Angiogenesis in the Avian Embryo Chorioallantoic Membrane: A Perspective on Research Trends and a Case Study on Toxicant Vascular Effects

Physiological and molecular responses of the chorioallantoic membranes to diluted bitumen exposures in multiple bird species

Embryotoxicity is a well-known consequence of polycyclic aromatic compound (PAC) exposure, but the molecular mechanisms of action of PAC mixtures, especially for unconventional crude petroleum types such as diluted bitumen (dilbit), remain to be fully elucidated in birds. To explore the mechanism of action of PAC in birds, the egg-injection model was used. Eggs of domestic chicken (Gallus gallus), double-crested cormorant (Nannopterum auritum), and northern gannet (Morus bassanus) were injected with 0.5 μL/g of average species-specific egg weight of 1:10-1:10,000 dilutions of Clearwater or Cold Lake Blend dilbits into the air cell on embryonic Day 0 and were artificially incubated until the liver was formed. The injections of <0.16-335 ng total PAC/g egg were consistent with PAC concentrations measured in wild bird eggs and in embryos exposed to dilbit through eggshell oiling. Mortality and frequency of malformations were low across treatments. The expression of genes involved in xenobiotic detoxification in both liver and chorioallantoic membrane (CAM) differed among species in response to dilbit exposure. Cytochrome P450 1a (cyp1a) in the CAM of dilbit-exposed chickens was induced to a higher fold-change at a lower PAC concentration than the liver, but this pattern was not consistent in wild birds. The expression of additional genes involved in the aryl hydrocarbon receptor activation adverse outcome pathway were variable in the double-crested cormorant and northern gannet CAMs. Our study demonstrates the usefulness of CAM as a target tissue for PAC metabolism in embryotoxicity. Future studies should address the differential CAM physiology across bird species to better understand the variation of species responses to contaminants and consider the use of CAM in addition to liver.

Automated non-invasive laser speckle imaging of the chick heart rate and extraembryonic blood vessels and their response to Nifedipine and Amlodipine drugs

Using our recently developed laser speckle contrast imaging (LSCI) to visualize blood vessels and monitor blood flow noninvasively, we test the utility of the developing chick heart as a functional model for drug screening. To this end, we examined the effects of antihypertensive agents Nifedipine and Amlodipine, belonging to the L-type calcium channel antagonist family, on blood flow visualized noninvasively through the intact shell. Guided by the live view mode, the drugs were injected through the shell and ventral to HH16-19 chick embryos. Our results show a significant reduction in the chick's heart rate, blood flow, and vascular size within 5-20 min after Nifedipine or Amlodipine injection. For moderate Nifedipine concentrations, these parameters returned to initial values within 2-3 h. Nifedipine showed a rapid reduction in heart rate and blood flow dynamics at a concentration ten times lower than Amlodipine. These findings show that our LSCI system can monitor and distinguish the chick heart's response to injected drugs from the same family. This serves as proof-of-concept, paving the way for a rapid, cost-effective, and quantitative test system for screening drugs that affect the cardiovascular system of live chick embryos. Live noninvasive imaging may also provide insights into the development and functioning of the vertebrate heart.

A morphometric and stereological study of the chorioallantoic membrane of the developing ostrich (Struthio camelus australis) embryo: a light and transmission electron microscopy investigation

The developing chorioallantoic membrane (CAM) of the ostrich (Struthio camelus) was studied between embryonic days 16 (E16) and E37. Egg masses and volumes were estimated prior to harvesting of the CAM. CAM volumes were obtained before the CAM was sampled for histology and transmission electron microscopy analysis. Stereological methods were used to estimate volume densities and absolute volumes of CAM structural components. Growth rate estimates of the CAM and its major components were obtained. At E16, the three layers of the CAM were clearly delineated, but large parts still had not developed the blood-gas barrier (BGB) portions. By E37, chorionic blood capillaries had assumed a superficial position with thin BGB portions covering most of the chorionic surface. On regression analyses, the CAM had two growth phases, namely phase I that occurred between E16 and E25, when the CAM grew rapidly from a volume of 5.55 ± 1.27 to 28.82 ± 5.62 cm3 to then decrease to 25.18 ± 4.79 cm3 during phase II (E25-E37). The latter decline was attributed to changes in the chorionic and allantoic layers, while regression in the mesoderm mainly characterized blood and lymphatic vessels.This article is part of the theme issue 'The biology of the avian respiratory system'.

