NAGOYA, JAPAN — Researchers successfully grew kidneys in rats by implanting stem cells from mice, according to the journal Nature Communications.

Researchers selected rat embryos that were genetically modified to not develop kidneys and injected them with stem cells from mice.

These embryos were then implanted into the womb of rats that would carry the pregnancy to term. The rats successfully grew kidneys.

However, genetically modifying their genes to not grow their own kidneys caused them to lose their sense of smell. Due to this alteration, they did not suckle properly and died shortly after birth. This made it hard for scientists to study the effectiveness of the kidneys they developed.

Another concern is that growing organs from another species would eventually lead to organ contamination in the cells of the host."

This technology could eventually lead to growing human organs in other animals.

However, the paper's research supervisor Masumi Hirabayashi stated that this poses a larger ethical concern. This is because injecting human stem cells into animals could cause them to develop consciousness and reproductive cells.