The kidneys play a vital role in removing waste and toxins from the blood, but how exactly cells transport this fluid through the organs remains a mystery. Researchers at Johns Hopkins University have now studied the mechanical forces at work and found an unprecedented pumping effect from kidney cells.
All the blood in your body passes through your kidneys dozens of times a day, passing through small tubes and filtering devices before the “pure” blood returns to the bloodstream. But the mechanical forces required for this were not clear – after all, the epithelial cells lining these tubes were thought to be immobile.
“Fundamental laws of physics say you need strength to move things,” said Sean Sun, author of the new study. “In this case, the cells are not moving, but they are moving fluid. Then the question is how do they do that?”
To study, researchers from John Hopkins modeled the organ using an artificial micro-fluid kidney pump. In this setting, fluids pass from a microchannel, through cultured renal epithelial cells, and into a second microchannel, while the device records fluid pressure in different areas.
And of course, the team monitored the renal epithelial cells, which function as mechanical fluid pumps. They actively generated a liquid pressure gradient that drives the liquid in a certain direction like a simple domestic water pump.
In subsequent experiments, the team investigated how the function of these cells could change in cases of disease. They tested the same device using renal epithelial cells from patients with autosomal dominant polycystic kidney disease (ADPKD), a disease that causes the formation of fluid-filled cysts.
It has been found that diseased cells pump fluid in the opposite direction to healthy cells. This changes the pressure profile of the renal tubules and changes their shape, which may play a major role in the development of cysts.
The researchers then tested a drug called Tolvaptan, which is used to slow the progression of ADPKD, in a microfluidic device to study how it works. They found that the drug caused cells to reduce their pumping flow and pressure gradients, which slowed the development of cysts.
The team says the discovery could unlock new potential drugs or treatments, while the device could find use as a tool to screen for ADPKD and other diseases of the kidneys and other organs.
The study was published in the journal Natural communications.
Source: Johns Hopkins University