The avian embryo as a time-honoured animal model in developmental, biomedical and agricultural research

Avian embryos have been at the core of embryological, morphological, physiological and biochemical/molecular research, especially involving research in three primary areas: developmental, biomedical and agricultural research. As developmental models, the avian embryo-especially that of the chicken-has been the single most used embryo model, perhaps in part from the combination of large size, ease of access and prior knowledge base. Developmental research with avian embryos has included organ system studies of the heart, vasculature, lungs, kidneys, nervous system, etc., as well as integrated physiological processes including gas-exchange, acid-base and ion/water regulation. In terms of translational research, avian embryos have modelled vascular development, based on the easily accessible chorioallantoic membrane under the eggshell. This same respiratory organ has enabled toxicological studies of how pollutants affect vertebrate development. Investigation of the transition to pulmonary breathing and the associated emergence of respiratory control has also relied heavily upon the avian embryo. In addition to developmental and biomedical investigations, the avian embryo has been studied intensively due to the huge importance of domesticated birds as a food source. Consequently, the effects of environment (including temperature, humidity, noise levels and photoperiod) during incubation on subsequent post-hatch phenotype are being actively investigated.This article is part of the theme issue 'The biology of the avian respiratory system'.

Automated non-invasive laser speckle imaging of the chick heart rate and extraembryonic blood vessels and their response to nifedipine and amlodipine drugs

Using our recently developed laser speckle contrast imaging (LSCI) to visualize blood vessels and monitor blood flow, here we test the utility of the chick embryo for drug screening. To this end, we examined the effects of antihypertensive agents Nifedipine and Amlodipine, belonging to the L-type calcium channel antagonist family, on blood flow visualized noninvasively through the intact shell. Guided by the live view mode, the drugs were injected through the shell and ventral to HH16-19 chick embryos. Our results show a significant reduction in the chick heart rate, blood flow, and vascular size within 5-20 minutes after Nifedipine or Amlodipine injection. For moderate Nifedipine concentrations, these parameters returned to initial values within 2-3 hours. In contrast, Amlodipine showed a rapid reduction in heart rate and blood flow dynamics at a more than ten times higher concentration than Nifedipine. These findings show that our LSCI system can monitor and distinguish the chick heart's response to injected drugs from the same family. This serves as proof-of-concept, paving the way for a rapid, cost effective, and quantitative test system for screening drugs that affect the cardiovascular system of live chick embryos. Live noninvasive imaging may also provide insights into the development and functioning of the vertebrate heart.

Highlights

Non-invasive Laser Speckle Contrast Imaging (LSCI) of the chick chorioallantoic membrane (CAM) in whole incubated eggsSimultaneous recording images of the CAM, dynamics of blood flow, and heart rateLive view mode to identify size, heart position, and location of the embryo in the eggAutomated system for data acquisition and analysisLongitudinal quantification of the impact of a calcium channel antagonists, nifedipidine and amlodipine on the embryonic heart rate, CAM's blood flow, size and number of vessels.

Non-invasive laser speckle contrast imaging (LSCI) of extra-embryonic blood vessels in intact avian eggs at early developmental stages

Imaging blood vessels in early-stage avian embryos has a wide range of practical applications for developmental biology studies, drug and vaccine testing, and early sex determination. Optical imaging, such as brightfield transmission imaging, offers a compelling solution due to its safe non-ionizing radiation, and operational benefits. However, it comes with challenges, such as eggshell opacity and light scattering. To address these, we have revisited an approach based on laser speckle contrast imaging (LSCI) and demonstrated a high-quality, comprehensive, and non-invasive visualization of blood vessels in few-days-old chicken eggs, with blood vessels as small as 100 µm in diameter (with LSCI profile full-width-at-half-maximum of 275 µm). We present its non-invasive use for monitoring blood flow, measuring the embryo's heartbeat, and determining the embryo's developmental stages using machine learning with 85% accuracy from stage HH15 to HH22. This method can potentially be used for non-invasive longitudinal studies of cardiovascular development and angiogenesis, as well as egg screening for the poultry industry.

