Wu Lab in the departments of Medicine & Radiology

Research

Our lab focuses on the translation of novel cellular and genetic therapy. Our group is composed of molecular biologists, cell biologists, biochemists and non-invasive imaging specialists. We are applying tools to study the biology of stem cells, better understand stem cell immunogenicity and tumorgenicity, derive stem cells from adult cells, and identify novel therapeutic targets.

Application of imaging technologies to track cell & gene therapy

The efficacy of cell and gene therapy remains uncertain and has many unanswered questions. These include the following: 1) What are the molecular and cellular factors that affect myocardial improvement? (2) What are the optimal cellular and/or genetic therapies, delivery times and techniques, and dosage? (3) Do these transplanted or genetically modified cells survive, integrate, and proliferate in the target organ?  (4) In the long-term, do these cells engraft, differentiate, and/ or proliferate? To address these important questions, we apply various in vivo imaging techniques including microSPECT/CT/PET, fluorescence, small animal MRI, bioluminescence, and ultrasound to track cell and gene therapy (Circulation 2011; 123:425-443).

Development of molecular imaging constructs for elucidation of biological processes

Molecular imaging enables the noninvasive, quantitative, and repetitive visualization of biological processes in vivo at the cellular and sub-cellular level in vivo. One of the most important advances has been the development of triple reporter gene constructs, composed of bioluminescent, fluorescent, and positron emission tomography (PET) reporter genes. We develop unique molecular imaging constructs to study biological processes. We have recently evaluated the role of signal transducers and activators of transcription 3 (STAT3) during embryonic cell differentiation by constructing a custom STAT3 reporter construct (Stem Cells and Development. 2009:18:2:205-214). 

Transcriptional profiling of human ES cells and human IPS cells

MicroRNAs (miRNAs) are endogenous class of small non-coding RNAs that target mRNAs for cleavage or translational repression, thus, playing an important role in post-transcriptional regulation. We utilize microarray analysis to better define the role of miRNAs in regulating self-renewal, pluripotency and differentiation of human induced pluripotent stem cells (iPS) and embryonic stem (ES) cells (Stem Cell Dev 2009;18(5):749-58 & Circ Cardiov Genet 2010;3:426-435).  Recently, we have also used single cell analysis to show that human iPS cells have more heterogeneity in gene expression levels compared to human ES cells, suggesting that human ES cells occupy an alternate, less stable pluripotent state (J Clinical Investigation 2011).

Understanding and prevention of acute donor cell death

Clinical translation of cell therapies depends on the knowledge of donor cell biology and physiology after transplantation; thus, it is critical to develop a strong understanding of the survival pattern of donor cells following transplantation.  Traditional methods of studying cell survival dynamics post-transplantation require animals to be sacrificed at different time points for histological analysis, enzyme assays or DNA quantification.  Molecular imaging enables the noninvasive quantification of cell survival in vivo.  We use molecular imaging to better understand and prevent donor cell death. Using reporter imaging technology and bioluminescence imaging, we have recently characterized survival trends of adult and embryonic stem cell populations following delivery into the myocardium (Circulation 2008;118:S121-S129).

Inducing immune tolerance for embryonic stem cells

Embryonic stem cells (ESCs) are pluripotent, meaning they have the capacity to differentiate into any cell type of the human body. Although ESCs have been found to express low levels of major histocompatibility antigen and can potentially inhibit T cell proliferation; thereby, allowing for their survival many weeks after tranplantation, we have found that transplantation of ESCs results in donor-specific immune recognition and rejection.   We are, therefore, developing new strategies to reduce and/or eliminate immunologic response following ESC-based transplantation  (PNAS. 2008;105:35:12991-12996)

Understanding tumorigenic potential of pluripotent stem cells

teratp,aA major clinical obstacle of pluripotent stem cell based therapies is the potential of embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) to form teratomas following in-vivo transplantation. Thus, a major focus of our lab is to better understand the tumorigenic potential of pluripotent stem cells and to develop novel methods of detecting and treating teratoma formation (Cell Cycle. 2009;8(16): 2608-2612).

Efficient derivation of iPS cells from adult somatic cell populations

Induced pluripotent stem (iPS) cells have been successfully derived from somatic expression of transcription factors. The generation of patient-specific and disease-specific iPS cells may enhance our understanding of specific disease mechanisms and further advance regenerative therapy.  We are developing various techniques to reprogram cells efficiently from various types of somatic cells.  Recently, We have described efficient reprogramming of adipose stromal cells into iPS cells under feeder-free conditions (PNAS 2009). More recently, we have also described reprogramming of human iPS cells using non-viral minicircle plasmid technique (Nature Methods 2010; Nature Protocol 2011).

Discovery of novel therapeutic targets for cardiac gene therapy

Better understanding of the molecular and genetic basis for cardiac disease has enabled the application of gene therapy as a novel treatment alternative.  The development of improved gene transfer techniques has allowed the modification of cardiac cells to over-express beneficial proteins or inhibit pathological proteins to achieve improved cell function and survival following injury. For example, up-regulation of hypoxia inducible factor-1 alpha transcriptional factor (HIF-1) can activate several downstream angiogenic genes during hypoxia, but HIF-1 is naturally degraded by the enzyme prolyl hydroxylase-2.  We have recently demonstrated that down-regulation of this enzyme by short hairpin RNA (shRNA) interference therapy results in activation of downstream angiogenic genes and proteins, resulting in angiogenesis and improvement in contractility (Circulation. 2008; 118: 121-29).

Cardiac iPSCs for Modeling Cardiomyopathies

Both familial hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) are prevalent hereditary cardiac disorder linked to arrhythmia and sudden cardiac death. While the causes of HCM have been identified as genetic mutations in the cardiac sarcomere, cytoskeletal, mitochondrial, and nuclear membrane proteins, the exact mechanistic pathways are not understood. To elucidate the mechanisms underlying HCM and DCM development, we have been generating patient-specific induced pluripotent stem cell cardiomyocytes for modeling these 2 prevalent diseases (Sun et al, Science Transl Med 2012 & Lan et al, Cell Stem Cell 2013).

Cardiac iPSCs for Drug Screening & Discovery

Drug attrition rates have increased in past years, resulting in growing costs for the pharmaceutical industry and consumers. The reasons for this include the lack of in vitro models that correlate with clinical results and poor preclinical toxicity screening assays. The in vitro production of human cardiac progenitor cells and cardiomyocytes from human pluripotent stem cells provides an amenable source of cells for applications in drug discovery, disease modeling, regenerative medicine, and cardiotoxicity screening (Liang et al, Circulation 2013 & Mordwinkin et al, J Cardiov Transl Res 2013).

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