MDI Biological Laboratory

A Post-Doc Builds Proto-Kidneys from Scratch

More than 30 million Americans suffer from chronic kidney disease (CKD), including thousands in Maine. 

When someone’s kidneys fail, they face limited choices for managing their health: a lifetime on dialysis or finding a suitable (and willing) kidney donor. At MDI Bio Lab an international research group is doing ground-breaking work on a potentially better alternative: new kidney tissue or even whole kidneys grown from a patient’s own stem cells.

The Bio Lab’s Cory Johnson, Ph.D., is growing prototype kidneys called “organoids” in carefully tended racks inside a laboratory incubator. When he pulls out a batch that’s nestled in a petri dish, it looks to the naked eye like a mass of tiny, transparent frog’s eggs.

“An organoid is basically a lump of cells that are grown from stem cells in a dish that resemble an organ or a tissue of interest,” Johnson explains. “It’s not quite a full organ like you would get in the human body, but it’s very similar and shows characteristics such as cell types and some functions that you would see in a fully functional organ in the human body.”

The work puts him on the leading edge of an emerging biotechnology that holds extraordinary promise.

“It’s very sci-fi, a frontier of science that’s just getting started,” says Johnson, a Maine native and University of Maine graduate now doing his post-doctoral work at MDI Bio Lab. “I believe that organoids hold the potential for growing organs outside of the body someday. It’s fascinating.”

And, he adds, it’s not just about satisfying scientific curiosity, “it’s something that can actually help people.”

Today, the demand for kidney transplants far exceeds availability. More than 90,000 patients in the United States are waiting for a kidney transplant, and it takes three-to-five years to find a donor match. Too many people suffering kidney failure die while waiting.

That’s partly due to the difficulty of finding a donor whose kidney won’t be rejected by a patient’s body. Growing a new kidney from a patient’s own stem cells could help solve that problem.

It is a complex challenge. Johnson and his mentor, MDI Bio Lab President Hermann Haller, M.D., are making headway on one key factor; how to get a fledgling kidney and blood vessels to grow close to and then attach to each other.

Over a series of experiments this summer, Johnson managed to grow successive generations of kidney organoids that show preliminary evidence of penetration by blood vessels – a first step in creating a functioning organ system.

Johnson starts with “off-the-shelf” human stem cells that are ready to differentiate into any cell type when given the appropriate signals. By adding specific compounds to the cell culture medium, he can encourage those cells to differentiate in defined ways – in this case, growing miniature kidneys complete with blood vessels.

“Vascularization is important because as kidney organoids get larger, cells on inner layers of organoids lack access to nutrients and eventually die,” Johnson says.

Investigators who study blood vessels in vitro often introduce a protein called VEGF – vascular-endothelial growth factor — to encourage blood vessel growth. While VEGF is usually well-controlled in the body, an imbalance of VEGF can be detrimental, encouraging inflammation and tumor growth.

Johnson wanted to find other ways to vascularize an organoid. He tried several this summer, including a form of cortisol, a steroid that’s naturally produced in the endocrine gland, next to the kidney. He applied cortisol at key moments in the organoids’ development, and saw success in a small number of samples.

“We found that those blood vessels appeared to be integrating into these organoids, instead of just going over the top, which is usually what you see,” he says. “So that was really exciting.”

Johnson is documenting and confirming that progress using MDI Bio Lab’s state-of-the-art 3D microscopes and laboratory techniques for identifying specific protein and gene activity at the molecular level.

Two views of organoid development by MDI Bio Lab’s Cory Johnson, Ph.D., Endothelial cells (green) are the building blocks for blood vessels and together with podocytes (red) they form the kidney’s critical filtration barrier. Disruption of this filtration barrier is a hallmark of chronic kidney disease. Most kidney organoids created so far lack integration of blood vessels and podocytes; these images show evidence that it can be done, using cortisol signaling pathways. (image – Hannah Somers, Haller Laboratory Research Assistant)

3D microscopy, he says, helps to show that the structures being created in the organoid could in fact be functional.

“Do these endothelial cell structures have the characteristics of a full blood vessel, which means; is it actually a tube? And is there a lumen — an empty space — inside?” he asks. “And when you zoom in on this, and then cut it in a cross section, digitally, you can see that these vessels do have a lumen. So yes, this tube is actually a tube.”

Johnson is working now to repeat the results, and to get a better fix on the exact signaling pathways that are in play. What receptors are being activated by cortisol? What structural proteins are being produced more (or “upregulated”). What gene-level activity is going on?

Johnson says that for the moment he is focused on basic science around how to construct a functioning organoid. But he sees the potential for translation to human therapies – whether by using organoids as a platform for the study of kidney regeneration, or to actually create whole, transplantable kidneys.

The Bio Lab, he says, is a good place to make that translational leap.

“I think it’s a combination of both,” he says. “Without basic science, you don’t have the ability to do translational research. Here, we also have faculty and visiting scientists, some of whom are physicians, who are able to take the basic research that someone like me does on a regular basis and translate that into a therapeutic context.”

Johnson honed his experimental skills earlier this year at Hannover Medical School in Germany, a European center for kidney transplantation and renal organoid research. He was sent there by Dr. Haller, who continues to serve as Professor of Medicine at Hannover.

Herman Haller. M.D., left,and Cory Johnson, Ph.D.

Under Haller’s leadership, MDI Bio Lab is gaining a foothold at the forefront of the science of aging and regeneration. In addition to sending Johnson to Germany to learn some new tools, he is also recruiting graduate students and post-doctoral scientists from Hannover and the University of Toulouse to do their graduate work here, creating a truly international nexus for cutting-edge work on aging and regeneration.

For at least 100 years, he notes, scientists at MDI Bio Lab have worked to understand the role of the kidney in maintaining overall health and to develop new diagnostic and therapeutic tools to treat kidney disease.

“While we are fortunate to have dialysis and transplantation as options in treating chronic kidney disease, kidney regeneration is the next transformative step,” Haller says. “If we are successful, our work to grow new kidneys will revolutionize transplantation and improve human health and well-being.”