China leads cutting-edge technology, successfully producing world-renowned cloned monkeys— “Zhong Zhong” and “Hua Hua”. At the beginning of 2018, these two somatic cell cloned monkeys, with their innocent large eyes and astonishing birth process, debuted in the internationally renowned journal Cell, instantly becoming a global focus, heralding the arrival of a new era in the field of experimental animals. The major impact of this achievement is comparable to the historic cloned sheep “Dolly”, swiftly becoming the darling of the internet, television, and news media, and receiving widespread discussion around the world.
The world-stunning cloning technology actually stems from an obscure research group. In 2009, a critical moment of life decision appeared before Sun Qiang. As a lecturer at East China Normal University, he led his team to complete the “973” program research, concentrating on primate reproductive physiology and the construction of transgenic monkeys. Despite successfully breeding China’s first batch of in vitro fertilization crab-eating monkeys during his time in Xishuangbanna with the monkeys, he was unable to achieve the research goal of transgenic monkeys, which brought him deep regret.
At the crossroads of his scientific career, Sun Qiang received an invitation from the Institute of Neuroscience of the Chinese Academy of Sciences (now called the Center for Excellence in Brain Science and Intelligence Technology). Researcher Luo Zhengge hoped he would attend an academic seminar in Sanya, Hainan, and share his findings on in vitro monkeys. Initially planning only a brief report at the seminar, Sun Qiang, due to the unexpected cancellation of director Pu Muming’s presentation, ended up having more time to discuss and exchange ideas—this process inadvertently became his “interview”.
The year 2009 was a key one for both the Institute of Neuroscience and Pu Muming. They not only celebrated the institute’s tenth anniversary, received more stable scientific support, and built a national key laboratory, but more importantly, decided to expand their research field to non-human primates—primarily monkeys—because of their closeness to human brain structure, making them crucial in the development of neuroscience, and the study and treatment of neurodegenerative diseases. In this significant strategy, would Sun Qiang become the key person to undertake the mission? Pu Muming’s nationwide talent search began.
Sun Qiang, who harbored a passion for scientific research, caught the attention of Duan Shumin, an academician of the Chinese Academy of Sciences and researcher at the Institute of Neuroscience, by chance. After witnessing Sun Qiang’s talent and enthusiasm, Academician Duan recommended Sun Qiang, who had been deeply interested in primate research and had been rooted in Yunnan for many years, to Pu Muming. A few months later, Sun Qiang was invited to the Institute, where Pu shared his vision for the institute’s layout and the development of non-human primate research. At the end of the speech, Pu directly asked Sun Qiang if he was willing to participate in monkey research.
This proposal sparked great interest in Sun Qiang, but he was also concerned that the strict examination system and the long-term nature of monkey research might make it difficult to meet the evaluation standards in the short term. Therefore, he expressed his wish to start as a senior engineer, foregoing positions such as researcher or project team leader. Pu Muming agreed to this, and thus, on June 1, 2009, Sun Qiang officially joined the Institute of Neuroscience.
Sun Qiang clearly recognized that establishing a primate research base in Shanghai would be a dual challenge of funding and time. To avoid pointless waiting, he turned his attention to a qualified experimental animal company on Suzhou’s Taihu Xishan Island. By renting facilities and hiring experienced technicians, Sun Qiang quickly began his new research work.
The journey of scientific research is full of challenges. Sun Qiang remembered the difficulties in the early days, such as one National Day rainy night when he braved the rain, riding an electric scooter to the laboratory to deliver reagents. In the darkness, the lights of a truck blinded him, causing a fall and injury. Although his left arm was broken, Sun Qiang did not seek immediate treatment, opting instead to return to the laboratory to complete his experiments until he had surgery ten days later.
