Differentiation of Human Embryonic Stem Cells to Heart Cells

Funding Type: 
SEED Grant
Grant Number: 
RS1-00428
ICOC Funds Committed: 
$0
Disease Focus: 
Cancer
Stem Cell Use: 
Embryonic Stem Cell
Public Abstract: 
Public Abstract California researchers will investigate how human embryonic stem cells can be transformed into working heart cells. This will, advance us toward a cure for chronic heart disease – for which there is now no cure other than heart transplantation. In so doing, they will broaden our understanding of how human embryonic stem cells, in general, can be transformed into functional cells that repair and regenerate parts of the body that are damaged by disease or injury. Each year there are 1.2 million heart attacks in the US. Although most do not result in immediate death, the cumulative damage leads to 500,000 deaths per year. When the oxygen supply to parts of the heart is shut off, heart muscle cells die leaving only scar tissue. Repeated small heart attacks build up this damage until the heart can no longer pump in response to exertion or excitement. At that stage, patients can die of congestive heart failure. It was previously thought that the scarring damage that leads to heart attacks was permanent. In recent years, however, researchers have shown how the scar tissue may be repaired with stem cells from bone marrow. However it is not known if the bone marrow stem cells become new heart cells or stimulate existing cells in the heart to perform better. This project’s researchers have one of the few laboratories world wide that are able to grow cardiac cells in large numbers and test them. This research project will build from the investigators’ ongoing stem cell research experience and study human embryonic stem cells because of the remarkable ability of such stem cells to turn into almost any type of adult cell. To convert the human embryonic stem cells into cardiac specific cells before they are delivered into the heart it is essential that we understand the molecular and biochemical process for differentiating human embryonic stem cells Researchers plan to study human embryonic stem cells with a chemical inducers to drive the transformation from stem cell to heart cells. The investigators will use a new technique which they have developed to label heart specified cells. They will study the molecular changes that underly the changes as the stem cell transforms. To understand this process fully, they will intensely analyze with computers, changes in newly discovered molecules that control the DNA code of life The resulting heart cells will be administer into the hearts to test if they are, in fact, turning into effective new cells that replace scar tissue in the heart ventricle as theorized. The fate of the transformed stem cells will be followed with a new magnetic imaging method to measure simultaneously the change in scar size, heart performance and the longevity of the stem cells.
Statement of Benefit to California: 
Benefits to Californians The citizens of California have a right to expect many benefits from their forward looking approval of stem cell research. The initiative to fund human embryonic stem cell research will bring breakthroughs in treatments for previously untreatable diseases and create unprecedented new business opportunities. This proposal is directed to saving the thousands of Californians who die or suffer from heart failure each year. The only known cure available now is a heart transplant, but because the demand for hearts is greater than the number of donors, an alternative source of heart cells is needed. We are engaged in using the potentiality of human embryonic stem cells to turn them into heart cells that could be injected into damaged hearts and make them heal. To do this we have to build our understanding of the fundamental process of making a stem cell into a heart cell and then testing how effectively such cells can repair injured hearts. Knowing the underlying scientific principles at work in such a process will create the potential to benefit not only heart disease patients, benefits to Californians The citizens of California have a right to expect many benefits from their forward looking approval of stem cell research. The initiative to fund human embryonic stem cell research will bring breakthroughs in treatments for previously untreatable diseases and create unprecedented new business opportunities. This proposal is directed to saving the thousands of Californians who die or suffer from heart failure each year. The only known cure available now is a heart transplant, but because the demand for hearts is greater than the number of donors, an alternative source of heart cells is needed. We are engaged in using the potentiality of human embryonic stem cells to turn them into heart cells that could be injected into damaged hearts and make them heal. To do this we have to build our understanding of the fundamental process of making a stem cell into a heart cell and then testing how effectively such cells can repair injured hearts. Knowing the underlying scientific principles at work in such a process will create the potential to benefit not only heart disease patients, but also others suffering from diseases for which treatment is inadequate or not available. We anticipate that the entrepreneurial business spirit for which California is famous, will generate new jobs and businesses that will build upon the discoveries made in this type of stem cell research. This will leverage the economy because to have an inexhaustible supply of heart cells (or any other type of organ cell) will require significant commercial manufacturing processes. Biologicals for growing cells will be an industry. Newly discovered drugs can be tested on such cells by pharmaceutical companies. California will become the world’s provider of human cells, for transplantation treatments and cures, and it will reap the rewards of its investment.
