Researchers at the Wyss Institute, Boston University and MIT have demonstrated a method to grow functional liver tissue inside living mice by reprogramming implanted constructs to expand on demand after engraftment.
The approach, called BOOST—bioengineered on-demand outgrowth via synthetic biology triggering—rewires gene expression in primary hepatocytes and supportive fibroblasts to activate a controlled growth program only after the tissue is implanted. This allows a minor, lab-built liver nodule to proliferate in vivo, potentially alleviating metabolic strain in a failing native liver while a patient awaits transplant.
End-stage liver disease affects an estimated 9,000 to 10,000 people on the U.S. Transplant waiting list at any time, with roughly one in five becoming too ill to receive an organ or dying while waiting. The liver’s renowned regenerative capacity is overwhelmed at this stage, making donor organs the sole lifeline—a resource chronically outstripped by demand.
Previous attempts to engineer full-scale liver organs outside the body have hit a size ceiling, preventing constructs from achieving therapeutic mass. Rather than pursuing larger ex vivo grafts, the team led by Christopher Chen and Sangeeta Bhatia flipped the logic: implant a minimal functional unit and let the body itself drive expansion.
“We asked if it would be possible to first implant a small-scale liver construct and then drive it to expand in the body following its engraftment,” Chen said. “A sufficiently grown, functional ‘satellite liver’ could immediately relieve the metabolic burden in a damaged liver and help bridge the time until a transplant becomes available.”
For more on this story, see Growing Liver Tissue On Demand Inside the Body.
The strategy builds on the team’s prior work in vascularized liver tissue engineering and nanoscale drug delivery, combining Chen’s expertise in cellular engineering with Bhatia’s background in biomedical technologies. Amy Stoddard, who conceived the approach during her doctoral research at MIT and refined it as a postdoctoral fellow, led the integration of synthetic biology circuits with tissue scaffolds.
In mouse models, the reprogrammed constructs engrafted successfully and initiated measurable proliferation only after implantation, confirming the on-demand switch functioned as designed. No uncontrolled growth or tumor formation was observed in the study period, a critical safety checkpoint for future translation.
While the proof-of-concept remains in early preclinical stages, the method addresses a core bottleneck in regenerative medicine: how to scale engineered tissues without losing control over growth dynamics. If replicated in larger animals and eventually humans, such satellite livers could reduce waitlist mortality by extending the window for transplant eligibility.
The work is supported by the ARPA-H PRINT-funded ImPLANT project, which aims to engineer whole implantable organs through parallel advances in bioprinting, cell sourcing, and now, in vivo amplification techniques.
How does the BOOST system prevent uncontrolled tissue growth after implantation?
The BOOST system uses synthetic biology to rewire gene expression so that the growth program is only activated after implantation and specific endogenous triggers are present, ensuring proliferation is contingent on the in vivo environment and not autonomous.
What is the primary goal of creating a ‘satellite liver’ using this method?
The primary goal is to alleviate the metabolic burden of a failing native liver by growing implanted tissue to functional size inside the body, thereby stabilizing patients long enough to receive a donor transplant.