Embryonic growth and effect of embryonic age on quantitative and functional characteristics of duck primary hepatocytes

Primary hepatocytes (PH) have been widely used in metabolic and disease-resistance mechanism research. However, hepatocyte isolation (HI) remains challenging in ducks. This study aimed to explore embryonic growth and the effect of embryonic age (EA) on the quantitative and functional characteristics of PH in ducks. For embryonic growth, the size and weight of the embryo and liver were determined from 6 to 28 EA (E6-E28, similar below). As EA increased, the corresponding size and weight grew significantly. Specifically, embryonic length varied from 12.5 mm to 133.0 mm, and liver width varied from 2.0 mm to 26.2 mm. Embryonic weight ranged from 0.259 g to 53.58 g, and liver weight ranged from 0.007 g to 1.765 g. Liver index initially decreased and then increased with a ratio ranging from 1.06 to 3.29%. For quantitative and functional characteristics, they were determined from E6 to E22, as there were no obvious liver features before E6 and few cells obtained after E22. The number of cells isolated in liver increased from E6 to E16 and then sharply decreased from E16 to E22. The viability remained relatively stable from E6 to E10 and then decreased from E12 to E22. The comprehensive intensity of hepatic glycogen was stronger at E8 and E14. Albumin expression increased markedly from E6 to E18 by qPCR, and the overall albumin expression was stronger at E8 and E14 by immunofluorescence assay. Hepatocyte purity exceeded 90% except for E20 and E22. During culture, cell clusters appeared after 24-h culture, which were identified as nonhepatocytes. The growth curve showed an initial increase in cell quantity followed by a decrease, another increase, and then remaining stable. In conclusion, EA had a significant effect on the quantitative and functional characteristics of PH, and the suitable EA for HI were E8 and E14. Considering better operability and quantity, E14 was the optimal EA, laying a solid foundation for further hepatocyte purification, nutrient metabolism, and disease-resistance mechanism explorations in ducks.

Advancements of 3D bioprinting in regenerative medicine: Exploring cell sources for organ fabrication

3D bioprinting has unlocked new possibilities for generating complex and functional tissues and organs. However, one of the greatest challenges lies in selecting the appropriate seed cells for constructing fully functional 3D artificial organs. Currently, there are no cell sources available that can fulfill all requirements of 3D bioprinting technologies, and each cell source possesses unique characteristics suitable for specific applications. In this review, we explore the impact of different 3D bioprinting technologies and bioink materials on seed cells, providing a comprehensive overview of the current landscape of cell sources that have been used or hold potential in 3D bioprinting. We also summarized key points to guide the selection of seed cells for 3D bioprinting. Moreover, we offer insights into the prospects of seed cell sources in 3D bioprinted organs, highlighting their potential to revolutionize the fields of tissue engineering and regenerative medicine.

Developmental Changes of Duckling Liver and Isolation of Primary Hepatocytes

The liver is the main site of fat synthesis and plays an important role in the study of fat deposition in poultry. In this study, we investigated the developmental changes of duckling livers and isolated primary duck hepatocytes. Firstly, we observed morphological changes in duckling livers from the embryonic period to the first week after hatching. Liver weight increased with age. Hematoxylin-eosin and Oil Red O staining analyses showed that hepatic lipids increased gradually during the embryonic period and declined post-hatching. Liver samples were collected from 21-day-old duck embryos for hepatocyte isolation. The hepatocytes showed limited self-renewal and proliferative ability and were maintained in culture for up to 7 days. Typical parenchymal morphology, with a characteristic polygonal shape, appeared after two days of culture. Periodic acid-Schiff (PAS) staining analysis confirmed the characteristics of duck embryo hepatocytes. PCR analysis showed that these cells from duck embryos expressed the liver cell markers ALB and CD36. Immunohistochemical staining and immunofluorescence analysis also confirmed ALB and CK18 expression. Our findings provide a novel insight regarding in vitro cell culture and the characteristics of hepatocytes from avian species, which could enable further studies concerning specific research on duck lipid metabolism.

