Special issue on canine genetics: animal models for human disease and gene therapies, new discoveries for canine inherited diseases, and standards and guidelines for clinical genetic testing for domestic dogs

Aligning with the 3Rs: alternative models for research into muscle development and inherited myopathies

Inherited and acquired muscle diseases are an important cause of morbidity and mortality in human medical and veterinary patients. Researchers use models to study skeletal muscle development and pathology, improve our understanding of disease pathogenesis and explore new treatment options. Experiments on laboratory animals, including murine and canine models, have led to huge advances in congenital myopathy and muscular dystrophy research that have translated into clinical treatment trials in human patients with these debilitating and often fatal conditions. Whilst animal experimentation has enabled many significant and impactful discoveries that otherwise may not have been possible, we have an ethical and moral, and in many countries also a legal, obligation to consider alternatives. This review discusses the models available as alternatives to mammals for muscle development, biology and disease research with a focus on inherited myopathies. Cell culture models can be used to replace animals for some applications: traditional monolayer cultures (for example, using the immortalised C2C12 cell line) are accessible, tractable and inexpensive but developmentally limited to immature myotube stages; more recently, developments in tissue engineering have led to three-dimensional cultures with improved differentiation capabilities. Advances in computer modelling and an improved understanding of pathogenetic mechanisms are likely to herald new models and opportunities for replacement. Where this is not possible, a 3Rs approach advocates partial replacement with the use of less sentient animals (including invertebrates (such as worms Caenorhabditis elegans and fruit flies Drosophila melanogaster) and embryonic stages of small vertebrates such as the zebrafish Danio rerio) alongside refinement of experimental design and improved research practices to reduce the numbers of animals used and the severity of their experience. An understanding of the advantages and disadvantages of potential models is essential for researchers to determine which can best facilitate answering a specific scientific question. Applying 3Rs principles to research not only improves animal welfare but generates high-quality, reproducible and reliable data with translational relevance to human and animal patients.

Metabolic gene therapy in a canine with pulmonary hypertension secondary to degenerative mitral valve disease

Myxomatous mitral valve disease (MMVD) stands out as the most prevalent acquired canine heart disease. Its occurrence can reach up to 40% in small breed dogs and escalates in geriatric canine populations. MMVD leads to thickening and incomplete coaptation of valve leaflets during systole, resulting in secondary mitral valve regurgitation. Serious complications may arise concurrently with the worsening of mitral valve regurgitation, including left-and right-sided congestive heart failure, and pulmonary hypertension (PH). Ultimately, the PH progression might contribute to the patient's demise or to the owner's decision of euthanasia. Most currently available FDA-approved therapies for PH are costly and aim to address the imbalance between vasoconstriction and vasodilation to restore endothelial cell function. However, none of these medications impact the molecular dysfunction of cells or impede the advancement of pulmonary vascular and right ventricular remodeling. Recent evidence has showcased successful gene therapy approaches in laboratory animal models of PH. In this manuscript, we summarize the latest advancements in gene therapy for the treatment of PH in animals. The manuscript incorporates original data showcasing sample presentations, along with non-invasive hemodynamic assessments. Our findings demonstrate that the use of metabolic gene therapy, combining synthetic adeno-associated virus with acid ceramidase, has the potential to significantly reduce the need for drug treatment and improve spontaneously occurring PH in dogs.

Evaluation of blastocyst re-expansion, quality in relation to storage temperature, and sexing using blastocoel fluid after manual perforation with a hand-held needle involving in vivo produced equine embryos

