Establishment and characterization of an epithelial cell line from thymus of Catla catla (Hamilton, 1822)

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.

Development, characterization and in vitro applications of a thymus cell line from Pangasianodon hypophthalmus (Sauvage 1878)

Pangasianodon hypophthalmus is an economically important catfish species cultured in India. In the present study, a continuous cell line from the thymus of P. hypophthalmus (PHT) was established using the explant method and subcultured 52 times since development. PHT cells showed optimal growth in L-15 medium containing 20% fetal bovine serum at 28°C. The species of the cell line from striped catfish was confirmed through PCR amplification and sequencing of 16S, and COI genes. The cell line was found to be Mycoplasma free. The modal chromosome number of PHT cells was 60 (2n). Immunophenotyping using different antibodies showed the epithelial nature of the cells. Cytotoxicity of arsenic and mercury was assessed using Neutral red and MTT assay, which revealed reduced cell survival with an increase in toxicant concentration. Cells transfected successfully with the GFP reporter gene using lipofectamine reagent indicated the suitability of the cell line for expression studies. The cell line has been submitted to NRFC, Lucknow with accession no. NRFC-078 at ICAR-NBFGR, Lucknow. The developed cell line will have applications in suspected viral disease investigation, transgenic, and immunological studies.

IGF-1 increases survival of CD4+ lineage in a 2D model of thymocyte/thymic stromal cell co-culture

Insulin-like growth factor-1 (IGF-1), in addition to its classic effects on cell proliferation and organism growth, has pleiotropic actions on the immune system, particularly on the thymus. Thus, the objective of this study was to evaluate the influence of IGF-1 on molecules involved in the survival of thymocytes in vitro using a co-culture system with thymic stromal cells obtained from C57BL/6 mice. The obtained thymic stroma has contained thymic epithelial cells, macrophages, dendritic cells, fibroblasts, and preserved the expression of the major histocompatibility complex (MHC) molecules. Fresh thymocytes were added to these cultures and the co-culture were treated daily with IGF-1 (100 ng/mL) for 3 days. In this scheme, the viability of the thymocytes was about 70%, either in the control (non-treated cells) or in the IGF-1-treated cultures. It was found that IGF-1 was able to increase the percentage of thymocytes from the CD4⁺ single-positive (SP) subset. This result was accompanied by an increase in the MHC II expression on thymic stromal cells and an augment on the interleukin-7 receptor (CD127) on the surface of the CD4 SP thymocytes after treatment with IGF-1. Finally, IGF-1 treatment increased the expression of the ThPOK encoding gene Zbtb7b, which is involved in the differentiation of CD4+ SP thymocytes. Our study demonstrates the participation of IGF-1 in the thymocyte/thymic stroma interactions, especially in the extended survival of the CD4⁺ lineage in the thymus.

Establishment and characterization of a continuous cell line from caudal fin of Labeo calbasu (Hamilton, 1822)

Labeo calbasu is an important food fish and candidate species for diversification of carp aquaculture. In the present study, we have established a continuous cell line, designated as L. calbasu fin (LCF), from caudal fin of L. calbasu using explant method. The cell line has been subcultured for over 73 passages and the LCF cells show optimal growth in Leibovitz's L-15 medium supplemented with 20% fetal bovine serum at a temperature of 28°C. In karyotype analysis, the modal chromosome number of LCF cells at 35th passage was found to be 50. The amplification and sequencing of partial fragments of mitochondrial genes, namely 16S rRNA and COI from LCF cells confirmed the origin of cell line from L. calbasu. The LCF cells could be successfully transfected with GFP reporter gene, indicating suitability of these cells for expression of foreign genes. Further, following inoculation with supernatant from Tilapia lake virus (TiLV) infected cell line, no cytopathic effects were observed in the LCF cells and cell pellet was negative for TiLV in RT-PCR, indicating that LCF cells were not susceptible to TiLV. The developed cell line has been submitted to National Repository of Fish Cell Lines being maintained at ICAR-National Bureau of Fish Genetic Resources, Lucknow (accession no. NRFC063). The newly developed LCF cell line would be helpful in investigating diseases affecting this candidate species particularly the ones suspected to be of viral etiology, and for cytotoxicity and transgenic 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.

Establishment and characterization of a caudal fin-derived cell line, AOF, from the Oscar, Astronotus ocellatus

Astronotus ocellatus, commonly called the oscar, is one of the popular cichlids among aquarium hobby. The present study deals with the development and characterization of a new cell line from caudal fin of A. ocellatus. The cell line was cultured in Leibovitz's L-15 medium supplemented with 10% fetal bovine serum at 28 °C. The optimum temperature and FBS concentration for cell growth were tested with temperature ranges from 20 to 37 °C and FBS concentrations of 5-20% at 28 °C. The Astronotus ocellatus fin cell line has been subcultured 45 times since its development and the modal chromosome number (2n) is 48. The cell line is composed mainly of epithelial cells as confirmed by immunocytological technique using anti-cytokeratin antibodies. The cell line was cryopreserved at different passage levels and the revival efficiency showed 80% survival rate. Partial sequence amplification and sequencing of two genes, mitochondrial 16S ribosomal RNA and cytochrome oxidase I, confirmed the origin of cell line. The cell line did not show Mycoplasma contamination. The cells showed good transfection efficiency when transfected with 2 μg of pAcGFP1-N1 expression vector. The extracellular products of fish bacterial pathogens viz., Aeromonas hydrophila and A. caviae, were cytotoxic to AOF cells but were not susceptible to Cyprinid herpes virus 2. The development of AOF cell line will have significant applications in fish virology and will prove useful to isolate pathogens in the event of sudden viral disease outbreak and for the development of vaccines and diagnostic kits.