In the days that followed, Sun Qiang was fortunate to meet the like-minded Liu Zhen, a master’s student from Shandong. Liu Zhen was not only willing to endure hardship and think independently but was also courageous enough to undertake challenging research work. When Liu Zhen was about to graduate from his master’s program and expressed an interest in further study, Sun Qiang posed a tough problem that might require a long struggle.
Faced with the potential long-term commitment, Liu Zhen simply asked how long it would take. His tenacity and dedication were essential for undertaking long-term scientific research projects.
“Until I retire!” Sun Qiang said half seriously but couldn’t help laughing afterwards, “At least 10 years.” “10 years it is!” Liu Zhen took up the challenge. The subject was “somatic cell cloned monkeys.”
Over those years, Sun Qiang led a small team of about seven people stationed on Xishan Island, as if they became “invisible men” left alone by the world, “almost forgotten by the field.” Yet, a legend was quietly brewing in this isolated silence.
With the rapid development of neuroscience, scientists’ dissatisfaction with traditional experimental animal models grew. Animals like rats/mice, rabbits, dogs, whose nervous systems, especially their brains, are not as complex as humans, were becoming inadequate. Furthermore, the frequent failures of drugs for neurological diseases like Alzheimer’s once entering human clinical trials underscored the urgent necessity of developing non-human primate models.
An ideal experimental animal model should have a clear, uniform genetic background. Therefore, mice were inbred to produce stable homozygous genetic strains. However, due to monkeys’ long gestation periods and small litter sizes, this method was inefficient and impractical. Scientists thus explored viable methods to obtain monkeys with uniform genetic backgrounds for research, and somatic cell cloning technology was one of them.
Although the word “cloning” is not unfamiliar to modern people, since the birth of Dolly the cloned sheep in 1996, scientists around the globe have successfully cloned animals like cows, pigs, and cats. However, on the journey to clone monkeys, scientists faced repeated setbacks. In 1999, the Oregon National Primate Research Center in the U.S. achieved embryo cell-derived cloned monkeys using early embryonic cleavage cells as nuclear donors, but these cells could not be cultured and amplified in vitro, hence their application was extremely limited. Despite continuous challenges, that “fortress” was never conquered.
Facing this “tough nut” subject, Liu Zhen quickly identified the key technical “sticking point”: the “delicate” nature of primate embryos, which leads to their extremely low tolerance for precise cloning operations. In addition, since monkeys are valuable lab animals with limited oocyte numbers, the success rate is astonishingly low, causing many renowned teams to return in defeat.
Through a careful review of the experience and lessons from predecessors, Liu Zhen believed that the time was ripe to undertake this work. With increasing understanding of the mechanisms of mammalian embryonic development, complemented by mature technologies such as single-cell sequencing, they might be able to leverage new methods to solve longstanding difficulties. “The most important thing is to do it.”
“Even if action leads to failure, inaction guarantees no success.” This was Liu Zhen’s firm belief as he strived in researching somatic cell nuclear transfer technology. After three years of hard study, he mastered this technique to perfection, even earning high praise from Pu Muming for his skill: having a pair of dexterous hands.
In their constant exploration, Liu Zhen and his team identified the key factors for cloning success: the cloning efficiency is greatly related to the source of the cell nucleus, especially those from fibroblasts being the most ideal; post-nuclear transfer, epigenetic regulatory technologies are needed to appropriately activate or deactivate genes that significantly affect embryonic development; even so, every step must be taken cautiously to avoid any possibility of failure.
After a key technological advancement in 2017, more than twenty female monkeys successfully became pregnant but subsequently suffered miscarriages. Despite the birth of two monkeys, neither lived more than a week. The practice of perseverance and retrying after failure became the norm for Liu Zhen’s work; yet, every failure on the brink of success still left him feeling frustrated and sad.
Finally, at the end of 2017, a healthy and lively monkey was born, and 12 days later, another healthy monkey followed. The birth of these two monkeys with identical nuclear genes confirmed the success of Liu Zhen and his team.
