Common lizard primary oviduct cell culture: A model system for the genetic and cellular basis of oviparity and viviparity

Reproduction by egg-laying (oviparity) or live-bearing (viviparity) is a genetically determined trait fundamental to the biology of amniotes. Squamates are an emerging model for the genetics of reproductive mode yet lack cell culture models valuable for exploring molecular mechanisms. Here, we report a novel primary culture model for reproductive biology: cell cultures derived from the oviduct tissues (infundibulum, uterus and vagina) of oviparous and viviparous common lizards (Lacertidae: Zootoca vivipara). We maintained and expanded these cultures for over 100 days, including repeated subculturing and successful revival of cryopreserved cells. Immunocytochemical investigation suggested expression of both epithelial and fibroblast-like proteins, and RNA sequencing of cultured cells as compared to in vivo oviduct tissue showed changes in gene expression in response to the cell culture environment. Despite this, we confirmed the maintenance of distinct gene expression patterns in viviparous and oviparous cells after 60+ days of cell culture, finding 354 differentially expressed genes between viviparous and oviparous cells. Furthermore, we confirmed the expression of 15 viviparity-associated candidate genes in cells maintained for 60+ days in culture. Our study demonstrates the feasibility and utility of oviduct cell culture for molecular analysis of reproductive mode and provides a tool for future genetic experiments.

An in vitro validation system for chicken bioreactors using immortalized chicken oviductal epithelial cells

The utilization of chicken oviductal epithelial cells (OECs) as a bioreactor to produce therapeutic proteins has shown promise, but the time taken to obtain transgenic offspring impedes efficient validation of protein production. To overcome this barrier, we focused on the immortalization of chicken OECs (cOECs) using retroviral vector-mediated c-MYC oncogene expression to establish an in vitro pre-validation system for chicken bioreactors. The resulting immortalized cOECs exhibited sustained proliferation, maintained a normal diploid chicken karyotype, and expressed key oviduct-specific genes (OVA, OVM, LYZ, AVD, and ESR1). Notably, hormonal administration of diethylstilbestrol (DES) or progesterone (P4) upregulated oviduct-specific genes in these cells. To enhance the utility of these immortalized cOECs as an in vitro validation system for chicken bioreactors, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technology was employed to knock-in (KI) an enhanced green fluorescence protein (EGFP) gene at the ovalbumin (OVA) locus. The resulting OVA EGFP KI immortalized cOECs secreted both EGFP and OVA proteins into the culture medium, with secretion enhanced under DES treatment. This successful integration of an exogenous gene into cOECs enhances their potential as a versatile in vitro validation system for chicken bioreactors. The established immortalized cOECs overcome previous challenges associated with long-term culture and maintenance, providing a reliable platform for efficient protein production validation. This study presents a comprehensive characterization of the immortalized cOECs, addressing critical limitations associated with in vivo systems and laying a foundation for the development of a streamlined and effective chicken bioreactor model.

Sustainable production of multimeric and functional recombinant human adiponectin using genome-edited chickens

BACKGROUND

Adiponectin (ADPN) plays a critical role in endocrine and cardiovascular functions, but traditional production methods, such as Escherichia coli and mammalian systems, have faced challenges in generating sufficiently active middle molecular weight (MMW) and high molecular weight (HMW) forms of recombinant human ADPN (hADPN). In our previous study, we proposed genome-edited chickens as an efficient platform for producing multimeric hADPN. However, the consistency of multimeric hADPN expression in this system across generations had not been further investigated.

RESULTS

In this study, subsequent generations of ovalbumin (OVA) ADPN knock-in chickens showed stable multimeric hADPN production, yielding ~ 26% HMW ADPN (0.59 mg/mL) per hen. Comparative analysis revealed that egg white (EW)-derived hADPN predominantly consisted of hexameric and HMW forms, similar to serum-derived hADPN. In contrast, hADPN obtained from human embryonic kidney (HEK) 293 and High-Five (Hi-5) cells also exhibited the presence of trimers, indicating variability across different production systems. Furthermore, transcriptional expression analysis of ADPN multimerization-associated endoplasmic reticulum chaperone genes (Ero1-Lα, DsbA-L, ERP44, and PDI) indicated upregulation in the oviduct magnum of ADPN KI hens, suggesting the chicken oviduct magnum as the optimal site for HMW ADPN production. Lastly, the functional analysis demonstrated that EW-derived hADPN significantly reduced lipid droplets and downregulated lipid accumulation-related genes (LOX-1, AT1R, FAS, and FABP4) in human umbilical vein endothelial cells (HUVECs).