Establishment methods and research progress of livestock and poultry immortalized cell lines: A review

An infinite cell line is one of the most favored experimental tools and plays an irreplaceable role in cell-based biological research. Primary cells from normal animal tissues undergo a limited number of divisions and subcultures in vitro before they enter senescence and die. On the contrary, an infinite cell line is a population of non-senescent cells that could proliferate indefinitely in vitro under the stimulation of external factors such as physicochemical stimulation, virus infection, or transfer of immortality genes. Cell immortalization is the basis for establishing an infinite cell line, and previous studies have found that methods to obtain immortalized cells mainly included physical and chemical stimulations, heterologous expression of viral oncogenes, increased telomerase activity, and spontaneous formation. However, some immortalized cells do not necessarily proliferate permanently even though they can extend their lifespan compared with primary cells. An infinite cell line not only avoids the complicated process of collecting primary cell, it also provides a convenient and reliable tool for studying scientific problems in biology. At present, how to establish a stable infinite cell line to maximize the proliferation of cells while maintaining the normal function of cells is a hot issue in the biological community. This review briefly introduces the methods of cell immortalization, discusses the related progress of establishing immortalized cell lines in livestock and poultry, and compares the characteristics of several methods, hoping to provide some ideas for generating new immortalized cell lines.

Al2O3 nanoparticles trigger the embryonic hepatotoxic response and potentiate TNF-α-induced apoptosis-modulatory effect of p38 MAPK and JNK inhibitors

Recent evidences illustrated that the release of aluminum oxide nanoparticles (Al₂O₃-NPs) into the biosphere may pose risk to the environment and cause adverse effects on living organisms including humans. The current study assessed the hepatotoxic effects of Al₂O₃-NPs on developing chicken embryo and cell culture models. Results demonstrated that Al₂O₃-NPs exposure causes histological abnormalities and increased the level of tissue damage markers (ALP, AST, and ALT) in the embryonic liver. Furthermore, increased oxidative stress (TBARS) and impaired function of antioxidant enzymes (SOD, CAT, and GPx) were also observed. Moreover, it adversely affects red blood cells (RBC) morphology, liver metabolism, and stress response gene expression (HO-1 and NQO-1). Dose-dependent ROS generation and cytotoxic response in addition to potentiating effect on tumor necrosis factor alpha (TNF-α)-induced apoptosis (caspase-3 activity) were also observed. Inhibition of p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase (JNK) pathways modulates Al₂O₃-NPs-induced apoptosis in HepG2 cells. Novel mechanisms behind embryonic hepatotoxicity, cytotoxic potentiating effects, and possible prevention strategies have been explored.

Generation and characterization of genome-modified chondrocyte-like cells from the zebra finch cell line immortalized by c-MYC expression

BACKGROUND

Due to their cost effectiveness, ease of use, and unlimited supply, immortalized cell lines are used in place of primary cells for a wide range of research purposes, including gene function studies, CRISPR-based gene editing, drug metabolism tests, and vaccine or therapeutic protein production. Although immortalized cell lines have been established for a range of animal species, there is still a need to develop such cell lines for wild species. The zebra finch, which is used widely as a model species to study the neurobiological basis of human speech disorders, has been employed in several functional studies involving gene knockdown or the introduction of exogenous transgenes in vivo; however, the lack of an immortalized zebra finch cell line has hampered precise genome editing studies.

RESULTS

Here, we established an immortalized cell line by a single genetic event, expression of the c-MYC oncogene, in zebra finch embryonic fibroblasts and examined its potential suitability for gene targeting investigations. Retroviral vector-mediated transduction of c-MYC was used to immortalize zebra finch primary fibroblasts; the transformed cells proliferated stably over several passages, resulting in the expression of chondrocyte-specific genes. The transfection efficiency of the immortalized cells was much higher than that of the primary cells. Targeted knockout of the SOX9 gene, which plays a role in the differentiation of mesenchymal progenitor cells into chondrocytes, was conducted in vitro and both apoptosis and decreased expression levels of chondrogenic marker genes were observed in edited cells.

CONCLUSIONS

The c-MYC induced immortalized chondrocyte-like cell line described here broadens the available options for establishing zebra finch cell lines, paves the way for in-depth biological researches, and provides convenient approaches for biotechnology studies, particularly genomic modification research.

