However, this methodology is still little employed, mainly because of the difficulty of standardization of cell cultures. In this study, we describe a methodology for the rapid acquisition of cell lineages and mitotic chromosomes for cytogenetic studies of fish species from muscle tissue cells. Our methodology is based on the use of a gelatin film, which provides better adhesion of a large number of cells and appropriate conditions for multiplication. The cells of Astyanax altiparanae, used as an experimental model, with fibroblast-like morphology, showed rapid cellular proliferation, resulting in a great number of cells. Chromosomal preparations of cultured cells showed the diploid number of the species, 2n = 50 chromosomes, in 80% of the cells examined, with chromosomes intact and distended. Cell populations were cryopreserved and after being recovered, these cells maintained their proliferative capacity. The development of this methodology represents an innovation for the fish cytogenetics area and it may bring a significant contribution to the conservation and study of several groups due to the difficulty of obtaining good-quality chromosome preparations.

Establishment of a new fish cell line from the caudal fin of golden pompano Trachinotus ovatus and its susceptibility to iridovirus

A new cell line derived from the caudal fin of golden pompano Trachinotus ovatus (TOCF) was successfully established and characterized. TOCF cells grew well at 28° C in L-15 medium supplemented with 10% foetal bovine serum (FBS). The cell line has been subcultured in more than 100 passages. Molecular characterization of 18S ribosomal (r)RNA and cytochrome oxidase subunit 1 (COI) confirmed that the TOCF cells were derived indeed from T. ovatus. TOCF cells have a modal chromosome number of 54. It was further showed that TOCF cells were transfected successfully with pEGFP-N3 and pDsRED-N1 plasmid, suggesting that TOCF cells could be used to research gene functions in vitro. Viral susceptibility tests showed that TOCF cells were susceptible to Singapore grouper iridovirus (SGIV), observed by the occurrence of the cytopathic effect (CPE) with the formation of inclusion bodies. In addition, the expression of major capsid protein (MCP) gene of SGIV changed during virus infection in TOCF cells. Thus, our present results described the characteristic of a TOCF cell line that could be a valuable tool for genetic manipulation, as well as isolation and propagation of iridovirus studies.

Advances in the study of nodavirus

Nodaviruses are small bipartite RNA viruses which belong to the family of Nodaviridae. They are categorized into alpha-nodavirus, which infects insects, and beta-nodavirus, which infects fishes. Another distinct group of nodavirus infects shrimps and prawns, which has been proposed to be categorized as gamma-nodavirus. Our current review focuses mainly on recent studies performed on nodaviruses. Nodavirus can be transmitted vertically and horizontally. Recent outbreaks have been reported in China, Indonesia, Singapore and India, affecting the aquaculture industry. It also decreased mullet stock in the Caspian Sea. Histopathology and transmission electron microscopy (TEM) are used to examine the presence of nodaviruses in infected fishes and prawns. For classification, virus isolation followed by nucleotide sequencing are required. In contrast to partial sequence identification, profiling the whole transcriptome using next generation sequencing (NGS) offers a more comprehensive comparison and characterization of the virus. For rapid diagnosis of nodavirus, assays targeting the viral RNA based on reverse-transcription PCR (RT-PCR) such as microfluidic chips, reverse-transcription loop-mediated isothermal amplification (RT-LAMP) and RT-LAMP coupled with lateral flow dipstick (RT-LAMP-LFD) have been developed. Besides viral RNA detections, diagnosis based on immunological assays such as enzyme-linked immunosorbent assay (ELISA), immunodot and Western blotting have also been reported. In addition, immune responses of fish and prawn are also discussed. Overall, in fish, innate immunity, cellular type I interferon immunity and humoral immunity cooperatively prevent nodavirus infections, whereas prawns and shrimps adopt different immune mechanisms against nodavirus infections, through upregulation of superoxide anion, prophenoloxidase, superoxide dismutase (SOD), crustin, peroxinectin, anti-lipopolysaccharides and heat shock proteins (HSP). Potential vaccines for fishes and prawns based on inactivated viruses, recombinant proteins or DNA, either delivered through injection, oral feeding or immersion, are also discussed in detail. Lastly, a comprehensive review on nodavirus virus-like particles (VLPs) is presented. In recent years, studies on prawn nodavirus are mainly focused on Macrobrachium rosenbergii nodavirus (MrNV). Recombinant MrNV VLPs have been produced in prokaryotic and eukaryotic expression systems. Their roles as a nucleic acid delivery vehicle, a platform for vaccine development, a molecular tool for mechanism study and in solving the structures of MrNV are intensively discussed.