Perspectives on chick embryo models in developmental and reproductive toxicity screening

Teratology, the study of congenital anomalies and their causative factors intersects with developmental and reproductive toxicology, employing innovative methodologies. Evaluating the potential impacts of teratogens on fetal development and assessing human risk is an essential prerequisite in preclinical research. The chicken embryo model has emerged as a powerful tool for understanding human embryonic development due to its remarkable resemblance to humans. This model offers a unique platform for investigating the effects of substances on developing embryos, employing techniques such as ex ovo and in ovo assays, chorioallantoic membrane assays, and embryonic culture techniques. The advantages of chicken embryonic models include their accessibility, cost-effectiveness, and biological relevance to vertebrate development, enabling efficient screening of developmental toxicity. However, these models have limitations, such as the absence of a placenta and maternal metabolism, impacting the study of nutrient exchange and hormone regulation. Despite these limitations, understanding and mitigating the challenges posed by the absence of a placenta and maternal metabolism are critical for maximizing the utility of the chick embryo model in developmental toxicity testing. Indeed, the insights gained from utilizing these assays and their constraints can significantly contribute to our understanding of the developmental impacts of various agents. This review underscores the utilization of chicken embryonic models in developmental toxicity testing, highlighting their advantages and disadvantages by addressing the challenges posed by their physiological differences from mammalian systems.

Effects of neratinib on angiogenesis and the early stage of the embryo using chicken embryo as a model

Angiogenesis is the process of forming new blood capillaries from pre-existing vessels. Even though it is essential during normal development, it plays a major role in cancer progression. Neratinib is a pan-human epidermal growth factor receptor (HER) inhibitor that has recently been approved for the treatment of HER2-positive breast cancer. However, its effects on angiogenesis and embryogenesis remain unknown. This study examined the antiangiogenic effects of neratinib using the chorioallantoic membrane (CAM) of chicken embryos. We also evaluated neratinib's toxicity during the early stages of normal development using the chicken embryos, primary embryonic fibroblasts (EFBs), and human umbilical vein endothelial cells (HUVEC). Our findings revealed that neratinib significantly inhibited the CAM angiogenesis compared to controls by reducing vessel percentage area and the average vessel length. Furthermore, neratinib downregulated vascular endothelial growth factor (VEGF), a key mediator of angiogenesis. At lower concentrations, neratinib was well-tolerated during early stages of normal development. Additionally, EFBs treated with neratinib showed no morphological or viability changes when compared to controls. However, at the highest concentration tested, neratinib treatment reduced HUVEC cell viability. This effect may be associated with the dysregulation of key apoptotic genes, including caspase-3, caspase-8, caspase-9, and the B-cell lymphoma 2 (Bcl2) gene. Our findings indicate a novel potential application of neratinib as an antiangiogenic agent, exhibiting tolerable toxicity in the early stages of embryogenesis.

In vivo evaluation of mebendazole and Ran GTPase inhibition in breast cancer model system

Aim: To investigate the therapeutic potential of mebendazole (MBZ)-loaded nanostructured lipid carriers (NLCs). Methodology: NLC-MBZ was prepared and characterized to evaluate the in vitro and in vivo anticancer effects and the inhibitory effect on RanGTP and its potential as an antimetastatic treatment in vivo. Results: NLC-MBZ exhibited a size and charge of 155 ± 20 nm and -27 ± 0.5 mV, respectively, with 90.7% encapsulation. Free MBZ and NLC-MBZ had a 50% inhibitory concentration of 610 and 305 nM, respectively, against MDA-MB-231 cell lines. NLC-MBZ decreased tumor size, suppressed tumor lung metastases, and lowered the expression of CDC25A, SKP2, RbX1 and Cullin1 while boosting the Rb proteins. Conclusion: NLC-MBZ displayed antiangiogenic potential and resulted in a reduced rate of lung metastasis in vivo.