Orexin system is expressed in avian liver and regulates hepatic lipogenesis via ERK1/2 activation

Orexins are originally characterized as orexigenic hypothalamic neuropeptides in mammals. Subsequent studies found orexin to be expressed and perform pleiotropic functions in multiple tissues in mammals. In avian (non-mammalian) species, however, orexin seemed to not affect feeding behavior and its physiological roles are poorly understood. Here, we provide evidence that orexin and its related receptors are expressed in chicken hepatocytes. Double immunofluorescence staining showed that orexin is localized in the ER, Golgi, and in the lysosomes in LMH cells. Brefeldin A treatment reduced orexin levels in the culture media, but increased it in the cell lysates. Administration of recombinant orexins upregulated the expression of orexin system in the liver of 9-day old chicks, but did not affect feed intake. Recombinant orexins increased fatty acid synthase (FASN) protein levels in chicken liver, activated acetyl-CoA carboxylase (ACCα), and increased FASN, ATP citrate lyase(ACLY), and malic enzyme (ME) protein expression in LMH cells. Blockade ERK1/2 activation by PD98059 attenuated these stimulating effects of orexin on lipogenic factors. Overexpression of ERK1/2 increased the expression of lipogenic genes, and orexin treatment induced the phosphorylated levels of ERK1/2^{Thr202/Tyr204}, but not that of p38 ^{Thr180/Tyr182} or JNK1/2 ^{Thr183/Tyr185} in chicken liver and LMH cells. Taken together, this is the first report evidencing that orexin is expressed and secreted from chicken hepatocytes, and that orexin induced hepatic lipogenesis via activation of ERK1/2 signaling pathway.

75-kDa glucose-regulated protein (GRP75) is a novel molecular signature for heat stress response in avian species

Glucose-regulated protein 75 (GRP75) was first characterized in mammals as a heat shock protein-70 (HSP70) family stress chaperone based on its sequence homology. Extensive studies in mammals showed that GRP75 is induced by various stressors such as glucose deprivation, oxidative stress, and hypoxia, although it remained unresponsive to the heat shock. Such investigations are scarce in avian (nonmammalian) species. We here identified chicken GRP75 by using immunoprecipitation assay integrated with LC-MS/MS, and found that its amino acid sequence is conserved with high homology (52.5%) to the HSP70 family. Bioinformatics and 3D-structure prediction indicate that, like most HSPs, chicken GRP75 has two principal domains (the NH2-terminal ATPase and COOH-terminal region). Immunofluorescence staining shows that GRP75 is localized predominantly in the avian myoblast and hepatocyte mitochondria. Heat stress exposure upregulates GRP75 expression in a species-, genotype-, and tissue-specific manner. Overexpression of GRP75 reduces avian cell viability, and blockade of GRP75 by its small molecular inhibitor MKT-077 rescues avian cell viability during heat stress. Taken together, this is the first evidence showing that chicken GRP75, unlike its mammalian ortholog, is responsive to heat shock and plays a key role in cell survival/death pathways. Since modern avian species have high metabolic rates and are sensitive to high environmental temperature, GRP75 could open new vistas in mechanistic understanding of heat stress responses and thermotolerance in avian species.

Discovery of an Australian Chelonia mydas papillomavirus via green turtle primary cell culture and qPCR

The number of reptilian viruses detected are continuously increasing due to improvements and developments of new diagnostic techniques. In this case we used primary cell culture and qPCR to describe the first Australian Chelonia mydas papillomavirus. Commercial chelonian cell lines are limited to one cell line from a terrestrial turtle (Terrapene Carolina). To establish primary cultures from green turtles (Chelonia mydas), turtle eggs were collected from Heron Island, Queensland, Australia. From day 35 of incubation at 29°, the embryos were harvested to establish primary cultures. The primary cell cultures were grown in Dulbecco's Modified Eagle Medium, 90% and foetal bovine serum, 10%. The cells became uniformly fibroblastic-shaped after 15 passages. The growth rate resembled that of cells originating from other cold-blooded animals and the average doubling time was ∼5 days from the 20th passage. Karyotyping and molecular analysis of mitochondrial DNA D-loop gene were carried out for cell authentication. The primary cell cultures were screened to exclude mycoplasma contamination. Two primary cell lineages were found to be susceptible to Bohle iridovirus. The primary cell cultures were used to screen samples from green turtles foraging along the East Coast of Queensland for the presence of viruses. Homogenates from eight skin tumour samples caused cytopathic effects and were confirmed by qPCR to be infected with papillomavirus.

