The National Transplant Organization of Spain makes it clear: The liver is one of the most requested organs on the transplant list, only behind the kidney. Only in the Spanish state in 2025 there were 310 people waiting and that Spain It is a world power in transplants. There are not enough donated and compatible organs to arrive in time for all those people who need them.
This historical gap that no country has managed to close is a double tragedy: for the sick person, who waits without guarantees, and for the health system, which cannot offer them another way out. Liver transplant remains the only cure for certain conditions, and the path to it is full of obstacles: surgical complexity, compatibility problems, the exclusion of patients too fragile for surgery or lifelong immunosuppression. Even when an organ arrives on time, not everyone can receive it. Until now, there was no alternative. That could be about to change.
The invention. An MIT research team led by Sangeeta Bhatia has developed “satellite livers”, a type of mini-livers capable of assuming the functions of the diseased liver without having to remove it. One is inside, its cells form a stable structure, connect to the person’s blood vessels and begin to produce proteins that the damaged liver can no longer make. They do not replace the entire organ, but they relieve it of its functions. They are actually small grafts of functional liver tissue that are administered via a syringe guided by ultrasound, that is, without surgery: minimal invasibility.
Why is it important. Because it addresses the two big problems for those who need a liver: the shortage of available organs and those who cannot face a transplant operation. If you can have surgery, they act as a bridge until they find a suitable organ. And if you can’t, these mini livers cover the liver functions that your liver can’t do. In this way, satellite livers increase the spectrum of treatable patients.
From a more general point of view, this invention is a milestone in liver tissue engineering: science has been trying to replicate the nearly 500 functions performed by the human liver for more than a decade. And if implemented in the different health systems, its impact is direct: according to the American Association for the Study of Liver Diseases (AASLD)chronic liver disease is the 12th leading cause of death in the United States and rising.
Context. Although the liver is an organ with a remarkable regenerative capacity, it does not work miracles: when it exceeds a certain threshold of damage, regeneration is not enough and only the transplant remains. Since the 90s, medical science has been trying to transplant isolated hepatocytes, but the results were poor. Bhatia is not new to this either: has been there for more than 25 years investigating bioartificial liver models, which has served as a basis for understanding what conditions hepatocytes need to remain functional outside the liver. This MIT work is precisely the practical application of all this knowledge.
How it works. The research team developed the idea of turning these cells into an injectable along with hydrogel microspheres and fibroblasts. The spheres are intended to enable this route of administration by ensuring uniformity. Fibroblasts act as a support, helping hepatocytes survive and promoting the growth of new vessels into the tissue.
Without blood supply, those cells would have their hours numbered. In the team’s experiments in mice, new vessels formed next to hepatocytes, allowing them to receive nutrients and function normally. In these rodents, the cells remained viable and secreting proteins during the eight weeks of the study.
Yes, but. Although the results are tremendously promising, it is a preclinical study done in mice and the leap to humans is enormous. The human liver contains between 100,000 and 130,000 million hepatocytes and replicating a sufficient functional mass with injected cells is a challenge that this study has not yet addressed. Even assuming that we extrapolate this finding as is to humans, immunosuppressants would still need to be used. And it is not a minor problem: the fact that the immune system attacks weakened patients increases the risk of infections, tumors and kidney damage.
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Cover | Elen Sher and Magnificent
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