Project Components
The research and clinical activities of stem cell biologists at Childrens Hospital Los Angeles have an international impact on the understanding and treatment of diseases in children and adults. Through rigorous exploration of the biology of stem cells, investigators are working to determine and compare the therapeutic potential of adult and human embryonic stem cells (hESC).
 Human Embryonic Stem Cells
Mouse embryonic stem cells " studied in many laboratories around the world " are relatively easy to culture. Childrens Hospital Los Angeles is one of only a handful of academic centers in the United States that has been successful in culturing human embryonic stem cells (hESC), which are very difficult to grow and study. Only available since 1998, many basic questions remain about optimal ways to grow and manipulate hESC for clinical purposes. Researchers in the Childrens Hospital Los Angeles Stem Cell Project have been working with federally approved hESC lines since 2002 and have carefully developed the critical scientific tools to move this young and exciting field forward. The focus is on developing methods to generate blood, pancreas, liver, lung and mesenchymal tissues from hESC
 Human Adult Stem Cells from Bone Marrow and Cord Blood
The first adult stem cells described were found in the bone marrow more than 30 years ago. Since then, these hematopoietic (blood-forming) stem cells have been used in bone marrow transplants to cure thousands of people with blood and immune disorders.
Stem cell biologists at The Saban Research Institute have been at the forefront of studies to identify and characterize human hematopoietic stem cells in the bone marrow and umbilical cord blood. Recently, stem cell biologists at Childrens Hospital Los Angeles, and elsewhere, discovered that adult bone marrow may have the potential to generate tissue beyond blood cells. In particular, adult stem cells in the bone marrow and cord blood may be able to repair and replace cells of such organs as the pancreas, liver and brain. Researchers at The Saban Research Institute are studying how these cells might be manipulated to differentiate into other tissues. When the mechanisms for this process can be understood and harnessed, tissue regeneration and repair, using adult stem cells, may be possible.
Childrens Hospital Los Angeles operates one of the largest pediatric Hematopoietic Stem Cell Transplant programs in the nation. Each year, 40 to 50 infants and children have transplants of hematopoietic stem cells to treat leukemia and childhood cancers, as well as to cure genetic blood and immune diseases, such as severe combined immune deficiency (SCID or "bubble baby disease"), sickle cell disease and others. This program is committed to translating the advances in basic science into clinical trials.
Lung Stem/Progenitor Cells
Investigators at Childrens Hospital Los Angeles were among the first to discover, isolate and purify the resident stem/progenitor cells of the alveolar epithelium in the lung. Since the lung has an extremely large (70 square meters) surface area, resident stem/progenitor cells play a major role in repairing alveolar injury. Additionally, organ specific stem/progenitor cells are critical in making the branched and differentiated organ structure of lungs, as well as cross-talking with the matched endothelial surface.
Mesenchymal Stem Cells
These primitive cells fall into two subclasses: resident and exogenous (arising from a source outside the organism or cell). Resident mesenchymal stem/progenitor cells are key in developing organ structure and supplying important positional information to form the organ-specific stem cell niche. Lung mesenchymal stem cell differentiation is an ongoing focus of research at Childrens Hospital Los Angeles. Exogenous mesenchymal stem cells, such as those derived from the bone marrow or adipose tissue, are attracted to areas of tissue damage. They may contribute to tissue repair, as in the alveolar epithelium, or to tissue fibrosis, as in pulmonary fibrosis, keloids or transplant rejection. Investigators at The Saban Research Institute are actively pursuing these questions.
Human Amniotic Fluid Stem Cells
This novel form of human stem cell can be manipulated as cell lines. Currently these cells can be driven to derive all three germ layers. The feasibility of engineering new kidney and lung tissue using these cells is being actively studied by investigators at Childrens Hospital Los Angeles.
Cancer Stem Cells
In recent years, the existence of so-called "cancer stem cells" has been definitively established. These cells constitute a minority population within a tumor and are likely to be the cells from which a tumor is originally derived and subsequently maintained. Like their normal counterparts, cancer stem cells are immortal. An entire tumor tissue can be regenerated from a single tumorigenic stem cell. ("Tumorigenic" means anything that causes the formation of a tumor.) Cancer stem cells, therefore, represent the root of the tumor, and must be eliminated or neutralized during treatment for cures to be sustained.
The corollary of the existence of cancer stem cells is that tumors are not homogeneous masses of cells as once thought, but rather are comprised of a heterogeneous or dissimilar assortment of abnormally differentiated cells which have been derived from an abnormal, clonal stem cell pool. Whether cancer stem cells are normal stem cells that have become malignant or are more differentiated cells that have reacquired stem cell characteristics during malignant transformation remains to be explained. However, it is likely that both situations occur in the evolution of human cancer and may not be mutually exclusive.