ESCDL-1, a new cell line derived from chicken embryonic stem cells, supports efficient replication of Mardiviruses

Marek’s disease virus is the etiological agent of a major lymphoproliferative disorder in poultry and the prototype of the Mardivirus genus. Primary avian somatic cells are currently used for virus replication and vaccine production, but they are largely refractory to any genetic modification compatible with the preservation of intact viral susceptibility. We explored the concept of induction of viral replication permissiveness in an established pluripotent chicken embryonic stem cell-line (cES) in order to derive a new fully susceptible cell-line. Chicken ES cells were not permissive for Mardivirus infection, but as soon as differentiation was triggered, replication of Marek’s disease virus was detected. From a panel of cyto-differentiating agents, hexamethylene bis (acetamide) (HMBA) was found to be the most efficient regarding the induction of permissiveness. These initial findings prompted us to analyse the effect of HMBA on gene expression, to derive a new mesenchymal cell line, the so-called ESCDL-1, and monitor its susceptibility for Mardivirus replication. All Mardiviruses tested so far replicated equally well on primary embryonic skin cells and on ESCDL-1, and the latter showed no variation related to its passage number in its permissiveness for virus infection. Viral morphogenesis studies confirmed efficient multiplication with, as in other in vitro models, no extra-cellular virus production. We could show that ESCDL-1 can be transfected to express a transgene and subsequently cloned without any loss in permissiveness. Consequently, ESCDL-1 was genetically modified to complement viral gene deletions thus yielding stable trans-complementing cell lines. We herein claim that derivation of stable differentiated cell-lines from cES cell lines might be an alternative solution to the cultivation of primary cells for virology studies.

Designing cell lines for viral vaccine production: Where do we stand?

Established animal cells, such as Vero, Madin Darby canine kidney (MDCK) or chicken embryo fibroblasts (CEFs), are still the main cell lines used for viral vaccine production, although new "designer cells" have been available for some years. These designer cell lines were specifically developed as a cell substrate for one application and are well characterized. Later screening for other possible applications widened the product range. These cells grow in suspension in chemically defined media under controlled conditions and can be used for up to 100 passages. Scale-up is easier and current process options allow cultivation in disposable bioreactors at cell concentrations higher than 1 × 10(7) cells/mL. This review covers the limitations of established cell lines and discusses the requirements and screening options for new host cells. Currently available designer cells for viral vaccine production (PER.C6, CAP, AGE1.CR, EB66 cells), together with other new cell lines (PBS-1, QOR/2E11, SogE, MFF-8C1 cells) that were recently described as possible cell substrates are presented. Using current process knowledge and cell line development tools, future upstream processing could resemble today's Chinese hamster ovary (CHO) cell processes for monoclonal antibody production: small scale bioreactors (disposable) in perfusion or fed-batch mode with cell concentrations above 1 × 10(8) cells/mL.

Transcription factor regulation and cytokine expression following in vitro infection of primary chicken cell culture with low pathogenic avian influenza virus

BACKGROUND

Avian influenza virus (AIV) induced proinflammatory cytokine expression is believed to contribute to the disease pathogenesis following infection of poultry. However, there is limited information on the avian immune response to infection with low pathogenic avian influenza virus (LPAIV).

METHODS

To gain a better understanding of the early viral-host interactions of LPAIV in chickens, primary chicken embryo hepatocytes (CEH) were infected with four different LPAIVs of U.S. origin. Kinetics of virus replication, transcription factor (c-Jun, p50 and IRF-3) activation and immune response gene (IL-6, IL-1beta, IFN-alpha and Mx) expression were studied at four different time points (6, 12, 24 and 48 hours) post infection and compared to non-infected controls.

RESULTS

CEH can support growth of the tested LPAIVs when with trypsin supplementation. All four immune response genes tested were upregulated following infection as were transcription factors c-Jun, p50 and IRF-3. Amplification of these genes was dependant on virus replication (e.g. inclusion of trypsin), such that immune response genes and transcription factors were upregulated as viral titers increased.

CONCLUSION

The results of these studies demonstrate the requirement of virus replication for innate immune regulation and broaden our understanding of transcription factor responses related to LPAIV infection in chickens.