Multifactorial interaction of growth factors on Penaeus monodon lymphoid cells and the impact of IGFs in DNA synthesis and metabolic activity in vitro

Transcriptomic Analysis across Crayfish (Cherax quadricarinatus) Claw Regeneration Reveals Potential Stem Cell Sources for Cultivated Crustacean Meat

In the face of rising global demand and unsustainable production methods, cultivated crustacean meat (CCM) is proposed as an alternative means to produce delicious lobster, shrimp, and crab products. Cultivated meat requires starting stem cells that may vary in terms of potency and the propensity to proliferate or differentiate into myogenic (muscle-related) tissues. Recognizing that regenerating limbs are a non-lethal source of tissue and may harbor relevant stem cells, we selected those of the crayfish Cherax quadricarinatus as our model. To investigate stem cell activity, we conducted RNA-Seq analysis across six stages of claw regeneration (four pre-molt and two post-molt stages), along with histology and real-time quantitative PCR (qPCR). Our results showed that while genes related to energy production, muscle hypertrophy, and exoskeletal cuticle synthesis dominated the post-molt stages, growth factor receptors (FGFR, EGFR, TGFR, and BMPR) and those related to stem cell proliferation and potency (Cyclins, CDKs, Wnts, C-Myc, Klf4, Sox2, PCNA, and p53) were upregulated before the molt. Pre-molt upregulation in several genes occurred in two growth peaks; Stages 2 and 4. We therefore propose that pre-molt limb regeneration tissues, particularly those in the larger Stage 4, present a prolific and non-lethal source of stem cells for CCM development.

Considerations for cultivated crustacean meat: potential cell sources, potential differentiation and immortalization strategies, and lessons from crustacean and other animal models

Cultivated crustacean meat (CCM) is a means to create highly valued shrimp, lobster, and crab products directly from stem cells, thus removing the need to farm or fish live animals. Conventional crustacean enterprises face increasing pressures in managing overfishing, pollution, and the warming climate, so CCM may provide a way to ensure sufficient supply as global demand for these products grows. To support the development of CCM, this review briefly details crustacean cell culture work to date, before addressing what is presently known about crustacean muscle development, particularly the molecular mechanisms involved, and how this might relate to recent work on cultivated meat production in vertebrate species. Recognizing the current lack of cell lines available to establish CCM cultures, we also consider primary stem cell sources that can be obtained non-lethally including tissues from limbs which are readily released and regrown, and putative stem cells in circulating hemolymph. Molecular approaches to inducing myogenic differentiation and immortalization of putative stem cells are also reviewed. Finally, we assess the current status of tools available to CCM researchers, particularly antibodies, and propose avenues to address existing shortfalls in order to see the field progress.

An optimized protocol for routine development of cell culture from adult oyster, Crassostrea madrasensis

Marine molluscan cell lines, required for virus screening and cultivation, form essential tools for developing health management strategies for these animals in the blue economy. Moreover, they are also crucial to develop cultivated seafood. As there is no valid marine molluscan cell line, primary cell cultures are relied upon for all investigations. A sound protocol for generating primary cell cultures from molluscs is entailed, but existing protocols often involve heavy antibiotic usage and depuration that invariably affect gene expression and cell health. This work presents an easy-to-adopt, time-saving protocol using non-depurated mollusc Crassostrea madrasensis, which requires only initial antibiotic treatment and minimal exposure or no use of antibiotics in the cell culture medium. The important experimental considerations for arriving at this protocol have been elucidated. Accordingly, sodium hypochlorite and neomycin sulfate were chosen for disinfecting tissues. The study is the first to use shrimp cell culture medium (SCCM) as a cell culture medium for molluscan cell culture. Despite being osmoconformers, the oysters exhibited stable intracellular osmotic conditions and pH, which, when provided in vitro, promoted effective cardiomyocyte formation. The cell viability could be enhanced using 10% fetal bovine serum (FBS), but healthy cell culture could also be obtained using SCCM without FBS. The optimized culture conditions allowed for regular beating cardiomyocyte clusters that could be retained for a month. Limited cell proliferation, as shown by the BrdU assay, demands further interventions, such as possibly producing induced pluripotent stem cells. The optimized protocol and culture conditions also align with some requirements for producing cultivated meat from marine molluscs.