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.

Development, characterization and application of a new epithelial cell line from caudal fin of Pangasianodon hypophthalmus (Sauvage 1878)

A cell line, designated as PHF, has been established from caudal fin of Pangasianodon hypophthalmus. The cell line was developed using explant method and PHF cells have been subcultured for more than 72 passages over a period of 14 months. The cells were able to grow at temperatures between 24 and 32° C, with an optimum temperature of 28° C. The growth rate of PHF cells was directly proportional to FBS concentration, with optimum growth observed at 20% FBS concentration. On the basis of immunophenotyping assay, PHF cells were confirmed to be of epithelial type. Karyotyping of PHF cells revealed diploid number of chromosomes (2n = 60) at 39th and 65th passage, which indicated that the developed cell line is chromosomally stable. The origin of the cell line was confirmed by amplification and sequencing of cytochrome oxidase c subunit I and 16S rRNA genes. The cell line was tested for Mycoplasma contamination and found to be negative. The cells were successfully transfected with GFP reporter gene suggesting that the developed cell line could be utilized for gene expression studies in future. The cell line could be successfully employed for evaluating the cytotoxicity of heavy metals, namely mercuric chloride and sodium arsenite suggesting that PHF cell line can be potential surrogate for whole fish for studying the cytotoxicity of water soluble compounds. The result of virus susceptibility to tilapia lake virus (TiLV) revealed that PHF cells were refractory to TiLV virus. The newly established cell line would be a useful tool for investigating disease outbreaks particularly of viral etiology, transgenic as well as cytotoxicity studies.

A new fish cell line derived from the caudal fin of freshwater angelfish Pterophyllum scalare: development and characterization

In this study, a new cell line derived from the caudal fin of the freshwater angelfish Pterophyllum scalare was developed and characterized. The cell line was designated angelfish fin (AFF) and subcultured 44 times since its development. These cells grew well in Leibovitz's -15 medium supplemented with 10% foetal bovine saline (FBS) at 28° C and the modal chromosome number (2n) was 48. The AFF cell-line is mainly comprised of epithelial cells as confirmed by immunocytological technique using anti-cytokeratin antibodies, an epithelial cell marker. This cell line was tested for growth in a temperatures range from 20 to 37° C and at various FBS concentrations of 5-20% at 28° C. The cell line was cryopreserved at different passage levels and revived successfully with 80% survival rate. Polymerase chain reaction amplification and sequencing of partial mitochondrial 16s rRNA and coI genes confirmed that the AFF cell-line originated from angelfish. Mycoplasma sp. contamination was not detected in AFF cells and checked by Hoechst 33258 fluorescence staining. At the 42nd passage the cells were transfected with 2 μg of pAcGFP1-N1 expression vector. The AFF cells exhibited cytotoxic effects when exposed to the bacterial extra cellular products from Serratia marcescens and Proteus hauseri. The AFF cells and cells from kidney and brain did not show cytopathic effect when exposed to cyprinid herpes virus2 and viral nervous necrosis virus. The newly developed AFF cell line will be useful for the isolation of viruses affecting angelfishes, such as iridoviruses, in the future.

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.

Establishment of a leukocyte cell line derived from peritoneal macrophages of fish, Labeo rohita (Hamilton, 1822)

A continuous leukocyte cell line with phagocytic activity was established from peritoneal macrophages of rohu, Labeo rohita (LRPM). LRPM was initiated from adherent mononuclear leukocytes isolated from peritoneal cavity of rohu, without use of any growth factors or feeder cells. These cells exhibited maximum growth at 30 °C in L-15 medium containing 20 % foetal bovine serum, and has been subcultured for more than 60 passages till date. The cells showed 85 % viability after 6 months of storage in liquid nitrogen. The species of origin of the LRPM was confirmed by the amplification and sequencing of 655 bp fragment of cytochrome oxidase subunit I of mitochondrial DNA. Functionally, LRPM showed phagocytic activity of yeast cells and fluorescent latex beads as evaluated by phase contrast and scanning electron microscopy, respectively. Immuno-modulators such as bacterial lipopolysaccharide and phorbol myristate acetate resulted in functional activation of LRPM; and enhanced their microbicidal activity through release of reactive oxygen species and nitric oxide. Culture supernatant from activated cells also revealed lysozyme activity. Cells of LRPM were positive for alpha-naphthyl acetate esterase enzyme indicating macrophage lineage. Our results indicate that this cell line can be a useful in vitro tool to study the role of macrophages in teleost immune system and to evaluate the effects of new aquaculture drugs. The LRPM cell line represents the first reported leukocyte cell line of peritoneal origin from any freshwater species of fish.