Derivation and culture of canine embryonic stem cells

Chromatin accessibility in canine stromal cells and its implications for canine somatic cell reprogramming

Naturally occurring disease in pet dogs is an untapped and unique resource for stem cell-based regenerative medicine translational research, given the many similarities and complexity such disease shares with their human counterparts. Canine-specific regulators of somatic cell reprogramming and pluripotency maintenance are poorly understood. While retroviral delivery of the four Yamanaka factors successfully reprogrammed canine embryonic fibroblasts, adult stromal cells remained resistant to reprogramming in spite of effective viral transduction and transgene expression. We hypothesized that adult stromal cells fail to reprogram due to an epigenetic barrier. Here, we performed assay for transposase-accessible chromatin using sequencing (ATAC-seq) on canine stromal and pluripotent stem cells, analyzing 51 samples in total, and establishing the global landscape of chromatin accessibility before and after reprogramming to induced pluripotent stem cells (iPSC). We also studied adult stromal cells that do not yield iPSC colonies to identify potential reprogramming barriers. ATAC-seq analysis identified distinct cell type clustering patterns and chromatin remodeling during embryonic fibroblast reprogramming. Compared with embryonic fibroblasts, adult stromal cells had a chromatin accessibility landscape that reflects phenotypic differentiation and somatic cell-fate stability. We ultimately identified 76 candidate genes and several transcription factor binding motifs that may be impeding somatic cell reprogramming to iPSC, and could be targeted for inhibition or activation, in order to improve the process in canines. These results provide a vast resource for better understanding of pluripotency regulators in dogs and provide an unbiased rationale for novel canine-specific reprogramming approaches.

In vitro production of canine blastocysts

Though blastocyst production in vitro has been successful in several animal species, a culture system to produce viable and normal canine blastocysts in vitro remains to be established. In this study, we report the development of an in vitro culture system for canine preimplantation embryos produced via parthenogenetic activation (PA) and somatic cell nucleus transfer (SCNT). Our results show that the medium developed by us, named "Qingdao Agricultural University's (QAU)-4 medium", successfully breaks the developmental arrest observed at the eight-cell stage in canine embryos grown in other culture systems. The blastocysts produced in QAU-4 displayed normal blastocyst structures, including a clear inner cell mass and blastocyst cavity. We also found that blastocyst formation in PA embryos cultured in QAU-4 medium was quite high, though this was not so in the case of SCNT embryos. However, supplementation of QAU-4 medium with 100 nM of scriptaid caused a sharp increase in blastocyst formation in SCNT embryos. After culture, hatched blastocysts were also observed to successfully adhere to collagen-coated dishes, where further growth and differentiation occurred. To our knowledge, this is the first in vitro canine preimplantation embryo culture system that can successfully produce canine blastocysts.

Concise Review: Canine Diabetes Mellitus as a Translational Model for Innovative Regenerative Medicine Approaches

Diabetes mellitus (DM) is a common spontaneous endocrine disorder in dogs, which is defined by persistent hyperglycemia and insulin deficiency. Like type 1 diabetes (T1D) in people, canine DM is a complex and multifactorial disease in which genomic and epigenomic factors interact with environmental cues to induce pancreatic β‐cell loss and insulin deficiency, although the pathogenesis of canine DM is poorly defined and the role of autoimmunity is further controversial. Both diseases are incurable and require life‐long exogenous insulin therapy to maintain glucose homeostasis. Human pancreatic islet physiology, size, and cellular composition is further mirrored by canine islets. Although pancreatic or isolated islets transplantation are the only clinically validated methods to achieve long‐term normoglycemia and insulin independence, their availability does not meet the clinical need; they target a small portion of patients and have significant potential adverse effects. Therefore, providing a new source for β‐cell replacement is an unmet need. Naturally occurring DM in pet dogs, as a translational platform, is an untapped resource for various regenerative medicine applications that may offer some unique advantages given dogs' large size, longevity, heterogenic genetic background, similarity to human physiology and pathology, and long‐term clinical management. In this review, we outline different strategies for curative approaches, animal models used, and consider the value of canine DM as a translational animal/disease model for T1D in people. stem cells translational medicine2019;8:450–455

Characterization of companion animal pluripotent stem cells

Pluripotent stem cells have the capacity to grow indefinitely in culture and differentiate into derivatives of the three germ layers. These properties underpin their potential to be used in regenerative medicine. Originally derived from early embryos, pluripotent stem cells can now be derived by reprogramming an adult cell back to a pluripotent state. Companion animals such as horses, dogs, and cats suffer from many injuries and diseases for which regenerative medicine may offer new treatments. As many of the injuries and diseases are similar to conditions in humans the use of companion animals for the experimental and clinical testing of stem cell and regenerative medicine products would provide relevant animal models for the translation of therapies to the human field. In order to fully utilize companion animal pluripotent stem cells robust, standardized methods of characterization must be developed to ensure that safe and effective treatments can be delivered. In this review we discuss the methods that are available for characterizing pluripotent stem cells and the techniques that have been applied in cells from companion animals. We describe characteristics which have been described consistently across reports as well as highlighting discrepant results. Significant steps have been made to define the in vitro culture requirements and drive lineage specific differentiation of pluripotent stem cells in companion animal species. However, additional basic research to compare pluripotent stem cell types and define characteristics of pluripotency in companion animal species is still required. © 2017 International Society for Advancement of Cytometry.