Bio-printing, organoids,

A possible weapon against the pandemic: Printing human tissue

01 August, 2020

NEW YORK — As shortages of personal protective equipment persist during the coronavirus pandemic, 3D printing has helped to alleviate some of the gaps. But Dr Anthony Atala, director of the Wake Forest Institute for Regenerative Medicine, and his team are using the process in a more innovative way: creating tiny replicas of human organs — some as small as a pinhead — to test drugs to fight Covid-19.

The team is constructing miniature lungs and colons — two organs particularly affected by the coronavirus — then sending them overnight by courier for testing at a biosafety lab at George Mason University in Fairfax, Virginia. While they initially created some of the organoids by hand using a pipette, they are beginning to print these at scale for research as the pandemic continues to surge.

In the last few years, Dr Atala’s institute had already printed these tiny clusters of cells to test drug efficacy against bacteria and infectious diseases like the Zika virus, “but we never thought we’d be considering this for a pandemic”, he said. His team has the ability to print “thousands an hour”, he said from his lab in Winston-Salem, North Carolina.

The process of constructing human tissue this way is a form of bioprinting. While its use in humans is still years away, researchers are honing the methods to test drugs and, eventually, to create skin and full-size organs for transplanting. Researchers are making strides in printing skin, critical for burn victims; managing diseases like diabetes in which wound healing is difficult; and for the testing of cosmetics without harming animals, or, of course, humans.

“Even to us it sometimes seems like science fiction,” said Dr Akhilesh Gaharwar, who directs a cross-disciplinary lab in the biomedical engineering department at Texas A&M University that focuses on bioprinting and other approaches to regenerative medicine.

Bioprinting’s importance for pharmaceutical analysis is paramount now, not only for potential Covid-19 treatments but also for testing treatments for cancer and other diseases. Dr Atala says that the organoids allow researchers to analyse a drug’s effect on an organ “without the noise” of an individual’s metabolism.

He cited Rezulin, a popular diabetes drug recalled in 2000 after there was evidence of liver failure. His lab tested an archived version of the drug, and Dr Atala said that within two weeks, the liver toxicity became apparent. What accounts for the difference? An organoid replicates an organ in its purest form and offers data points that might not occur in clinical trials, he said, adding that the testing is additive to, rather than in lieu of, clinical trials.

Testing on bioprinted skin or other miniature organs also can more readily determine which drugs that work in animals like rats might not perform well in people.

“The 3D models can circumvent animal testing and make the pathway stronger from the lab to the clinic,” Dr Gaharwar said. That has importance for consumer goods as well as pharmaceuticals; since 2013, the European Union, for example, has prohibited cosmetics companies from testing products on animals.

The foundation for a printed organ is known as a scaffold, made of biodegradable materials. To provide nutrition for the organoid, microscopic channels only 50 microns in diameter — roughly half the size of a human hair — are included in the scaffold. Once completed, the “bioink”, a liquid combination of cells and hydrogel that turns into gelatin, is then printed onto the scaffold “like a layer cake”, Dr Atala said.

Another important part of the process is constructing blood vessels as part of the printing. Dr Pankaj Karande, an assistant professor of chemical and biological engineering at Rensselaer Polytechnic Institute, has been experimenting with skin printing since 2014 and recently had success in this step.

Using a cell known as a fibroblast, which helps with growth, along with collagen, as a scaffold, researchers at the institute printed the epidermis and dermis, the first two layers of skin. (The hypodermis is the third layer.) “It turns out the skin cells don’t mind being sheared,” Dr Karande said, and they could ultimately survive.

But their work hit a snag: Without incorporating blood vessels, the skin eventually sloughs off. Collaborating with Yale University’s Jordan Pober and W. Mark Saltzman, they eventually succeeded in constructing all three layers of human skin as well as vasculature, or blood vessels, which Dr Karande said was essential to the skin’s surviving after it had been grafted.

The three began experimenting with integrating human endothelial cells, which line blood vessels, and human pericyte cells, which surround the endothelial cells, into the skin as it was printed. Eventually, after much trial and error, they were able to integrate the blood vessels with the skin and found that connections were formed between new and existing blood vessels.

While the work is preliminary — tested in mice — Dr Karande said he was hopeful that the success in printing integrated skin and vasculature would set the stage for successful grafting in humans eventually.

The research, according to Dr Karande, is painstaking and involves a lot of trial and error. “We have Plan A, which we often know won’t work, and then we go down the list. We can often write about what works in five pages but have 5,000 pages of what didn’t work,” he added.

