Mechanisms of Viral-Induced Myocardial Injury in Multicellular Cardiac “Mini-Hearts”

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Summary of  Biofabrication https://doi.org/10.1088/1758-5090/ae38d7 
Dr. Matt D Johansen  et al.

Points

Researchers developed a 3D human cardiac spheroid model to demonstrate that the SARS-CoV-2 virus directly infects heart tissue and triggers damaging inflammatory responses linked to significantly impaired organ function.
The study found that while the virus could not infect individual heart cell types grown in isolation, it successfully invaded and multiplied within the complex multicellular structure of cardiac spheroids.
Analysis of cardiovascular disease genes showed substantial increases in pathways associated with apoptosis and fibrosis which may explain why patients experience serious heart complications during and after COVID-19 infection.
High-resolution confocal imaging confirmed the presence of viral nucleocapsid proteins within the 3D tissue model to support the theory that direct infection contributes to clinical cardiac injury phenotypes.
These innovative human-based models offer a valuable therapeutic testing platform for identifying new strategies to protect the heart from viral threats and reduce the long-term consequences of pandemic-related damage.

Summary

This study investigated the mechanisms of COVID-19-induced cardiovascular complications using human cardiac spheroids (CSs), or “mini-hearts,” to determine if SARS-CoV-2 causes injury through direct infection or secondary systemic inflammation. While over 185,000 cases were reported nationally in the past year, the etiology of associated cardiac phenotypes remained debated. The research established that SARS-CoV-2 directly infects 3D cardiac tissue, a process notably absent in isolated, individual heart cell types, highlighting the necessity of multicellular structural organization for viral entry and replication.

Transcriptomic analysis of the infected CS models revealed significant up-regulation of pathways associated with apoptosis, chemotaxis, fibrosis, and contractile dysfunction. Confocal imaging and 3D rendering confirmed the presence of the SARS-CoV-2 nucleocapsid protein within the cardiac tissue, providing definitive evidence of viral niche establishment. These molecular changes correlate with the clinical observation of impaired heart function and damaging inflammation, even in patients without pre-existing cardiovascular disease.

The findings suggest that the cardiac spheroid model effectively recapitulates the complex pathophysiology of COVID-19-related heart injury. By identifying specific cell-mediated effects and interferon response profiles, the study provides a clinically-amenable platform for evaluating future therapeutic interventions. Although specific hazard ratios for long-term outcomes were not generated in this in vitro phase, the model’s ability to mirror patient-specific structural changes offers a critical tool for mitigating viral-induced cardiac morbidity.

Link to the article: https://iopscience.iop.org/article/10.1088/1758-5090/ae38d7

References

Johansen, M. D., Ming, C. L. C., Hansbro, P. M., & Gentile, C. (2026). SARS-CoV-2 infection of 3D in vitro cardiac spheroids models the activation of antiviral, inflammatory, fibrotic, and contractile responses in a dose-dependent manner. Biofabrication, 18(1), 015028. https://doi.org/10.1088/1758-5090/ae38d7