Biological self-assembly is crucial in the processes of development, tissue regeneration, and maturation of bioprinted tissue-engineered constructions. The cell aggregates-spheroids-have become widely used model objects in the study of this phenomenon. existing approaches describe the fusion of cell aggregates by analogy with the coalescence of liquid droplets and ignore the complex structural properties of spheroids. Here, we analyzed the fusion process in connection with structure and mechanical properties of the spheroids from human somatic cells of different phenotypes: mesenchymal stem cells from the limbal eye stroma and epithelial cells from retinal pigment epithelium. A nanoindentation protocol was applied for the mechanical measurements. We found a discrepancy with the liquid drop fusion model: the fusion was faster for spheroids from epithelial cells with lower apparent surface tension than for mesenchymal spheroids with higher surface tension. this discrepancy might be caused by biophysical processes such as extracellular matrix remodeling in the case of mesenchymal spheroids and different modes of cell migration. The obtained results will contribute to the development of more realistic models for spheroid fusion that would further provide a helpful tool for constructing cell aggregates with required properties both for fundamental studies and tissue reparation. Modern approaches to the rapidly evolving fields of regenerative medicine and tissue engineering are closely associated with the development and formation of tissue-engineered constructions, where cellular components play a crucial role 1-3. Monolayer cell culture is the most widely used approach to the growing and studying of cells in vitro. Nevertheless, 2D culture conditions cause cell flattening and remodeling of the cell's internal structure, which can eventually affect the gene expression 4. On the other hand, 3D cell culture better reflects the in vivo microenvironment both morphologically and physiologically. The extra dimension which 3D cell cultures have, compared to monolayers, helps to establish intercellular junctions, to reorganize the cytoskeleton, to polarize and to differentiate in conditions similar to native tissue conditions 5. Multicellular spheroids obtained under nonadhesive conditions represent one possible 3D cell culture system. There is a great deal of unexplored potential in spheroid-based research, as tissue engineering using spheroids is a relatively new field 6-8. Three-dimensional bioprinting of scaffold-based and scaffold-free tissue-engineered constructions is widely used for tissue substitution and modeling of organs-on-chips 9-12. Cell spheroids with prefabricated intercellular junctions and extracellular matrix provide a new promising type of bioinks suitable for processing by an

While the number of studies related to severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) is constantly growing, it is essential to provide a framework of modeling viral infections. Therefore, this review aims to describe the background presented by earlier used models for viral studies and an approach to design an “ideal” tissue model for SARS-CoV-2 infection. Due to the previous successful achievements in antiviral research and tissue engineering, combining the emerging techniques such as bioprinting, microfluidics, and organoid formation are considered to be one of the best approaches to form in vitro tissue models. The fabrication of an integrated multi-tissue bioprinted platform tailored for SARS-CoV-2 infection can be a great breakthrough that can help defeat coronavirus disease in 2019.