A model of a human kidney.
Science's dream of creating perfect custom organs on demand as soon as a patient needs one is still a long way off. But tiny versions are already serving as useful research tools and stepping stones toward full-fledged replacements.
Although organoids cannot yet replace kidneys, they are invaluable tools for research.
The Lowdown
Australian researchers have grown hundreds of mini human kidneys in the past few years. Known as organoids, they function much like their full-grown counterparts, minus a few features due to a lack of blood supply.
Cultivated in a petri dish, these kidneys are still a shadow of their human counterparts. They grow no larger than one-sixth of an inch in diameter; fully developed organs are up to five inches in length. They contain no more than a few dozen nephrons, the kidney's individual blood-filtering unit, whereas a fully-grown kidney has about 1 million nephrons. And the dish variety live for just a few weeks.
An organoid kidney created by the Murdoch Children's Institute in Melbourne, Australia.
Photo Credit: Shahnaz Khan.
But Melissa Little, head of the kidney research laboratory at the Murdoch Children's Institute in Melbourne, says these organoids are invaluable tools for research. Although renal failure is rare in children, more than half of those who suffer from such a disorder inherited it.
The mini kidneys enable scientists to better understand the progression of such disorders because they can be grown with a patient's specific genetic condition.
Mature stem cells can be extracted from a patient's blood sample and then reprogrammed to become like embryonic cells, able to turn into any type of cell in the body. It's akin to walking back the clock so that the cells regain unlimited potential for development. (The Japanese scientist who pioneered this technique was awarded the Nobel Prize in 2012.) These "induced pluripotent stem cells" can then be chemically coaxed to grow into mini kidneys that have the patient's genetic disorder.
"The (genetic) defects are quite clear in the organoids, and they can be monitored in the dish," Little says. To date, her research team has created organoids from 20 different stem cell lines.
Medication regimens can also be tested on the organoids, allowing specific tailoring for each patient. For now, such testing remains restricted to mice, but Little says it eventually will be done on human organoids so that the results can more accurately reflect how a given patient will respond to particular drugs.
Next Steps
Although these organoids cannot yet replace kidneys, Little says they may plug a huge gap in renal care by assisting in developing new treatments for chronic conditions. Currently, most patients with a serious kidney disorder see their options narrow to dialysis or organ transplantation. The former not only requires multiple sessions a week, but takes a huge toll on patient health.
Ten percent of older patients on dialysis die every year in the U.S. Aside from the physical trauma of organ transplantation, finding a suitable donor outside of a family member can be difficult.
"This is just another great example of the potential of pluripotent stem cells."
Meanwhile, the ongoing creation of organoids is supplying Little and her colleagues with enough information to create larger and more functional organs in the future. According to Little, researchers in the Netherlands, for example, have found that implanting organoids in mice leads to the creation of vascular growth, a potential pathway toward creating bigger and better kidneys.
And while Little acknowledges that creating a fully-formed custom organ is the ultimate goal, the mini organs are an important bridge step.
"This is just another great example of the potential of pluripotent stem cells, and I am just passionate to see it do some good."
Silkworm silk is fragile, which limits its uses, but a few extra genes can help.
Today, biomimetics is everywhere. Shark-inspired swimming trunks, gecko-inspired adhesives, and lotus-inspired water-repellents are all taken from observing the natural world. After millions of years of evolution, nature has quite a few tricks up its sleeve. They are tricks we can learn from. And now, thanks to some spider DNA and clever genetic engineering, we have another one to add to the list.
The elusive spider silk
We’ve known for a long time that spider silk is remarkable, in ways that synthetic fibers can’t emulate. Nylon is incredibly strong (it can support a lot of force), and Kevlar is incredibly tough (it can absorb a lot of force). But neither is both strong and tough. In all artificial polymeric fibers, strength and toughness are mutually exclusive, and so we pick the material best for the job and make do.
Spider silk, a natural polymeric fiber, breaks this rule. It is somehow both strong and tough. No surprise, then, that spider silk is a source of much study.The problem, though, is that spiders are incredibly hard to cultivate — let alone farm. If you put them together, they will attack and kill each other until only one or a few survive. If you put 100 spiders in an enclosed space, they will go about an aggressive, arachnocidal Hunger Games. You need to give each its own space and boundaries, and a spider hotel is hard and costly. Silkworms, on the other hand, are peaceful and productive. They’ll hang around all day to make the silk that has been used in textiles for centuries. But silkworm silk is fragile. It has very limited use.
The elusive – and lucrative – trick, then, would be to genetically engineer a silkworm to produce spider-quality silk. So far, efforts have been fruitless. That is, until now.
We can have silkworms creating silk six times as tough as Kevlar and ten times as strong as nylon.
Spider-silkworms
Junpeng Mi and his colleagues working at Donghua University, China, used CRISPR gene-editing technology to recode the silk-creating properties of a silkworm. First, they took genes from Araneus ventricosus, an East Asian orb-weaving spider known for its strong silk. Then they placed these complex genes – genes that involve more than 100 amino acids – into silkworm egg cells. (This description fails to capture how time-consuming, technical, and laborious this was; it’s a procedure that requires hundreds of thousands of microinjections.)
This had all been done before, and this had failed before. Where Mi and his team succeeded was using a concept called “localization.” Localization involves narrowing in on a very specific location in a genome. For this experiment, the team from Donghua University developed a “minimal basic structure model” of silkworm silk, which guided the genetic modifications. They wanted to make sure they had the exactly right transgenic spider silk proteins. Mi said that combining localization with this basic structure model “represents a significant departure from previous research.” And, judging only from the results, he might be right. Their “fibers exhibited impressive tensile strength (1,299 MPa) and toughness (319 MJ/m3), surpassing Kevlar’s toughness 6-fold.”
A world of super-materials
Mi’s research represents the bursting of a barrier. It opens up hugely important avenues for future biomimetic materials. As Mi puts it, “This groundbreaking achievement effectively resolves the scientific, technical, and engineering challenges that have hindered the commercialization of spider silk, positioning it as a viable alternative to commercially synthesized fibers like nylon and contributing to the advancement of ecological civilization.”
Around 60 percent of our clothing is made from synthetic fibers like nylon, polyester, and acrylic. These plastics are useful, but often bad for the environment. They shed into our waterways and sometimes damage wildlife. The production of these fibers is a source of greenhouse gas emissions. Now, we have a “sustainable, eco-friendly high-strength and ultra-tough alternative.” We can have silkworms creating silk six times as tough as Kevlar and ten times as strong as nylon.
We shouldn’t get carried away. This isn’t going to transform the textiles industry overnight. Gene-edited silkworms are still only going to produce a comparatively small amount of silk – even if farmed in the millions. But, as Mi himself concedes, this is only the beginning. If Mi’s localization and structure-model techniques are as remarkable as they seem, then this opens up the door to a great many supermaterials.
Nature continues to inspire. We had the bird, the gecko, and the shark. Now we have the spider-silkworm. What new secrets will we unravel in the future? And in what exciting ways will it change the world?
This article originally appeared on Freethink, home of the brightest minds and biggest ideas of all time.
