By Kyle Hui
As science advances worldwide, technology in healthcare sectors improve as well. This progress is a double-edged sword. On one hand, stronger vaccinations and medicine gift society with better public health. On the other hand, the decrease in availability of organs can be devastating to those in need of transplants. Growing up in the bustling city Hong Kong, a place populated with over 7 million people, I have always been worried about how the healthcare system sustains the city. In fact, Hong Kong is among the world’s worst for organ donations, with only 5.8 donors for every million people in the city. Many patients in the city die because of the absence of suitable organs.
Having a strong passion for biology, I keep my eyes open to solutions that can alleviate this ever-growing problem in my hometown. Last summer, I took a course in Stanford on Tissue Engineering and 3D bio-printing. During the course, I had a sudden moment of eureka. Can’t we just print more organs to put an end to this crisis? Little did I know that the answer to this question is theoretical in many ways. In fact, we are still quite a long way from printing body parts like how we print paper.
In essence, 3D bio-printing can be broken into a few key steps. First, scientists concoct bioink. In order to create this, they differentiate stem cells into specific cells, then encapsulate them in hydrogels. Afterwards, medical imaging technology is employed to understand the 3D structure of organs, allowing medical professionals to design patient-specific constructs. The 3D digital model is then sliced into a number of 2D horizontal layers, facilitating the additive printing process later on. Finally, the bioink is printed onto scaffolds (may or may not contain cells by the technique of cell seeding) or scaffold-free molds. Theoretically, an organ would then be printed out. However, there are many difficulties and limitations during each step. For example, cells will die quickly if not exposed to suitable environments in the ink. In addition, many existing 3D printers are not powerful enough to create structures strong enough to support the tissue.
Despite the numerous challenges faced by scientists, researchers have been taking small but exciting steps towards a future of artificial organs. In late 2018, scientists from the University of Utah published a paper in the Journal of Tissue Engineering. In the paper, they described their success in manufacturing human tissues like ligaments and tendons through bio-printing. The team harvested stem cells from human fat and printed them onto a layer of hydrogel. Over time, the structure developed into tissues resembling ligaments and tendons. Since connective tissue is a complex of different kinds of cells, these researchers developed a special printhead that could lay down specific cells at specific locations in a controlled manner. This discovery was important because current tissue replacement methods rely on tissues from other parts of the patient’s body.
These tissues may not be of high quality and the harvested locations may be damaged. The University’s research can effectively these issues and even serve to recreate spinal discs for transplants.
Another recent and ground-breaking discovery is the printing of a half-functioning organ. In early 2019, researchers at the Tel Aviv University of Israel managed to engineer a cherry-sized heart using human cells. Like the scientists in the University of Utah, the Israeli researchers took fatty tissue from humans and reprogrammed the cells to become cardiac cells and blood vessel cells that know how to circulate blood through the cardiac system. Trapping these cells in bioink, they then printed out the organ. What makes this discovery stand out is that the researchers succeeded in creating the working blood cells to keep the organ alive, something no other scientist could before. Although the heart can contract, the cells do not work in perfect harmony to form a pumping ability. Moreover, the current 3D-printers lack precision and resolution that can accurately print the tiniest of human blood vessels. This pint-sized heart may still not yet be functional in humans, but it marks a huge milestone in biomedical sciences.
These results are amazing, pointing us towards an era where we can literally print out new ears or noses for ourselves. The common medical obstacle of immuno-rejection of cells can also be eliminated in the future with patient-derived organs. However, in the midst of all excitement, I believe that careful and small steps must be taken. There are many ethical considerations on the technology of 3D bio-printing. Is it morally right to create a new body part? Is it morally correct to harvest cells from an embryo to reprogram them? Recently, Chinese scientist He Jiankui claimed to have use CRISPR to disable the gene for making CCR5 in babies, making them immune to HIV. This has caused uproar amongst the scientific community, saying that the study infringed on the babies’ rights, and that the technology was still unsteady at the time. Hopefully, scientists and the government can work hand in hand, taking slow but steady steps so that we can print organs safely and ethically in the future.
“3D Printing Human Ligaments, Tendons and More . . .” State of Utah Center of Excellence for Biomedical Microfluidics, 17 Oct. 2018, mems.utah.edu/2018/10/17/3d-printing-human-ligaments-tendons-and-more/.
Cheung, Elizabeth. “Hong Kong among World's Worst for Organ Donations.” South China Morning Post, 20 July 2018, www.scmp.com/news/hong-kong/health-environment/article/1989904/hong-kong-among-worlds-worst-organ-donations.
Cui, Haitao, et al. “3D Bioprinting for Organ Regeneration.” Advanced Healthcare Materials, U.S. National Library of Medicine, Jan. 2017, www.ncbi.nlm.nih.gov/pmc/articles/PMC5313259/.
Lazarus, David. “Israeli Scientists Unveil World's First 3D-Printed Heart with Human Tissue.” The Times of Israel, Apr. 2019, www.timesofisrael.com/israeli-scientists-unveil-worlds-first-3d-printed-heart-with-human-tissue/.
Park, Alice. “Chinese University 'Shocked' By News of First CRISPR Babies.” Time, Time, 26 Nov. 2018, time.com/5463741/crispr-human-babies/.
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