Research

Zebrafish embryos are provide an excellent animal model into which various human cells can be introduced. The engrafted human cells can be easily observed under microscopes through the highly transparent bodies of the embryos. This model can be easily generated with a microinjection system and simple zebrafish husbandry. It can be used as a rapid cancer diagnostic method in biomedical research and as an animal model of diverse human cancers. It can be also used for high-throughput drug screening and toxicity assessments.

Shellfishes are also good models for environmental toxicological studies. Oysters are used in the LEH for this purpose. Beside using the oyster individuals for ecotoxicity assessment, we also utilize the primary cell cultures from different tissues of the oyster. The two major types of oyster cells used in our lab are cardiomyocytes (CvCMs), which are isolated from the heart of Crassostrea virginica, and the epithelial cells (CvMEs) cultured from the mantle tissue of C. virginica. The CvCMs have been used to evaluate the toxic effects of fungicides in agriculture while the CvMEs are applied to understand the environmental effects on the bivalve shell formation.

Instead of culturing skin keratinocytes in two-dimensional plates, we induce kertinocytes to form multiple layers simulating the stratified squamous epithelial structure of skin epidermis. The stratified keratinocyte culture can be grown on top of various matrices, such as medium, collagen, or acellular dermis. Dermal fibroblast and other stromal cells can be also seeded in the matrices as a co-culture of the keratinocytes. This model can be used to build a skin-on-a-chip platform for the studies of skin diseases and environmental toxicology.

Many environmental pollutants can be accumulated on human skin. Some chemical compounds in these pollutants can penetrate the surface barrier and absorbed by the skin keratinocytes. The toxicities of these chemicals can cause skin irritation, which ultimately results in the inflammatory skin diseases. In some severe cases, chemicals initiate skin cancers through the mutagenic effects on skin cells. Similar symptoms can be created on our mouse models to provide in vivo tools for the studies in the pathogenic effects of environmental pollutants. These models also help us develop strategies to protect our skin from the toxicities of the pollutants.

Modifications of a major environmental pollutant family, polycyclic aromatic hydrocarbons (PAHs), by environmental factors result in unpredictable changes in the toxicity of these chemicals. Recent studies demonstrated the relationship between a number of acute human skin diseases and the exposure to PAH compounds altered by environmental factors, such as sunlight, water salinity, and water acidification. Understanding the responses of human skin cells to the toxic effects of PAH chemicals under environmental pressure in molecular level will help us predict our risk of skin diseases caused by environment-engineered PAH chemicals.

Funded by NIH/NIEHS (1R15ES030955-01), this project is aiming to understand the molecular mechanism of human inflammatory skin diseases caused by the PAH compounds, and how environmental factors affect the dermatoxicities of these compounds. The toxicities of the PAH chemicals with photo-modification at different salinity and pCO2 levels are evaluated using three-dimensional human keratinocyte culture and keratinocyte/fibroblast co-culture models. A putative PAH pathogenic pathway in keratinocytes are validated using the 3D keratinocytes constructs. The relationship between the identified pathway and the skin inflammatory responses is investigated using the mouse skin inflammation model. As a study in predictive toxicology, the approach of this study takes advantage of the basic knowledge of biological pathways to develop in vitro and animal-based tests to predict adverse effects of chemical exposure, which is a priority component of the Environmental Health Sciences. 

Fish and shellfish serve as an important source of high-quality protein and non-saturated fat. Near-shore aquaculture supplies over 50% of the seafood production globally. Though over the past decades seafood species and their production have been severely affected by water contamination as a result of energy production and climate change. In this study, investigators from Texas A&M University-Corpus Christi, Louisiana State University, and Dalian Ocean University in China will identify potential risks of oyster production systems exposed to the contamination of petroleum products and the adverse environmental factors due to stresses from environmental stress. An ocean model containing simulated environmental stresses will be developed to predict how petroleum products impact the development and growth of oysters in near-shore habitats in the Gulf of Mexico (GoM), and Bohai Bay (BhB), China. 