In vivo label-free tissue histology through a microstructured imaging window

Tissue histopathology, based on hematoxylin and eosin (H&E) staining of thin tissue slices, is the gold standard for the evaluation of the immune reaction to the implant of a biomaterial. It is based on lengthy and costly procedures that do not allow longitudinal studies. The use of non-linear excitation microscopy in vivo, largely label-free, has the potential to overcome these limitations. With this purpose, we develop and validate an implantable microstructured device for the non-linear excitation microscopy assessment of the immune reaction to an implanted biomaterial label-free. The microstructured device, shaped as a matrix of regular 3D lattices, is obtained by two-photon laser polymerization. It is subsequently implanted in the chorioallantoic membrane (CAM) of embryonated chicken eggs for 7 days to act as an intrinsic 3D reference frame for cell counting and identification. The histological analysis based on H&E images of the tissue sections sampled around the implanted microstructures is compared to non-linear excitation and confocal images to build a cell atlas that correlates the histological observations to the label-free images. In this way, we can quantify the number of cells recruited in the tissue reconstituted in the microstructures and identify granulocytes on label-free images within and outside the microstructures. Collagen and microvessels are also identified by means of second-harmonic generation and autofluorescence imaging. The analysis indicates that the tissue reaction to implanted microstructures is like the one typical of CAM healing after injury, without a massive foreign body reaction. This opens the path to the use of similar microstructures coupled to a biomaterial, to image in vivo the regenerating interface between a tissue and a biomaterial with label-free non-linear excitation microscopy. This promises to be a transformative approach, alternative to conventional histopathology, for the bioengineering and the validation of biomaterials in in vivo longitudinal studies.

Fabrication, Characterization and Wound-Healing Properties of Core-Shell SF@chitosan/ZnO/Astragalus Arbusculinus Gum Nanofibers

AIM

Silk fibroin/chitosan/ZnO/Astragalus arbusculinus (Ast) gum fibrous scaffolds along with adipose-derived mesenchymal stem cells (ADSCs) were investigated for accelerating diabetic wound healing.

METHODS

Scaffolds with a core-shell structure and different compositions were synthesized using the electrospinning method. Biological in vitro investigations included antibacterial testing, cell viability analysis and cell attachment evaluation. In vivo experiments, including the chicken chorioallantoic membrane (CAM) test, were conducted to assess wound-healing efficacy and histopathological changes.

RESULTS

The incorporation of Ast to the silk fibroin@ chitosan/ZnO scaffold improved wound healing in diabetic mice. In addition, seeding of ADSCs on the scaffold accelerated wound healing.

CONCLUSION

These findings suggest that the designed scaffold can be useful for skin regeneration applications.

Multi-parametric investigations on the effects of vascular disrupting agents based on a platform of chorioallantoic membrane of chick embryos

Background

Vascular disrupting agents (VDAs) are known to specifically target preexisting tumoural vasculature. However, systemic side effects as safety or toxicity issues have been reported from clinical trials, which call for further preclinical investigations. The purpose is to gain insights into their non-specific off-targeting effects on normal vasculature and provide clues for exploring underlying molecular mechanisms.

Methods

Based on a recently introduced platform consisting laser speckle contrast imaging (LSCI), chick embryo chorioallantoic membrane (CAM), and assisted deep learning techniques, for evaluation of vasoactive medicines, hemodynamics on embryonic day 12 under constant intravascular infusion of two VDAs were qualitatively observed and quantitatively measured in real time for 30 min. Blood perfusion, vessel diameter, vessel density, and vessel total length were further analyzed and compared between blank control and medicines dose groups by using multi-factor analysis of variance (ANOVA) analysis with factorial interactions. Conventional histopathology and fluorescent immunohistochemistry (FIHC) assays for endothelial cytoskeleton including ß-tubulin and F-actin were qualitatively demonstrated, quantitatively analyzed and further correlated with hemodynamic and vascular parameters.

Results

The normal vasculature was systemically negatively affected by VDAs with statistical significance (P<0.0001), as evidenced by four positively correlated parameters, which can explain the side-effects observed among clinical patients. Such effects appeared to be dose dependent (P<0.0001). FIHC assays qualitatively and quantitatively verified the results and exposed molecular mechanisms.

Conclusions

LSCI-CAM platform combining with deep learning technique proves useful in preclinical evaluations of vasoactive medications. Such new evidences provide new reference to clinical practice.

Discovery and Development of Tumor Angiogenesis Assays

The angiogenesis process was described in its basic concepts in the works of the Scottish surgeon John Hunter and terminologically assessed in the early twentieth century. An aberrant angiogenesis is a prerequisite for cancer cells in solid tumors to grow and metastasize. The sprouting of new blood vessels is one of the major characteristics of cancer and represents a gateway for tumor cells to enter both the blood and lymphatic circulation systems. In vivo, ex vivo, and in vitro models of angiogenesis have provided essential tools for cancer research and antiangiogenic drug screening. Several in vivo studies have been performed to investigate the various steps of tumor angiogenesis and in vitro experiments contributed to dissecting the molecular bases of this phenomenon. Moreover, coculture of cancer and endothelial cells in 2D and 3D matrices have contributed to improve the recapitulation of the complex process of tumor angiogenesis, including the peculiar conditions of tumor microenvironment.