CONCLUSION

In summary, stable and functional multimeric hADPN can be produced in genome-edited chickens even after generations. This highlights the potential of using chicken bioreactor for producing various high-value proteins.

Electroporation-based Easi-CRISPR yields biallelic insertions of EGFP-HiBiT cassette in immortalized chicken oviduct epithelial cells

Laying hens are an excellent experimental oviduct model for studying reproduction biology. Because chicken oviduct epithelial cells (cOECs) have a crucial role in synthesizing and secreting ovalbumin, laying hens have been regarded an ideal bioreactor for producing pharmaceuticals in egg white through transgene or gene editing of the ovalbumin (OVA) gene. However, related studies in cOECs are largely limited because of the lack of immortalized model cells. In addition, the editing efficiency of conventional CRISPR-HDR knock-in in chicken cells is suboptimal (ranging from 1 to 10%) and remains elevated. Here, primary cOECs were isolated from young laying hens, then infected with a retrovirus vector of human telomerase reverse transcriptase (hTERT), and immortalized cOECs were established. Subsequently, an electroporation-based Easi-CRISPR (Efficient additions with ssDNA inserts-CRISPR) method was adopted to integrate an EGFP-HiBiT cassette into the chicken OVA locus (immediately upstream of the stop codon). The immortalized cOECs reflected the self-renewal capability and phenotype of oviduct epithelial cells. This is because these cells not only maintained stable proliferation and normal karyotype and had no potential for malignant transformation, but also expressed oviduct markers and an epithelial marker and had a morphology similar to that of primary cOECs. EGFP expression was detected in the edited cells through microscopy, flow cytometry, and HiBiT/Western blotting. The EGFP-HiBiT knock-in efficiency reached 27.9% after a single round of electroporation, which was determined through genotyping and DNA sequencing. Two single cell clones contained biallelic insertions of EGFP-HiBiT donor cassettes. In conclusion, our established immortalized cOECs could act as an in vitro cell model for gene editing in chicken, and this electroporation-based Easi-CRISPR strategy will contribute to the generation of avian bioreactors and other gene-edited (GE) birds.

Development and in vitro evaluation of recombinant chicken promoters to efficiently drive transgene expression in chicken oviduct cells

Virus injection into EGK-X embryos is a well-defined approach in avian transgenesis. This system uses a chicken ovalbumin gene promoter to induce transgene expression in the chicken oviduct. Although a reconstructed chicken ovalbumin promoter that links an ovalbumin promoter and estrogen-responsive enhancer element (ERE) is useful, a large viral vector containing the ovalbumin promoter and a target gene restricts viral packaging capacity and produces low-titer virus particles. We newly developed recombinant chicken promoters by linking regulatory regions of ovalbumin and other oviduct-specific genes. Putative enhancer fragments of the genes, such as ovotransferrin (TF), ovomucin alpha subunit (OVOA), and ovalbumin-related protein X (OVALX), were placed at the 5`-flanking region of the 2.8-kb ovalbumin promoter. Basal promoter fragments of the genes, namely, pTF, lysozyme (pLYZ), and ovomucoid (pOVM), were placed at the 3`-flanking region of the 1.6-kb ovalbumin ERE. The recombinant promoters cloned into each reporter vector were evaluated using a dual luciferase assay in human and chicken somatic cells, and LMH/2A cells treated with 0-1,000 nM estrogen, and cultured primary chicken oviduct cells. The recombinant promoters with linking ovalbumin and TF, OVOA, pOVM, and pLYZ regulatory regions had 2.1- to 19.5-fold (P < 0.05) higher luciferase activity than the reconstructed ovalbumin promoter in chicken oviduct cells. Therefore, recombinant promoters may be used to efficiently drive transgene expression in transgenic chickens.

Isolation and characterization of cultured chicken oviduct epithelial cells and in vitro validation of constructed ovalbumin promoter in these cells

Objective

Transgenic hens hold a great promise to produce various valuable proteins. Through virus transduction into stage X embryo, the transgene expression under the control of constructed chicken ovalbumin promoters has been successfully achieved. However, a validation system that can evaluate differently developed ovalbumin promoters in in vitro, remains to be developed.

Methods

In the present study, chicken oviduct epithelial cells (cOECs) were isolated from oviduct tissue and shortly cultured with keratinocyte complete medium supplemented with chicken serum. The isolated cells were characterized with immunofluorescence, western blot, and flow cytometry using oviduct-specific marker. Chicken mutated ovalbumin promoter (Mut-4.4-kb-pOV) was validated in these cells using luciferase reporter analysis.

