There has been much interest in the development of organoids grown from human stem cells for their potential to serve as better test models for drugs or be used for organ transplant, but before they can be used for such purposes optimization is needed. According to a new study, rogue cells mostly consisting of brain and muscle cells, can make up 10 to 20 percent of kidney organoid’s cells. These findings, published in Cell Stem Cell, indicate that the “recipes” scientists use to crate these organoids are producing unintended cell types along with the target cells.
The researchers from Washington University School of Medicine who identified the problem also found an easy way to prevent most of these unintended cells from forming. They claim the technique could be used by scientists to find rogue cells in other organoids.
For the study, the researchers looked at two recipes commonly used to grow kidney organoids—one that starts with stem cells approved for research by the NIH, and another that begins with induced pluripotent stem cells reprogrammed from adult cells. According to protocol for growing kidney organoids, a cocktail of drugs and growth factors were added to the stem cells and the cells were grown into organoids over a period of four weeks.
After this process, the researchers used single cell RNA sequencing to analyze the activity of thousands of genes in 83,130 cells from 65 kidney organoids. Using an artificial intelligence program, the data was analyzed and cells were grouped together based on their gene expression.
This revealed that 10 to 20 percent of cells in the organoids instead became brain and muscle cells, regardless of the recipe used. The researchers then reconstructed the step-by-step process by which stem cells developed into other cells, which allowed them to see precisely where the off-target cells started to form. They used this knowledge to block these off-target events, thus reducing the formation of unintended cell types by 90%.
These findings could pave the way for further research into kidney organoid use to provide better care for patients with kidney failure. The researchers also believe this technique can be applied to off-target cells in other organoid types.
Image: Brain, muscle cells found lurking in kidney organoids grown in lab. Image courtesy of Humphreys lab.