Bovine in vitro reproduction models can contribute to the development of (female) fertility preservation strategies.

Recent increases in the number of successful cancer treatments have stimulated interest in fertility preservation strategies in women of reproductive age and in prepubertal girls. However, research on the application of such programs under clinical conditions suffers from the scarce availability of human tissue for research purposes and from concurrent relevant ethical issues. To partly address this problem, this review focuses on the possibilities of ruminant in vitro models providing additional insights into several aspects of fertility preservation, ranging from preantral follicle collection to oocyte and follicle cryopreservation, to noninvasive quality assessment, and to follicle culture. After a brief introduction, we discuss currently available techniques involved in (human) fertility preservation, together with their inherent advantages and limitations. On the basis of literature, we describe specific points for improvement or urgent additional research, such as (1) the lack of noninvasive methods to assess viability and developmental capacity of preantral follicles (either isolated or "in situ"); (2) autotransplantation and cryopreservation of ovarian cortex and follicles; (3) ischemia, follicular burnout, and graft rejection as major causes of preantral follicle loss; and (4) the development of routine in vitro follicle culture methods. Within each section, an overview is given of similar available techniques in (ruminant) assisted reproduction, with suggestions as to where and how these research models might contribute to fill the identified gaps. After the identification of the remaining issues in the development of integrated fertility preservation strategies, available ruminant in vitro models are introduced, described, and matched to these challenges to define common grounds for reproductive research. Ruminant in vitro models are increasingly considered as being very relevant for human preimplantation reproductive research. Because ruminant in vitro models are not hampered by restrictive ethical constraints, they will undoubtedly boost research progress in fertility preservation. At the end of the review, future common research goals are proposed through which human and animal scientists can meet and hasten the development of integrated fertility preservation strategies.