Calcium carbonate supplementation to chorioallantoic membranes improves hatchability in shell-less chick embryo culture

Intra-allantoic injection of calcium promotes hatching of chick embryos grown in shell-less culture

The hatch rate of chick embryos cultured outside of the eggshell with 350 mg calcium l-lactate hydrate (CaL) and 3.5 mL water is fourfold greater in cultures in which the chorioallantoic membrane (CAM) surrounds the egg contents by incubation day 17.5 (E17.5) an event which occurs in ovo by E13. It was first investigated whether decreasing the volume of water added with 350 mg CaL would promote CAM expansion due to the smaller volume to enclose. When 350 mg CaL was present, the CAM did not surround the egg contents by E13. By E17.5, the CAM surrounded the egg contents in 53%-74% of cultures; however, CAM expansion was not significantly different when 0, 1, 2, or 3.5 mL water was present. The hatch rate with 2 or 3.5 mL water was greater than 50% but was not improved with less water. Second, it was investigated whether CaL or water inhibits CAM expansion. In the absence of CaL, the CAM surrounded the egg contents in up to two-thirds of cultures by E13, whether 2 mL water was present or not. Thus CaL, but not water, inhibits expansion of the CAM by E13, even though CaL promotes hatching. Finally, it was investigated whether injection of aqueous CaL into the allantoic fluid, in conjunction with not adding CaL to culture hammocks, would promote CAM expansion. Allantoic injection of CaL starting at E13 did not promote CAM expansion at E17.5 but resulted in hatch rates of approximately 30%. Allantoic injection is a novel route for supplementation of calcium in cultured chick embryos.

Developmental toxicity of short-chain chlorinated paraffins on early-stage chicken embryos in a shell-less (ex-ovo) incubation system

Short-chain chlorinated paraffins (SCCPs) are listed as a category of globally controlled persistent organic pollutants (POPs) by the Stockholm Convention in 2017. However, SCCP toxicity, particularly their developmental toxicity in avian embryos, has not been well studied. In this study, we observed the early development of chicken embryos (Gallus gallus domesticus) by applying a shell-less (ex-ovo) incubation system developed in our previous studies. After exposing embryos at Hamburger Hamilton stage (HHS) 1 to SCCPs (control, 0.1% DMSO; SCCPs-L, 200 ng/g; SCCPs-M, 2000 ng/g; SCCPs-H, 20,000 ng/g), we observed the development of embryos from the 3rd to 9th incubation day. Exposure to SCCPs-M and -H induced a significant reduction in survival, with an LD50 of 3100 ng/g on the 9th incubation day. Significant dose-dependent decreases in body length were observed from days 4-9. We also found that SCCPs-H decreased the blood vessel length and branch number on the 4th incubation day. Additionally, SCCPs-H significantly reduced the heart rate on the 4th and 5th incubation days. These findings suggest that SCCPs may have potential of developmental and cardiovascular toxicity during the early stages of chicken embryos. Quantitative PCR of the mRNA of genes related to embryonic development showed that SLC16A10 (a triiodothyronine transporter) level decreased in the SCCPs-H group, showing a significant positive correlation with the body length of embryos. THRA level, a thyroid hormone receptor, was significantly decreased in the SCCPs-H group, whereas that of DIO3 level, a deiodinase was significantly increased. These results suggest that SCCPs exposure induces developmental delays via the thyroxine signaling pathway. Analysis of thyroid hormones (THs) in blood plasma also indicated a significant reduction in thyroxine (T4) levels in the SCCPs-H group on the 9th incubation day of embryos. In conclusion, SCCPs induce developmental toxicity by disrupting thyroid functions at the early-life stage of chicken embryos.

Tris(2-chloroethyl) phosphate (TCEP) exposure inhibits the epithelial-mesenchymal transition (EMT), mesoderm differentiation, and cardiovascular development in early chicken embryos

Tris(2-chloroethyl) phosphate (TCEP) is an organophosphorus flame retardant used worldwide and has been detected in the tissues and eggs of wild birds. Our previous study reported that exposure to TCEP induced developmental delay and cardiovascular dysfunction with attenuated heart rate and vasculogenesis in early chicken embryos. This study aimed to investigate the molecular mechanisms underlying the cardiovascular effects of TCEP on chicken embryos using cardiac transcriptome analysis and to examine whether TCEP exposure affects epithelial-mesenchymal transition (EMT) and mesoderm differentiation during gastrulation. Transcriptome analysis revealed that TCEP exposure decreased the expression of cardiac conduction-related genes and transcription factors on day 5 of incubation. In extraembryonic blood vessels, the expression levels of genes related to fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) were significantly reduced by TCEP exposure and vasculogenesis was suppressed. TCEP exposure also attenuated Snail family transcriptional repressor 2 (SNAI2) and T-box transcription factor T (TBXT) signaling in the chicken primitive streak, indicating that TCEP inhibits EMT and mesoderm differentiation during gastrulation at the early developmental stage. These effects on EMT and mesoderm differentiation may be related to subsequent phenotypic defects, including suppression of heart development and blood vessel formation.

