3D Organ

The 3D-printed liver

The tissue that turned bioprinting into a business — and the reason pharmaceutical companies, not surgeons, became the industry's first customers.

Bioprinted liver tissue is the closest thing the industry has to a commercial success story — not because anyone has printed a transplantable liver, but because printed liver tissue turned out to be worth paying for long before that. Understanding why explains how the whole field is funded.

Why the liver came first

Drug-induced liver injury is the single most common reason a drug is withdrawn from the market or fails late in development. It is also badly predicted by animal testing, because the enzymes that metabolise drugs differ substantially between species: a compound that a rat liver handles cleanly can be converted by a human liver into something toxic.

The traditional alternative — human liver cells grown flat in a dish — has a crippling limitation. Hepatocytes plated on plastic begin to lose their liver-specific functions within hours and are largely dedifferentiated within a couple of days. That is far too short a window to detect toxicity that develops over weeks of dosing.

Arrange the same cells in three dimensions, with the supporting cell types they normally live alongside, and they behave quite differently: they keep producing albumin and urea, keep expressing drug-metabolising enzymes, and stay usable for weeks. That difference is what created a market.

Organovo and exVive3D

Organovo, founded in San Diego in 2007 and built on Gabor Forgacs's work on tissue self-assembly, launched exVive3D human liver tissue in 2014 — the first bioprinted human tissue sold commercially.

The product was a small printed construct combining hepatocytes with endothelial and stellate cells, arranged to resemble native liver organisation and viable for around four weeks. Pharmaceutical companies used it for toxicity screening, and it demonstrated something the field badly needed: that bioprinted tissue could be manufactured reproducibly enough to sell to demanding customers.

Organovo later restructured significantly and moved away from the tissue-services business, which is a useful reminder that scientific firsts and commercial durability are different things. The precedent, though, stood.

What has happened since

Printed and engineered liver tissue has become considerably more sophisticated:

  • Perfusable constructs. Printed vascular channels allow medium to flow through the tissue rather than around it, extending viable thickness and lifespan.
  • Patient-derived models. Hepatocytes differentiated from a specific patient's iPS cells make it possible to ask whether this person will metabolise a drug safely — the beginning of genuinely personalised toxicology.
  • Disease models. Printed constructs that reproduce fatty liver disease and fibrosis give a human platform for conditions that are common, poorly treated and hard to model in animals.
  • Liver-on-chip integration. Combining printed tissue with microfluidics produces systems where a compound passes through printed gut tissue, then liver, then heart, closer to what happens in a body.

The FDA Modernization Act 2.0, signed in December 2022, removed the blanket statutory requirement for animal testing before human trials and explicitly acknowledged cell-based and organ-chip alternatives. That does not mandate bioprinted tissue, but it removes a structural barrier to its adoption.

A printed liver for transplant

This is a different problem by orders of magnitude.

An adult human liver weighs around 1.5 kilograms and contains on the order of hundreds of billions of cells. It performs something in the region of 500 distinct functions — protein synthesis, bile production, detoxification, glycogen storage, immune functions — simultaneously. It has a dual blood supply, receiving both oxygenated arterial blood and nutrient-rich portal blood from the gut, and a separate biliary drainage tree.

Its microarchitecture is also a strict requirement rather than a nicety: hepatocytes are arranged in plates one or two cells thick, between vascular sinusoids, with different metabolic jobs assigned by position along the oxygen gradient from the portal triad to the central vein. Reproducing that zonation across an entire organ is not something any current method can do.

There is one consolation. The liver has genuine regenerative capacity — a healthy liver can regrow after substantial resection, which is what makes living-donor transplantation possible. That raises the prospect of a printed construct that supports regeneration rather than replacing the organ.

The realistic intermediate goals

  • Liver patches. A printed sheet of hepatocytes implanted to supplement a failing liver — thin enough to survive on diffusion until host vessels grow in.
  • Extracorporeal assist devices. A bioartificial liver outside the body, through which the patient's blood is perfused, buying time until a donor organ becomes available or the native liver recovers. This is a device problem rather than an organ problem, and it is much closer.
  • Recellularised scaffolds. A decellularised donor or pig liver, retaining its complete vascular and biliary architecture, reseeded with the recipient's cells.
  • Better drug testing. Unglamorous, already working, and preventing harm today.

Related

Last reviewed . Educational information only — not medical advice.