Development of high-concentration lipoplexes for in vivo gene function studies in vertebrate embryos

Nanoplastics causes extensive congenital malformations during embryonic development by passively targeting neural crest cells

Nanomaterials are widespread in the human environment as pollutants, and are being actively developed for use in human medicine. We have investigated how the size and dose of polystyrene nanoparticles affects malformations in chicken embryos, and have characterized the mechanisms by which they interfere with normal development. We find that nanoplastics can cross the embryonic gut wall. When injected into the vitelline vein, nanoplastics become distributed in the circulation to multiple organs. We find that the exposure of embryos to polystyrene nanoparticles produces malformations that are far more serious and extensive than has been previously reported. These malformations include major congenital heart defects that impair cardiac function. We show that the mechanism of toxicity is the selective binding of polystyrene nanoplastics nanoparticles to neural crest cells, leading to the death and impaired migration of those cells. Consistent with our new model, most of the malformations seen in this study are in organs that depend for their normal development on neural crest cells. These results are a matter of concern given the large and growing burden of nanoplastics in the environment. Our findings suggest that nanoplastics may pose a health risk to the developing embryo.

Bridging the In Vitro to In Vivo gap: Using the Chick Embryo Model to Accelerate Nanoparticle Validation and Qualification for In Vivo studies

We postulate that nanoparticles (NPs) for use in therapeutic applications have largely not realized their clinical potential due to an overall inability to use in vitro results to predict NP performance in vivo. The avian embryo and associated chorioallantoic membrane (CAM) has emerged as an in vivo preclinical model that bridges the gap between in vitro and in vivo, enabling rapid screening of NP behavior under physiologically relevant conditions and providing a rapid, accessible, economical, and more ethical means of qualifying nanoparticles for in vivo use. The CAM is highly vascularized and mimics the diverging/converging vasculature of the liver, spleen, and lungs that serve as nanoparticle traps. Intravital imaging of fluorescently labeled NPs injected into the CAM vasculature enables immediate assessment and quantification of nano-bio interactions at the individual NP scale in any tissue of interest that is perfused with a microvasculature. In this review, we highlight how utilization of the avian embryo and its CAM as a preclinical model can be used to understand NP stability in blood and tissues, extravasation, biocompatibility, and NP distribution over time, thereby serving to identify a subset of NPs with the requisite stability and performance to introduce into rodent models and enabling the development of structure-property relationships and NP optimization without the sacrifice of large populations of mice or other rodents. We then review how the chicken embryo and CAM model systems have been used to accelerate the development of NP delivery and imaging agents by allowing direct visualization of targeted (active) and nontargeted (passive) NP binding, internalization, and cargo delivery to individual cells (of relevance for the treatment of leukemia and metastatic cancer) and cellular ensembles (e.g., cancer xenografts of interest for treatment or imaging of cancer tumors). We conclude by showcasing emerging techniques for the utilization of the CAM in future nano-bio studies.

PEGylation and folic-acid functionalization of cationic lipoplexes-Improved nucleic acid transfer into cancer cells

Efficient and reliable transfer of nucleic acids for therapy applications is a major challenge. Stabilization of lipo- and polyplexes has already been successfully achieved by PEGylation. This modification reduces the interaction with serum proteins and thus prevents the lipoplexes from being cleared by the reticuloendothelial system. Problematically, this stabilization of lipoplexes simultaneously leads to reduced transfer efficiencies compared to non-PEGylated complexes. However, this reduction in transfer efficiency can be used to advantage since additional modification of PEGylated lipoplexes with functional groups enables improved selective transfer into target cells. Cancer cells overexpress folate receptors because of a significantly increased need of folate due to high cell proliferation rates. Thus, additional folate functionalization of PEGylated lipoplexes improves uptake into cancer cells. We demonstrate herein that NHS coupling chemistries can be used to modify two commercially available transfection reagents (Fuse-It-DNA and Lipofectamine® 3000) with NHS-PEG-folate for increased uptake of nucleic acids into cancer cells. Lipoplex characterization and functional analysis in cultures of cancer- and healthy cells clearly demonstrate that functionalization of PEGylated lipoplexes offers a promising method to generate efficient, stable and selective nucleic acid transfer systems.

