Considerations of the validity of mouse-to-rat xenograft combinations in xenograft testing

These results indicate that both the choice of species combination as well as the choice of the donor organ studied can be crucial in the reproducibility, validity, and probably the relevance of xenograft testing. The vexatious results often encountered in a variety of mouse strains should lead to caution in the use of mouse models in general. Perhaps it is fair to say that the authors of mouse studies should indicate some particular reason for choice of the combination of rat-to-mouse transplant rather than mouse-to-rat as their primary model, or utilize the reciprocal species combination as a control. In regard to choice of organ xenograft transplant, the primarily vascularized heart xenograft is an excellent model. In contrast to skin, isolated pancreas islet, and some other xenograft organ models, the primarily vascularized heart model is a valid one and shows little variance in mean survival with a given treatment in the mouse. If a choice of rat-to-mouse or other species xenograft to mouse recipients is necessary or desirable, the primarily vascularized heart should be used as the organ of choice. In the emerging field of xenograft testing, the reproducibility, validity, and relevance of these xenograft models will be crucially important in deriving information useful for expansion of xenografting and to higher animals ultimately into clinical practice. There is little doubt that the rodent studies in both xenografts and allografts have provided a wealth of the immunological and surgical information that was obtained in a cost-effective manner with minimal ethical problems.(ABSTRACT TRUNCATED AT 250 WORDS)