-The first subunit of a bioengineered kidney-
When the kidneys are damaged and can’t filter blood in the correct way someone suffers from kidney failure. Between the occurrence of kidney damage and the development of symptoms quite some time passes. Generally, symptoms occur when the kidney function is down to 30%. In the Netherlands, 1.7 million people have chronic kidney damage (10.6% of the population) and of these 40% are not aware of this.
On a worldwide scale, end-stage kidney disease can be counted as an epidemic as it is estimated that 8-16% of adults have chronic kidney damage. At present, the only treatment options are dialysis and transplantation. Currently, 6,500 people in the Netherlands depend on dialysis of which approximately 1,300 will die this year.i
Disrupted kidney function can be caused by several factors such as long-term high blood pressure and heavy medication. Often the loss of kidney function is not noticed until a later stage and certain symptoms not recognized as related. Common complaints at an early stage are fatigue, loss of physical condition, and concentration problems. However, there are various complaints and symptoms which can emerge when one's kidneys are not functioning properly anymore. These and the precise consequences of kidney damage differs per person. Both current treatment options are far from optimal.
The first treatment option is dialysis; this is a very heavy treatment which compensates only for max. 20 % of the kidney function. It has a high mortality rate (1 in 6 dialyzes patients) and decreases the quality of life of the patient immensely. The second option is kidney transplantation, for this, a suitable donor kidney has to be found. After the transplantation, immunosuppressive medication needs to be taken lifelong which can have severe side effects. Furthermore, a kidney of a deceased donor lasts on average 10 years, a kidney from a living donor on average 20 years.ii
What do we do in the RegMed XB Moonshot?
The Kidney Moonshot of RegMed XB is working towards creating a functioning subunit of a bioengineered kidney. RegMed XB researchers have developed a method to grow human cells in so-called organoids which are also known as ‘mini kidneys’. These mini kidneys have to be further developed before they can perform all the functions of the kidney. Nephrons (the microscopic structural and functional unit of the kidney) can be cultured from different cells (such as skin cells, kidney cells, or cells from the urine from the patient self). The advantage of using cells directly from the patient is that it prevents rejection after transplantation of the nephrons. This makes immunosuppressive medication and associated side effects unnecessary. However, we also investigate an approach via the shelve stemcells (IPSC). The advantage of those is robustness, speed, and improvement possibilities.
RegMed XB researchers have developed a method to grow human cells in so-called organoids which are also known as ‘mini kidneys’. The Kidney Moonshot consists of two parallel lines in which organoids derived from induced Pluripotent Stem Cells (iPSC) or adult stem cells (ASC) (from urine or a biopsy) are investigated for their potential to form functional kidney subunits (nephrons/tubuloids). In both lines, the researchers are working on growing sufficient organoids and making these organoids functional.
IPSC derived organoids
The Moonshot is currently able to build 100 nephrons per organoid which grow and mature in vivo. The product is scalable as we can currently grow large organoid sheets of up to 2500mm2 (equaling 50.000 nephrons). We have shown that these large sheets maintain structural integrity in vitro. The large organoid sheets still need to be tested in vivo to study their potential to connect to the vascularisation. Furthermore, crucial concerning organoid size and nephron numbers is knowledge on the number of nephrons needed to obtain a functional transplant.
The moonshot is now focusing on determining the correct timing of differentiation before transplantation to allow functional in vivo maturation and decrease in vivo off-target differentiation. This is a new milestone that has been identified based on the studies in 2018 and 2019 which sought to investigate why organoids degenerate over time and why transplantation in vivo further promotes organoid maturity. Part of this work was to characterize the ECM composition of “young” and “old” kidney organoids using a protein-based approach. Besides changes in the aberrant deposition of several types of collagen, we also observed a myofibroblast population appearing.
ASC derived organoids
The Moonshot found that leak-tightness values in one of our optimized differentiation conditions improved by ~50%, indicating an improved leak-tightness. Furthermore, we tested new differentiation conditions aimed at further proximal tubule differentiation (now over 125 conditions tested). So far, we did not find conditions that were superior to our current most effective protocols.
The researchers have created a 2D set up where they culture mature renal epithelial cells on a coated substrate with variable stiffness. We found that renal cells derived from organoids form a polarized monolayer on hollow fibers, which is a crucial step in valorizing this technology towards a clinically applicable device.
iFactsheets [Internet]. Nierstichting. 2020 [cited 3 June 2020]. Available from: https://nierstichting.nl/professionals/factsheets/
iiSymptomen van chronische nierschade [Internet]. Nieren.nl. 2020 [cited 3 June 2020]. Available from: https://www.nieren.nl/bibliotheek/24-symptomen-van-chronische-nierschade