Results

The isolated cOECs revealed that the oviduct-specific marker, ovalbumin protein, was clearly detected by immunofluorescence, western blot, and flow cytometry analysis revealed that approximately 79.40% of the cells contained this protein. Also, luciferase reporter analysis showed that the constructed Mut-4.4-kb-pOV exhibited 7.1-fold (p<0.001) higher activity in the cOECs.

Conclusion

Collectively, these results demonstrate the efficient isolation and characterization of cOECs and validate the activity of the constructed ovalbumin promoter in the cultured cOECs. The in vitro validation of the recombinant promoter activity in cOECs can facilitate the production of efficient transgenic chickens for potential use as bioreactors.

Genes involved in angiogenesis and circulatory system development are differentially expressed in porcine epithelial oviductal cells during long-term primary in vitro culture – a transcriptomic study

An oviduct is an essential organ for gamete transport, oocyte maturation, fertilization, spermatozoon capacitation and early embryo development. The epithelium plays an important role in oviduct functioning. The products of secretory cells provide an optimal environment and influence gamete activities and embryonic development. The oviduct physiology changes during the female cycle, thus, the ratio of the secreted molecules in the oviduct fluid differs between phases. In this study, a differential gene expression in porcine oviduct epithelial cells was examined during the long-term primary in vitro culture. The microarray expression analysis revealed 2552 genes, 1537 of which were upregulated and 995 were downregulated after 7 days of culture, with subsequent changes in expression during 30 day-long culture. The obtained genes were classified into 8 GO BP terms, connected with angiogenesis and circulatory system development, extracted by DAVID software. Among all genes, 10 most up-regulated and 10 most down-regulated genes were selected for further investigation. Interactions between genes were indicated by STRING software and REACTOME FIViz application to the Cytoscape 3.6.0 software. Most of the genes belonged to more than one ontology group. Although studied genes are mostly responsible for angiogenesis and circulatory system development, they can also be found to be expressed in processes connected with fertilization and early embryo development. The latter function is focused on more, considering the fact that these genes were expressed in epithelial cells of the fallopian tube which is largely responsible for reproductive processes.

Involvement of P38 and ERK1/2 in mitochondrial pathways independent cell apoptosis in oviduct magnum epithelial cells of layers challenged with vanadium

Vanadium (V) can induce cell apoptosis in layers' oviduct resulting in egg quality reduction. In this study, we investigated the relationship between the mitogen-activated protein kinase (MAPK)-signaling pathway and V-induced apoptosis in poultry oviduct magnum epithelial cells (OMECs). Cultured OMECs were divided into 8 treatment groups: 0 μmol/L V (control), 100 μmol/L V (V100), V100 + P38MAPK inhibitor (SB203580), SB203580, V100 + extracellular signal-regulated kinases 1 and 2 (ERK1/2) inhibitor (U0126), U0126, V100 + c-JUN NH₂ -terminal kinase (JNK) inhibitor (SP600125), and SP600125. The OMECs were pretreated with the MAPK inhibitors before their treatment with V100 for 12 h. V100 increased the apoptosis of OMECs (P < .05), while 3 MAPK inhibitors suppressed V100-induced apoptosis P < .05); V100 enhanced the depolarization of △ψm (P < .05), and SB203580 and U0126 alleviated the V100-induced △ψm decrease (P < .05); V100 downregulated B-cell lymphoma-2 (Bcl-2) and poly [Adenosine diphosphate ribose] polymerase 1 (PARP1) mRNA expression (P < .05), meanwhile it upregulated Bcl-2 associated x (Bax), Apaf1, cytochrome C (CytC) and cysteine aspartase (caspase) 3, 8, 9 mRNA expression (P < .05). All MAPKs inhibitors alleviated the up-regulation of V100 for Bax and caspase 3 mRNA expression and down-regulation of V100 for Bcl-2 expression (P < .05). SB203580 and U0126 upregulated CytC expression treated by V100 (P < .05), except SP600125, while SB203580 administration resulted in a similar upregulation of PARP1 expression (P < .05). SP600125 can alleviated V triggered p-P38MAPK (phosphor-P38), p-ERK1/2 (phosphor-ERK1/2), p-JNK (phosphor-JNK) increase on OME cells, and SB203580 and U0126 had a similar response to phosphor-P38 and p-JNK (P < .05). It concluded that V-induced apoptosis in OMECs through the activation of P38 and ERK1/2, and by increasing the ratio of Bax/Bcl-2, which resulted in △ψm decrease, CytC release into the cytosol; consequently caspase 3 is recruited and activated, PARP1 is cleaved, eventually leading to apoptosis.

