Can’t keep waiting on the transplant list? How about an injectable “satellite liver” instead? After an MIT research project showed early success, the idea of a mini organ that could be injected into the body to take over for a failing liver doesn’t sound so far-fetched.

Okay, this early success was in mice, but after eight weeks of watching liver cells suspended in a lattice of hydrogel microspheres, assembled using ultrasound-guided needles within the mice's abdomens, integrate and support liver function, the success is pretty substantial.

The point of such an experiment was to find a way to restore the function of hepatocytes, which are the specific functional cells of the liver that do all of its important things like filtering the blood, synthesizing and storing protein, and transforming carbohydrates, without the need for full-on surgery. 

In this case, the researchers used what they call Injected, Self-assembled, Image-guided Tissue Ensembles (INSITE), a mixture of hepatocytes and hydrogel microspheres that assemble in place after injection to form supportive scaffolds. The material can flow during injection and is delivered using ultrasound guidance to precisely place the graft.

The hepatocytes are mixed with the microspheres before injection, and over time blood vessels grow into the graft, integrating the cells with the host’s circulation and enabling them to carry out key liver functions. The injected cells, and the microsphere structure, kept on working for the entire eight-week run of the test. 

MIT postdoc and lead author Vardhman Kumar told MIT News that the big breakthrough of the project was the INSITE hydrogel structures, which formed the perfect environment for ensuring that nearby blood vessels could supply nutrients to the hepatocytes and keep them viable.

"What we did is use this technology to create an engineered niche for cell transplantation," Kumar told the publication. "If the cells are injected in the absence of these spheres, they would not integrate efficiently with the host, but these microspheres provide the hepatocytes with a niche where they can stay localized and become connected to the host circulation much faster."

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The success in mice, the team said in the paper, paves the way for the same hydrogel microsphere concept to be tested on humans at human scales, and potentially for "other cell therapies that face similar barriers" as liver transplants. That will require future work, and it's not clear if any is planned right now. We didn't hear back from the researchers about their plans. 

Nonetheless, the team appears to have hope that the technology they've developed could serve as a replacement for open organ transplant surgery, if not permanently, then at least as a way to ease the burden on the already stressed transplant system. 

"Injectable, self-assembling niches represent a significant step toward regenerative treatments that are more scalable and accessible to patients who may not receive a donor organ," the researchers explained. 

As for when such technology might reach human trials, much less the market, that's an open question. ®