New methods for chicken embryo manipulations

The Chicken Embryo: An Old but Promising Model for In Vivo Preclinical Research

The chicken embryo has emerged as a valuable model for preclinical studies due to its unique combination of accessibility, affordability, and relevance to human biology. Its rapid development, external growth environment, and clear structural visibility offer distinct advantages over traditional mammalian models. These features facilitate the study of real-time biological processes, including tissue development, tumor growth, angiogenesis, and drug delivery, using various imaging modalities, such as optical imaging, magnetic resonance imaging, positron emission tomography, computed tomography, and ultrasound. The chicken embryo model also minimizes ethical concerns compared to mammalian models, as it allows for early-stage research without the complexity of a fully developed animal. Moreover, its ability to integrate human tumor cells into xenograft models provides a reliable platform for cancer research, enabling high-throughput screening of therapeutic interventions and tracking molecular dynamics in vivo. Advances in molecular imaging techniques further enhance the resolution and depth of data obtained from these studies, offering insights into cellular and molecular mechanisms underlying disease. Given its versatility, cost-effectiveness, and translational potential, the chicken embryo represents a promising tool for advancing preclinical research, particularly in drug development, cancer biology, and regenerative medicine.

The double-edged sword role of TGF-β signaling pathway between intrauterine inflammation and cranial neural crest development

Intrauterine infection would harm a developing embryo/fetus, thereby increasing the risk of developmental malformation. But, whether or not the infection-induced inflammation affects neural crest development still remains obscure. In this study, we employed meta-analysis to demonstrate the potential correlation between infection-induced inflammation and craniofacial anomalies, which was usually derived from the problems in neural crest cell development. The correlation was further verified by inflammatory cytokine release and the activation of nuclear factor kappa-light-chain enhancer of activated B cells signaling in lipopolysaccharide-treated HH10 chicken embryos. In such an inflammatory condition, AP-2α- and Pax7-labeled pre-migratory and migratory neural crest cells in HH10 chicken embryos were significantly less than the ones in control. The bioinformatics analysis of RNA-seq data demonstrated that the principal differential gene expression occurred in transforming growth factor-beta (TGF-β) signaling pathway, which was confirmed by the subsequent experimental results of quantitative PCR and immunofluorescent staining. Under this inflammatory circumstance, whole-mount in situ hybridization, immunofluorescence, and quantitative PCR showed the gene expression changes of key EMT-related transcription factors including upregulated Msx1, downregulated Slug, and FoxD3, as well as adhesion molecules and extracellular matrix protein including upregulated Cadherrin6B, E-cadherin, N-cadherin, and Laminin at the dorsal portion of neural tube of HH10 chicken embryos. Meanwhile, the bioinformatics analysis of RNA-seq data also manifested the differential gene expressions relevant to cell proliferation, which was confirmed by proliferating cell nuclear antigen Western blot data and co-immunofluorescence staining of human natural killer-1 and phosphorylated histone H3. In brief, this study revealed for the first time that the double-edged sword role of TGF-β signaling pathway between intrauterine inflammation (protective role) and cranial neural crest development (harmful role).

Formation and contraction of multicellular actomyosin cables facilitate lens placode invagination

Embryonic morphogenesis relies on the intrinsic ability of cells, often through remodeling the cytoskeleton, to shape epithelial tissues during development. Epithelial invagination is an example of morphogenesis that depends on this remodeling but the cellular mechanisms driving arrangement of cytoskeletal elements needed for tissue deformation remain incompletely characterized. To elucidate these mechanisms, live fluorescent microscopy and immunohistochemistry on fixed specimens were performed on chick and mouse lens placodes. This analysis revealed the formation of peripherally localized, circumferentially orientated and aligned junctions enriched in F-actin and MyoIIB. Once formed, the aligned junctions contract in a Rho-kinase and non-muscle myosin dependent manner. Further molecular characterization of these junctions revealed a Rho-kinase dependent accumulation of Arhgef11, a RhoA-specific guanine exchange factor known to regulate the formation of actomyosin cables and junctional contraction. In contrast, the localization of the Par-complex protein Par3, was reduced in these circumferentially orientated junctions. In an effort to determine if Par3 plays a negative role in MyoIIB accumulation, Par3-deficient mouse embryos were analyzed which not only revealed an increase in bicellular junctional accumulation of MyoIIB, but also a reduction of Arhgef11. Together, these results highlight the importance of the formation of the multicellular actomyosin cables that appear essential to the initiation of epithelial invagination and implicate the potential role of Arhgef11 and Par3 in their contraction and formation.

