Scientists in China persist in their controversial primate cloning endeavors, with a team from the Chinese Academy of Sciences reporting success- a cloned monkey surviving over two years.
After multiple efforts, a robust rhesus monkey clone was born in July 2020 but recently disclosed. Falong Lu, a team member, confirmed the cloned monkey's well-being at the age of 3, emphasizing its health during routine check-ups.
Two-Year Survival of Cloned Rhesus Macaque Signals Progress in Primate Cloning Challenges
Survival beyond two years represents a significant breakthrough in primate cloning, particularly for rhesus macaques (Macaca mulatta). Cloned macaque embryos traditionally face high mortality rates, with almost half succumbing around the 60th gestational day.
The newly revealed two-year-old male macaque, a product of Chinese cloning endeavors, stands out as a hopeful exception, utilizing an innovative approach to enhance placental development outcomes.
Cloning attempts with macaque embryos often encounter challenges linked to gene expression issues during development, leading to variable survival periods. In response, Chinese researchers employed a novel method aimed at addressing these challenges, with a specific focus on improving the genetic expression profiles of cloned fetuses' placenta as they grow and change during fetal development.
Identifying a key contributor to survival challenges, researchers pinpointed dysfunction or defects in the outer trophoblast layer's cells of the cloned embryo, a critical component providing nutrients and forming a substantial part of the placenta post-implantation.
To mitigate these issues, the team implemented a trophoblast replacement method, strategically embedding inner layers of cloned embryos into non-clone trophoblasts before implantation.
This innovative approach, described as "rescuing" development, involves injecting the inner cell mass from a cloned embryo into a second non-cloned embryo formed through in-vitro processes, resulting in a 'hybrid' embryo with a trophoblast belonging to a non-clone.
The initial cloning process employed somatic cell nucleus transfer (SCNT), the same advanced method that produced Dolly the Sheep in 1996. Despite previous successes with pigs, dogs, mice, cattle, and rabbits, achieving primate cloning through SCNT remained challenging.
A significant milestone was reached in 2018 when Chinese scientists successfully created Zhong Zhong and Hua Hua, two clones of a crab-eating macaque (Macaca fascicularis), utilizing SCNT. The recent survival of a rhesus macaque further underscores progress in overcoming obstacles related to primate cloning, particularly the optimization of survival outcomes.
Can Scientists Clone Humans Now?
Despite employing an intricate cloning technique, the research team has, so far, managed to clone only fetal cells and not adult ones. This raises significant uncertainty about the feasibility of cloning adult humans using their method. Lu firmly states that cloning a human being is entirely unacceptable, refusing to speculate on the potential application of their technique in that context.
Shoukhrat Mitalipov from Oregon Health & Science University, who works on cloning but wasn't part of this study, points out that the technique's suitability for creating cloned humans is unclear, emphasizing the ethical issues involved and highlighting the unknown factors regarding potential placental abnormalities in human cloned embryos.
Lu pointed out that the primary objective of primate cloning is to advance research, especially in the fields of cognitive and biomedical studies. Rhesus monkeys are crucial laboratory animals in these domains.
On the other hand, Mitalipov envisions the application of cloning for generating matched stem cells, aiming to provide rejection-proof embryonic stem cells for treating various conditions. The goal is to replace diseased nerve, muscle, blood, and other cells, or to produce eggs for infertility treatments in the future.
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