Assessment of cytotoxicity and AhR-mediated toxicity in tropical fresh water sediments under the influence of an oil refinery

Oil refinery effluents contain many chemicals at variable concentrations. Therefore, it is difficult to predict potential effects on the environment. The Atibaia River (SP, Brazil), which serves as a source of water supply for many municipalities, receives the effluents of one of the biggest oil refinery of this country. The aim of this study was to identify the (eco)toxicity of fresh water sediments under the influence of this oil refinery through neutral red (cytotoxicity) and ethoxyresorufin-O-deethylase (EROD) assays (AhR-mediated toxicity) in RTL-W1 cells (derived from fish liver). Once the refinery captures the waters of Jaguarí River for the development of its activities and discharges its effluents after treatment into the Atibaia River, which then flows into Piracicaba River, sediments from both river systems were also investigated. The samples showed a high cytotoxic potential, even when compared to well-known pollution sites. However, the cytotoxicity of samples collected downstream the effluent was not higher than that of sediments collected upstream, which suggested that the refinery discharges are not the main source of pollution in those areas. No EROD activity could be recorded, which could be confirmed by chemical analyses of polycyclic aromatic hydrocarbons (PAHs) that revealed a high concentration of phenanthrene, anthracene, fluoranthene, and pyrene, which are not EROD inducers in RTL-W1 cells. In contrast, high concentrations of PAHs were found upstream the refinery effluent, corroborating cytotoxicity results from the neutral red assay. A decrease of PAHs was recorded from upstream to downstream the refinery effluent, probably due to dilution of compounds following water discharges. On the other hand, these discharges apparently contribute specifically to the amount of anthracene in the river, since an increase of anthracene concentrations could be recorded downstream the effluent. Since the extrapolation of results from acute toxicity to specific toxic effects with different modes of action is a complex task, complementary bioassays covering additional specific effects should be applied in future studies for better understanding of the overall ecotoxicity of those environments.

A novel fish cell line derived from the brain of Chinese perch Siniperca chuatsi: development and characterization

In this study, a continuous cell line (named as CPB) was established from Siniperca chuatsi brain and has been subcultured >140 times. CPB cell line predominantly consisted of fibroblast-like cells that could grow better in Leibovitz's L-15 supplemented with 10% foetal bovine serum at 28° C. Polymerase chain reaction amplification of 18s recombinant (r)RNA confirmed the origin of this cell line from S. chuatsi. The CPB cell line was cryopreserved at different passage levels and revived successfully with 80-90% survival. The cell line was further characterized by chromosome number and transfection. The CPB cells were highly susceptible to infectious spleen and kidney necrosis virus (ISKNV) with a titre of 6·58-6·62 log TCID50 ml(-1) and numerous ISKNV particles were observed in the cytoplasm by transmission electron microscopy. At the same time, ISKNV infection was confirmed by reverse transcriptase polymerase chain reaction, immunodot blot and individual challenge experiments. The development and characterization of a new brain cell line from S. chuatsi were described in this study and it could be used as an in vitro tool for propagation of ISKNV and gene expression studies.

Cytotoxicity, genotoxicity and oxidative stress of malachite green on the kidney and gill cell lines of freshwater air breathing fish Channa striata

The cytotoxicity, genotoxicity and oxidative stress of malachite green (MG) was investigated using the fish Channa striata kidney (CSK) and Channa striata gill (CSG) cell lines. Five concentrations ranging from 0.001 to 10 μg mL(-1) were tested in three independent experiments. Cytotoxicity was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Rhodamine 123 and Alamar Blue. The mitochondrial changes and apoptosis of MG-exposed cells were observed by Rhodamine 123 and acridine orange/ethidium bromide (AO/EB) staining, respectively. In vitro potential DNA damaging effect of MG was tested using comet assay. Mitochondrial damage, apoptosis and DNA fragmentation increased in a concentration-dependent manner. Additionally, DNA electrophoretic mobility experiments were carried out to study the binding effect of MG to double-stranded DNA (dsDNA) of cells. DNA shift mobility experiments showed that MG is capable of strongly binding to linear dsDNA causing its degradation. Biochemical parameters such as lipid peroxidation (MDA), catalase (CAT) activity and reduced glutathione (GSH) levels were evaluated after exposure to MG. In CSK and CSG cell lines exposed to MG for 48 h, a significant increase in lipid peroxidation, which might be associated with decreased levels of reduced glutathione and catalase activity in these cell lines (p < 0.001), was observed.

A new epithelial cell line, HBF from caudal fin of endangered yellow catfish, Horabagrus brachysoma (Gunther, 1864)

A new epithelial cell line, Horabagrus brachysoma fin (HBF), was established from the caudal fin tissue of yellow catfish, H. brachysoma and characterized. This HBF cell line was maintained in Leibovitz's-15 medium supplemented with 15 % fetal bovine serum (FBS) and subcultured more than 62 times over a period of 20 months. The HBF cell line consists predominantly of epithelial cells and is able to grow at temperatures between 20 and 35 °C with an optimum temperature of 28 °C. The growth rate of these cells increased as the proportion of FBS increased from 5 to 20 % at 28 °C with optimum growth at the concentrations of 15 % FBS. Partial amplification and sequencing of fragments of two mitochondrial genes 16S rRNA and COI confirmed that HBF cell line originated from yellow catfish. The HBF cells showed strong positive reaction to the cytokeratin marker, indicating that it was epithelial in nature. HBF cell line was inoculated with tissue homogenate from juveniles of Sea bass, Lates calcarifer infected with viral nervous necrosis virus (VNNV) and found not susceptible to VNNV. The extracellular products of Vibrio cholerae MTCC 3904 were toxic to the HBF cells. These cells were confirmed for the absence of Mycoplasma sp by PCR.