Egg yolk proves key to establishing genuine embryonic stem cells from birds

Egg whites could also be good for a health-conscious breakfast, however egg yolks turned out to be the important thing ingredient for cultivating fowl embryonic stem cells (ESCs) within the lab. Using a rising medium of egg yolk together with just a few different key elements, a USC Stem Cell-led staff of scientists has succeeded in deriving and sustaining genuine ESCs from chickens and 7 different fowl species.

These fowl ESCs maintain large promise for functions starting from finding out embryonic improvement to producing lab-grown poultry to reviving endangered and even extinct birds.

The research appears in Nature Biotechnology.

“A true embryonic stem cell has two key qualities: it is self-renewing and can multiply to produce more stem cells; and it is pluripotent, meaning it can differentiate into all cell types of the embryo—both in a culture dish and after being reintroduced into an embryo,” mentioned corresponding writer Qi-Long Ying, Ph.D., a professor of stem cell biology and regenerative medication on the Keck School of Medicine of USC.

“In this study, we successfully derived and maintained true self-renewing and pluripotent ESCs from chicken, quail, pheasant, turkey, duck, goose, peafowl, and ostrich.”

First writer Xi Chen, now at Caltech, spent a decade advancing this analysis, first throughout his Ph.D. and postdoctoral coaching within the Ying Lab at USC, and later whereas persevering with the work in Carlos Lois’s lab at Caltech. The challenge enhances earlier analysis from Ying’s lab, which independently derived the primary true ESCs from rats and printed the findings in Cell in 2008, in parallel with a separate report from Austin Smith’s lab on the University of Cambridge.

In the present research, Chen and his collaborators first optimized situations to assist ESCs from chickens, probably the most well-studied avian species.

Starting with cells from the early embryonic stage referred to as the blastoderm, they added two chemical substances identified to encourage ESC formation by inhibiting indicators that generally promote stem cell differentiation.

The first chemical, IWR-1, inhibits cell indicators associated to the proteins Wnt and β-catenin, and the second chemical, Gö6983, inhibits cell indicators from the protein kinase C household. When uncovered to those two chemical substances, the rooster cells exhibited genetic markers of stem cell pluripotency, however nonetheless couldn’t be maintained within the lab long-term.

The scientists then made a game-changing remark: when the blastoderm cells have been transferred from their eggs together with bigger quantities of yolk, they tended to self-renew higher within the lab. The scientists started to suspect that the lacking ingredient of their ESC-promoting cocktail was a pure part of egg yolk.

A cautious research of the yolk revealed that it does certainly comprise a protein, ovotransferrin, that accomplished their cocktail and enabled them to derive and keep ESCs from a number of rooster breeds.

Surprisingly, the three-ingredient cocktail that labored for rooster ESCs did not present the identical success in selling ESCs from different avian species. Different species required variations of the cocktail.

For instance, pheasant, duck, and turkey ESCs wanted a fourth ingredient, the chemical SB431542, to dam differentiation into beating coronary heart muscle cells and allow upkeep of stem cell id. Quail, geese, and peafowl ESCs required all 4 of those parts plus a fifth ingredient, the pluripotency-related signaling protein LIF derived from chickens.

Meanwhile, ostrich ESCs failed on this five-ingredient cocktail, however efficiently maintained their stem cell id when the scientists eliminated the rooster LIF and reverted to the four-ingredient model.

When uncovered to the five-ingredient cocktail moderately than the unique three-ingredient cocktail, rooster ESCs may self-renew over an extended time frame whereas sustaining a excessive diploma of pluripotency.

Under these optimized situations, rooster ESCs may type the three main cell layers of the early embryo that in the end give rise to all tissues and organs within the physique—the hallmark of true pluripotency. They may additionally differentiate into reproductive germ cells resembling sperm, in addition to non-reproductive or “somatic” cells that make up different tissues within the physique—one other signal of pluripotency.

Chicken ESCs additionally handed the gold commonplace take a look at for pluripotency: the flexibility to make a “chimera,” an animal composed of a mosaic of cells from two genetically distinct people. When rooster ESCs have been launched right into a growing rooster embryo, the ensuing animal developed from a mosaic of cells from each sources.

As a transparent demonstration, when the growing embryo was albino, rooster ESCs may contribute pigmented feathers to the chimera.

Chicken ESCs is also genome edited utilizing CRISPR and different instruments, increasing their usefulness for functions in each analysis and biotechnology.

“Compared to naïve ESCs derived from mice, chicken ESCs are a little less stem cell-like but are not primed to commit to specific cell lineages,” mentioned Chen. “This type of ESC sits on the developmental continuum between naïve and primed.”

ESCs from the opposite avian species additionally handed key exams of pluripotency. Quail, goose, and ostrich ESCs displayed basic pluripotency-associated genetic markers. Quail ESCs may differentiate into all three early embryonic layers, whereas goose ESCs may contribute to germ cells. And quail and goose ESCs may each contribute to chimeras.

Importantly, the lab of co-author Professor Guojun Sheng at Kumamoto University in Japan has independently derived chimera-competent rooster and peafowl ESCs utilizing the strategies described on this research—demonstrating that the strategy is strong and reproducible.

“By demonstrating that we can derive and maintain authentic ESCs from several avian species, this research opens up so many possibilities,” mentioned Ying.

“As we continue to expand our ability to derive avian ESCs, we can imagine engineering healthier chickens for the poultry industry, incubating therapeutic proteins inside of eggs for pharmaceutical development, or reviving endangered or extinct species to support conservation and biodiversity efforts. There are so many exciting applications of this technology, and this study is only the beginning.”

Ying, Chen, Zheng Guo, Xinyi Tong and Xugeng Liu are inventors on patent WO2023158627A3, titled “Methods for derivation and propagation of avian pluripotent stem cells and applications thereof” that arose from this work.