Cutting edge technology for vascularized kidney organoids
Professor Ryuji Morizane, a renowned expert in renal research at Harvard Medical School, discusses his award-winning research* where organoid and bioengineering technology was successfully combined to create a kidney organoid with vascular structure.
To help facilitate this pioneering work, Professor Morizane’s research group used StemFit® – a feeder-free culture medium for embryonic (ES) and induced pluripotent stem cells (iPSC) without human or animal-derived components.
*Professor Morizane’s research was selected for the NIH Director’s New Innovator Award in 2019.
Overview of current research and progress
I started research on kidney differentiation using mouse ES cells at Keio University in Japan, and then went to the United States in 2012 to study human ES cells. At that time, Feeder-free media appeared, and I switched from Feeder culture to Feeder-free culture, but the cells did not adapt easily. We reported hPSC-derived kidney organoids in 2015*; however, the organoids at that time did not have a vascular structure in the nephron. The kidney is an organ through which a large amount of blood flows, and the vascular structure is essential for reproducing the function of the kidney. Therefore, we have focused on organoids with vascular structure. Around that time, StemFit medium appeared, and it became possible to successfully switch from Feeder culture to Feeder-free culture, and the cell culture became stable. Since then, I have continued to use StemFit to carry out research**. *Nature Biotechnology volume 33, pages1193–1200(2015) **Nature Protocols volume 12, pages195–207(2017)
Important and difficult points in improving kidney organoid maturation and vascularization
Organoids provide multicellular 3D models for physiology and disease studies, yet they are cultured in static conditions which are not the same as in vivo microenvironments. Particularly in kidneys, blood flow plays an important role in their organ function to produce urine. Hence, we united technologies of the organ-on-chip and organoids, creating a new model of organoid-on-a-chip. With this new approach together with the feeder-free culture, we were able to enhance the vascularization and maturation of kidney organoids***. The organoids-on-chip models now serve as additional tools for developmental and disease studies, expected to accelerate translational research. *** Nature Methods volume 16, pages255–262(2019)
Important and difficult points in genome editing and disease models
Previous studies have used GFP markers co-transfected with Cas9 to sort, isolate, and propagate cells, but the cell viability was too low to obtain enough edited clones. The efficiency of transfection was 1-2%, and it was necessary to improve the efficiency of transfection or the survival rate of isolated cells. This problem was solved by switching the medium to StemFit, which has higher cell growth performance and increased cell viability. Combining with the organoid-on-chip technology, more faithful models of polycystic kidney disease are developed, identifying potential therapeutic targets for drug development****.
New research and technology that have recently attracted attention
Organoids were thought to be immature for adult disease studies in earlier work. To understand the functional maturation of kidney organoids, team efforts with renal physiologists have been made by NIH ReBuilding Kidney Consortium. These recent studies have confirmed the tubular transporter functionality of kidney organoids, expanding the applications of kidney organoids to adult diseases such as autosomal dominant polycystic kidney disease and kidney fibrosis. Using more matured kidney organoids, a recent study identified an intrinsic repair mechanism by which kidney fibrosis, a phenotype of chronic kidney disease, can be attenuated*****. ***** Science Translational Medicine volume 14, eabj4772(2022)
Reasons for using StemFit medium and feeling of use
There were cases where switching from feeder culture to feeder-free culture did not work well with other media, but StemFit medium enabled a smooth transition to feeder-free culture. Cell viability and cloning efficiency were also high, which contribute to the efficiency of genome editing. It is also useful that a large amount of cell stock can be created at one time. In order to reduce the difference between experiments, it is important to make cell stocks from cells of the same passage number at one time. Since only one cell stock was obtained from 1 well in the feeder culture, it was difficult to make a large amount of stock. StemFit can create cell stocks from 1 well to nearly 20 vials, so cell stocks can be created efficiently. Now we can carry out stable research projects. In addition, the flexibility of scaffold and skipping medium exchange on weekends are also helpful.
Future prospects, issues, etc.
In the future, I would like to focus on translational research such as drug screening using kidney organoids. We also want to consider clinical applications in the future. The challenge is to produce high-quality cells used for transplantation, which is a general issue of PSC. In recent years, in particular, gene mutations in culture have been drawing attention, and how to control cell quality is an issue. Depending on the target disease, it may be a risk-benefit issue to consider. The cost-benefit perspective is also important, and it is necessary to develop the cost-efficient culture methods of iPSCs and the differentiation protocols of organoids.