Neuregulin-1 is a chemoattractant and chemokinetic molecule for trunk neural crest cells

BACKGROUND

Trunk neural crest cells migrate rapidly along characteristic pathways within the developing vertebrate embryo. Proper trunk neural crest cell migration is necessary for the morphogenesis of much of the peripheral nervous system, melanocytes, and the adrenal medulla. Numerous molecules help guide trunk neural crest cell migration throughout the early embryo.

RESULTS

The trophic factor NRG1 is a chemoattractant through in vitro chemotaxis assays and in vivo silencing via a DN-erbB receptor. Interestingly, we also observed changes in migratory responses consistent with a chemokinetic effect of NRG1 in trunk neural crest velocity.

CONCLUSIONS

NRG1 is a trunk neural crest cell chemoattractant and chemokinetic molecule. Developmental Dynamics 247:888-902, 2018.. © 2018 Wiley Periodicals, Inc.

Investigating developmental cardiovascular biomechanics and the origins of congenital heart defects

Innovative research on the interactions between biomechanical load and cardiovascular (CV) morphogenesis by multiple investigators over the past 3 decades, including the application of bioengineering approaches, has shown that the embryonic heart adapts both structure and function in order to maintain cardiac output to the rapidly growing embryo. Acute adaptive hemodynamic mechanisms in the embryo include the redistribution of blood flow within the heart, dynamic adjustments in heart rate and developed pressure, and beat to beat variations in blood flow and vascular resistance. These biomechanically relevant events occur coincident with adaptive changes in gene expression and trigger adaptive mechanisms that include alterations in myocardial cell growth and death, regional and global changes in myocardial architecture, and alterations in central vascular morphogenesis and remodeling. These adaptive mechanisms allow the embryo to survive these biomechanical stresses (environmental, maternal) and to compensate for developmental errors (genetic). Recent work from numerous laboratories shows that a subset of these adaptive mechanisms is present in every developing multicellular organism with a “heart” equivalent structure. This chapter will provide the reader with an overview of some of the approaches used to quantify embryonic CV functional maturation and performance, provide several illustrations of experimental interventions that explore the role of biomechanics in the regulation of CV morphogenesis including the role of computational modeling, and identify several critical areas for future investigation as available experimental models and methods expand.

A technique to increase accessibility to late-stage chick embryos for in ovo manipulations

BACKGROUND

During early development, avian embryos are easily accessible in ovo for transplantations and experimental perturbations. However, these qualities of the avian embryonic model rapidly wane shortly after embryonic day (E)4 when the embryo is obscured by extraembryonic membranes, making it difficult to study developmental events that occur at later stages in vivo.

RESULTS

In this study, we describe a multistep method that involves initially windowing eggs at E3, followed by dissecting away extraembryonic membranes at E5 to facilitate embryo accessibility in ovo until later stages of development. The majority of the embryos subjected to this technique remain exposed between E5 and E8, then become gradually displaced by the growing allantois from posterior to anterior regions.

CONCLUSIONS

Exposed embryos are viable and compatible with embryological and modern developmental biology techniques including tissue grafting and ablation, gene manipulation by electroporation, and protein expression. This technique opens up new avenues for studying complex cellular interactions during organogenesis and can be further extrapolated to regeneration and stem cell studies.