Finite cell lines of turkey sperm storage tubule cells: ultrastructure and protein analysis

Cell lines of turkey sperm storage tubule (SST) epithelial cells were established. Turkey SSTs were dissected from freshly obtained uterovaginal junction (UVJ) tissue and placed in explant culture on various substrates and media. Primary cultures of SST epithelium only survived and grew from SST explants that were cultured on inactivated Sandoz inbred strain, thioguanine- and ouabain-resistance (STO) mouse feeder-cell layers in 12% fetal bovine serum-supplemented Dulbecco's Modified Eagle Medium mixed 1:1 with F12 nutrient mixture. Three independent primary colonies gave rise to 3 finite cell lines, SST-1, -2, and -3, which were continuously cultured for 8 to 16 passages at 1:3 passage ratios over a period of 3 to 4 mo. The cells were passaged by pretreatment with Y27632 and dissociation with Accutase. The SST cells grew as tightly knit monolayers on top of the feeder cells at a slow rate (approximately 96 h doubling time) at a medium pH of approximately 6.9. Lipid vacuoles were visible by light microscopy in the cells particularly at the periphery of growth. Transmission electron microscopy revealed the cells to be a polarized epithelium with apical microvilli and to have lateral tight-junction-like unions and associated desmosomes. Numerous secretory vesicles filled the upper portion of the cells’ cytoplasm, and nuclei and other major organelles such as mitochondria, rough endoplasmic reticulum, and Golgi apparatus were distributed somewhat lower in the cytoplasm. The secretory vesicles resembled mucin secretory vesicles. Proteomic analysis by mass spectroscopy of the conditioned medium of the cells, and of the cells themselves, showed the cell lines did not secrete large amounts of any particular protein, and the analysis confirmed their epithelial character. In conclusion, the SST-derived cell lines resembled the mucus-secreting cells found in the epithelium lining the UVJ of the turkey's reproductive tract.

Three-dimensional culture of chicken primordial germ cells (cPGCs) in defined media containing the functional polymer FP003

Scalable production of avian cell lines exhibits a valuable potential on therapeutic application by producing recombinant proteins and as the substrate for virus growth due to the special glycosylation occurs in avian species. Chicken primordial germ cells (cPGCs), a germinal pluripotent avian cell type, present the ability of self-renewal, an anchorage-independent cell growth and the ability to be genetically modified. This cell type could be an interesting bioreactor system for industrial purposes. This study sought to establish an expandable culture system with defined components for three-dimensional (3D) culture of cPGCs. cPGCs were cultured in medium supplemented with the functional polymer FP003. Viscoelasticity was low in this medium but cPGCs did not sediment in culture and efficiencies of space and nutrient utilization were thus enhanced and consequently their expansion was improved. The total number of cPGCs increased by 17-fold after 1 week of culture in 3D-FAot medium, an aseric defined medium containing FP003 polymer, FGF2 and Activin A as growth factors and Ovotransferrin as protein. Moreover, cPGC cell lines stably expressed the germline-specific reporter VASA:tdTOMATO, as well as other markers of cPGCs, for more than 1 month upon culture in 3D-FAot medium, indicating that the characteristics of these cells are maintained. In summary, this novel 3D culture system can be used to efficiently expand cPGCs in suspension without mechanical stirring, which is available for long-term culture and no loss of cellular properties was found. This system provides a platform for large-scale culture of cPGCs.

Vanadate oxidative and apoptotic effects are mediated by the MAPK-Nrf2 pathway in layer oviduct magnum epithelial cells

