Structures similar to macaque embryos have been achieved from monkey embryonic stem cells, which were transferred to the uterus of several females, achieving a hormonal response similar to that of a gestation, although they disappeared after a week.
The research published by Cell Stem Cell is endorsed by Chinese researchers, who hope that, since monkeys are closely related to humans from an evolutionary point of view, the study of these models "will deepen the understanding of human embryonic development and shed light on some of the causes of early spontaneous abortions.
These structures similar to macaque embryos do not have full potential for development, point out the authors, who acknowledge the ethical concerns that surround this type of research and the importance, for this field to advance, of debates between the scientific community and the public.
The researchers stress that many differences remain between these embryo-like structures and natural blastocysts. The development of the human embryo and early organ formation remain largely unexplored due to ethical issues and the limited availability of materials for their study.
"The molecular mechanisms of human embryogenesis and organogenesis are largely uncertain," said co-author Zhen Liu, from the Chinese Academy of Sciences (CAS) in Shanghai, quoted by the publication.
This research has created in macaques "a system similar to the embryo that can be induced and cultivated indefinitely", which "provides new tools and perspectives for the subsequent exploration of primate embryos and reproductive medical health", added the also signatory of the CAS Whoan Sun.
The researchers started with macaque embryonic stem cells, which they exposed to a series of growth factors in cell culture, which induced them to form embryo-like structures using cells from non-human primates for the first time.
These embryonic structures, called blastoids, had a morphology similar to natural blastocysts and, as they developed in vitro, formed amnion- and yolk-sac-like structures, the publication explains.
The blastoids began to form the types of cells that would eventually make up the three germ layers of the body, which make up the organs. Single-cell RNA sequencing revealed that the various cell types found within the structures had gene expression patterns similar to those of cells found in natural blastocysts or postimplantation embryos.
These blastoids were transferred to the uteri of eight monkeys, although implantation only occurred in three of them, in which cases they led to the release of progesterone and chorionic gonadotropin, hormones normally associated with pregnancy.
In addition, the blastoids formed early gestation sacs (fluid-filled structures that develop early in pregnancy to enclose an embryo and amniotic fluid), but did not form fetuses, and these structures disappeared within a week.
The team plans to focus on further developing the embryo-like structure culture system from monkey cells, which will provide "a useful model for future studies."
Co-author Fan Zhou, from Tsinghua University, considered that "further application of monkey blasts may help to dissect the molecular mechanisms of primate embryonic development."
