Scientists used human stem cells to create precursors to human livers like those in fetuses, and the early organs functioned as livers when transplanted into mice.
These buds didn’t grow into regular livers and any treatment for humans is at least a decade away, according to the research published in the journal Nature. Still, the study demonstrated the first steps toward potentially creating new organs for transplants, researchers said.
Demand for organ transplant outpaces the number of donors, with more than 118,000 Americans waiting for a life-saving transplant, according to the U.S. Department of Health and Human Services. An average of 18 people die each day waiting for an organ transplant. Stem cells, which can grow into any other type of cell, have long held the promise of bridging this gap.
“The study holds out real promise for a viable alternative approach to human organ transplants,” said Matthew Smalley, a senior lecturer at Cardiff University’s European Cancer Stem Cell Research Institute who wasn’t involved in the study.
Japanese scientists, mostly from Yokohama City University, planted the liver buds on the heads and abdomens of mice, according to the paper released yesterday. The heads allowed for a better view of how the liver buds grew blood vessels to feed themselves. The buds processed some drugs and compounds that human livers can handle but mouse livers cannot. However, their function wasn’t as good as that of a regular liver.
In April, Harvard scientists rebuilt rat kidneys that successfully filtered blood and allowed the animals to urinate, according to a previous report in Nature Medicine. Unlike this technique, those Harvard researchers used donor organs to create a scaffolding where new cells could grow. That allowed for direct transplant, and the lab kidneys held their shape.
The liver buds were created using induced pluripotent stem cells, or skin cells that were tricked into becoming stem cells that, like embryonic ones, can grow into any type of tissue. When they were mixed with other cell types, including those that are liver progenitors, they formed the liver buds.
The researchers didn’t see signs of tumor formation, a danger when working with stem cells. Stem cells are known to carry a risk of non-cancerous tumors called teratomas, which contain a mixture of different kinds of cells. In studies with animals whose immune systems are suppressed, injected human embryonic stem cells cause these tumors, which can create pressure on sensitive organs such as the spine.
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