"Scientists 3D print a heart" is a headline that has run, in some form, almost every year since 2019. The underlying work is usually real and usually impressive. What gets lost is the distance between a laboratory result and something a surgeon could implant. This page keeps that distance in view.
The one-line answer
No solid internal organ has ever been 3D-printed and transplanted into a human. Simpler printed tissues have — skin, cartilage, bone and, in 2022, an ear. Everything below is sorted by how far it actually travelled.
How to read the status labels
| Label | What it means |
|---|---|
| In patients | Implanted in at least one human, in a trial or in care. |
| Pre-clinical | Works in animals, or is sold as a laboratory product. Not yet implanted in people. |
| Research | Demonstrated in the laboratory. Years from any patient. |
Skin — in patients
The most clinically advanced bioprinted tissue, for a structural reason: skin is thin and layered, so no cell in it sits far from a nutrient source. That removes the vascularisation problem that blocks everything else.
Printed skin constructs combine keratinocytes and fibroblasts in a collagen or fibrin matrix. Two approaches exist. Grafts can be printed in the laboratory and applied like a conventional dressing, or printed in situ — a mobile printer scans a wound and deposits the patient's own cells directly onto it, a technique developed at the Wake Forest Institute for Regenerative Medicine and taken into early human testing.
Cosmetics, not medicine, paid for much of this. The EU banned animal testing for cosmetics in 2013, and companies including L'Oréal invested heavily in engineered human skin as a replacement test system.
Full article on 3D-printed skin →
Ear and cartilage — in patients
Cartilage is the ideal bioprinting target: avascular by nature, so it needs no printed blood supply, and structurally simple.
In June 2022 the US company 3DBio Therapeutics announced that a patient with microtia had received AuriNovo, an ear implant 3D-printed from her own cartilage cells and shaped to mirror her opposite ear. It is the clearest example to date of a printed, cell-containing implant placed in a human as part of a regulated clinical trial.
Earlier work made it possible. In 2016 Anthony Atala's group at Wake Forest published the Integrated Tissue and Organ Printing system in Nature Biotechnology, printing human-scale ear, bone and muscle constructs with microchannels for nutrient diffusion and implanting them successfully in animals.
Bone — in patients
Patient-specific bone implants are the least exotic and most widely used part of this field. Printed from titanium or from resorbable polymers such as PCL, often combined with calcium-phosphate ceramics, they are shaped from the patient's own CT scan to fit a defect exactly.
Tissue Regeneration Systems and others have brought resorbable patient-specific implants through regulatory clearance: the scaffold holds the space and provides mechanical support while the patient's own bone grows into it, then gradually disappears. Cranio-maxillofacial reconstruction is the most common application.
Cornea — pre-clinical
A thin, transparent, avascular disc — on paper, almost purpose-built for bioprinting. In 2018 a team at Newcastle University led by Che Connon reported printing a human corneal stroma in under ten minutes using a bioink of alginate, collagen and corneal stromal stem cells.
Millions of people are blind from corneal damage and donor tissue is scarce, so the incentive is large. Several groups and companies, including Precise Bio and Pandorum Technologies, are pursuing printed corneal tissue towards clinical use. The remaining challenges are optical clarity that lasts, correct curvature, and mechanical strength that survives suturing.
Blood vessels and trachea — pre-clinical
Tubes are a natural fit for printing. Small-diameter vascular grafts are a genuine clinical need, because synthetic grafts below about six millimetres in diameter tend to clot. Printed and tissue-engineered vessels seeded with the patient's own endothelial cells are in advanced development.
Printed tracheal splints have already been used under compassionate-use provisions: at the University of Michigan, resorbable printed splints were placed in infants with tracheobronchomalacia, holding the airway open while it grew and then dissolving. This is scaffold printing rather than cell printing, but it is one of the clearest cases of a printed device saving lives.