Progress Report: 
  • Human embryonic stem cells (hESCs) originate directly from human embryos, whereas induced pluripotent stem cells (iPSCs) originate from body (somatic) cells that are re-programmed by producing or introducing proteins that control the process making specific RNAs. Together, both these pluripotent cell types are referred to as human pluripotent stem cells (hPSCs). Several reports have observed that in hESCs grown for long times, their genetic material, DNA, is unstable. The stable maintenance of DNA is performed by groups of proteins functioning in different systems globally known as DNA repair pathways. Since the development of aneuploidy is closely linked to cancer and to deficiencies in DNA repair, we have studied the propensity of hPSCs to repair their DNA efficiently by 4 major known DNA repair pathways. In addition, we are also investigating if specific damage to DNA in either hPSCs or somatic cells is processed differently and could lead to deleterious mutations.
  • One major goal of the CIRM SEED grant mission is to bring new researchers into the hPSC field. The results we obtained during the funding period indicate that we have succeeded in that objective, since initially our laboratory had little experience with hESC culture. However, through courses and establishing critical collaborations with other hESC laboratories, we developed expertise in hPSC culture techniques. Most conditions for hPSCs growth require cells (feeder cells) that serve as a matrix and provide some factors needed for the pluripotent cells to divide. In accomplishing this aim, we perfected a method to generate reproducible feeder cells that significantly reduces the time and cost of feeder cell maintenance, and also developed a non-enzymatic and non-mechanical way to expand hPSCs. We now have experience with at least 5 hPSC lines and have methods to introduce foreign DNAs into hESCs and iPSCs to monitor DNA repair in hPSCs.
  • In Aim II of our grant, we used our accumulated knowledge of hPSCs and DNA repair to investigate 4 DNA repair mechanisms in hPSCs and in somatic cells. Depending on the DNA damage, there is often a preferred DNA repair pathway that cells use to alleviate potential harm. We initiated our investigation by treating hPSCs using different DNA damaging agents, including ultraviolet light and gamma radiation. However, we found that hPSCs exposed to these agents rapidly died compared to treatments that allowed somatic cells to continue growing. Therefore, we developed methods to study DNA repair in hPSCs without directly treating the cells with external agents. We treated closed, circular DNA (plasmids) with damaging agents separately, outside the hPSCs and then introduced them into the hPSCs. The plasmid DNA has a sequence that codes for a protein that is produced only when the damage is repaired. The length of time for repair both in hPSCs and in somatic cells was followed by determining the protein production. We have shown superior DNA repair ability and elevated protection against DNA damage in hPSCs compared to somatic cells for ultraviolet light and oxidative damage, two common sources of damage in cells. A major pathway for joining double-strand DNA breaks in mammalian cells, non-homologous end-joining (NHEJ) repair (error prone), is greater in H9 cells than in iPSCs. Another way to repair double-strand DNA breaks that uses similar (i.e., homologous) sequences is lower in iPSCs compared to hESCs and somatic cells. Further study of these repair pathways is warranted, since several methods can be used to form iPSCs. Therefore, the genomic stability for iPSCs could depend on the method used for their generation.
  • DNA repair analysis is critical to understanding how hPSCs protect against damage, but if left unrepaired, cells can turn damage into mutations when the damage is copied by enzymes (DNA polymerases) before repair occurs. Therefore, to monitor the mutations that ultimately lead to cancer or alter hPSC biology, we are using a plasmid that is damaged outside the cells and will make copies in hPSCs and somatic cells. That plasmid is introduced into cells and then the copies are recovered. The number of mutations found in the plasmid DNA indicates the likelihood of observing mutations in hPSCs compared to mutations in somatic cells. Together, these results will yield data on the stability of hPSCs and also a basis to monitor cells for stability which could serve as an indicator of safety for clinical use.

© 2013 California Institute for Regenerative Medicine