COVID-19 directly damages, creates scar tissue on the kidneys

NIJMEGEN, Netherlands — Although studies show COVID-19 is capable of infecting a patient’s kidneys, the virus’s exact impact on the organs has been unclear – until now. A team of German and Dutch scientists report COVID-19 causes direct cellular damage within the kidneys, contributing to tissue scarring.

Conducted at the RWTH Uniklinik Aachen in Germany and the Radboud University Medical Center in the Netherlands, study authors assessed and compared kidney tissues among COVID-19 ICU patients, other patients in the hospital for a non-COVID-related lung issue, and a group of healthy people. Results show kidney tissue from the COVID-19 patients showed much more tissue scarring than others.

The first phase of the investigation clearly established that COVID-19 damages the kidneys. Next, researchers set out to determine how the virus accomplishes this.

Many recent studies indicate that some of COVID-19’s more severe symptoms emerge due to an overreaction of the body’s immune response and too much inflammation, not coronavirus itself. Is this the case for the kidneys as well, or is COVID-19 inflicting damage on these organs directly?

Lab-grown kidneys reveal the same scarring

kidney covid
Kidney sections from healthy control (left) and COVID-19 patient (right). Scar tissue is blue. (CREDIT: Jitske Jansen and Bart Smeets, Radboudumc)

The team created a series of mini kidneys, called organoids, by culturing them in a lab setting. Developed using stem cells, the organoids featured many different kidney cells, except immune cells. Researchers infect each organoid with COVID, allowing the team to observe the virus’ direct impact on kidney cells. Once again, scientists noted kidney organoid scarring as well as “accompanied signals that contribute to the scarring process.”

These findings strongly indicate that the coronavirus itself, not inflammation or any other systemic effects, is responsible for the observed kidney damage seen in COVID-19 patients.

“In our study, we thoroughly investigated the causal damaging effects of the Coronavirus in the kidneys. The infected kidney organoids show that the virus directly causes cell damage, independent of the immune system. With this work, we found a piece of the puzzle showing the deleterious effects the virus can have in the body,” says co-researcher Jitske Jansen in a media release.

These conclusions are quite similar to the findings of another, larger American study encompassing over 90,000 COVID-19 survivors. Just like this work, that research found that reported declines in kidney functioning among COVID-19 patients is likely due to the coronavirus itself.

“Kidney fibrosis, or scarring, is a serious long-term consequence that can occur virtually after any injury to the kidney and correlates with kidney function. Our work shows kidney scarring in COVID-19 patients, which provides an explanation why the virus might cause kidney functional decline as demonstrated in other studies. Long-term follow-up studies will provide further insights into kidney-related pathologies caused by SARS-CoV-2,” concludes co-researcher Katharina Reimer.

The study is published in the journal Cell Stem Cell.

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