New layer of kidney cells can purify blood

Researchers at Eindhoven University of Technology (TU/e) and the University Medical Center Groningen have succeeded in culturing a layer of kidney cells in the lab. These cells maintained their functional properties, and are able to purify blood. The key to this success is a new kind of bioactive synthetic membrane developed at TU/e with a structure resembling that of human basement membrane in the kidney. This is a step towards improved kidney dialysis. The ultimate aim of the scientists is to be able to grow whole biological artificial kidneys using autologous cells.

Kidney function is vitally important; for example the kidneys filter toxic metabolic waste products from the blood. Many people suffer from kidney failure, and more than 6000 people in the Netherlands (and over 350.000 in the United States) require artificial blood cleansing by kidney dialysis. Unfortunately this technique is not yet perfect: its purifying capacity is only 15 to 20% of that of healthy kidneys. Scientists are therefore looking for ways to restore kidney function using cultured kidney cells.

Nanofibers
Dr. Patricia Dankers, who has a central role in this research, explains that there are two essential characteristics of the synthetic membranes on which she cultures the kidney cells: their structure and their bioactivity. Structurally the membranes consist of nanofibers that are part of larger, micrometer-size fibers. This structure resembles that of a human kidney membrane. The kidney cells grow on this fibrous membrane, but cease to function after several days. Dankers was only able to maintain the cell function by adding bioactive signals to the synthetic membrane.

Signals
These signals enable the kidney cells to adhere and survive, and ensure that they continue to function. Dankers was able to achieve this by supramolecular attachment of bioactive peptides (small pieces of protein) to the synthetic membranes. To do this Dankers used a kind of 'Velcro' binding, also relatively recently developed at TU/e. This allows the bioactive groups to be coupled to the membrane without the complex processes that were formerly needed.

Better dialysis
The researchers now intend to work on a biological artificial kidney to supplement the existing dialysis systems. This will increase the quality of dialysis treatment, because the kidney cells are able to filter exactly the right substances out of the blood. Dankers also hopes that the kidney cells will, in the longer term, produce hormones made by normal kidneys. These are important in making red blood cells, for example. However she is unable to say how long it may take to reach this stage. "It's difficult to predict, and we don't want to create unrealistic expectations."

After that the next step will be to develop a mobile dialysis system, so that kidney patients do not repeatedly have to visit hospitals. "Our ultimate dream is to make an implantable, living artificial kidney", says Dankers.