Molecular Mechanisms Underlying Human Cardiac Cell Junction Maturation and Disease Using Human iPSC

Molecular Mechanisms Underlying Human Cardiac Cell Junction Maturation and Disease Using Human iPSC

Funding Type: 
Basic Biology III
Grant Number: 
RB3-05103
Approved funds: 
$1,341,955
Disease Focus: 
Heart Disease
Pediatrics
Stem Cell Use: 
iPS Cell
Cell Line Generation: 
iPS Cell
Status: 
Active
Public Abstract: 
Heart disease is the number one cause of death and disability in California and in the United States. Especially devastating is Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC), an inherited form of heart disease associated with a high frequency of arrhythmias and sudden cardiac death in young people, including young athletes, who despite their appearance of health are struck down by this type of heart disease. Even though it is inherited, early detection is hindered because people carrying the genetic code have highly variable clinical symptoms, making ARVC and catastrophic cardiac events very hard to predict and avoid. Evidence suggests that this heart disease is caused by mistakes in the genetic code essential for holding the mechanical integrity of heart muscle cells together or cell junctions. What is missing is an understanding of the basic biology of these heart muscle cell junctions in humans and appropriate human model systems to study their dynamics in heart disease, which is important since other heart diseases also share some of these same heart cell defects. Our goal is to understand the basic biology of how human heart muscle cell junctions mature and what happens in disease, by studying ARVC. Human iPS cells are a unique population of stem cells from our own tissues, such as skin, that have the same genetic information as the rest of our bodies. Thus, hiPS from people who carry the ARVC heart disease mistakes can be used in our laboratory to provide a true human model of that disease. We will generate heart muscle cells from hiPS from normal and ARVC donors that carry mistakes in the genetic code for cell junction components. We have identified new pathways that may be important causes of ARVC, thus we will also use our hiPS lines, to confirm whether these new pathways are truly important in human ARVC disease progression and if our approaches reverse disease progression. Characterization of our hiPS derived heart cells can also be exploited for translational medicine to predict an individual's heart cell response to drug treatment and provides a promising platform to identify new drugs for heart diseases, such as ARVC, which are currently lacking in the field. Recent advances in stem cell biology have highlighted the unique potential of hiPS to be used in the future as a source of cells for cell-based therapies for heart disease. However, prior to clinical application, a detailed understanding of the basic biology and maturation of these hiPS into heart muscle cells is required. Our studies seek to advance our understanding of how cell-cell junctions mature in hiPS and highlight tools that influence the microenvironment of the hiPS in a dish, to accelerate this process. This knowledge can also be exploited in regenerative medicine to achieve proper electromechanical integration of cardiac stem cells when using stem cells for heart repair, to improve longterm successful clinical outcomes of cardiac stem cell therapies.
Statement of Benefit to California: 
Heart disease is the number one cause of death and disability within the United States and the rates are calculated to be even higher for citizens of the State of California when compared to the rest of the nation. These diseases place tremendous financial burdens on the people and communities of California, which highlights an urgency to understand the underlying molecular basis of heart diseases as well as find more effective therapies to alleviate these growing burdens. Our goal is to improve heart health and quality of life of Californians by generating human stem cell models from people with an especially devastating form of genetic heart disease that affects young people and results in sudden cardiac death, to improve our molecular and medical understanding of how cardiac cells go wrong in the early stages of heart disease in humans. We will also test current drugs used to treat heart disease and new candidate pathways, that we have uncovered, to determine if and how they reverse and intervene with these defects. We believe that our model systems have tremendous potential in being used to diagnose, test an individual's heart cell's response to drug treatment, as well as predict severity of symptoms in heart diseases at an early stage, to monitor drug treatment strategies for the heart. We believe our studies also have a direct impact on regenerative medicine as a therapy for Californians suffering from heart disease, since data from our studies can identify ways to improve cardiac stem cell integration into the diseased heart when used for repair, as a way to improve long-term successful clinical outcomes of cardiac stem cell therapies. We also believe that our development of multiple human heart disease stem cells lines with unique genetic characteristics could be of tremendous value to biotechnology companies and academic researchers interested in large scale drug screening strategies to identify more effective compounds to rescue defects and treat Californians with heart disease, as well as provide important economic revenue and resources to California, which is stimulated by the development of businesses interested in developing these therapies further.
Progress Report: 

