Ovarian transplantation is one of the ways to conserve the fertility in mammals. In human, ovarian transplantation has been applied at the medical center for those undergoing cancer therapies, which is known as gonadotoxic treatments. This procedure is usually initiated with the cryopreservation of ovarian tissue and grafting back at its original location through surgery. Beyond this application, this procedure offers wide implementation to other mammals, especially in an effort to conserve the endangered wildlife species. In animal model like mice, numerous studies have been attempted with varied rate of success.
Some disadvantageous of this OTT are histocompatibility-related matters and the degraded quality of the ovary in producing fully competent oocytes. In my attempt to graft fresh ovary through OTT, the number of ovulated metaphase II oocytes was significantly lower than that of non-transplanted following hormonal stimulation; some had abnormal morphology [1]. Moreover, even if only unilateral grafting was performed, another non-transplanted ovary would generate oocytes with abnormal morphology relatively high as compared to fresh oocytes from non-transplanted mice; probably due to hormonal interference during the procedures.
Regarding histocompatibility, it is well known that anything we put or transplant that has distinct genes would likely be rejected by the antibodies of recipients. Therefore, a prerequisite for engraftment of transplanted tissue is the histocompatibility between donor and recipient, determined by the genes of the major histocompatibility complex (MHC) [2]. A possible strategy to overcome this incompatibility problem is to use very young recipients without a fully developed immune system, using genetically modified mice breed expressing green fluorescence protein (GFP) or tomato within the same breeds, or adult immunodeficient mouse mutants which serve as universal recipients.
The following are some of my documentation when doing OTTs in mice.
A growing foetus was observed around 45 days after mating, following ovarian transplantation and 14 days of recovery.
All photos are personal documentation.
References:
[1] Kamoshita et. al. 2016. Investigation of in vitro parameters and fertility of mouse ovary after storage at an optimal temperature and duration for transportation. Human Reproduction.
[2] Kolbe et. al. 2019. Influence of graft size, histocompatibility, and cryopreservation on reproductive outcome following ovary transplantation in mice. Fertility Preservation.
