An Overview of Zebrafish Modeling Methods in Drug Discovery and Development

A review on current advancement in zebrafish models to study chronic inflammatory diseases and their therapeutic targets

Chronic inflammatory diseases are caused due to prolonged inflammation at a specific site of the body. Among other inflammatory diseases, bacterial meningitis, chronic obstructive pulmonary disease (COPD), atherosclerosis and inflammatory bowel diseases (IBD) are primarily focused on because of their adverse effects and fatality rates around the globe in recent times. In order to come up with novel strategies to eradicate these diseases, a clear understanding of the mechanisms of the diseases is needed. Similarly, detailed insight into the mechanisms of commercially available drugs and potent lead compounds from natural sources are also important to establish efficient therapeutic effects. Zebrafish is widely accepted as a model to study drug toxicity and the pharmacokinetic effects of the drug. Moreover, researchers use various inducers to trigger inflammatory cascades and stimulate physiological changes in zebrafish. The effect of these inducers contrasts with the type of zebrafish used in the investigation. Hence, a thorough analysis is required to study the current advancements in the zebrafish model for chronic inflammatory disease suppression. This review presents the most common inflammatory diseases, commercially available drugs, novel therapeutics, and their mechanisms of action for disease suppression. The review also provides a detailed description of various zebrafish models for these diseases. Finally, the future prospects and challenges for the same are described, which can help the researchers understand the potency of the zebrafish model and its further exploration for disease attenuation.

(Zebra)fishing for nephrogenesis genes

Kidney disease is a devastating condition affecting millions of people worldwide, where over 100,000 patients in the United States alone remain waiting for a lifesaving organ transplant. Concomitant with a surge in personalized medicine, single-gene mutations, and polygenic risk alleles have been brought to the forefront as core causes of a spectrum of renal disorders. With the increasing prevalence of kidney disease, it is imperative to make substantial strides in the field of kidney genetics. Nephrons, the core functional units of the kidney, are epithelial tubules that act as gatekeepers of body homeostasis by absorbing and secreting ions, water, and small molecules to filter the blood. Each nephron contains a series of proximal and distal segments with explicit metabolic functions. The embryonic zebrafish provides an ideal platform to systematically dissect the genetic cues governing kidney development. Here, we review the use of zebrafish to discover nephrogenesis genes.

Stem Cell-Based Modeling Protocol for Parkinson's Disease

Parkinson's disease is a progressive neurodegenerative disorder, which is mainly characterized by unintended or uncontrollable body movements. Pathophysiologically, disturbances in the neurotransmission system of the brain like dopaminergic system and synaptic dysfunction are classified as top-rated causes of the onset of Parkinson's disease, which symptoms can be different according to the involvement of neurotransmission system type and the effect of the disease on the motor and non-motor systems. Although some pharmacological and non-pharmacological approaches have been applied to control and slow down the progression of the disease, a definitive cure has not yet been discovered. One of the factors involved in this issue is the lack of appropriate laboratory models to investigate the pathological mechanisms involved in the disease as well as various aspects of candidate drugs, which ultimately leads to the failure of drug discovery and development pipelines. To deal with these challenges, the application of stem cells, especially cellular reprogramming of somatic cells to human pluripotent stem cells, also known as induced pluripotent stem cells, has been able to promise a new chapter in the modeling of Parkinson's disease. Induced pluripotent stem cells have the stemness capability; therefore, they can differentiate into any type of cell such as nerve cells. Also, since these cells are obtained from the reprogramming of somatic cells in the patient's body, they maintain the patient's genetic content, which can play an important role in increasing the quality of disease modeling and the validity of the results of laboratory studies. Therefore, the procedure for modeling induced pluripotent stem cells for Parkinson's disease is explained in this chapter.

Development and Validation of Type 2 Diabetic Zebrafish Model for Cell-Based Treatments

Diabetes mellitus can be categorized as one of the prolonged metabolic disorders that are associated with inappropriately elevated blood glucose levels. Among the subgroups of this disease, type 2 diabetes accounts for the most patients. Although pharmaceutical and non-pharmaceutical treatments have been employed to control the progression of the disease, as with any treatment approach, both therapeutic approaches are associated with side effects and challenges. Nowadays, the emergence of treatment methods based on stem cells has attracted the attention of researchers in order to treat diabetes fundamentally and provide a long-term solution. Since there are still blind spots regarding the positive and negative effects of these types of treatments, animal studies can give researchers a detailed insight into the effects of stem cell-based treatments. Recently, zebrafish has been proposed as a valuable animal model due to its outstanding genetic and physiological characteristics in biomedical studies including diabetes. Hereupon, in this protocol, the development and validation of type 2 diabetic zebrafish model for cell-based treatments have been explained.

Preparation and Validation of Zebrafish Psoriasis Model to Investigate the Therapeutic Effects of Stem Cells

Psoriasis is a chronic, inflammatory, autoimmune disease with systemic symptoms including seborrheic psoriasis, pustular lesions, plaque lesions, intestinal eruptions, and sometimes arthritis. Moreover, most of the psoriatic subjects report life challenges due to the condition, impacting social activities and daily tasks. Generally, psoriasis treatment options depend on the severity, coexisting conditions, and medical availability. Although psoriasis therapies reduce symptoms and appearance, still it is not curable. Hereupon, searching for optimal therapeutic options continues. Accordingly, stem cell therapy is considered an advanced psoriasis treatment. Subsequently, stem cell therapies' efficacy is uncertain yet. Therefore, further studies are needed. In this context, preclinical studies such as animal experiments are essential for evaluation of treatment modalities. Herein, zebrafish offer advantages in testing treatments and biomedical research applications compared to other vertebrate models. Further, zebrafish skin shares similarities with human skin, making it suitable for studying inflammatory disorders. Hence, the authors discuss the zebrafish psoriasis development method for evaluating the stem cell therapeutic influence.

Zebrafish as a Model to Study Retinoic Acid Signaling in Development and Disease

Retinoic acid (RA) is a metabolite of vitamin A (retinol) that plays various roles in development to influence differentiation, patterning, and organogenesis. RA also serves as a crucial homeostatic regulator in adult tissues. The role of RA and its associated pathways are well conserved from zebrafish to humans in both development and disease. This makes the zebrafish a natural model for further interrogation into the functions of RA and RA-associated maladies for the sake of basic research, as well as human health. In this review, we explore both foundational and recent studies using zebrafish as a translational model for investigating RA from the molecular to the organismal scale.

Zebrafish Modeling of Autism Spectrum Disorders, Current Status and Future Prospective

Autism spectrum disorder (ASD) refers to a complicated range of childhood neurodevelopmental disorders which can occur via genetic or non-genetic factors. Clinically, ASD is associated with problems in relationships, social interactions, and behaviors that pose many challenges for children with ASD and their families. Due to the complexity, heterogeneity, and association of symptoms with some neuropsychiatric disorders such as ADHD, anxiety, and sleep disorders, clinical trials have not yielded reliable results and there still remain challenges in drug discovery and development pipeline for ASD patients. One of the main steps in promoting lead compounds to the suitable drug for commercialization is preclinical animal testing, in which the efficacy and toxicity of candidate drugs are examined in vivo. In recent years, zebrafish have been able to attract the attention of many researchers in the field of neurological disorders such as ASD due to their outstanding features. The presence of orthologous genes for ASD modeling, the anatomical similarities of parts of the brain, and similar neurotransmitter systems between zebrafish and humans are some of the main reasons why scientists draw attention to zebrafish as a prominent animal model in preclinical studies to discover highly effective treatment approaches for the ASD through genetic and non-genetic modeling methods.