The present study was designed to evaluate equine blastocyst re-expansion rate, quality, and sex following perforation of the blastocoel, collection of blastocoel fluid (BF), and PCR amplification of free DNA. Experiment 1 tested the feasibility of the BF sample collection with a hand-held, small-gauged needle (26g) and subsequent PCR amplification of the TSP-Y gene for males and AMEL-Y gene for males and AMEL-X gene for females. Experiment 2 tested the application of the technique. Equine embryos were collected via uterine flushes 8d after ovulation. Thereafter, embryos (n = 19) were initially assessed and transferred to a 50 μL droplet of holding medium in which the blastocoel was manually perforated as in Experiment 1. Within 1 min of detecting a diameter decrease or collapse, the entire volume of each droplet of medium was collected and stored at -20 °C until PCR. In Experiment 1, amplification of the TSP-Y gene was positive for males at 60% (9/15) and negative for females at 40% (6/15). In Experiment 2, a total of 42 embryos were randomly assigned to a collapsed embryo (CE) or intact embryo (IE) groups and stored at room temperature (RT, 25 °C) or cold temperature (CT, 5 °C) for 24h as follows: 1) CERT, n = 11; 2) CECT n = 11; 3) IERT, n = 10; and 4) IECT, n = 10. After 24h, embryo diameter and quality were reassessed. For all collapsed embryos (n = 19), blastocoel fluid was subjected to double PCR amplification of the TSPY gene with blood from adult male and female horses as controls. Positive gene amplification indicated 57.9% (11/19) of embryos were male and negative amplification indicated 31.6% (6/19) of embryos were female. Relative to the least diameter (0%) after perforation of collapsed embryos or fullest diameter (100%) of intact embryos at T0, percentage change in diameter and quality Grade 1 or 2 embryos after 24h of storage for all groups were, respectively: 31.2% and 54% for CERT group, 28.2% and 0% for CECT group, 25.9% and 100% for IERT group, 4.3% and 80% for IECT group, respectively. Thus, needle-induced leakage and collapse of the blastocoel at T0 resulted in a high rate of blastocyst re-expansion (69%) with many embryos (54%) achieving good quality at T24 with potential for transfer as either male or female embryos. For both collapsed and intact embryos, it was observed that storage for 24h at room temperature (25 °C) was associated with improved embryo growth and morphological quality compared to storage at cold temperature (5 °C).

Manifestations of systemic disease in the retina and fundus of cats and dogs

The fundus is unique in that it is the only part of the body that allows for a noninvasive and uninterrupted view of vasculature and nervous tissue. Utilization of this can be a powerful tool in uncovering salient incidental findings which point to underlying systemic diseases, and for monitoring response to therapy. Retinal venules and arterioles allow the clinician to assess changes in vascular color, diameter, outline, and tortuosity. The retina and optic nerve may exhibit changes associated with increased or decreased thickness, inflammatory infiltrates, hemorrhages, and detachments. While some retinal manifestations of systemic disease may be nonspecific, others are pathognomonic, and may be the presenting sign for a systemic illness. The examination of the fundus is an essential part of the comprehensive physical examination. Systemic diseases which may present with retinal abnormalities include a variety of disease classifications, as represented by the DAMNIT-V acronym, for Degenerative/Developmental, Anomalous, Metabolic, Neoplastic, Nutritional, Inflammatory (Infectious/Immune-mediated/ischemic), Toxic, Traumatic and Vascular. This review details systemic illnesses or syndromes that have been reported to manifest in the fundus of companion animals and discusses key aspects in differentiating their underlying cause. Normal variations in retinal anatomy and morphology are also considered.

Organ-on-a-chip technologies for biomedical research and drug development: A focus on the vasculature

Current biomedical models fail to replicate the complexity of human biology. Consequently, almost 90% of drug candidates fail during clinical trials after decades of research and billions of investments in drug development. Despite their physiological similarities, animal models often misrepresent human responses, and instead, trigger ethical and societal debates regarding their use. The overall aim across regulatory entities worldwide is to replace, reduce, and refine the use of animal experimentation, a concept known as the Three Rs principle. In response, researchers develop experimental alternatives to improve the biological relevance of in vitro models through interdisciplinary approaches. This article highlights the emerging organ-on-a-chip technologies, also known as microphysiological systems, with a focus on models of the vasculature. The cardiovascular system transports all necessary substances, including drugs, throughout the body while in charge of thermal regulation and communication between other organ systems. In addition, we discuss the benefits, limitations, and challenges in the widespread use of new biomedical models. Coupled with patient-derived induced pluripotent stem cells, organ-on-a-chip technologies are the future of drug discovery, development, and personalized medicine.

