Editor’s Note (September 2026): This article was originally published in July 2020 and reflects the research available at that time. It has since been reviewed for accuracy and clarity. The description of the experimental heart pump has been clarified to distinguish it from a complete or transplantable human heart.
Key Takeaways
University of Minnesota researchers created a small 3D-bioprinted chambered heart muscle model using human induced pluripotent stem cells.
The approximately 1.5-centimeter structure developed cardiac muscle that contracted spontaneously and synchronously and demonstrated pump-like function.
The experimental structure was designed as a research model for studying heart function, disease, and potential treatments; it was not a complete or transplantable human heart.
Researchers at the University of Minnesota developed a small, functional 3D-bioprinted heart muscle pump using human cells, providing researchers with a new laboratory model for studying cardiac function and disease.
The research, published in Circulation Research, involved creating a chambered structure containing human induced pluripotent stem cells and then differentiating those cells into cardiomyocytes, the muscle cells responsible for heart contraction.
The resulting structure was able to beat and demonstrate pump-like behavior.
Why Previous Approaches Were Difficult
Scientists have long investigated ways to create functional human cardiac tissue in the laboratory.
One major challenge is achieving a sufficiently high density of cardiomyocytes. Mature heart muscle cells have a limited ability to proliferate, making it difficult to directly print enough cardiomyocytes to produce a continuous, functioning muscle structure.
The University of Minnesota researchers therefore took a different approach.
Rather than beginning by printing mature cardiomyocytes, they developed a specialized bioink containing extracellular matrix proteins and human induced pluripotent stem cells.
Researchers Print Stem Cells First
The researchers used the stem cell-containing bioink to print structures containing two chambers along with an inlet and outlet.
Instead of immediately converting the stem cells into heart muscle cells, the team first allowed the induced pluripotent stem cells to proliferate within the printed structure.
Once a sufficiently high cell density had been achieved, the researchers differentiated the cells into cardiomyocytes.
This approach allowed cardiac muscle to develop throughout the printed structure.
The resulting chambered muscle pumps demonstrated spontaneous beating and coordinated electrical activity. The researchers also reported that the structures responded to drugs and electrical pacing.
A Small Model With Potential Research Applications
The experimental heart muscle model was approximately 1.5 centimeters long and was specifically designed at that size so it could potentially fit within the abdominal cavity of a mouse for further research.
Despite its small size, the structure allowed researchers to examine pressure-volume relationships involved in heart function.
The team suggested that the model could eventually provide a useful platform for investigating how cardiac tissue responds to disease, injury, drugs, and other treatments.
Lead researcher Brenda Ogle explained that the model could allow scientists to examine changes occurring at the cellular and molecular levels and introduce disease or damage to study potential therapies.
Not a Complete 3D-Printed Human Heart
Although the research represented an important advance in cardiac tissue engineering, the structure should not be confused with a complete artificial human heart.
The researchers created a small chambered organoid composed of human cardiac muscle that demonstrated coordinated contraction and pump-like function in laboratory conditions.
It did not reproduce all of the anatomical structures or biological functions of a full human heart and was not intended for transplantation into patients at this stage of the research.
The achievement instead provided researchers with a more sophisticated experimental model for studying cardiac muscle and the mechanisms involved in heart function.
Final Thoughts
The University of Minnesota team’s 3D-bioprinted cardiac muscle pump represented an important step in the development of functional human heart tissue models.
By printing proliferating human induced pluripotent stem cells first and differentiating them into cardiomyocytes afterward, researchers overcame one of the challenges associated with achieving sufficiently dense, connected cardiac muscle.
The resulting centimeter-scale structure could contract synchronously, conduct electrical signals, move fluid, and respond to drugs and pacing.
However, the achievement should be understood in its 2020 research context. The researchers created an experimental chambered cardiac organoid rather than a complete replacement heart. Its immediate value was primarily as a laboratory model that could help researchers study heart function, disease, medical devices, and potential treatments.
References
Kupfer, M. E., Lin, W.-H., Ravikumar, V., Qiu, K., Wang, L., Gao, L., Bhuiyan, D. B., Lenz, M., Ai, J., Mahutga, R. R., Townsend, D., Zhang, J., McAlpine, M. C., Tolkacheva, E. G., & Ogle, B. M. (2020). In situ expansion, differentiation, and electromechanical coupling of human cardiac muscle in a 3D bioprinted, chambered organoid. Circulation Research, 127(2), 207–224. https://doi.org/10.1161/CIRCRESAHA.119.316155