Renal tubular cells grow on a support between fluids
resembling blood (outer fluid) and precursor urine (inner)

"Renal tubular cells are important to study as many drugs are secreted into the kidneys via these cells". Cell culture using microfluidics is an expanding research area, as scientists work to create in vitro models that are physiologically relevant. Such cell cultures can lead to new insights into cell and organ function and be used for drug screening. Now, Kyung-Jin Jang and Kahp-Yang Suh from Seoul National University have used the method to grow renal tubular cells.

Renal tubules are small structures within the kidney that are involved in filtering the blood and producing urine. Renal tubular cells are important to study as many drugs are secreted into the kidneys via these cells. The cells also play pivotal roles in many kidney diseases, from cancer to acute tubular necrosis, which are often due to the tubules being damaged or reacting to various molecules.

However, the flow of blood and urine means that renal tubular cells are exposed to shear stresses and the effect of this flow on the cells is not yet understood. It also brings challenges to making physiologically relevant models using the cells. To counter this Jang and Suh developed a multilayer microfluidic device and optimised the growth conditions for the renal tubular cells. The cells are grown on a permeable support that is placed over a well containing outer tubular fluid (playing the role of blood) whilst a continuous stream of inner tubular fluid (precursor urine mimic) is passed over the cells. This leads to the cells growing and functioning as they would in the body.

Jang and Suh were able to use their device to show that hormone stimulation causes a water-transporting protein to move within the cells. 'This finding suggests that our device can be used as a simple drug screening tool,' Suh explains.

"This finding suggests that our device can be used as a simple drug screening tool"
- Kahp-Yang SuhShuichi Takayama of the University of Michigan, Ann Arbor, US, who also works on trying to understand cell function using microfluidics, agrees that the device could potentially lead to better tests for drugs. He describes the kidney as 'a great organ to mimic' using an approach like Jang and Suh's. He adds that because this model more accurately mimics how the cells respond in vivo, the approach 'can lead to a more relevant understanding of cellular mechanisms of disease.'

Jang and Suh point out they have several future directions to explore. As well as drug screening and cell characterisation, they suggest the system could be used to try to culture different kidney cells to study the networking between different kidney parts