I have injected human fibroblasts into mice. On harvesting the tumors, will I have a combination of mouse and human fibroblasts or human fibroblasts transformed into mouse like. How can they be differentiated?
Human primary fibroblasts do not get transformed and will not grow as tumors when injected sc in mice. They need to be transformed first.
If you are injecting human fibroblast cell lines (e.g. MRC5) they will also knot grow, because they are immortalized but not transformed.
Supposing however that you inject transformed human fibroblasts sc, and that theyx form a tumor, you will find mostly human cells, with invading mouse endothelial cells for the blood and lymphatic vessels, as well as macrophages and other supporting cells.
Histologically, with a little experience, you can distinguish huaman from mouse nuclei, but is not an optimal way. You will need to perform a staining with a specific marker. There is a lot of different ones, but I have no direct experience.
Although it is a rare event human cells can transform mouse cells when injected orthotopically and subcutaneously. You can either do a chromosomal analysis or look at the specific STR markers to distinguish mouse cells from human.
This action is rare ,because they arent adaptation from HLA antigen but this practice is intrest about experimental study
I agree with Michele Bernasconi, normal fibroblasts will not produce tumors in (immunodefficient) mice. To differentiate human from mouse cells, you can use the anti human nuclei antibody from Millipore- works nicely on frozen sections in my hands. I think, there is also a specific antibody against human vimentin(?), but I do not have direct experience with it.