In the field of stem cell therapy, research on the application of mesenchymal stem cells (MSCs) has flourished because of the various functions. On the other hand, research on the method of cell transplantation has developed from the administration of cell suspensions to cell-sheet engineering and 3D technology. In the trend, a cell transplantation platform named CellSaic, which is a combination of xeno-free recombinant scaffolds in a cell aggregate-like shape, was developed. CellSaic is the cell transplantation platform that can prevent the central necrosis within cell aggregates by arranging the cells and petaloid pieces of recombinant peptide (RCP) in a mosaic. The prevention of central necrosis is the most significant advantage over other 3D culture systems. This review details the unique characteristics of CellSaic including safety examination results and describes its future application for MSC transplantation. Particularly, in the application of MSCs, it has been reported that the MSC CellSaics increased the effect on improving various symptoms compared with MSCs only in the application of the therapy to inflammatory bowel disease (IBD), cerebral infarction, bone cartilage regeneration in joints, and islet transplantation. In accordance with the "One Health" concept, it is anticipated that this technology is expected to contribute to companion animal therapy and human therapy in the future.