27 december 2021 – 20:23
Scar tissue in the kidneys can lead to reduced kidney function
The coronavirus SARS-CoV-2 infects the kidneys and causes scar tissue, researchers from Radboudumc and RWTH Uniklinik Aachen in Germany show. The infection creates scar tissue in the kidney with a potential long-term adverse effect on the kidney function of ex-COVID patients.
It is already known that the coronavirus can cause considerable damage in the body and that the kidneys are also a victim of the virus. But we do not yet know exactly what happens in the kidneys and how much damage is caused. In this study, published in Cell Stem Cell, the researchers looked at the kidney tissue of deceased COVID-19 patients admitted to intensive care. The tissue contained a lot of scar tissue, more than in patients with a non-COVID respiratory infection in the ICU or in a healthy control group. Scar tissue can lead to reduced kidney function, and in the worst case, severe kidney failure.
Mini kidneys from the lab
The researchers’ follow-up question: what causes the kidney damage? Is that due to the virus itself, or to a violent inflammatory response of the immune system? For more insight, the researchers grew tiny mini kidneys in the lab, kidney organoids. These cultured kidney organoids come from stem cells and contain many different types of kidney cells, but no immune cells. They infected the kidney organoids with SARS-CoV-2. In these mini-kidneys, the researchers examined the direct effects of the virus on the kidney cells, so independent of any effects by the immune system, such as an overreaction. Here too, as with the patients’ kidney tissue, the researchers saw more scar tissue and signals that lead to the development of scar tissue.
This scar tissue is caused by virus particles that enter the kidney cell during an infection. They use the cell as a factory for the production of new virus particles, with the machinery present in the cell. This causes great stress for the cell, because it disrupts normal biochemical processes. An inflammatory reaction also develops in the tissue. This leads to the production of connective tissue and collagen. This creates scar tissue in the kidneys and in the kidney organoids.
Reduced kidney function due to the coronavirus
The findings of the Dutch and German researchers are in line with the results of a large American study, in which the researchers saw that kidney function decreases due to an infection with the coronavirus (Bowe et al, JASN). People who contracted a corona infection with mild symptoms had a 15 percent higher risk of developing serious kidney problems than people who were not affected by the virus. As a result, patients may end up on dialysis.
Lead researcher Jitske Jansen of Radboudumc: “With this research, we have looked in depth at the cause of kidney damage caused by a COVID infection. The infected kidney organoids show that the damage is done by the virus itself, not just an overreaction of the immune system. This provides us with a new piece of the puzzle that shows what direct damage the coronavirus can cause in the body.”