Modeling the interaction of gametes and embryos with the maternal genital tract: from in vivo to in silico.

Understanding the complex interaction between gametes or embryos and the maternal genital tract requires the use of experimental models. The selection of the right model is an important task to undertake, and despite many new developments in this area, an ideal model system has not yet been developed. In this review article, we focus on how the most appropriate model species and model system can be selected, each with its particular advantages and disadvantages. Selection criteria need to be based on the evaluation of the aim of the experiment, the tools that are available to the scientist, and the ethics that are involved in working with particular animal species and model systems. Society and politics direct scientists to "Refine, Reduce, and Replace" the use of experimental animals, which means that the use of in vivo models is increasingly being discouraged. An in vivo model allows experimentation in the full biological environment of a living organism. In contrast with in vivo models, in vitro models are less complex and are abstracts of in vivo systems, leading often to results that are different from the in vivo situation. If an investigator could understand all the components of a complex biological system and re-create them as individual smaller models in a computer, he or she could create in silico models that would completely represent the complexity of in vivo models. We predict that in the future, in silico modeling will be the natural departure from in vivo, in situ, and in vitro modeling approaches. In addition to numerous advantages that this modeling approach can bring to studying maternal interaction with gametes and embryo, it is perhaps the only true alternative method to animal experimentation.