Basic Biology I
For the millions of Americans who are born with or develop heart disease, stem cell research offers the first hope of reversing or repairing heart muscle damage. Thus, early reports suggesting heart regeneration after transplantation of adult bone marrow-derived stem cells were met with great excitement in both the scientific and lay community. However, although adult stem cell transplantation was shown to be safe, results from over a dozen clinical trials concluded that the benefits were modest at best and whether any true regeneration is occurring was questionable. The basis for these disappointing results may be related to poorly characterized cell types used that have little capacity for true regeneration and an inadequate understanding the factors necessary for survival and differentiation of transplanted stem cells. In this application, we are proposing to study the growth and differentiation properties of an authentic endogenous human cardiac progenitor cell that can differentiate into cardiac muscle cells, smooth muscle cells and endothelial cells. We will also determine the factors that support its growth and renewal during normal development. This knowledge will be applied to future clinical trials of cardiovascular cell therapy that allow truly regenerative therapy.
Statement of Benefit to California:
Heart disease, stroke and other cardiovascular diseases are the #1 killer in California. Despite medical advances, heart disease remains a leading cause of disability and death. Recent estimates of its cost to the U.S. healthcare system amounts to almost $300 billion dollars. Although current therapies slow the progression of heart disease, there are few, if any options, to reverse or repair damage. Thus, regenerative therapies that restore normal heart function would have an enormous societal and financial impact not only on Californians, but the U.S. more generally. The research that is proposed in this application could lead to new therapies that would restore heart function after and heart attack and prevent the development of heart failure and death.
The goal of this proposal is to understand mechanisms controlling cardiovascular progenitor cell (CPC) self-renewal and fate decisions. Recent publications have reported the presence of cardiac progenitor cells that can differentiate into cardiac myocytes, endothelial cells and smooth muscle cells. These CPC would be attractive therapeutic candidates for cardiovascular repair, however, our understanding and the characterization of human CPCs is limited. This proposal has three specific aims. The first aim will determine if endogenous CPCs and CPC-like cells differentiated from human pluripotent stem cells share common cell fate, gene expression (phenotypic) and epigenetic signatures. The second aim will explore signaling pathways that regulate CPC self-renewal and cardiovascular differentiation. The third aim will determine the importance of niche microenvironment in regulating CPC self-renewal and cell fate, first in two-dimensional culture and then in a three-dimensional model system Reviewers uniformly praised the proposal's potential significance. If successful, the work will contribute to the understanding of CPC self renewal and cell fate decisions and enable potential alternative CPC sources for cardiovascular cell therapy, thereby potentially having a tremendous impact on the field Reviewers found the proposal to be rational, well-presented and delineated appropriate milestones and timelines. They considered as strengths the proposal's combination of basic stem cell biology and tissue engineering. Reviewers appreciated the extensive preliminary data. The work builds upon published data to describe surface markers expressed in human CPCs, and exploits this data to characterize matrix proteins in the human CPC niche. Considering that a portion of the research plan was contingent upon comparison of isolated resident CPCs to those generated from pluripotent stem cells, data that CPCs survive, renew and differentiate following isolation would benefit the proposal. Discussion of alternative potential signaling pathways would have further improved solid preliminary data supporting a role for the pathway proposed to regulate CPC self renewal. A lack of detail was noted relating to the three dimensional niche model selected for specific aim 3. Methods used to generate the preliminary data were incomplete, and potential effects of the selected material on the cells were not discussed in the experimental design. However the importance of regulation of CPC by the niche microenvironment, even if only studied in two dimensions, was universally appreciated. The PI and the team are strong, and possess the expertise in cardiovascular biology, stem cells and tissue engineering required to perform the proposed experiments. A biomaterials expert could further strengthen the approach in Aim 3. The host institution's resources and facilities provide one of the best environments available for the proposed study. In summary, reviewers were enthusiastic about the potential impact and high likelihood of success for this proposal given its rational approach, solid preliminary data and experienced team.