The technique could mean transplant organs can be created on demand Miromatrix

Will we ever be able to grow transplant organs like the heart, lungs and liver on demand? A method that uses pig organs as scaffolding for creating new organs suggests it may be possible.

In an effort to tackle lengthy waiting lists for organ transplants, researchers have been trying several approaches for creating replacement organs. One approach is to grow organs in the lab from stem cells. Another would be to take organs from pigs that have been genetically altered so their cells are more human-like, and less likely to be attacked by a person’s immune system.

Now an in-between method is taking off. The approach starts with an organ from an ordinary pig, but involves dissolving the cells away from it to leave a protein scaffold in the original shape of the organ. This is then reinfused with human cells.


Until now this technique – dubbed “decel/recel” – has been mainly investigated for small or thin structures such as layers of skin because it is hard to dissolve away the inside a large organ. But a new technique is now making that possible, leading a US biotech firm called Miromatrix to announce this month that it has successfully created livers this way.

Protein scaffold

So far, the team at Miromatrix has only created new whole livers with pig cells rather than human cells. But this first step means the livers can be tested as transplant organs in pigs without the risk of them being rejected by the animals’ immune systems.

They managed to decellularise whole livers by pumping detergent through the blood vessel network of the organ, so it reaches everywhere. This removes every living cell, leaving behind only the structural proteins that held the organ in shape. With a pig liver, this process takes 24 hours.

The liver scaffold is then reinfused with new cells, pumped through the same blood vessel network. The three main types of cell within a liver – liver cells, blood vessel wall, and bile duct cells – automatically home in on their right places within the scaffold, says Jeff Ross, of Miromatrix. “It takes tissue engineering from a single layer to whole organs,” he says.

Ross and his colleagues have begun to try doing this with human cells. In a first step, the team pumped cells from human umbilical cords into the protein scaffolding, where they re-made the blood vessels of the liver. When these scaffolds with blood vessels were implanted into pigs, the vessels survived and allowed blood to flow throughout the scaffold, before they were then rejected by the pigs’ immune systems. These results were presented at a meeting of the American Association for the Study of Liver Diseases in Washington DC this month.

Transplant hope

Ross says his team is now working on reinfusing liver scaffolds with human liver and bile duct cells, and plans to implant these into pigs by the end of this year. They hope to have livers made entirely from human cells that could be transplanted into people within three years by using liver cells from donated organs that are not in quite good enough shape to transplant into a patient as they are.

Laura Niklason of Yale University, who is using the decel/recel method to make blood vessels and lungs says the real test will be to see how well the livers work. “The decellularisation and repopulation is not the tricky part – the tricky part is getting all the cells you put back in to behave properly.”

The organ transplant field has suffered setbacks recently, including a scandal over trachea replacements at the Karolinska Institute in Stockholm, Sweden, where surgeon Paolo Macchiarini was found to have put them into patients without enough safety testing. In several of the procedures the patient later died or their trachea failed.