Abstract: There are provided a cell aggregate that can be used as a cell preparation in regenerative medicine, maintains the original characteristics of cells, and has high safety, and a method for simply and safely maintaining the cell aggregate size, the cell characteristics and viability suitable for use as a cell preparation in regenerative medicine. According to an aspect of the present invention, a cell aggregate maintaining method is a method including a maintenance process of maintaining a liquid containing a plurality of the cell aggregates at a temperature which is lower than a culture temperature of the cells and at which the liquid is not frozen.

Abstract: A medium for culturing and expanding nephron progenitor cells, the medium containing a GSK-3? inhibitor, a ROCK inhibitor, and at least one fibroblast growth factor selected from the group consisting of FGF9 and FGF20. Also, a method for culturing and expanding nephron progenitor cells using the medium. Also, a method for producing renal organoids, the method including a step of culturing and expanding nephron progenitor cells using the above method for culturing and expanding nephron progenitor cells, and a step of differentiating the cultured and expanded nephron progenitor cells into renal organoids.

Abstract: Provided is a method for isolating a ureteric bud tip cell from cells, a tissue, or an organoid comprising the ureteric bud tip cell, comprising the following steps of contacting the cells, tissue, or organoid comprising the ureteric bud tip cell with a very low density lipoprotein receptor (VLDL-R) binding agent, and isolating the ureteric bud tip cell using the binding agent as an indicator.