Ca2+ addition facilitates the shell repair with eggs production of Pomacea canaliculata through biomineralization and food intaking regulation

Pomacea canaliculata was by far one of the most harmful invasive organisms in the world, causing serious harm to aquatic crops and ecosystem. Calcium carbonate is a common component of aquatic environment, which is important for the growth of Pomacea canaliculata. Therefore, the objective of this study was to investigate the response characteristics of P. canaliculata suffered shell breakage to the addition of calcium carbonate in water environment. In this experiment, we explored the effects of calcium carbonate addition on the P. canaliculata shell repair rate, food intake, egg production, shell strength, and calcium content through breaking the snails shell and the addition of calcium carbonate treatment. The results showed that snail broken-shell repaired mostly within 21 days. The snails experienced a significant increase in shell repair rates during earlier days of the treatment, especially for female snails. Food intake of snails exhibited different patterns when their shells were broken and calcium carbonate was added. Shell breakage treatment combined with calcium carbonate addition significantly increased the diameter of snail eggs compared with the control and the calcium carbonate addition treatment without shell-broken snail group. There was no significant difference in shell strength or calcium content of male snails between the treatments. The study suggests that P. canaliculata exhibits a sex-dependent response pattern when subjected to shell damage and calcium carbonate addition. The findings can provide some references to better understand the invasion mechanism and survival strategy of the P. canaliculata.

Supplemental calcium increases hatch rate but not hatchling mass of chick embryos in shell-less culture

A method is described for culturing 64-70 h-old chicken embryos and egg contents outside of the eggshell through to hatching. Cultured egg contents were suspended in polymethylpentene kitchen wrap (F.O.R. wrap; Riken Fabro) supported in polyvinyl chloride tripods. Tripods were incubated in Plexiglas environmental chambers which were rocked automatically through an angle of ±20°. The concentration of CO₂ was maintained at 2% throughout incubation, while that of O₂ was increased from ambient to 50%, and relative humidity was decreased from 90%-92% to 83%-84% at incubation Day 9. Cultured embryos not supplemented with calcium did not hatch. The Hatch rate increased when supplemental calcium L-lactate hydrate was increased between 250 and 350 mg. A maximal hatch rate of 54.8% was achieved when cultures were supplemented with 350 mg of calcium L-lactate hydrate and 3.5 ml of sterile water. Adding 400 or 450 mg of calcium L-lactate hydrate did not increase the hatch rate further. The mass of cultured hatchlings (including the retracted yolk) and yolk-free carcass wet and dry mass and length of the right third toe were significantly less than the corresponding parameters observed in hatchlings in ovo. No statistically significant differences in hatchling mass, yolk-free carcass wet or dry mass, or length of the right third toe were noted among cultured hatchlings supplemented with 250-450 mg of calcium L-lactate hydrate. Failure to completely absorb albumen was the most common abnormality observed in cultures which failed to hatch. The present technique allows a unique approach to study the physiology of the developing chicken embryo.

The Chick Embryo and Its Structures as a Model System for Experimental Ophthalmology

The possibilities of using the chick embryo and its individual structures as a model system in experimental ophthalmology are considered. Cultures of the retina and spinal ganglia from chick embryos are used in the development of new methods for the treatment of glaucomatous optic neuropathy and ischemic optic neuropathy. The chorioallantoic membrane is used for modelling vascular pathologies of the eye, screening of anti-VEGF drugs, and assessing biocompatibility of implants. Co-culturing of chick embryo nervous tissue and human corneal cells makes it possible to study the processes of corneal reinnervation. The use of chick embryo cells and tissues in the "organ-on-a-chip" system opens up wide opportunities for fundamental and applied ophthalmological studies.

Avian Embryonic Culture: A Perspective of In Ovo to Ex Ovo and In Vitro Studies

The avian embryos growing outside the natural eggshell (ex ovo) were observed since the early 19th century, and since then chick embryonic structures have revealed reaching an in-depth view of external and internal anatomy, enabling us to understand conserved vertebrate development. However, the internal environment within an eggshell (in ovo) would still be the ideal place to perform various experiments to understand the nature of avian development and to apply other biotechnology techniques. With the advent of genetic manipulation and cell culture techniques, avian embryonic parts were dissected for explant culture to eventually generate expandable cell lines (in vitro cell culture). The expansion of embryonic cells allowed us to unravel the transcriptional network for understanding pluripotency and differentiation mechanism in the embryos and in combination with stem cell technology facilitated the applications of avian culture to the next levels in transgenesis and wildlife conservation. In this review, we provide a panoramic view of the relationship among different cultivation platforms from in ovo studies to ex ovo as well as in vitro culture of cell lines with recent advances in the stem cell fields.

Effects of Calcium Lactate on the Development of Chicken Embryos in a Shell-less Culture System up to Day Seventeen of Incubation

This study examined the effects of calcium lactate on the development of chicken embryos in a shell-less culture system (cSLCS) up to the seventeenth day of incubation. In the presence of calcium lactate, a significant reduction in embryo viability was observed during the first week of incubation in cSLCS. On day 17 of embryo development, no significant difference was observed in the blood plasma calcium concentration or tibia bone density between cSLCS and intact control embryos, whereas the tibia length was significantly shorter in cSLCS embryos than in the intact control. These results suggest that calcium lactate supplementation in cSLCS supports bone formation in developing chicken embryos, but has adverse effects on the viability of embryos, particularly during the first week of embryo development.