Liver — pre-clinical
Bioprinted liver tissue was the industry's first product. Organovo's exVive3D human liver tissue, launched in 2014, gave pharmaceutical companies human hepatocytes arranged in three dimensions that stayed metabolically active for weeks rather than the hours typical of flat culture — long enough to detect the slow-onset toxicity that flat culture misses.
A printed liver for transplant is a different proposition entirely. The liver performs hundreds of distinct metabolic functions and is one of the most densely vascularised organs in the body. Realistic near-term targets are patches to support a failing liver and extracorporeal assist devices, not replacement.
Full article on the 3D-printed liver →
Heart — research
Two milestones define public perception. In April 2019 Tal Dvir's group at Tel Aviv University printed a small, vascularised heart from a patient's own cells combined with a personalised dECM bioink — roughly the size of a cherry, with chambers and vessels, and cells that contracted, though it could not pump as an organ. Later that year Adam Feinberg's laboratory used FRESH printing to produce a full-size collagen heart scaffold, anatomically accurate but without cells.
Between them the two results are a fair summary of the field: living tissue at small scale, or correct anatomy at full scale, but not both. The nearer-term clinical target is a bioprinted cardiac patch to support muscle damaged by a heart attack.
Full article on the 3D-printed heart →
Kidney — research
The organ with the longest transplant waiting list is also the hardest to build. A kidney contains roughly a million nephrons, each a precisely arranged filtration unit, served by an extraordinarily dense vascular bed.
Progress has come mainly through organoids. Melissa Little's group in Melbourne developed methods to grow kidney organoids from stem cells and then to bioprint them at scale with reproducible cell numbers — work that matters enormously for drug screening and disease modelling, and only indirectly for transplantation.
Full article on the 3D-printed kidney →
Pancreas and islets — research
Type 1 diabetes is an unusually tractable target, because the job is not to rebuild an organ but to deliver working insulin-producing beta cells and protect them from the immune system. Printed constructs that encapsulate islets in a protective, permeable matrix have restored normal blood glucose in diabetic animals. Immune protection and long-term islet survival remain the obstacles.
Ovary — research
In 2017 a team at Northwestern University led by Teresa Woodruff and Ramille Shah reported a 3D-printed gelatin scaffold seeded with ovarian follicles. Implanted into mice whose ovaries had been removed, it restored hormone cycles, and the mice went on to give birth to healthy pups. The eventual aim is fertility restoration for people whose ovarian function was destroyed by cancer treatment.
Lung — research
A lung has around 300 million alveoli and a gas-exchange surface of tens of square metres, across membranes less than a micrometre thick. It is arguably the least printable organ in the body.
The most striking result remains the 2019 Science paper from Jordan Miller's and Kelly Stevens' groups, which printed a hydrogel air sac with an entangled surrounding vessel network and showed it could oxygenate human red blood cells while a nearby channel "breathed". It is a proof of principle about printed architecture, not a lung.
Nerve, muscle and other tissues — research
Printed nerve guidance conduits — tubes that direct regrowing axons across a gap — have restored some function in animal models of nerve injury. Skeletal muscle constructs with aligned fibres contract on electrical stimulation. Meniscus, tendon, intervertebral disc and periodontal tissue all have active printed programmes. None is close to routine clinical use, but all are considerably simpler than a solid organ.
Why the pattern is so consistent
Look down the list and one variable predicts everything: thickness.
Tissues that are thin or avascular — skin, cartilage, cornea — have reached patients. Tissues that are tubular — vessels, trachea — are close behind, because a tube is essentially a rolled-up sheet. Solid organs, where every cell must sit within about 200 micrometres of a capillary, are all stuck at the research stage, and they are stuck for the same reason.
Printer resolution is not the bottleneck. Blood supply is. The vascularisation problem explains why in more detail.
Organ by organ
- HeartThe Tel Aviv heart and FRESH scaffolds
- KidneyOrganoids and a million nephrons
- LiverThe industry's first product
- SkinGrafts and in-situ printing
- TimelineEvery milestone, dated
- Why it mattersThe transplant shortage in numbers
Last reviewed . Educational information only — not medical advice.