Dr Gaharwar’s lab is also investigating whether human bone tissue can be printed for eventual transplantation. His hope, he says, is that in the future, patient radiographic scans can be translated into the exact shape needed for implantation, especially important in repairing craniofacial defects in which the curvature needed can be difficult to re-create.

Like Dr Gaharwar, Dr Karande says that personalisation is important. He says that his work has already shown that skin can be fabricated to match an individual’s colour. And, because the skin is also critical in regulating body temperature, he is also working to engineer sweat glands into the skin, along with hair follicles.

“When we graft, we want to be able to re-create the full functionality of the skin,” Dr Karande said. And by using the cells from a patient, rather than a donor, the risk of rejection is minimised or eliminated altogether.

Not surprisingly, researchers are also exploring the collection of data from testing. The team at Wake Forest is partnering with technology company Oracle to capture the data from the organoids and analyse it with artificial intelligence. The project, known generally as the body-on-a-chip system, involves printing living tissue on a microchip to allow drugs to be studied for toxicity and efficacy even before clinical trials begin. The chips can be the size of a nickel or quarter, which is big enough to hold 10 to 12 miniature organs.

“We work a lot with researchers, pharmaceutical companies and biotech companies, and we are trying to seed advances as quickly as possible, analyse data and develop new drugs,” said Ms Rebecca Laborde, master principal scientist in Oracle’s health sciences division. “This is the most exciting project I’ve worked on in a long time.” 

THE NEW YORK TIMES

Researchers in Singapore grow ‘mini kidneys’ in lab, paving way for potential kidney disease therapies

By Justin Ong

20 August, 2019

SINGAPORE — Patients with kidney disease could eventually benefit from “mini kidneys” grown in a laboratory by an international team of researchers led by Nanyang Technological University (NTU), the university said on Tuesday (Aug 20).

These mini kidneys — derived from the patient’s cells — could be used to test certain drugs and help researchers better ascertain which treatment plans a patient with kidney disease needs, NTU said in a media statement.

Tailoring treatment to an individual patient is important as genetic errors that cause kidney failure differ from patient to patient, NTU said.

Using the mini kidneys to test the therapeutic effects of drugs removes the need to carry out drug screening on the patients themselves, it added.

The researchers grew the kidney “organoids” — a miniature version of an organ — from skin cells of patients with a common inherited cause of kidney failure known as polycystic kidney disease, a genetic disorder where multiple cysts develop within the kidney. The mini kidneys measured 1mm to 2mm in diameter.

The cells were grown outside the body in a laboratory and were “reprogrammed” to obtain pluripotent — or self replicating — stem cells, which, under the right conditions, can develop into the mini kidneys, which are similar to human foetal kidneys.

In growing the mini kidneys from the induced stem cells, the research team said it has "paved the way for tailoring treatment plans specific to each patient, which could be extended to a range of kidney diseases’’.

NTU Singapore Assistant Professor Xia Yun, who led the research, said: “Our kidney organoids, grown from the cells of a patient with inherited polycystic kidney disease, have allowed us to find out which drugs will be most effective for this specific patient.”

Dr Xia, who is from the NTU Lee Kong Chian School of Medicine (LKC Medicine), added that this approach could be extended to study many other types of kidney disease, such as diabetic nephropathy — kidney damage that results from having diabetes.

Professor Juan Carlos Izpisua Belmonte, a stem cell scientist and an international collaborator on this study, said: “We are still quite far away from using these kidney organoids for replacement therapy.” But the research represents “a small step closer to this ultimate goal”, he noted. 

Prof Belmonte is based at the Salk Institute for Biological Studies in San Diego, California.

NEW INSIGHTS INTO KIDNEY DEVELOPMENT

While the origin of kidney blood vessel networks is not fully known, the examination of cells within a kidney organoid has led Dr Xia’s team to discover a new source of stem cells — called nephrons — that contribute to making these blood vessel networks.

NTU LKC Medicine Assistant Professor Foo Jia Nee said that these nephrons can be better used to understand the kidney’s development from birth, where being born with higher nephrons appears to “provide some degree of protection” against hypertension and kidney failure later in life.

Dr Xia added: “A thorough understanding of human embryonic kidney development may help us develop ways to promote a high birth nephron number for foetuses as they develop during pregnancy.”

The research was published in the July edition of Cell Stem Cell, a United States-based scientific journal.