Year 1

Heart disease is the number one cause of death and disability in California and in the United States. Especially devastating is Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC), an inherited form of heart disease associated with a high frequency of arrhythmias and sudden cardiac death in young people, including young athletes, who despite their appearance of health are struck down by this type of heart disease. Even though it is inherited, early detection is hindered because people carrying the genetic code have highly variable clinical symptoms, making ARVC and catastrophic cardiac events very hard to predict and avoid. Evidence suggests that this heart disease is caused by mistakes in the genetic code essential for holding the mechanical integrity of heart muscle cells together or cell junctions. What is missing is an understanding of the basic biology of these heart muscle cell junctions in humans and appropriate human model systems to study their dynamics in heart disease, which is important since other heart diseases also share some of these same heart cell defects. Our goal is to understand the basic biology of how human heart muscle cell junctions mature and what happens in disease, by studying ARVC. Human iPS cells are a unique population of stem cells from our own tissues, such as skin, that have the same genetic information as the rest of our bodies. Thus, hiPS from people who carry the ARVC heart disease mistakes can be used in our laboratory to provide a true human model of that disease. During the first year of our grant, we have enrolled sufficient numbers of normal and ARVC donors into our study. We have collected skin biopsy tissues from donors as means to generate hiPS cells. Our results show that hiPS cell lines can be efficiently generated from both normal and ARVC donors and we have extensively characterized their profiles, such that we know they are bona fide stem cell lines and can be used as a model system to dissect defects in cardiac cell junction biology between these various different hiPS lines. We have also developed efficient and robust methodologies to generate heart muscle cells from hiPS from normal and ARVC donors that carry mistakes in the genetic code for cell junction components and are now in the midst of characterizing their molecular, genetic, biochemical and functional profiles to identify features in these cells that are unique for ARVC. Through our previous studies, we identified new pathways that may be important causes of ARVC, thus we will also use our hiPS lines, to confirm whether these new pathways are truly important in human ARVC disease progression and if our approaches reverse disease progression. Towards this goal, we have generated novel tools to increase and decrease a component of this pathway in order to test these approaches and have preliminary data to show that these tools are efficient in altering levels of this component in heart muscle cells, which we are now applying towards understanding these pathways in hiPS derived heart muscle cells and reversing defects in heart muscle cells from ARVC hiPS derived lines. Based on our progress, we have met all of the milestones stated in our grant proposal and in some cases, surpassed some milestones. We believe progress over the next year, will allow us to define some of the key cellular defects in ARVC and advance our understanding of how cell-cell junctions mature in hiPS and highlight tools that influence the microenvironment of the hiPS in a dish, to accelerate this process.

Year 2

Overall, we have been able to achieve the milestones proposed for Year 2 of the grant. We have generated a panel of control and ARVC hiPSC lines using integration-free based methods. We provide evidence of our method to generate robust numbers of hiPSC-derived cardiac cells that express desmosomal cell-cell junction proteins. We show ARVC lines that display disease symptom-specific features (adipogenic or arrhythmic), which phenocopy the striking and differential symptoms found in respective individual ARVC-patients as tools to study human ARVC. We also uncover desmosomal defects in hiPSC-derived cardiac muscle cells that underlie the disease features found in ARVC cells. We have also published two reviews in the field of cell-cell junctional remodeling and stem cell approaches that helps to further our understanding of this field in cardiomyocytes, that is relevant to human disease and our research using hiPS.

© 2013 California Institute for Regenerative Medicine