To date, cancer stem have been definitively identified in human leukemias, breast and brain tumors. Stem cells from other solid tumor types, including many that primarily affect children, have yet to be isolated but there can be little doubt of their existence. Leukemia, breast and brain tumor stem cells demonstrate remarkable similarity to normal blood, mammary and nervous system stem cells, respectively. Studies of normal stem cells are destined to offer tremendous insights into the origins and biology of human cancer. Ultimately, understanding cancer stem cell biology will aid in the development of novel therapies designed to specifically target these cells, thereby disabling the cancer at its roots and improving the chance of long-term cure.
Investigators in the Childrens Hospital Los Angeles Stem Cell Project have identified the leukemic stem cell that gives rise to the most common form of childhood leukemia, Acute Lymphoblastic Leukemia. Other investigators are studying oncogene expression and biology of Ewing’s sarcoma and related tumors in the context of embryonic stem cells.
In this emerging medical modality, diseases are treated at their root genetic causes. The first types of diseases considered for gene therapy were inherited, such as sickle cell disease, immune deficiencies and cystic fibrosis. As techniques have been developed, the use of gene therapy is now being considered for other conditions, such as cancer, AIDS, neurologic diseases and cardiovascular disease. One approach is to genetically modify stem cells to provide a continuous source of gene-corrected cells. For example, gene transfer to the hematopoietic stem cells of a patient’s own bone marrow could provide a more effective and safer treatment than bone marrow transplant from another person.
In 1993, physician-scientists and researchers at Childrens Hospital Los Angeles conducted the first clinical trial to correct the genetic defect of "bubble baby disease" (a lethal, inherited form of immune deficiency), by transplanting gene-corrected cord blood stem cells into newborn babies. The Gene Therapy Program remains at the leading edge of the field, performing ongoing bench-to-bedside studies of gene therapy that target hematopoietic stem cells for immune deficiencies, AIDS, leukemia and sickle cell disease.
This group also has extensive experience with the design, construction, analysis and use of gene transfer vectors, especially for the modification of human stem cells. In addition to the application of gene transfer to correct genetic deficiencies in a patient’s genome, gene transfer to hESC may be an important tool for basic research into the role of genes in stem cell development and differentiation. Gene modification of stem cells may be used to adapt the properties of stem cells, for example to induce proliferation, support survival, direct differentiation (specialization) or decreasing immunogenicity (the ability of a substance to provoke an immune response).
The Developmental Biology Program in The Saban Research Institute seeks to discover the basic genetic mechanisms of human organ development and to understand the impact of disease on the developing human being, then to apply this information in devising rational therapeutic approaches to engineer organ repair and regeneration. Its investigators are working on lung, heart, kidney, gut, liver and skin organogenesis, the stage of embryonic development where the body's main organs develop, and regeneration. These studies focus on understanding the contribution of stem cells to tissue development, repair and regeneration. Exciting progress is being made in applying this rapidly emerging technology to children and adults who are either born with missing tissues or who have lost tissue due to disease or injury. So far, intellectual property has been filed on stem cell applications to lung and skin, with more planned soon on stem cells in kidney, gut, liver and heart.
Organ Development & Embryonic Stem Cells
The fertilized human egg contains all of the genetic information necessary to make a new human being. The question is: How does the information in the human genome unfold to make a new tissue, organ or indeed a person? hESC show outstanding promise of being able to translate their genetic information into useful cells, tissues and organs. However, the molecular and genetic signals that direct the process of human tissue and organ development are not well understood. If the genome can be considered the blueprint for life, then the Developmental Biology Program has been endeavoring for many years to understand the working drawings. This is a necessary step in harnessing the potential of hESC or any other stem cell type for tissue and organ regeneration.
Recent advances in the program hold great promise in many areas of human adult and child health. Therapeutic targets include lung hypoplasia or injury caused by prematurity, smoking or other toxic exposures, cleft palate, congenital heart disease, scarless skin wounds, short gut and intestinal atresia.
Investigators in the Cardiothoracic Research Program at The Saban Research Institute bring enormous expertise in cardiovascular tissue engineering, as well as in the molecular aspects of organ and tissue rejection and fibrosis. Tissue engineering activities have primarily focused on development of improved artificial heart valves. Biological materials found in the natural tissues " elastin, collagen and glycosaminoglycans " are being explored. These molecules can be synthesized by cells in culture or purified from tissues, then manipulated to mimic the normal structural framework of the aortic valve. This approach is particularly relevant to connective tissues that have limited ability for self-repair, such as the cardiac valves or the cartilage of joints, or for replacing absent tissues, such as those found in congenital defects.
