Little livers
Transplanted hepatic progenitor cells can self-renew (yellow) and differentiate into hepatocytes (green) to repair the damaged liver (Image: Wei-Yu Lu, MRC Centre for Regenerative Medicine, The University of Edinburgh’)
The MRC Centre for Regenerative Medicine researchers used liver stem cells, called hepatic progenitor cells, to regrow damaged livers in mice. After extracting the stem cells from healthy adult mice and maturing them in the lab, the researchers transplanted the cells into mice with liver failure.
In three months the cells had grown enough to partly restore the structure and function of the animals’ livers, providing hope that this technique could one day replace the need for liver transplants in humans. [1]
Itty-bitty intestines
In a study at the Cincinnati Children’s Hospital Medical Center, researchers used induced pluripotent stem cells to grow human intestinal tissue in the lab. They then connected the tissue to the kidney of a mouse, providing it with a blood supply to allow it to mature into a piece of human intestine. This technique could provide a useful way of studying and ultimately treating gastrointestinal diseases in the future. [3] Other work involving organoid intestines has been pioneered by EuroStemCell partner Hans Clevers.
Compact kidneys
Working lab-grown kidneys have been transplanted into rats by researchers from the Center for Regenerative Medicine in the US. The team stripped down a rat kidney to a scaffold-like structure, before introducing rat kidney and blood vessel cells that grew into a new functioning kidney. They then transplanted the organ into rats where it successfully filtered blood and produced urine. [4]
Small skin
An MRC-funded team led by King’s College London and the San Francisco Veteran Affairs Medical Center has grown a 3D piece of skin in the lab. Using induced pluripotent stem cells, they produced an unlimited supply of skin cells, some of which were then used to grow a small piece of skin. The lab-grown skin has a working natural barrier that protects it from losing moisture, and prevents it from absorbing chemicals and toxins. This makes it particularly useful for studying a range of skin conditions, and for testing drugs and cosmetics. [5]
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| Thymus cells (dark blue) against a background of kidney cells (pink) (Image: MRC Centre for Regenerative Medicine, the University of Edinburgh) |
Tiny thymi
The thymus is an immune system organ which sits just in front the heart. Another group of researchers at the MRC Centre for Regenerative Medicine have reprogrammed mouse cells called fibroblasts, which normally become connective tissue, to instead become thymus cells. When mixed with other thymus cell types and transplanted into mice, the cells grew into a functioning mouse thymus. [2]
Teeny tickers
Miniature human hearts have been grown in the lab using a mouse heart ‘scaffold’. Researchers from the University of Pittsburgh removed all the cells from a mouse heart, leaving a skeleton-like structure, before reintroducing immature human heart cells. After just a few weeks the cells developed into beating heart tissue [6].
Small-scale stomachs
Three-dimensional human gastric tissue has been grown by a team at the Cincinnati Children’s Hospital Medical Center using human pluripotent stem cells that were coaxed into becoming stomach cells. The structures are only three millimetres in diameter, but could turn out to be useful disease models for understanding how the stomach develops and is affected by different diseases. Plans are already underway to use these tiny organs for studying how the bacterium, H. pylori, causes stomach ulcers and gastric disease. [7]
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| A cross-section of a cerebral organoid (Image copyright: IMBA/ Madeline A. Lancaster) |
Bijou brains
A team of scientists from the Institute of Molecular Biotechnology in Austria, in collaboration with scientists at the MRC Human Genetics Unit at the University of Edinburgh, has grown miniature brain-like ‘organoids’ with distinct brain regions, including a cerebral cortex and retina.
The team used human embryonic and human induced pluripotent stem cells that were provided with the oxygen and nutrients needed to mature into brain organoids. No one’s going to be growing brains – or even parts of brains for transplant – but the work will help us to understand the brain and any diseases and disorders that affect it: already, the team has grown organoids with a disorder called microcephaly.