Vanadium is a metal of high physiological, environmental and industrial importance. However, vanadium-induced oxidative stress can reduce the egg quality of poultry, and be potentially harmful to humans, and the underlying mechanism is not clear. In this study, we investigated the underlying relationship between the oxidant-sensitive mitogen-activated protein kinase (MAPK) signaling pathway and vanadium-induced oxidative stress in oviduct magnum epithelial (OME) cells. Cultured OME cells were treated with 100 μmol L^-1 vanadium and/or MAPK inhibitors [P38 MAPK inhibitor, SB203580; extracellular regulated protein kinase 1 and 2 (ERK1/2) inhibitor, U0126; c-JUN N-terminal kinases (JNK) inhibitor, SP600125]. Cell viability, apoptosis, and generation of reactive oxygen species (ROS) were assessed using flow cytometry. The expression of oxidative stress-related genes and their proteins was measured by reverse transcription-polymerase chain reaction and western blotting. Vanadium treatment reduced cell viability, whereas pretreated OME cells with SB203580 and U0126 prevented the reducing effect of vanadium on cell viability (P < 0.05). Likewise, MAPK inhibitors effectively suppressed vanadium-induced apoptosis and ROS generation (P < 0.05). In the OME cells treated with vanadium, SB203580 (P < 0.05) and SP600125 (P = 0.08) increased catalase activity by 89.3% and 55.3%; SB203580 and U0126 increased (P < 0.05) glutathione peroxidase activity by 44.9% and 51.1%, respectively. Incubation of OME cells with MAPK inhibitors also prevents malondialdehyde concentration increase and lactic dehydrogenase activity decrease in response to vanadium (P < 0.05). Vanadium downregulated P38, ERK1/2, JNK, Nrf2, sMaf, GCLC, NQO1 and HO-1 mRNA expression (P < 0.05). In contrast, inhibition of JNK with SP600125 upregulated P38, ERK1/2, JNK, Nrf2, GCLC and HO-1 mRNA expression (P < 0.05); inhibition of P38 with SB203580 upregulated JNK, NQO1 and HO-1 mRNA expression (P < 0.05); and inhibition of ERK1/2 with U0126 upregulated ERK1/2, GCLC and HO-1 mRNA expression (P < 0.05). Moreover, phosphorylation of P38, ERK1/2, JNK, and Nrf2 proteins was enhanced by V incubation; however, SP600125 blocked the phosphorylation of these proteins, whereas SB203580 blocked the phosphorylation of P38 and Nrf2. These results indicate that vanadium inducing oxidative stress in OME cells might be, at least, associated with the phosphorylation of the P38MAPK/JNK-Nrf2 pathway, which reduces the expression of phase II detoxifying enzymes.

Molecular signatures of epithelial oviduct cells of a laying hen (Gallus gallus domesticus) and quail (Coturnix japonica)

Background

In this work we have determined molecular signatures of oviduct epithelial and progenitor cells. We have proposed a panel of selected marker genes, which correspond with the phenotype of oviduct cells of a laying hen (Gallus gallus domesticus) and quail (Coturnix japonica). We demonstrated differences in characteristics of those cells, in tissue and in vitro, with respect to different anatomical and functional parts of the oviduct (infundibulum (INF), distal magnum (DM, and proximal magnum (PM)). The following gene expression signatures were studied: (1) oviduct markers (estrogen receptor 1, ovalbumin, and SPINK7 - ovomucoid), (2) epithelial markers (keratin 5, keratin 14, and occludin) and (3) stem-like/progenitor markers (CD44 glycoprotein, LGR5, Musashi-1, and sex determining region Y-box 9, Nanog homebox, OCT4/cPOUV gene encoding transcription factor POU5F3).

Results

In chicken, the expression of oviduct markers increased toward the proximal oviduct. Epithelial markers keratin14 and occludin were high in distal oviduct and decreased toward the proximal magnum. In quail oviduct tissue, the gene expression pattern of oviduct/epithelial markers was similar to chicken. The markers of progenitors/stemness in hen oviduct (Musashi-1 and CD44 glycoprotein) had the highest relative expression in the infundibulum and decreased toward the proximal magnum. In quail, we found significant expression of four progenitor markers (LGR5 gene, SRY sex determining region Y-box 9, OCT4/cPOUV gene, and CD44 glycoprotein) that were largely present in the distal oviduct. After in vitro culture of oviduct cells, the gene expression pattern has changed. High secretive potential of magnum-derived cells diminished by using decreased abundance of mRNA. On the other hand, chicken oviduct cells originating from the infundibulum gained ability to express OVM and OVAL. Epithelial character of the cells was maintained in vitro. Among progenitor markers, both hen and quail cells expressed high level of SOX9, LGR5 and Musashi-1.

Conclusion

Analysis of tissue material revealed gradual increase/decrease pattern in majority of the oviduct markers in both species. This pattern changed after the oviductal cells have been cultured in vitro. The results can provide molecular tools to validate the phenotype of in vitro biological models from reproductive tissue.

Electronic supplementary material

The online version of this article (10.1186/s12861-018-0168-2) contains supplementary material, which is available to authorized users.