During the rush to write their paper, Sun Qiang and Liu Zhen realized that the two monkeys had not been named. Following Pu Muming’s suggestion, they were named “Zhong Zhong” and “Hua Hua.” The birth of the somatic cell cloned monkeys drew widespread attention and praise in the academic world. John Rasko, president of the International Society for Cellular Therapy, hailed it as an unprecedented major technological breakthrough; Emilie Marcus, editor-in-chief of the journal Cell, considered it to be a milestone achievement leading to a revolution in animal experimentation and aiding the development of methods to treat human diseases.
Despite the public attention and media spotlight turning this once obscure research team into the focus of everyone’s gaze, Sun Qiang and Liu Zhen did not feel comfortable with this. To them, relative to the clamor under the flashlights, the serenity and comfort inadvertently brought by touching Monkey Hill and Monkey Island is the work and living environment they truly long for.
In July 2018, celebrating his 30th birthday, Liu Zhen was appointed as a researcher at the Institute of Neuroscience without the need for overseas studies. His deeds became a benchmark for local outstanding young scientists, and he was frequently invited to report and speak at various research institutions. However, he quickly realized that he was not good at showcasing so-called “success stories,” so he gradually reduced his participation in such activities, preferring instead to devote himself wholeheartedly to scientific research in the laboratory.
Currently, in Songjiang District, Shanghai, over 1500 model monkeys have migrated from Xishan Island in Suzhou. Through years of effort, the once barren Xishan Island has perfectly completed its mission. These model monkeys play a crucial role in key experiments combatting various brain diseases such as Alzheimer’s, epilepsy, insomnia, Angelman syndrome, and Fragile X syndrome. They form a valuable sample library for research on neurobiological problems, critically important not only for Chinese scientists but also for global researchers.
Like many studies involving primates, these efforts have been continuously under the scrutiny and concern of both domestic and international research ethics standards. In preparation for this, as early as 2005, the Shanghai Institutes for Biological Sciences at the Chinese Academy of Sciences established a Life Science Ethical Committee made up of ethicists, biologists, medical experts, and community members, to ensure that related research undergoes strict review and oversight.
Since Pu Muming returned to China in 1999 to establish the neuroscience institute, China, despite a difficult start in brain science research, has gradually moved from following to developing in parallel. By 2017, with the birth of “Zhong Zhong” and “Hua Hua,” China announced a huge leap from parallel development to leading the field to the world. However, Pu Muming is fully aware that there is still a long way to go to reach his goal of making China a global leader in brain science research. He firmly believes that the young researchers, with their fearlessness and vigor, will be the pioneers in exploring uncharted territories of scientific research.
Pu Muming constantly encourages young scientists to bravely venture out and focus on the core issues of scientific research. During an annual conference, he shared the story of a scientist who started from scratch in the academic world, focused on solving a major problem in his field, and ultimately won the Nobel Prize for this contribution. This story inspired the attending Sun Qiang and Liu Zhen, making them see a future full of infinite possibilities. This teacher-student pair has steadfastly remained in their precious non-human primate research field, continuously releasing new scientific surprises to the world.
In 2019, the world’s first batch of biological rhythm disorder somatic cell cloned monkeys was born, initiating a new era of mass production and standardization in China’s creation of disease model cloned monkeys. In 2023, the birth of the first batch of chimeric monkeys derived from a significant proportion of embryonic stem cells laid a solid foundation for the gene editing technology and model establishment techniques based on monkey embryonic stem cell chimeras.
“Is there anything in the world that is difficult? If you do it, then difficult things become easy; if you don’t, then easy things become difficult.” This saying enlightens us that whatever the endeavor, as long as we take action, the peaks that seem insurmountable will become easy; but if we stand by idly, even a small stone on the flat ground may trip us.
The secret to becoming the “number one in the world” is embodied in such wisdom. Only through continuous pursuit and practice can we turn challenges into opportunities and difficulties into victory.
