Of human embryonic stem cells, the retina is grown

Human stem cells spontaneously form a tissue that develops into the retina - that tissue of the eye that allows us to see. This is reported in an article published in the journal Cell Stem Cell. In the future, transplantation of such a three-dimensional tissue can help patients with visual impairment.

"This is an important milestone in the new stage of the development of regenerative medicine," said Yoshiki Sasai, MD, PhD, director of the organogenesis and neurogenesis group, from the RIKEN Center for Developmental Biology ), Japan. "Our approach opens new prospects in using complex tissues derived from human stem cells for treatment, as well as for medical research related to the pathogenesis and development of drugs."

In the process of development, the retina is a photosensitive tissue lining the inner surface of the eye - it is formed from a structure known as the visual or eye glass. In the new work of Japanese researchers, this structure spontaneously formed from human embryonic stem cells (hESCs) - cells derived from human embryos that have the potential to differentiate into different tissues. This was made possible by the methods of cell cultivation, optimized by Professor Sasai and his group.

Cells derived from hESCs are organized into the correct three-dimensional structure with two layers of the eye cup, one of which contains a large number of photosensitive cells - photoreceptors. Since degeneration of the retina is primarily a result of damage to the photoreceptors, the hESCs tissue obtained from them can become an ideal material for transplantation.

The study of Japanese scientists not only opens up further prospects for the use of stem cells in regenerative medicine, but, undoubtedly, will accelerate the development of such a field of natural science as developmental biology. In the course of the experiments, the researchers became convinced that the eye glass, formed from human embryonic stem cells, is much thicker than that grown from mouse embryonic stem cells. In addition, it contains both rods and cones, while in mouse ESCs, differentiation into cones is rare. This means that embryonic cells carry a species-specific instructions for creating this eye structure.

"Our research opens the way to understanding the peculiarities of eye development that are specific to humans, the study of which was previously impossible," Professor Sasai is sure.

This is not the first major success of Professor Sasai's group. At the end of last year, scientists have grown from mouse embryonic stem cells a functional anterior portion of the pituitary (adenohypophysis), consisting of several different types of hormone-producing cells. An article on the results of this work The self-formation of functional adenohypophysis in three-dimensional culture was published in the journal Nature.

The pituitary gland is a small endocrine gland at the base of the brain, which produces several important hormones. It is especially important in the period of early development, and the ability to imitate his education in the laboratory will help scientists better understand embryogenesis. Disorders in the pituitary gland are associated with growth disorders, such as gigantism, and vision problems, including blindness.

This experiment would not be possible without a three-dimensional cell culture. The pituitary gland is a separate organ, but for its development, chemical signals are needed from the brain region located directly above it - the hypothalamus. In a three-dimensional culture, scientists could simultaneously grow two types of tissues closely together, resulting in stem cells that self-organized into the pituitary gland in two weeks.

Fluorescent staining showed that the grown pituitary tissue expresses the corresponding biomarkers and secretes typical for the anterior pituitary gland hormones. The researchers went further and tested the functionality of the organs synthesized by them, replacing them with mice deprived of the pituitary gland. The experiments ended in success: the bioengineered pituitary gland restored the levels of glucocorticoid hormones in the blood of animals and eliminated behavioral symptoms such as lethargy. The state of mice with implanted stem cell structures that were not exposed to the necessary signaling factors and therefore did not become a functional pituitary did not improve.

Professor Sasai and his colleagues plan to repeat the experiment on human stem cells and, in their opinion, this work will take at least three years.

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