In June 2024, surgeons at the University Medical Center Göttingen carefully sutured a patch of lab-grown heart muscle onto Steffen Eyring's scarred and weakened heart—a moment that represented a quiet revolution in treating one of the world's most devastating conditions. Four years earlier, a severe heart attack had nearly killed the 58-year-old German, leaving him with a pumping capacity of just 18 to 20 percent. He could barely walk without stopping to catch his breath. But when he and his wife Ina saw a television report about an experimental study using laboratory-grown tissue to repair damaged hearts, they saw something else: a lifeline.
The breakthrough that gave Eyring hope has now been published in the New England Journal of Medicine. Researchers at the University Medical Center Göttingen and the University Hospital of Schleswig-Holstein have become the first to demonstrate in a clinical trial that heart muscle tissue grown in the laboratory can actually improve the pumping function of severely failing hearts—a discovery that addresses a problem affecting millions worldwide. According to the German Heart Foundation, approximately four million people in Germany alone live with heart failure, a condition that develops when scar tissue replaces damaged muscle after a heart attack.
The innovation lies in how the tissue is created. Under the scientific direction of Prof. Dr. Wolfram-Hubertus Zimmermann at UMG, the team uses induced pluripotent stem cells (iPS cells) produced from blood cells in the laboratory. These are then differentiated into cardiac muscle and connective tissue cells, combined with collagen as a natural scaffold, and coaxed into beating heart tissue. Up to 20 such tissue units are assembled into a heart patch measuring approximately three to four millimeters thick. The entire process takes place in specially designed clean rooms at UMG under the supervision of the Department of Transfusion Medicine.
What makes this approach so significant is that it addresses a fundamental limitation of current medicine. "The treatments available today can often slow the progression of the disease, but they cannot replace damaged heart muscle," explains Prof. Zimmermann. "Our goal is therefore to generate new, functional heart muscle tissue to provide targeted support to the weakened heart." Until now, severe heart failure patients like Eyring have faced grim options: heart transplants, which depend on scarce donor organs, or mechanical cardiac assist devices that come with their own risks and lifestyle restrictions.
The surgery itself is elegant in its simplicity. Surgeons use a minimally invasive approach to suture the cultured tissue patch onto the outside of the damaged heart, where it forms a new layer of functional muscle designed to stabilize and support the weakened organ. For Eyring, the procedure was conducted as part of the BioVAT-HF-DZHK20 study, a joint collaboration between institutions that is part of a broader German Center for Cardiovascular Research (DZHK) program.
The impact extends far beyond one patient's recovery. This clinical first opens a pathway for regenerative medicine in cardiology—a field that has long struggled to translate laboratory advances into real clinical benefit. Heart failure remains one of the most common serious heart conditions globally, and current treatments, despite their sophistication, cannot restore the fundamental ability of damaged muscle to contract. By demonstrating that lab-grown tissue can actually work, Eyring and other study participants have shown that the human heart may be more repairable than medicine previously dared to hope.