    The project is currently funded by the NSF. It uses the oyster as a model aquaculture species to assess the toxicity changes of crude oil compounds in response to environmental stresses. The locations to be studied in this project, the GoM in the US and the BhB in China, share the common characteristics of robust seafood harvesting in conjunction with a vigorous petroleum production industry. However, these marine environments have distinct differences due to their geographic locations. This diversity of the networks is expected to be explored by the computational modeling approach developed in this study.

​    The strategies and methods employed can be further extended to other marine aquaculture species. Moreover, this investigation on the marine impact of crude oil can translate to other marine contaminants such as pesticides and pharmaceutical products, which have also become of concern in onshore/offshore aquaculture. Research results will provide 1) a better understanding of the toxicological alterations of petroleum products under global environmental change; 2) the impacts of the modification in petroleum products on the health of aquaculture species; 3) identification of environmental stress modified petrogenic products and their toxicities to oyster that should serve as references for the management of onshore/offshore aquaculture and oil production; and 4) prediction of impacts of oil production on global ocean environments and world aquaculture concurrent with climate change. 

Formation of the shell provides physical support and protection for bivalves. It also encloses a sealed gill-chamber for filter feeding. Failure of larvae to complete shell formation prevents food intake through filtration and eventually causes mortality. It is well known that the shell development, during the early life history stages of bivalves, is vulnerable to environmental stressors. The habitats of marine bivalves are commonly seen along the coastal and estuarine areas. These areas often show great environmental variations caused by unique geographic conditions and human activities. Due to the lack of mobility during most of their life cycle, bivalves employ a rapid acclimation mechanism to adapt to highly dynamic and stressful environments. As one of the most critical stages during the bivalve embryo development, shell formation, regulated by mantle cell calcification, is sensitive to a wide range of environmental changes. Although a few studies revealed the potential impact of environmental stress on bivalve shell formation, efforts in understanding the mechanism of this impact are very limited.

    The goal of the project is to understand the molecular mechanisms of alteration in bivalve shell formation under environmental stress using the eastern oyster (Crassostrea virginica) as a model. Scientific benefits from this project include 1) a better understanding of the bivalve shell formation mechanism; 2) finding the relationship between marine bivalve calcification and the dynamics of CO2 and water salinity in the environment; 3) identification of the roles of calcium-binding proteins in the regulation of calcification genetic pathway in response to the environmental stress; 4) establishment of a reliable animal model to study the aquatic animal biomineralization; and 5) the development of a potential strategy to protect the development of marine bivalve species from being disrupted by environmental stress.  

A number of human diseases and their pathological processes have been modeled by zebrafish including leukaemogenesis, melanoma oncogenesis, iron-storage disorder, hypothyroidism, vitamin deficiency, etc. Because of the high optical transparency of body and rapid development of the embryo, zebrafish model has the unique advantage in displaying the onset and course of a pathological process. It also contributes to the high-throughput screening for the development of therapeutics against various human diseases. 

    To better utilize the zebrafish model in the biomedical research, the zebrafish can be humanized by engrafting the human cells into the fish embryos. A zebrafish xenograft model has been created in my previous study.  Depending on the purpose of the study, the xenograft model can be prepared using human cells from different sources. Human cells inside the fish embryos can be labeled by the live cell dyes in vitro. The engrafted cells can be tracked afterward by fluorescent imaging. The migration and proliferation of transplanted cells will be evaluated. 

    ​Zebrafish biomedical models have been established through my previous research project. We have a zebrafish holding system allowing us to perform artificially spawning, fertilization, nursing, as well as daily maintenance of zebrafish. Our laboratory facility has the ability to hold multiple zebrafish strains with well regulate conditions to maintain the consistent temperature, pH, salinity, and oxygen levels. We have also introduced the CRISPR/Cas9 technique to our projects to study the gene functions in vivo.