Step by Step about Germ Cells Development in Canine

Simple Summary

The progression of germ cells is a remarkable event that allows biological discovery in the differ-entiation process during in vivo and in vitro development. This is crucial for understanding one toward making oogenesis and spermatogenesis. Companion animals, such as canine, could offer new animal models for experimental and clinical testing for translation to human models. In this review, we describe the latest and more relevant findings on germ cell development. In addition, we showed the methods available for obtaining germ cells in vitro and the characterization of pri-mordial germ cells and spermatogonial stem cells. However, it is necessary to further conduct basic research in canine to clarify the beginning of germ cell development.

Abstract

Primordial germ cells (PGCs) have been described as precursors of gametes and provide a connection within generations, passing on the genome to the next generation. Failures in the formation of gametes/germ cells can compromise the maintenance and conservation of species. Most of the studies with PGCs have been carried out in mice, but this species is not always the best study model when transposing this knowledge to humans. Domestic animals, such as canines (canine), have become a valuable translational research model for stem cells and therapy. Furthermore, the study of canine germ cells opens new avenues for veterinary reproduction. In this review, the objective is to provide a comprehensive overview of the current knowledge on canine germ cells. The aspects of canine development and germ cells have been discussed since the origin, specifications, and development of spermatogonial canine were first discussed. Additionally, we discussed and explored some in vitro aspects of canine reproduction with germ cells, such as embryonic germ cells and spermatogonial stem cells.

Positioning canine induced pluripotent stem cells (iPSCs) in the reprogramming landscape of naïve or primed state in comparison to mouse and human iPSCs

AIMS

Deriving canine-induced pluripotent stem cells (ciPSCs) have paved the way for developing novel cell-based disease models and transplantation therapies in the dog. Though ciPSCs have been derived in the presence of Leukemia inhibitory factor (LIF) as well in the presence of basic fibroblast growth factor (bFGF), the positioning of ciPSCs in the naïve or the primed state of pluripotency remains elusive. This study aims to understand whether canine iPSCs belong to naïve or prime state in comparison to mouse (m) iPSCs and human (h) iPSCs.

MAIN METHODS

In the present study, we derived ciPSCs in presence of LIF and compared their state of pluripotency with that of miPSCs and hiPSCs by culturing them in the presence of LIF, bFGF, and LIF + bFGF. Gene expression level at transcript level was performed by RT-PCR and qRT-PCR and at the protein level was analysed by immunofluorescence. We also attempted to understand the pluripotency state using lipid body analysis by bodipy staining and blue fluorescence emission.

KEY FINDINGS

In contrast to miPSCs, the naïve pluripotent stem cells, ciPSCs showed the expression of FGF5 similar to that of primed pluripotent stem cell, hiPSCs. Compared to miPSCs, ciPSCs cultured in presence of LIF showed enhanced expression of primed pluripotent marker FGF5, similar to hiPSCs cultured in presence of bFGF. Upon culturing in hiPSC culture condition, ciPSCs showed enhanced expression of core pluripotency genes compared to miPSCs cultured in similar condition. However, ciPSCs expressed naïve pluripotent marker SSEA1 similar to miPSCs and lacked the expression of primed state marker SSEA4 unlike hiPSCs. Interestingly, for the first time, we demonstrate the ciPSC pluripotency using lipid body analysis wherein ciPSCs showed enhanced bodipy staining and blue fluorescence emission, reflecting the primed state of pluripotency. ciPSCs expressed higher levels of fatty acid synthase (FASN), the enzyme involved in the synthesis of palmitate, similar to that of hiPSCs and higher than that of miPSCs. As ciPSCs exhibit characteristic properties of both naïve and primed pluripotent state, it probably represents a unique intermediary state of pluripotency that is distinct from that of mice and human pluripotent stem cells.

SIGNIFICANCE

Elucidating the pluripotent state of ciPSCs assists in better understanding of the reprogramming events and development in different species. The study would provide a footprint of species-specific differences involved in reprogramming and the potential implication of iPSCs as a tool to analyse evolution.