Differentiation and Maturation of Muscle and Fat Cells in Cultivated Seafood: Lessons from Developmental Biology

Cultivated meat, also known as cultured or cell-based meat, is meat produced directly from cultured animal cells rather than from a whole animal. Cultivated meat and seafood have been proposed as a means of mitigating the substantial harms associated with current production methods, including damage to the environment, antibiotic resistance, food security challenges, poor animal welfare, and-in the case of seafood-overfishing and ecological damage associated with fishing and aquaculture. Because biomedical tissue engineering research, from which cultivated meat draws a great deal of inspiration, has thus far been conducted almost exclusively in mammals, cultivated seafood suffers from a lack of established protocols for producing complex tissues in vitro. At the same time, fish such as the zebrafish Danio rerio have been widely used as model organisms in developmental biology. Therefore, many of the mechanisms and signaling pathways involved in the formation of muscle, fat, and other relevant tissue are relatively well understood for this species. The same processes are understood to a lesser degree in aquatic invertebrates. This review discusses the differentiation and maturation of meat-relevant cell types in aquatic species and makes recommendations for future research aimed at recapitulating these processes to produce cultivated fish and shellfish.

Status in molluscan cell line development in last one decade (2010–2020): impediments and way forward

Despite the attempts that have started since the 1960s, not even a single cell line of marine molluscs is available. Considering the vast contribution of marine bivalve aquaculture to the world economy, the prevailing viral threats, and the dismaying lack of advancements in molluscan virology, the requirement of a marine molluscan cell line is indispensable. This synthetic review discusses the obstacles in developing a marine molluscan cell line concerning the choice of species, the selection of tissue and decontamination, and cell culture media, with emphasis given on the current decade 2010-2020. Detailed accounts on the experiments on the virus cultivation in vitro and molluscan cell immortalization, with a brief note on the history and applications of the molluscan cell culture, are elucidated to give a holistic picture of the current status and future trends in molluscan cell line development.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-022-00539-x.

A Novel Approach of Transducing Recombinant Baculovirus into Primary Lymphoid Cells of Penaeus monodon for Developing Continuous Cell Line

Cell line development from shrimp is not a novel venture as researchers across the globe have been trying to have crustacean cell lines over 30 years. The reason for not attaining a crustacean or precisely a shrimp cell line is believed to be the replicative senescence and the inability to maintain telomere length in vitro. Moreover, spontaneous in vitro transformations do not happen in shrimp cells. Oncogenic induction in primary cell culture is one of the ways to attain in vitro transformation by way of disrupting the mechanisms which involve cellular senescence. In this context, a recombinant baculovirus with shrimp viral promoter IHHNV-P2 was used for the transduction aimed at immortalization. An oncogene, H-ras, was successfully amplified and cloned in to the baculoviral vector, downstream to shrimp viral promoter IHHNV-P2 and upstream to GFP. Recombinant baculovirus with H-ras was generated and used for transduction into shrimp lymphoid cells during early dividing stage. Accordingly, fibroblast-like primary cell culture got developed, and H-ras and GFP expression could be confirmed. The study suggests that the simple method of incubating recombinant baculovirus with minced tissue enables in vitro transduction during early dividing stage of the cells, and the transduction efficiency gets enhanced by adding 5 mM sodium butyrate to the culture medium.