Generation of transgenic chickens by the non-viral, cell-based method: effectiveness of some elements of this strategy

Transgenic chickens have, in general, been produced by two different procedures. The first procedure is based on viral transfection systems. The second procedure, the non-viral method, is based on genetically modified embryonic cells transferred directly into the recipient embryo. In this review, we analyzed the effectiveness of important elements of the non-viral, cell-based strategy of transgenic chicken production. The main elements of this strategy are: isolation and cultivation of donor embryonic cells; transgene construction; cell transfection in vitro; and chimera production: injection of cells into recipient embryos, raising and identification of germline chimeras, mating germline chimeras, transgene inheritance, and transgene expression. In this overview, recent progress and important limitations in the development of transgenic chickens are presented.

Enhanced in vitro maturation of canine oocytes by oviduct epithelial cell co-culture

Canine-assisted reproductive techniques have been successful for several years; however, the lack of an oocyte in vitro maturation system has limited their application. The aim of this study was to evaluate the effect of canine oviduct epithelial cells (cOECs) on canine oocyte maturation in vitro. Specifically, the method used for isolation of cOECs did not affect the expression of epithelial markers, E-cadherin and cytokeratin, on fresh, cultured and cryopreserved cells. Moreover, BrdU analysis showed that cOECs cultured in Medium 171 supplemented with mammary epithelial growth supplement were more proliferative than counterparts in advanced Dulbecco's modified Eagle medium or Medium 199. Maturation rate of canine oocytes collected from bitches at diestrus was significantly increased when oocytes were co-cultured with either fresh, cultured or frozen/thawed cOECs (13.23 ± 1.15%, 10.38 ± 4.89%, or 10.54 ± 2.96%, respectively) than that of control oocytes cultured without cOECs (2.48 ± 2.16%, p < 0.05). Additionally, the number of oocytes collected from bitches at estrus the reached metaphase II was increased ∼4 fold in co-culture with fresh, cultured, or frozen/thawed cOECs (47.2 ± 3.82%, 45.4 ± 7.34%, and 46.9 ± 1.51%, respectively) as compared with oocytes cultured without cOECs (11.9 ± 3.18%, p < 0.05). Nuclear maturation was further confirmed by assessing the formation of normal metaphase-II spindles, whereas cytoplasmic maturation was confirmed by inducing parthenogenetic oocyte activation. Embryonic development to the 8-cell stage was similar between in vivo and in vitro matured oocytes. These results suggested that co-culturing immature canine oocytes with cOECs facilitated canine oocyte maturation and early stages of embryonic development.

Female Reproductive System and Immunology

Health of the reproductive organs is essential for formation and production of high quality and hygienic eggs. It is of importance to review the structures and functions of female reproductive system for better understanding of the mechanism by which the eggs are formed. The unique functions of ovarian cells for follicular growth and differentiation as well as steroidogenesis and oocyte maturation are regulated by gonadotropins and gonadal steroids. The oviduct is responsible for egg formation, while the unique function to store sperms for a prolonged period takes place in the specific tissue of this organ. The unique innate and adaptive immuno-defense systems that play essential role to prevent infection are developed in the ovary and oviduct. Toll-like receptors (TLRs) that recognize the molecular pattern of microbes and initiate the immunoresponse are expressed in those organs. Avian β-defensins (AvBDs), a member of antimicrobial peptides, are synthesized by the ovarian and oviductal cells. Challenge of those cells by TLR ligands upregulates the expression of proinflammatory cytokines, which in turn stimulate the expression of AvBDs. The adaptive immune system in the ovary and oviduct is also unique, since the migration of lymphocytes is enhanced by estrogens. In contrast to the development of immuno-defense system, spontaneous ovarian cancer and uterine fibroids appear more frequently in chickens than in mammals, and thus chickens could be used as a model for studying these diseases. Thus the avian reproductive organs have unique functions not only for egg formation but also for the immuno-defense system, which is essential for prevention of infection and production of hygienic eggs.

Obtaining chicken primordial germ cells used for gene transfer: in vitro and in vivo results