Recent accomplishments include the fabrication of tissue-engineered mitral valve chordae with a strength and stiffness 10 times greater than any other material produced using similar approaches. Much of this success lies in the use of optimized cell and collagen ratios, nutrition-fortified media and special purpose-built dynamic bioreactors that stretch the tissue-engineered chordae during maturation in vitro.
The work with mesenchymal stem cells at The Saban Research Institute has characterized their performance as "factories for matrix". The application of human embryonic stem cells (hESC) in these engineered tissues will ensure that they are absent of the contaminants found in animal cell lines, and thus make them ready for immediate implantation. The expertise we offer in the molecular aspects of antigen-antibody recognition and binding will be brought to bear on any residual antigenicity or foreign body reactions that may result in the destruction or fibrotic overgrowth of tissues based on transplanted hESC.
Hematopoietic Stem Cell Transplantation
The Division of Research Immunology/ Bone Marrow Transplant (BMT) directs the Hematopoietic Stem Cell Transplant Program at Childrens Hospital Los Angeles, one of the largest pediatric transplant research centers in the country. Established in 1983 by Robertson Parkman, MD, the BMT Program performs hematopoietic stem cell transplantation (HSCT) using autologous, matched-sibling marrow, matched-unrelated donor bone marrow and umbilical cord blood cells.
Approximately 60 patients have HSC transplants each year for diseases such as leukemia, lymphoma, neuroblastoma, other malignancies, aplastic anemia, as well as a variety of genetic diseases including immune deficiency syndromes (such as Severe Combined Immune Deficiency, Wiskott-Aldrich syndrome, X-linked Hyper IgM syndrome, Chronic Granulomatous Disease), hemoglobinopathies (sickle cell disease, thalassemia), metabolic diseases (Gaucher disease, mucopolysaccharidoses, adrenoleukodystrophy) and marrow failure states (Fanconi’s anemia, Schwachman-Diamond syndrome).
The BMT Unit has 11 laminar HEPA-filtered air flow isolation rooms and an outstanding nursing workforce with great expertise in the care of pediatric BMT patients, including highly immune-deficient patients. The Division also houses the Clinical Immunology Laboratory for Childrens Hospital Los Angeles, which has certification by the Clinical Laboratory Improvement Act (CLIA). Under the direction of Dr. Gay Crooks, the lab performs immune function studies for patients from Childrens Hospital Los Angeles and throughout Southern California.
The Division of Research Immunology also has a Clinical Stem Cell Processing Lab for handling stem cell products for patients on the pediatric BMT unit, which is regulated by the State of California Department of Health and Human Services, as well as by the Foundation for Cellular Therapy (FACT). The Stem Cell Lab performs processing of HSCT products, including CD34+ cell isolation, T cell depletion, cryopreservation and thawing of bone marrow peripheral blood stem cells and umbilical cord blood.
Cardiac and Lung Transplantation
In 1939, the first pediatric heart surgery on the West Coast took place at Childrens Hospital Los Angeles. Today, The Heart Institute at Childrens Hospital Los Angeles " the largest pediatric cardiovascular center in the West " serves as a global referral center, receiving patients from across the nation and around the world. The Heart Institute sets the standard for care of children with congenital and acquired cardiovascular disease, providing diagnosis, consultation, treatment, and ongoing management for children from the fetus to the young adult. More than 800 patients have cardiac surgery at Childrens Hospital Los Angeles annually, while another 5,000 patients receive non-invasive and invasive cardiology procedures.
Liver Transplant Program
The Childrens Hospital Los Angeles Liver Transplant Program is an integral part of the Center for Liver Diseases at the University of Southern California. It is one of the largest of its kind at any freestanding pediatric facility in the United States. Childrens Hospital Los Angeles has become a leader in living-donor liver transplantation, in which a healthy adult donates a segment of his or her liver, and split liver transplants, which involve use of a cadaver organ.
Childrens Hospital Los Angeles also has been a pioneer in "bloodless" liver transplants, which involve medical and surgical care without the transfusion of blood or blood products, reducing the risk of infection and immunologic complications. The survival rate for transplant recipients at Childrens Hospital Los Angeles is 96-percent at six years. Its surgeons perform more living-donor transplants annually than any other hospital in California. As a result, patients come here from across the nation. In ongoing research, investigators at Childrens Hospital Los Angeles are collaborating in a multi-center study to reveal the mysteries of acute liver failure, the reason many transplants are performed.
|
Tissue Engineering