Nikhil Prasad Fact checked by:Thailand Medical News Team Sep 24, 2026 52 minutes ago
SARS-CoV-2 spike proteins from the Alpha, Delta, and Omicron variants can trigger distinctly different structural and molecular changes in human heart muscle cells, according to new laboratory research examining how viral proteins affect the cellular machinery needed for normal cardiac function.
Alpha, Delta, and Omicron spike proteins produced different structural and molecular remodeling patterns in
laboratory-grown human cardiomyocytes
The findings suggest that the variants do not produce a single, uniform cellular response. Delta caused the most obvious disruption to the overall architecture of cardiomyocytes, while Omicron produced broader changes in proteins involved in cellular structure and signaling.
Researchers were from the Borch Department of Medicinal Chemistry and Molecular Pharmacology at Purdue University; Department of Biology at the University of Puerto Rico, Cayey Campus; Department of Biology, School of Sciences & Technology at Ana G. Méndez University, Gurabo Campus; Department of Sciences & Technology at Inter American University, Arecibo Campus; and Department of Biology at the University of Puerto Rico, Rio Piedras Campus.
Testing How Spike Proteins Affect Heart Cells
Cardiomyocytes depend on a precisely organized cytoskeleton to maintain their shape, generate force, transport material inside cells, and support electrical signaling. Damage to this internal framework could therefore have important consequences for cardiac function.
For this
Thailand Medical News report, the researchers studied human AC16 cardiomyocytes exposed to purified recombinant spike proteins representing Alpha, Delta, and Omicron. Cells received a concentration of 1 nanomolar and were examined after 24, 48, and 72 hours. Three independent biological samples were used for the microscopy experiments.
Confocal microscopy and quantitative image analysis measured F-actin filament numbers and length, phalloidin fluorescence intensity, and cell solidity. Separately, tandem mass tag-based proteomics examined protein abundance after 72 hours.
Structural Damage Became Clearer Over Time
At 24 hours, cells exposed to the three spike variants generally resembled untreated controls. By 48 hours, their overall appearance remained relatively preserved, but quantitative measurements revealed that F-actin filaments had become significantly shorter following exposure to all three variants, with p-values below 0.0001.
The changes became more striking after 72 hours. F-actin filament numbers were significantly lower following Alpha, Delta, and Omicron exposure. The reductions were especially statistically strong for Alpha and Delta, both at p<0.0001, while Omicron produced a significant reduction at p=0.0089.
Filament length also remained significantly reduced after 72 hours with Alpha and Omicron. Although Delta-treated cells showed a reduction, it did not reach statistical significance at that time point.
Importantly, Delta produced the most pronounc
ed visible disruption of overall cellular architecture at 72 hours. This indicates that the scale of visible structural damage did not necessarily mirror the breadth of underlying molecular changes.
Omicron Produced a Very Different Cellular Pattern
Additional measurements revealed an intriguing contrast. At 72 hours, Alpha and Delta reduced phalloidin fluorescence intensity, whereas Omicron caused a marked increase. Delta and Omicron also significantly altered cell solidity, but in opposite directions: solidity increased with Delta and decreased with Omicron.
These findings indicate that SARS-CoV-2 spike-associated cytoskeletal disruption is more complicated than simply losing actin filaments. Different variants appear capable of reorganizing heart-cell architecture in fundamentally different patterns.
Omicron Triggered Broader Protein Changes
Proteomic analysis reinforced that distinction. Omicron produced the broadest changes in protein abundance, including increased abundance of proteins involved in membrane signaling, extracellular-matrix interactions and mechanosensation, including EPHA2, FAP, CSPG4, CD44 and PIEZO1.
Meanwhile, proteins involved in actin regulation, adhesion and cytoskeletal organization—including FERMT2, ITGAV, NCKAP1 and CFL1—showed reduced abundance following Omicron exposure. Delta displayed fewer proteomic changes despite producing the strongest visible structural abnormalities.
All spike-treated groups also showed increased ACTB abundance compared with controls, while Alpha and Omicron increased TUBA1A abundance. Gene Ontology analysis identified enrichment involving microtubules, actin filament bundles, cortical cytoskeleton, contractile actin structures and membrane ruffles.
Findings Do Not Reproduce COVID-19 Infection
The researchers stressed important limitations. The experiment used purified recombinant spike proteins rather than infectious SARS-CoV-2, and the study lacked a matched recombinant-protein control. The experimental concentration also should not be interpreted as equivalent to spike concentrations circulating during natural infection.
The experiments additionally did not directly measure cell death, cardiac contraction, or electrical activity. Consequently, the findings demonstrate cellular structural and proteomic responses under laboratory conditions rather than proving that the same changes cause heart dysfunction in people with COVID-19.
Conclusions
The study provides evidence that Alpha, Delta, and Omicron spike proteins can produce time-dependent but distinctly different remodeling of human cardiomyocytes. The contrast between Delta's pronounced structural disruption and Omicron's broader molecular response suggests that visible cellular damage and proteomic remodeling may represent related but separate dimensions of the cardiac cellular response to SARS-CoV-2 spike exposure. Further studies using infectious-virus models and direct measurements of contractile and electrical function are needed to determine their physiological importance.
The study findings were published in the peer reviewed journal: BioMed.
https://www.mdpi.com/2673-8430/6/4/20
Read Also:
https://www.thailandmedical.news/articles/coronavirus
https://www.thailandmedical.news/articles/long-covid 
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