Recently, several attempts have been made to create a generation of transgenic chickens via chimeric intermediates produced by primordial germ cells (PGCs) transfer. This study aimed to compare the influences of different chicken PGCs isolated from circulating blood (bPGCs) or gonads (gPGCs), purification (ACK, Percoll or trypsin) and transfection methods (electroporation or lipofection) on the expression of transgenes in vitro and the migration of modified donor cells to the recipient gonads. The highest average frequency of pEGFP-N1 plasmid-transfected bPGCs (75.8 %) was achieved with Percoll density gradient centrifugation and electroporation. After ammonium chloride-potassium (ACK) treatment and lipofection, in vitro transgene expression was only detected in 35.2 % of bPGCs. Chimeric chickens were produced from these purified, transfected and cultured cells, and the transgene was detected in the gonads of 44 and 42 % of the recipient embryos that had been injected with bPGCs and gPGCs, respectively. These data confirmed that the combination of PGC purification via Percoll centrifugation and electroporation was an effective method for producing transgenic chickens. Subsequently, we used this method with expression vectors for gene hIFNα 2a/hepatitis B virus surface antigen (HBsAg) under the control of the ovalbumin promoter to generate G0 transgenic chickens. Consequently, we observed that 4.9 % of the hens and 3.5 % of the roosters carried the hIFNα 2a gene, whereas 16.7 % of the hens and 2.4 % of the roosters carried the HBsAg gene, thus undisputedly confirming the exceptional effectiveness of the applied methods.

Characterization and miRNA-mediated posttranscriptional regulation of vitelline membrane outer layer protein I in the adult chicken oviduct

The laying hen is the best model for oviduct growth and development. The chicken oviduct produces the egg components, including the egg white and eggshell. However, the mechanism of egg component production during oviduct development requires further investigation. Vitelline membrane outer layer protein 1 (VMO-1) is found in the outer layer of the vitelline membrane of avian eggs. Comparison of the chicken VMO-1 protein-coding sequence and the human, mouse, rat, and bovine VMO-1 proteins via multiple sequence alignment analysis revealed high degrees of homology of 55%, 53%, 48%, and 54%, respectively. Although the avian homologue of VMO-1 is highly expressed in the magnum of the oviduct, little is known about the transcriptional and posttranscriptional regulation of VMO-1 during oviduct development. The results of this study revealed that estrogen induces VMO-1 messenger RNA (mRNA) expression in oviduct cells in vitro. The expression of genes interacting with VMO-1 by RNA interference (RNAi) functional analysis revealed that ovomucin expression was decreased by VMO-1 silencing. In addition, gga-miR-1623, 1552-3p, and 1651-3p influenced VMO-1 expression via its 3'-UTR, suggesting the posttranscriptional regulation of VMO-1 expression in chickens. Collectively, these results suggest that VMO-1 is an estrogen-induced gene that is posttranscriptionally regulated by microRNAs (miRNAs). The present study may contribute to an understanding of egg component production during chicken oviduct development.

Differences in the tissue tropism to chicken oviduct epithelial cells between avian coronavirus IBV strains QX and B1648 are not related to the sialic acid binding properties of their spike proteins

The avian coronavirus (AvCoV) infectious bronchitis virus (IBV) is a major poultry pathogen. A characteristic feature of IBV is the occurrence of many different strains belonging to different serotypes, which makes a complete control of the disease by vaccinations a challenging task. Reasons for differences in the tissue tropism and pathogenicity between IBV strains, e.g. a predilection for the kidneys or the oviduct are still an open question. Strains of the QX genotype have been major pathogens in poultry flocks in Asia, Europe and other parts of the world. They are the cause of severe problems with kidney disease and reproductive tract disorders. We analysed infectivity and binding properties of the QX strain and compared them with those of the nephropathogenic strain B1648. As most IBV strains do not infect permanent cell lines and show infection only in primary chicken cells of the target organs, we developed a culture system for chicken oviduct explants. The epithelial cells of the oviduct showed a high susceptibility to infection by the QX strain and were almost resistant to infection by the nephropathogenic B1648 strain. Binding tests with isolated primary oviduct epithelial cells and soluble S1 proteins revealed that S1 proteins of two IBV strains bound with the same efficiency to oviduct epithelial cells. This attachment was sialic acid dependent, indicating that the sugar binding property of IBV spike proteins is not the limiting factor for differences in infection efficiency for the oviduct of the corresponding viruses.

Current genomic editing approaches in avian transgenesis

The chicken was domesticated from Red Jungle Fowl over 8000years ago and became one of the major food sources worldwide. At present, the poultry industry is one of the largest industrial animal stocks in the world, and its economic scale is expanding significantly with increasing consumption. Additionally, since Aristotle used chicken eggs as a model to provide remarkable insights into how life begins, chickens have been used as invaluable and powerful experimental materials for studying embryo development, immune systems, biomedical processes, and hormonal regulation. Combined with advancements in efficient transgenic technology, avian models have become even more important than would have been expected.

