tracing after injection
You can
1. Label your cells before injection, e.g. transfect a report gene into the cells and pick out the expression clones for injection; or try some alive cell dyes for short term tracing;
2. Use different genders for the donor and the acceptor and microscope the gender-related markers;
3. If the cells injected are exclusive, you could see them by the specific staining, e.g. tumor cells in normal tissue, bone cells in soft tissue, etc.
Have fun!