Microvascular Experimentation in the Chick Chorioallantoic Membrane as a Model for Screening Angiogenic Agents including from Gene-Modified Cells

The chick chorioallantoic membrane (CAM) assay model of angiogenesis has been highlighted as a relatively quick, low cost and effective model for the study of pro-angiogenic and anti-angiogenic factors. The chick CAM is a highly vascularised extraembryonic membrane which functions for gas exchange, nutrient exchange and waste removal for the growing chick embryo. It is beneficial as it can function as a treatment screening tool, which bridges the gap between cell based in vitro studies and in vivo animal experimentation. In this review, we explore the benefits and drawbacks of the CAM assay to study microcirculation, by the investigation of each distinct stage of the CAM assay procedure, including cultivation techniques, treatment applications and methods of determining an angiogenic response using this assay. We detail the angiogenic effect of treatments, including drugs, metabolites, genes and cells used in conjunction with the CAM assay, while also highlighting the testing of genetically modified cells. We also present a detailed exploration of the advantages and limitations of different CAM analysis techniques, including visual assessment, histological and molecular analysis along with vascular casting methods and live blood flow observations.

The Chicken Embryo Model: A Novel and Relevant Model for Immune-Based Studies

Dysregulation of the immune system is associated with many pathologies, including cardiovascular diseases, diabetes, and cancer. To date, the most commonly used models in biomedical research are rodents, and despite the various advantages they offer, their use also raises numerous drawbacks. Recently, another in vivo model, the chicken embryo and its chorioallantoic membrane, has re-emerged for various applications. This model has many benefits compared to other classical models, as it is cost-effective, time-efficient, and easier to use. In this review, we explain how the chicken embryo can be used as a model for immune-based studies, as it gradually develops an embryonic immune system, yet which is functionally similar to humans'. We mainly aim to describe the avian immune system, highlighting the differences and similarities with the human immune system, including the repertoire of lymphoid tissues, immune cells, and other key features. We also describe the general in ovo immune ontogeny. In conclusion, we expect that this review will help future studies better tailor their use of the chicken embryo model for testing specific experimental hypotheses or performing preclinical testing.

Beyond the Chicken: Alternative Avian Models for Developmental Physiological Research

Biomedical research focusing on physiological, morphological, behavioral, and other aspects of development has long depended upon the chicken (Gallus gallus domesticus) as a key animal model that is presumed to be typical of birds and generally applicable to mammals. Yet, the modern chicken in its many forms is the result of artificial selection more intense than almost any other domesticated animal. A consequence of great variation in genotype and phenotype is that some breeds have inherent aberrant physiological and morphological traits that may show up relatively early in development (e.g., hypertension, hyperglycemia, and limb defects in the broiler chickens). While such traits can be useful as models of specific diseases, this high degree of specialization can color general experimental results and affect their translational value. Against this background, in this review we first consider the characteristics that make an animal model attractive for developmental research (e.g., accessibility, ease of rearing, size, fecundity, development rates, genetic variation, etc.). We then explore opportunities presented by the embryo to adult continuum of alternative bird models, including quail, ratites, songbirds, birds of prey, and corvids. We conclude by indicating that expanding developmental studies beyond the chicken model to include additional avian groups will both validate the chicken model as well as potentially identify even more suitable avian models for answering questions applicable to both basic biology and the human condition.

Experimental Models to Study Skin Wound Healing with a Focus on Angiogenesis

A large number of models are now available for the investigation of skin wound healing. These can be used to study the processes that take place in a phase-specific manner under both physiological and pathological conditions. Most models focus on wound closure, which is a crucial parameter for wound healing. However, vascular supply plays an equally important role and corresponding models for selective or parallel investigation of microcirculation regeneration and angiogenesis are also described. In this review article, we therefore focus on the different levels of investigation of skin wound healing (in vivo to in virtuo) and the investigation of angiogenesis and its parameters.