Long-term culture of primary porcine oviduct epithelial cells: validation of a comprehensive in vitro model for reproductive science

Recently, we established a protocol for the cultivation of primary porcine oviduct epithelial cells (POEC), which promoted tissue-like morphology for a prolonged culture period. The present study focuses on developing this model into a comprehensive, standardized culture system, as a candidate tool for reproductive toxicity testing and basic research. We cultivated POEC isolated from 25 animals in our culture system for both 3 and 6 weeks and systematically analyzed effects of medium conditioning, supplementation with standardized sera, and culture duration in both freshly isolated and cryopreserved cells. The differentiation status was evaluated via histomorphometry, transepithelial electrical resistance (TEER) measurement, and expression analyses. The culture system possessed high reproducibility, more than 95% of cultures achieved a fully differentiated phenotype. Cells recapitulated in vivo-like morphology and ultrastructure from 3 to 6 weeks. Cryopreservation of the cells prior to cultivation did not affect culture quality of POEC. Employment of conditioned medium ensured optimal promotion of POEC differentiation, and different standardized sera induced fully differentiated phenotypes. Consistent TEER establishment indicated the presence and maintenance of cell type-specific intercellular junctions. The functionality of POEC was proven by consistent mucin secretion and stable expression of selected markers over the whole culture duration. We conclude that POEC are suitable for experiments from 3 weeks up to at least 6 weeks of culture. Therefore, this culture system could be used for in vitro estrous cycle simulation and long-term investigation of toxic effects on oviduct epithelium.

Effect of plant derived antimicrobials on Salmonella enteritidis adhesion to and invasion of primary chicken oviduct epithelial cells in vitro and virulence gene expression

Salmonella Enteritidis (SE) is a major foodborne pathogen in the United States and one of the most frequently reported Salmonella serotypes globally. Eggs are the most common food product associated with SE infections in humans. The pathogen colonizes the intestinal tract in layers, and migrates to reproductive organs systemically. Since adhesion to and invasion of chicken oviduct epithelial cells (COEC) is critical for SE colonization in reproductive tract, reducing these virulence factors could potentially decrease egg yolk contamination. This study investigated the efficacy of sub-inhibitory concentrations of three plant-derived antimicrobials (PDAs), namely carvacrol, thymol and eugenol in reducing SE adhesion to and invasion of COEC, and survival in chicken macrophages. In addition, the effect of PDAs on SE genes critical for oviduct colonization and macrophage survival was determined using real-time quantitative PCR (RT-qPCR). All PDAs significantly reduced SE adhesion to and invasion of COEC (p < 0.001). The PDAs, except thymol consistently decreased SE survival in macrophages (p < 0.001). RT-qPCR results revealed down-regulation in the expression of genes involved in SE colonization and macrophage survival (p < 0.001). The results indicate that PDAs could potentially be used to control SE colonization in chicken reproductive tract; however, in vivo studies validating these results are warranted.

AHCYL1 is mediated by estrogen-induced ERK1/2 MAPK cell signaling and microRNA regulation to effect functional aspects of the avian oviduct

S-adenosylhomocysteine hydrolase-like protein 1 (AHCYL1), also known as IP(3) receptor-binding protein released with IP(3) (IRBIT), regulates IP(3)-induced Ca(2+) release into the cytoplasm of cells. AHCYL1 is a critical regulator of early developmental stages in zebrafish, but little is known about the function of AHCYL1 or hormonal regulation of expression of the AHCYL1 gene in avian species. Therefore, we investigated differential expression profiles of the AHCYL1 gene in various adult organs and in oviducts from estrogen-treated chickens. Chicken AHCYL1 encodes for a protein of 540 amino acids that is highly conserved and has considerable homology to mammalian AHCYL1 proteins (>94% identity). AHCYL1 mRNA was expressed abundantly in various organs of chickens. Further, the synthetic estrogen agonist induced AHCYL1 mRNA and protein predominantly in luminal and glandular epithelial cells of the chick oviduct. In addition, estrogen activated AHCYL1 through the ERK1/2 signal transduction cascade and that activated expression of AHCYL1 regulated genes affecting oviduct development in chicks as well as calcium release in epithelial cells of the oviduct. Also, microRNAs, miR-124a, miR-1669, miR-1710 and miR-1782 influenced AHCYL1 expression in vitro via its 3'-UTR which suggests that post-transcriptional events are involved in the regulation of AHCYL1 expression in the chick oviduct. In conclusion, these results indicate that AHCYL1 is a novel estrogen-stimulated gene expressed in epithelial cells of the chicken oviduct that likely affects growth, development and calcium metabolism of the mature oviduct of hens via an estrogen-mediated ERK1/2 MAPK cell signaling pathway.