RESEARCH PROJECTS
 

ENGINEERING A FUNCTIONAL AORTIC HEART VALVE USING A 3D BIOPRINTING APPROACH

Aortic valve disease is one of the most common congenital heart defects and affects over 5% of children with heart disease. Often times, pediatric patients are treated by replacing or less commonly repairing the valve. The issue with clinically available valve implants for children is that they come at a fixed size and are incapable of growth. Thus, this requires multiple surgeries for valve revisions. Our goal is to address this need with a tissue engineered heart valve that is capable of remodeling and growth within a growing child. To do so, we are using induced pluripotent stem cells to generate patient specific valve cells. In addition, we are engineering cell-laden biomaterials to be 3D printed using 3D models generated from patient CT. Using this approach, we will generate a 3D tissue engineered heart valve that has the potential to grow and repair in a child.

3D BIOPRINTED CARDIAC EXTRACELLULAR MATRIX BASED HEART PATCH FOR TREATMENT OF PEDIATRIC HEART DISEASE

Congenital heart defects effect 35,000 newborns annually, resulting in significant hindrance to heart function. Although surgical treatments have shown improvements, many children develop cardiac dysfunction and right ventricular failure. The main standard of care in these cases is transplantation, which is limited by donor availability and transplant rejection. In collaboration with Christman lab at the University of California, San Diego, we are developing a heart patch, composed of cardiac matrix material and pediatric stem cells, for treatment of pediatric heart failure. The use of cardiac stem cells will allow for targeted and effective regeneration of heart function, while the inclusion of cardiac matrix will decrease hypertrophy and improve ejection fraction. The patch will be bioprinted for control of device structure and properties, allowing for a personalized treatment platform.

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USING SYSTEMS BIOLOGY AND BIOINFORMATICS TO IDENTIFY POTENITAL THERAPEUTIC RNA CLUSTERS IN HUMAN CARDIAC C-KIT+ CELLS

The regenerative potential of human cardiac c-kit+ progenitor cells (hCPCs) to repair myocardium after injury has been shown in multiple studies. In this project, we sequence RNA from a large pool of patient-derived hCPCs  for miRNAs  of interest. Bioinformatics and systems biology-based approaches will be used to (1) identify miRNA clusters which covary with functional, pro-reparative outcomes, and (2) identify potential targets of interest for further study. We aim to gain insight into the molecular mechanisms by which hCPCs regenerate cardiac tissue.

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ENGINEERING EXOSOME-LIKE VESICLES

Stem cell based cardiac regeneration occurs mainly through paracrine signaling to local tissues. A key component of the paracrine signals released by the stem cells are nano-sized vesicles called exosomes. These are vehicles used to transfer microRNA, proteins and lipids to the native tissue. The therapeutic effects of such signaling persists long after the implanted stem cells have been flushed out, highlighting their importance in regenerative therapies. We want to artificially engineer exosomes in-vitro so we can modulate the type and concentration of cargo delivered and also target specific tissues based on membrane proteins we attach. This will provide a highly controllable and specific avenue of paracrine signaling for regenerative therapies.

EXOSOMAL RNA CONTENT MANIPULATION FOR ENHANCED MYOCARDIAL REPAIR 

Despite recent advances in cell therapy, donor-to-donor variability challenges its therapeutic potential. With bioinformatics approaches, it is possible to identify and predict essential molecules such as miRNA, mRNA, and lncRNA that are important in cardiac repair. In this project, we are deciphering specific RNAs' role and mode of action on cardiac repair in an ischemia-reperfusion model of MI. Specific miRNA, identified from previous bioinformatics studies, are inhibited or overexpressed in CPC exosomes to enhance therapeutic potential in various cardiac diseases.

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DEVELOPING A TISSUE-ENGINEERED CARDIAC PATCH FOR CHILDREN'S HEART DISEASE

In collaboration with the Xia Lab at Georgia Tech, we are currently investigating the use of electrospun polycaprolactone-based cardiac patch to enhance the reparative capabilities of pediatric human cardiac progenitor cells.  Specifically, we are interrogating the effects of fiber alignment and the inclusion of bioactive adhesion factors gelatin and fibronectin on cell behavior.  We hope to utilize these patches to repair injured hearts and to provide treatment for patients with congenital heart defects.

INVESTIGATING THE ROLE OF NOTCH1 ACTIVATION IN CARDIAC PROGENITOR CELLS

CPCs are a prime candidate for cell-based therapies to repair the damage caused by myocardial infarction (MI). We are working to improve cell retention and differentiation by designing novel injectable biomaterials for CPC delivery. We are also interested in the importance of the Notch1 signaling pathway in promoting survival and differentiation of CPCs.

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CARDIAC PROGENITOR CELL DELIVERY WITH EXTRACELLULAR MATRIX HYDROGEL FOR CARDIAC REPAIR

Our lab has demonstrated that CPCs isolated from human tissue biopsies confer cardiac regenerative potential through paracrine signaling. However, cell therapy is limited due to poor retention. The Christman lab at UCSD has developed an acellular biomaterial derived from decellularized porcine cardiac muscle. The acellular biomaterial promotes endogenous repair while maintaining reparative cues for longer time periods. In collaboration with the Christman lab, we are studying cardiac-derived cells delivered with myocardial extracellular matrix hydrogel as a combination therapy for congenital heart defects. This therapy may outweigh the benefits of standalone therapies while overcoming current limitations.

 

DESIGN OF A CONTRACTILE AUXETIC CARDIAC PATCH

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Typically, cardiac patches are designed with material properties to match native cardiac tissue and provide a scaffold for repair and regeneration. However, the material design rarely accounts for ventricle anisotropy and ranges in mechanical properties. A cardiac patch with the ability to account for this behavior could be used to improve cardiac function post myocardial infarction. In collaboration with the Dr. Hollister lab at Georgia Tech, we are designing an auxetic cardiac patch using hiPSC-derived cardiomyocytes. The auxetic scaffold allows for favorable anisotropy, tunable strength, and improved shear resistance. We hope to investigate cardiomyocyte maturation and promote favorable remodeling of the infarcted region.

IN VITRO CARDIAC CHAMBER MODEL

Heart diseases are an increasing clinical burden associated with high morbidity and mortality. Despite advances in tissue engineering and in vitro cardiac tissue models, a cellularized 3-dimensional scaffold with physiological mechanical properties has yet to be developed. Here, in collaboration with the Dr. Scott Hollister lab at Georgia Tech, we aim to replicate the chamber architecture and anisotropic beating using the auxetic polycaprolactone (PCL) framework to generate a novel cardiac chamber model with better mechanical properties recapitulating heart beat. Our design uses a human induce-pluripotent stem cell-derived cardiomyocytes (iCMs)-laden gelMA hydrogel to mimic heart wall in 3D cell culture environment. By recapitulating the anisotropic chamber movement using a bioreactor, we can generate a in vitro 3D cardiac chamber with better mechanical properties and biological integration. 

 

SINGLE CELL RNA SEQUENCING TO IDENTIFY REGENERATIVE CELL SUBPOPULATIONS

Regenerative therapies utilizing ckit+ cardiac progenitor cells for repairing the myocardium exhibit age-dependent capabilities, with older patient cells inducing increased fibrotic and immunogenic responses. We are utilizing the high-resolution capabilities of single cell RNA sequencing to analyze cells collected from neonates, children, and adults to identify subpopulations driving these differences in outcomes. We have identified subpopulations of cells in neonate and adult populations corresponding to proliferation, wound healing, and immunogenic activity. Ultimately, we are seeking a way to separate more regenerative cell types from patient samples to improve therapeutic outcomes.