'PmLyO-Sf9 - WSSV complex' could be a platform for elucidating the mechanism of viral entry, cellular apoptosis and replication impediments

White spot syndrome virus (WSSV) is the most devastating pathogen found in shrimp aquaculture. The lack of certified continuous/established cell lines from penaeid shrimp restricts in vitro studies on the viruses to bring out effective prophylactic and therapeutic measures. In this context, a novel hybrid cell line named, PmLyO-Sf9, consisting of shrimp and Sf9 genomes has been established and employed to study WSSV susceptibility and multiplication. The hybrid cells were exposed to the shrimp virus WSSV and cytopathic effects (CPE) such as (a) enlargement of cells, (b) cessation cell division, (c) granulation of cytoplasm, (d) rounding off of cells, shortening and disappearance of tail-like structures and (e) detachment from the flask. Expression of immediate early genes such as ie 1, dnapol, rr1, tk-tmk, and pk 1could be confirmed indicating that viral DNA replication in the PmLyO-Sf9 took place followed by the expression of late genes such as VP-28, VP-26, VP-15 and VP-19. Electron micrograph of WSSV infected cells demonstrated marginated dense zones in the nucleus with clumped chromatin, and the mid zone with virus-like particles. However, neither discrete virus particles nor the culture supernatant having infectivity could be observed suggesting that virions were not getting formed in the cells. This is the first report of the susceptibility of PmLyO-Sf9 to WSSV, and the 'PmLyO-Sf9 - WSSV Complex' formed, defined as the infected status of PmLyO-Sf9 with WSSV, could be of use for unraveling at molecular level the mechanism of viral entry, replication impediments and cellular apoptosis.

Antiviral Activity of Ctn[15-34], A Cathelicidin-Derived Eicosapeptide, Against Infectious Myonecrosis Virus in Litopenaeus vannamei Primary Hemocyte Cultures

The shrimp farming has been converted into a mature aquaculture industry dealing with over millions of metric tonnes of processed commodities. Nevertheless, the global shrimp productions are constantly threatened by disease outbreaks, mainly triggered by rapidly disseminating viruses. Infectious myonecrosis virus (IMNV) is one of these epizootic agents affecting shrimp production in Brazil, of which no treatment exists. Herein, the antiviral activity against IMNV of an eicosapeptide, named Ctn[15-34], derived from a member of the cathelicidin family of antimicrobial peptides, was demonstrated. Cultures of hemocytes from Litopenaeus vannamei were established that support IMNV replication and infectivity titration. The cytotoxic effect of IMNV in culture and the in vitro anti-IMNV activity of Ctn[15-34] were assessed using a high-sensitive fluorescent-based method in combination with quantitative PCR. The Ctn[15-34] (<12.5 µM) neutralized the toxic effects of IMNV at loads sufficient to kill 50% of shrimp hemocytes. This study reported for the first time the replication of IMNV in vitro and the employment of a straightforward methodology to assess cell viability and viral/antiviral activities. In addition, it provided the basis for the development of the anti-infective multi-effector Ctn[15-34] eicosapeptide and analogs as components of antiviral formulations against shrimp viral diseases.

Transgene expression in Penaeus monodon cells: evaluation of recombinant baculoviral vectors with shrimp specific hybrid promoters

It has been realized that shrimp cell immortalization may not be accomplished without in vitro transformation by expressing immortalizing gene in cells. In this process, efficiency of transgene expression is confined to the ability of vectors to transmit gene of interests to the genome. Over the years, unavailability of such vectors has been hampering application of such a strategy in shrimp cells. We report the use of recombinant baculovirus mediated transduction using hybrid promoter system for transgene expression in lymphoid cells of Penaeus monodon. Two recombinant baculovirus vectors with shrimp viral promoters (WSSV-Ie1 and IHHNV-P2) were constructed (BacIe1-GFP and BacP2-GFP) and green fluorescent protein (GFP) used as the transgene. The GFP expression in cells under the control of hybrid promoters, PH-Ie1 or PH-P2, were analyzed and confirmed in shrimp cells. The results indicate that the recombinant baculovirus with shrimp specific viral promoters (hybrid) can be employed for delivery of foreign genes to shrimp cells for in vitro transformation.

