This research was conducted on four human induced pluripotent stem cell lines:

In our previous work, we generated a trisomy 21 iPS cell line derived from skin fibroblasts and three induced disomy iPS cell lines with different combinations of HSA21 (ΔP, ΔM1, and ΔM2) using the chromosome elimination technique

Here’s the previous work

How did you even come to the conclusion mice were involved? Mice aren’t mentioned anywhere