The tree · Replacing lost cells and parts
Heart muscle grown from stem cells is grafted onto a person's failing heart
A heart that has lost muscle to a heart attack does not grow it back, and heart failure is among the commonest ways an old person dies. A Göttingen group grows sheets of beating heart muscle from stem cells and sews them onto the outside of the heart. In 2025 they reported that in monkeys the patches took, grew blood vessels and strengthened the heart's pumping, and that in a 46-year-old woman with heart failure, given ten patches in 2021 while she waited for a donor heart, the patches were alive and vascularised when her old heart was removed three months later. That small trial in people, with no comparison group, reported in the New England Journal of Medicine on 2026-05-27: of 20 people given the patches, three died during the study and one had a heart transplant; among 12 given the highest dose who had reached the 3-month interim check, the heart's pumping (ejection fraction) was 3.9 percentage points higher and the treated wall 4.5 mm thicker. The 2025 case remains the first grafted human heart muscle found alive in a person.
What would count
Heart muscle grown from stem cells is grafted onto a person's failing heart and is afterwards found alive and supplied with blood there, or the heart's pumping measurably improves, in a peer-reviewed report. The animal rung is the same in a living animal with improved pumping. For the clinic rung: a regulator approves such a graft for heart failure.
Who settles it: The peer-reviewed report; the trial registry; the regulator's approval record for the clinic rung.
Where it stands
First human. Reached 29 January 2025, on the record of doi.org. Next rung within 5 to 20 years.
When it reaches the clinic: the project's estimate
This is the one thing on this page that is a judgment rather than a record. The project's estimate of the year it reaches the clinic is 2038, no earlier than 2031 and no later than 2070; the model draws from that range every run, with the likely year the most probable draw. Set 16 October 2026, a first pass awaiting an outside review.
| Rung | No earlier than | Most likely | No later than | |
|---|---|---|---|---|
| In clinical use | 2031 | 2038 | 2070 | feeds the year at the top |
Why. A small trial with no comparison group was running in 2026, with the heart's pumping among its main measures; the likely year assumes it reports positive around 2030 and a larger trial carries the graft to approval in the late 2030s. The earliest assumes a conditional approval in Europe or Japan on the first trial; the latest allows for the grafts not improving pumping enough to matter, which the monkey data suggest but do not prove in people. [Note 2026-10-17, from the weekly reading of that date: the reasoning above assumes the small trial reports around 2030. It reported an interim analysis on 2026-05-27 (zimmermann-2026): pumping and wall thickness were higher at 3 months in the highest-dose group, with three deaths among 20 people and every patient having at least one adverse event. The years are unchanged; John may want to weigh at the next review whether the reporting year in the reasoning (and so the earliest, 2031) should move earlier, and what the deaths and the need for rejection drugs mean for the latest year.]
Changes to this record
- 17 October 2026, description: later. A small trial in people, with no comparison group, was under way. It is the first grafted human heart muscle found alive in a person. became later. That small trial in people, with no comparison group, reported in the New England Journal of Medicine on 2026-05-27: of 20 people given the patches, three died during the study and one had a heart transplant; among 12 given the highest dose who had reached the 3-month interim check, the heart's pumping (ejection fraction) was 3.9 percentage points higher and the treated wall 4.5 mm thicker. The 2025 case remains the first grafted human heart muscle found alive in a person.. [reading 2026-10-17] The description said the trial was under way; it reported on 2026-05-27. The entry was already at first human on the 2025 case, so the stage does not move, and the new paper is an interim, uncontrolled report, not an approval. Source: Zimmermann and 7 others, 27 May 2026.
- 17 October 2026, estimate.why: (nothing; a dated note added at the end of the reasoning; no year changed) became [Note 2026-10-17, from the weekly reading of that date: the reasoning above assumes the small trial reports around 2030. It reported an interim analysis on 2026-05-27 (zimmermann-2026): pumping and wall thickness were higher at 3 months in the highest-dose group, with three deaths among 20 people and every patient having at least one adverse event. The years are unchanged; John may want to weigh at the next review whether the reporting year in the reasoning (and so the earliest, 2031) should move earlier, and what the deaths and the need for rejection drugs mean for the latest year.]. [reading 2026-10-17] A dated note that the estimate's premise about when the first trial reports has been overtaken; no year changed. Source: Zimmermann and 7 others, 27 May 2026.
The last readings
- 17 October 2026 Left for the author
Nothing dated in the window, but the record is behind: the Göttingen trial it describes as under way (BioVAT-HF-DZHK20) was reported in the New England Journal of Medicine on 2026-05-28, per the University Medical Centre Göttingen, the German Centre for Cardiovascular Research and the sponsor Repairon's releases seen in search results. Twenty patients with advanced heart failure were enrolled, sixteen got the full dose, and among those the left ventricle's ejection fraction rose by 3.9 percentage points and the treated wall thickened by 4.5 mm, with three deaths during the trial and one heart transplant; follow-up ranged from 6 to 52 months. This does not meet the next rung (a regulator's approval), so it is not a move, but the leaf's description and estimate were written as if the trial had not reported. Left for the author, resolved on 17 October 2026: I would rewrite the description's last sentences (the small trial has reported: pumping improved by a few percentage points of ejection fraction in sixteen patients at full dose, with three deaths) and the estimate's why line, which assumes the trial reports positive around 2030; I would also log the 2026-05-28 NEJM paper in the publications log and consider it as the stage record for the first-human rung, since it reports the heart's pumping measurably improving, which the test names, in a larger group than the single 2025 case. The stage itself stays first-human. It is the author's call because it corrects an entry written on 2026-10-16, changes an estimate, and I could not open the paper's own page to check its title, authors or DOI. To log in the publications log once its page has been read, as the reading's rule asks: Stem-Cell-Derived Biologic Ventricular Assist Tissue in Heart Failure (New England Journal of Medicine (2026), 2026-05-28; https://dzhk.de/en/newsroom/news/paper-of-the-month/article/engineered-heart-muscle-allografts-for-cardiac-repair-in-ischemic-heart-failure).source 1, source 2, source 3, source 4, source 5
What the story so far says about it
On the record
Notes
The animal rung is settled by the same 2025 paper (rhesus monkeys), so no separate earlier stage is recorded. The patches are made from a donor stem cell line, not the patient's own cells, and need anti-rejection drugs; a version from the patient's own cells is the next step and is not yet in people.
Not yet verified
These facts in the record were written from memory or from a secondary source and have not yet been checked against the paper, the regulator's record or the registry. Nothing here is presented as settled until it is cleared, by checking it and either deleting the line or correcting the record.
- The patient details in the description (a 46-year-old woman, grafts in 2021) are from secondary coverage; the paper itself gives ten patches holding about 400 million cells in all and a donor heart three months later, but not her age, sex or the year.