Exclusive generation of rat spermatozoa in sterile mice utilizing blastocyst complementation with pluripotent stem cells

Generation of allogenic and xenogeneic functional muscle stem cells for intramuscular transplantation

Satellite cells, the stem cells of skeletal muscle tissue, hold a remarkable regeneration capacity and therapeutic potential in regenerative medicine. However, low satellite cell yield from autologous or donor-derived muscles hinders the adoption of satellite cell transplantation for the treatment of muscle diseases, including Duchenne muscular dystrophy (DMD). To address this limitation, here we investigated whether satellite cells can be derived in allogeneic or xenogeneic animal hosts. First, injection of CRISPR/Cas9-corrected mouse DMD-induced pluripotent stem cells (iPSCs) into mouse blastocysts carrying an ablation system of host satellite cells gave rise to intraspecies chimeras exclusively carrying iPSC-derived satellite cells. Furthermore, injection of genetically corrected DMD-iPSCs into rat blastocysts resulted in the formation of interspecies rat-mouse chimeras harboring mouse satellite cells. Remarkably, iPSC-derived satellite cells or derivative myoblasts produced in intraspecies or interspecies chimeras restored dystrophin expression in DMD mice following intramuscular transplantation, and contributed to the satellite cell pool. Collectively, this study demonstrates the feasibility of producing therapeutically competent stem cells across divergent animal species, raising the possibility of generating human muscle stem cells in large animals for regenerative medicine purposes.

Innovations in poultry reproduction using cryopreserved avian germ cells

Meat and eggs from chicken are the major source of animal protein for the human population. The cryopreservation of poultry species is needed to guarantee sustainable production. Here, we describe the existing cryopreservation technologies for avian reproductive cells using embryonic germ cells, spermatozoa and ovarian tissues. We outline strategies to reconstitute chicken breeds from their cryopreserved embryonic germ cells using surrogate hosts and discuss the perspectives for genetic conservation and reconstitution of chicken and wild avian species using surrogate host animals.

Generation of rat forebrain tissues in mice

Interspecies blastocyst complementation (IBC) provides a unique platform to study development and holds the potential to overcome worldwide organ shortages. Despite recent successes, brain tissue has not been achieved through IBC. Here, we developed an optimized IBC strategy based on C-CRISPR, which facilitated rapid screening of candidate genes and identified that Hesx1 deficiency supported the generation of rat forebrain tissue in mice via IBC. Xenogeneic rat forebrain tissues in adult mice were structurally and functionally intact. Cross-species comparative analyses revealed that rat forebrain tissues developed at the same pace as the mouse host but maintained rat-like transcriptome profiles. The chimeric rate of rat cells gradually decreased as development progressed, suggesting xenogeneic barriers during mid-to-late pre-natal development. Interspecies forebrain complementation opens the door for studying evolutionarily conserved and divergent mechanisms underlying brain development and cognitive function. The C-CRISPR-based IBC strategy holds great potential to broaden the study and application of interspecies organogenesis.

The impact of induced pluripotent stem cells in animal conservation

It is widely acknowledged that we are currently facing a critical tipping point with regards to global extinction, with human activities driving us perilously close to the brink of a devastating sixth mass extinction. As a promising option for safeguarding endangered species, induced pluripotent stem cells (iPSCs) hold great potential to aid in the preservation of threatened animal populations. For endangered species, such as the northern white rhinoceros (Ceratotherium simum cottoni), supply of embryos is often limited. After the death of the last male in 2019, only two females remained in the world. IPSC technology offers novel approaches and techniques for obtaining pluripotent stem cells (PSCs) from rare and endangered animal species. Successful generation of iPSCs circumvents several bottlenecks that impede the development of PSCs, including the challenges associated with establishing embryonic stem cells, limited embryo sources and immune rejection following embryo transfer. To provide more opportunities and room for growth in our work on animal welfare, in this paper we will focus on the progress made with iPSC lines derived from endangered and extinct species, exploring their potential applications and limitations in animal welfare research.

Chimaeras, complementation, and controlling the male germline

Animal breeding drives genetic progress mainly through the male germline. This process is slow to respond to rapidly mounting environmental pressures that threaten sustainable food security from animal protein production. New approaches promise to accelerate breeding by producing chimaeras, which comprise sterile host and fertile donor genotypes, to exclusively transmit elite male germlines. Following gene editing to generate sterile host cells, the missing germline can be restored by transplanting either: (i) spermatogonial stem cells (SSCs) into the testis; or (ii) embryonic stem cells (ESCs) into early embryos. Here we compare these alternative germline complementation strategies and their impact on agribiotechnology and species conservation. We propose a novel breeding platform that integrates embryo-based complementation with genomic selection, multiplication, and gene modification.

Review: Progress in producing chimeric ungulate livestock for agricultural applications

The progress made in recent years in the derivation and culture of pluripotent stem cells from farm animals opens up the possibility of creating livestock chimeras. Chimeras producing gametes exclusively derived from elite donor stem cells could pass superior genetics on to the next generation and thereby reduce the genetic lag that typically exists between the elite breeding sector and the commercial production sector, especially for industries like beef and sheep where genetics is commonly disseminated through natural service mating. Chimeras carrying germ cells generated from genome-edited or genetically engineered pluripotent stem cells could further disseminate useful genomic alterations such as climate adaptation, animal welfare improvements, the repair of deleterious genetic conditions, and/or the elimination of undesired traits such as disease susceptibility to the next generation. Despite the successful production of chimeras with germ cells generated from pluripotent donor stem cells injected into preimplantation-stage blastocysts in model species, there are no documented cases of this occurring in livestock. Here, we review the literature on the derivation of pluripotent stem cells from ungulates, and progress in the production of chimeric ungulate livestock for agricultural applications, drawing on insights from studies done in model species, and discuss future possibilities of this fast-moving and developing field. Aside from the technical aspects, the consistency of the regulatory approach taken by different jurisdictions towards chimeric ungulate livestock with germ cells generated from pluripotent stem cells and their progeny will be an important determinant of breeding industry uptake and adoption in animal agriculture.