Research gives new hope to patients with idiopathic nephrotic syndrome

18 April 2023

Professor Moin Saleem, University of Bristol

New research by Professors Moin Saleem, Gavin Welsh and their team at the University of Bristol, supported by Kidney Research UK, has provided important new clues into idiopathic nephrotic syndrome (INS) with exciting implications for improved treatments in the future.

The kidneys filter the blood by allowing waste products out of the blood to form urine. Sometimes this filtration system becomes faulty, and protein can leak out into the urine. Nephrotic syndrome is the name given to a collection of symptoms that involves large amounts of protein in the urine, low amounts of a protein in the blood and oedema which can cause the face and joints to swell up with fluid. Nephrotic syndrome can either be genetic or non-genetic. The non-genetic form of nephrotic syndrome (idiopathic nephrotic syndrome or INS) is caused by a currently unidentified molecule released by the immune system and is not secondary to other diseases such as lupus.

A new way to target INS

We know that INS must be caused by something (known as a ‘factor’) in the blood. INS patients that receive a transplant can suffer rapid disease recurrence in their new kidney, sometimes this can happen within hours of the transplant surgery. Trying to identify this factor has proved to be challenging. Researchers have investigated bags of plasma (the liquid part of the blood) filtered from patients, knowing that this factor must be in there, but have so far been unable to find it. Theories on what might be involved have been suggested, but none of them have fully satisfied the scientific community as being the definite cause.

Clues for disease pathways in INS

Doctors don’t necessarily need to know what factor is leading to INS, but they do need to know what it does. Dr Carl May, under the guidance of Professors Moin Saleem and Gavin Welsh, has shown that this unknown factor works via a receptor known as PAR-1, found on a part of the kidney called the podocyte. Carl treated podocytes in the lab with an activator of PAR-1 and with plasma from patients with INS and saw the exact same response to both. This response was also seen in kidney samples from patients with INS but not in patients with genetic nephrotic syndrome or other kinds of kidney disease.

Aisling McMahon, executive director of research at Kidney Research UK added: “We are proud to be supporting Carl’s research. Our priority is to drive research that brings real benefits to the kidney disease community. This work not only represents a major breakthrough in our understanding of INS, but crucially opens up new possibilities for more effective treatment options”

Dr Carl May with plasma samples

What does this mean for patients?

Thanks to Carl’s work we now have what is called a ‘therapeutic target’. Drugs can be developed that target this receptor in the podocyte and block the unknown factor. Carl commented: “by developing treatments that target the problem we might be able to stop treating INS with steroids. Steroids are a non-specific treatment. They suppress the immune system and presumably reduce the concentration of the unknown factor. However, they come with a lot of side effects and don’t work at all for 20-30% of patients. New treatments targeting PAR-1 could work for more patients and be easier to tolerate”.