Avian facial morphogenesis is regulated by c-Jun N-terminal kinase/planar cell polarity (JNK/PCP) wingless-related (WNT) signaling

Wingless-related proteins (WNTs) regulate extension of the central axis of the vertebrate embryo (convergent extension) as well as morphogenesis of organs such as limbs and kidneys. Here, we asked whether WNT signaling directs facial morphogenesis using a targeted approach in chicken embryos. WNT11 is thought to mainly act via β-catenin-independent pathways, and little is known about its role in craniofacial development. RCAS::WNT11 retrovirus was injected into the maxillary prominence, and the majority of embryos developed notches in the upper beak or the equivalent of cleft lip. Three-dimensional morphometric analysis revealed that WNT11 prevented lengthening of the maxillary prominence, which was due in part to decreased proliferation. We next determined, using a series of luciferase reporters, that WNT11 strongly induced JNK/planar cell polarity signaling while repressing the β-catenin-mediated pathway. The activation of the JNK-ATF2 reporter was mediated by the DEP domain of Dishevelled. The impacts of altered signaling on the mesenchyme were assessed by implanted Wnt11- or Wnt3a-expressing cells (activates β-catenin pathway) into the maxillary prominence or by knocking down endogenous WNT11 with RNAi. Host cells were attracted to Wnt11 donor cells. In contrast, cells exposed to Wnt3a or the control cells did not migrate. Cells in which endogenous WNT11 was knocked down were more oriented and shorter than those exposed to exogenous WNT11. The data suggest that JNK/planar cell polarity WNT signaling operates in the face to regulate several morphogenetic events leading to lip fusion.

Morpholinos: studying gene function in the chick

The use of morpholinos for perturbing gene function in the chick, Gallus gallus, has led to many important discoveries in developmental biology. This technology makes use of in vivo electroporation, which allows gain and loss of function in a temporally, and spatially controlled manner. Using this method, morpholinos can be transfected into embryonic tissues from early to late developmental stages. In this article, we describe the methods currently used in our laboratory to knock down gene function using morpholinos in vivo. We also detail how morpholinos are used to provide consistency of the results, and describe two protocols to visualise the morpholino after electroporation. In addition, we provide guidance on avoiding potential pitfalls, and suggestions for troubleshooting solutions. These revised techniques provide a practical starting point for investigating gene function in the chick.

Dual functions for WNT5A during cartilage development and in disease

Mouse and human genetic data suggests that Wnt5a is required for jaw development but the specific role in facial skeletogenesis is unknown. We mapped expression of WNT5A in the developing chicken skull and found that the highest expression was in early Meckel's cartilage but by stage 35 expression was decreased to background. We focused on chondrogenesis by targeting a retrovirus expressing WNT5A to the mandibular prominence prior to cell differentiation. Unexpectedly, there were no phenotypes in the first 6days following injection; however later the mandibular bones and Meckel's cartilage were reduced or missing on the treated side. To examine the effects on cartilage differentiation we treated micromass cultures from mandibular mesenchyme with Wnt5a-conditioned media (CM). Similar to in vivo viral data, cartilage differentiates normally, but, after 6days of culture, nearly all Alcian blue staining is lost. Collagen II and aggrecan were also decreased in treated cultures. The matrix loss was correlated with upregulation of metalloproteinases, MMP1, MMP13, and ADAMTS5 (codes for Aggrecanase). Moreover, Marimastat, an MMP and Aggrecanase inhibitor rescued cartilage matrix in Wnt5a-CM treated cultures. The pathways mediating these cartilage and RNA changes were investigated using luciferase assays. Wnt5a-CM was a potent inhibitor of the canonical pathway and strongly activated JNK/PCP signaling. To determine whether the matrix loss is mediated by repression of canonical signaling or activation of the JNK pathway we treated mandibular cultures with either DKK1, an antagonist of the canonical pathway, or a small molecule that antagonizes JNK signaling (TCS JNK 6o). DKK1 slightly increased cartilage formation and therefore suggested that the endogenous canonical signaling represses chondrogenesis. To test this further we added an excess of Wnt3a-CM and found that far fewer cartilage nodules differentiated. Since DKK1 did not mimic the effects of Wnt5a we excluded the canonical pathway from mediating the matrix loss phenotype. The JNK antagonist partially rescued the Wnt5a phenotype supporting this non-canonical pathway as the main mediator of the cartilage matrix degradation. Our study reveals two new roles for WNT5A in development and disease: 1) to repress canonical Wnt signaling in cartilage blastema in order to promote normal differentiation and 2) in conditions of excess to stimulate degradation of mature cartilage matrix via non-canonical pathways.

Experimental approaches for gene regulatory network construction: the chick as a model system

Setting up the body plan during embryonic development requires the coordinated action of many signals and transcriptional regulators in a precise temporal sequence and spatial pattern. The last decades have seen an explosion of information describing the molecular control of many developmental processes. The next challenge is to integrate this information into logic "wiring diagrams" that visualize gene actions and outputs, have predictive power and point to key control nodes. Here, we provide an experimental workflow on how to construct gene regulatory networks using the chick as model system.