Establishing Epiblast Complementation as a Robust Strategy for Species Preservation

Growing an animal inside another animal: a novel and innovative alternative to cloning, where stem cells from one species can be used to grow an entire embryo. These methods will enable Revive & Restore’s ongoing work to increase genetic diversity for the Black-footed ferret.

Two healthy Black-footed Ferret kits at 3 weeks old, born to cloned Black-footed Ferret Antonia in 2024. The kits marked the first time a cloned U.S. endangered species produced offspring. | Photo credit: Smithsonian’s National Zoo and Conservation Biology Institute

The preservation of endangered species is hindered by limited reproductive capacity and insufficient genetic diversity. Although assisted reproductive technologies (ARTs) such as IVF and somatic cell nuclear transfer (SCNT) have been used in conservation, their effectiveness in wild species can be affected by multiple factors. Blastocyst and epiblast complementation offer powerful alternatives to cloning. These methods involve integrating stem cells derived from a host animal into the embryo of another animal. Excitingly, this can be performed between species, avoiding the use of embryos from endangered species.

While blastocyst complementation enables donor stem cells to replace some of the embryo, having been successfully used to generate multiple interspecies organs, including rat pancreas and mouse kidney, this approach produces chimeric animals. Our team hypothesizes that inhibiting key genes in a host embryo will create a completely empty developmental niche that can be fully occupied by donor stem cells, enabling the generation of offspring entirely derived from the donor species with higher efficiency than cloning. Because the entire embryo is derived from the donor animal’s stem cells, this approach also avoids the problem of mitochondrial DNA inherited from the oocyte, which occurs in interspecies cloning. 

Building on a successfully demonstrated foundation in mice, this team now seeks to extend epiblast complementation to domestic ferrets as a proof-of-concept for conserving endangered black-footed ferrets. Translated to other species, this method provides an efficient way to use historic cell lines from animals with higher genetic diversity to produce live offspring.