Attempts on producing lymphoid cell line from Penaeus monodon by induction with SV40-T and 12S EIA oncogenes

In an attempt of in vitro transformation, transfection mediated expression of Simian virus-40 (T) antigen (SV40-T) and transduction mediated expression of Adenovirus type 12 early region 1A (12S E1A) oncogene were performed in Penaeus monodon lymphoid cells. pSV3-neo vector encoding SV40-T oncogene and a recombinant baculovirus BacP2-12S E1A-GFP encoding 12S E1A oncogene under the control of hybrid promoters were used. Electroporation and lipofection mediated transformation of SV40-T in lymphoid cells confirmed the transgene expression by phenotypic variation and the expression of GFP in co-transfection experiment. The cells transfected by lipofection (≥ 5%) survived for 14 days with lower toxicity (30%), whilst on electroporation, most of the cells succumbed to death (60%) and survived cells lived up to 7 days. Transduction efficiency in primary lymphoid cells was more than 80% within 14 days of post-transduction, however, an incubation period of 7 days post-transduction was observed without detectable expression of 12S E1A. High level of oncogenic 12S E1A expression were observed after 14 day post-transduction and the proliferating cells survived for more than 90 days with GFP expression, however, without in vitro transformation and immortalization. The study put forth the requirement of transduction mediated 'specific' oncogene expression along with telomerase activation and epigenetic induction for the immortalization and establishment of shrimp cell line.

Cellular and molecular markers in monitoring the fate of lymphoid cell culture from Penaeus monodon Fabricius (1798)

Lymphoid cell culture from penaeid shrimps has gained much acceptance as an in vitro platform to facilitate research on the development of prophylaxis, and therapeutic strategies against viruses and for cell line development. However, lymphoid cells can be used as platform for in vitro research, only if they are in metabolically and mitotically active state in vitro with unaltered cell surface receptors. Through this study, we addressed the response of lymphoid cells to a new microenvironment at cellular and molecular levels; including the study of mitotic events, DNA synthesis, expression profile of cell cycle genes, cytoskeleton organization, metabolic activity and viral susceptibility. The S-phase entry and synthesis of new DNA was recorded by immunoflourescent technique. Cdc2, CycA, CycB, EF-1α and BUB3 genes involved in cell cycle were studied in both the cells and tissue, of which EF-1α showed an elevated expression in cells in vitro (∼ 19.7%). Cytoskeleton network of the cell was examined by studying the organization of actin filaments. As the markers for metabolic status, mitochondrial dehydrogenase, protein synthesis and glucose assimilation by the cells were also assessed. Viral susceptibility of the cell was determined using WSSV to confirm the preservation of cellular receptors. This study envisages to strengthen the shrimp cell line research and to bring forth lymphoid cell culture system as a 'model' in vitro system for shrimp and crustaceans altogether.

Impaired telomerase activity hinders proliferation and in vitro transformation of Penaeus monodon lymphoid cells

Retaining terminal transferase activity of telomerase, the ribonucleoprotein enzyme which add telomeric repeats on chromosome end is thought to be required to prevent cellular ageing. Additionally, telomerase considered as a marker for cell proliferation and immortalization in eukaryotes. We examined telomerase activity in tissues and lymphoid cell culture of Penaeus monodon. Along with telomerase activity, telomere repeats and an attempt on identification of telomerase reverse transcriptase (PmTERT) were made. Telomeric repeat amplification protocol revealed that telomerase-dependent telomeric lengthening has been taking place in P. monodon and the adult tissues were retaining this capacity throughout their lifespan with the highest activity in ovary, testis and lymphoid organ. However, telomerase activity could not be detected in lymphoid cells in culture. The canonical telomeric repeats added by telomerase of lymphoid tissue extract were identified as TTAGG, but pentameric repeats GGTTA and AGGTT were also added by the telomerase. PmTERT protein sequence (partial) shared 100 % identity with the TERT sequence of Daphnia pulex, 27 % sequence identity with Purple sea urchin and 24-25 % with Zebra fish. Undetectable telomerase activity in lymphoid cell culture supports the hypothesis that the inadequate telomerase activity or gene expression may be a reason that prevents neoplastic transformation and spontaneous immortalization of the cells in vitro. Thus, it is envisaged that telomerase activation in lymphoid cells may surmount cellular ageing for in vitro transformation and cell line establishment.