Isolation, purification, cryopreservation, expansion, differentiation and characterization of homogeneous populations of cells derived from the placenta and amnion for therapeutic use.
Early Translational I
Embryonic stem cells (ESC) are able to be grown indefinitely and be differentiated into all types of tissues such as blood, bone, brain, bone, liver, etc. Unfortunately, a number of bottlenecks in regard to the use of these cells in clinical trials exist. These include the possibility that these tissues may give rise to tumors, the need to grow these cells in ways that might introduce contaminants, many social and ethical issues, technical challenges to growing large numbers of cells, and the difficulties associated with initiating clinical trials using these cells . Adult stem cells found in cord blood and bone marrow are currently used in clinical trails and have demonstrated efficacy. Stem cells (SC) collected from the umbilical cord at the time of birth (called cord blood) have been shown to be an important resource for transplantation for malignant and genetic conditions. These cells have a number of advantages over hematopoietic stem cells collected from the bone marrow later in life, including greater proliferative potential, greater potential to differentiate into diverse types of cells, reduced presence of infectious agents such as CMV, and less exposure to environmental mutagens. However, cell number, costs, logistics of collection, and limited banking of collected units due to the limited number of stem cells per unit of cord blood and limited pluripotency represent bottlenecks to cord blood derived. Furthermore, there are differences in certain characteristics of cord blood units collected from African Americans that limit the number of cord blood units appropriate for African Americans. This has a serious detrimental impact on the care of African American patients who need a stem cell transplantation. Another type of stem cells -- induced pluripotent stem (iPS) cells -- constitute an exciting new area or research believed to generate cells similar to ESCs. The current technology involved in generating these cells however, poses other concerns about causing tumors if such cells were to be transplanted into humans. Thus, there remains a need to identify a source of pluripotent stem cells that can be used for clinical trials in the near term. We believe that our proposal which will use stem cells derived from the human placenta or a membrane surrounding the placenta, called the amnion, will generate such a source of pluripotent stem cells. The availability and quantity (over 600,000 births/year in California, 4 million/year in the United States and over 250,000/year in Australia) of placenta and amnionic membranes and the easy non-invasive access and minimal ethical, legal, moral issues associated with their collection and usage, makes these gestational, fetal-like tissues an attractive source of pluripotent stem cells. But first, it is necessary to prove that pluripotent stem cells can be derived from the placenta and amnion and that they are not subject to the limitations associated with embryonic stem cell sources.
Statement of Benefit to California:
The proposed research holds the promise of providing a new source of pluripotent stem cells that potentially could become any type of tissue. The overall objective of our collaboration is to develop procedures whereby pluripotent stem cells found in the placenta and its amnionic membrane can be readily obtained, isolated, stored, and characterized so that they can be used safely in near term clinical trials to evaluate their efficacy in treating human diseases. Our hypothesis is that these stem cells will overcome many of the bottlenecks limiting near-term therapeutic applications associated with other sources of stem cells, particularly embryonic.
This application proposes to address several bottlenecks in the development of stem cell-based therapies: 1) the potential for undifferentiated human embryonic stem cells (hESCs) to form teratomas after transplantation; 2) the widespread use of non-human feeder cells to culture and expand hESCs; and 3) the general difficulties in obtaining and processing hESCs, including ethical, legal and moral issues associated with their collection and use. The applicant hypothesizes that the amnion, chorion and placenta are abundant sources of pluripotent stems cells that may have similar utility to hESCs in regenerative medicine applications without the potential to form teratomas or the need for non-human feeder cells for expansion. In Aim 1 the applicant proposes to develop standard operating procedures for GMP-compliant collection, processing and cryopreservation of cells and tissue from amnion, chorion and placenta. In Aim 2 the applicant will thoroughly characterize these cell populations at the cellular and molecular levels and compare them to hESCs. In Aim 3 the applicant proposes to investigate the expansion and differentiation potentials of these cells and monitor their in vivo fate following transplantation into immunodeficient mice. Reviewers agreed that the rationale for this proposal is strong but raised significant doubts about its feasibility and noted that several mechanistic studies were needed before the technique might be considered ready for translation to the clinic. Amnion, chorion and placenta represent plentiful sources of stem cells with minimal ethical or legal issues associated with their collection. Preliminary data from these stem cells indicate expression of transcription factors associated with pluripotency (Oct-4, Sox-2 and Nanog) as well as the capacity to differentiate into the three germ lineages and multiple cell types in vitro. Unlike hESCs, these cells do not form teratomas when injected into immune-compromised mice and may have immunosuppressive characteristics. However, the reviewers noted that the proposal is missing crucial preliminary data concerning these cells. There is no evidence that stem cells obtained from amnion, chorion or placenta can be expanded in vitro without loss of pluripotency. One reviewer noted that groups have not been able to accomplish this with umbilical cord blood-derived stem cells. There is also no data presented that these cells can engraft or differentiate in vivo. Reviewers would have been reassured by a proof-of-principle study demonstrating these capabilities. One reviewer noted that although preliminary data suggests multiple lineage differentiation potential within the starting tissues, it’s unclear whether individual pluripotent stem cells exist. Another reviewer noted that while the cells have interesting properties, they more closely resemble mesenchymal stem cells than hESCs. In terms of experimental design, reviewers noted a lack of detail about novel methods for expanding cells using a 3D scaffold bioreactor, and tracking their movement in vivo using gold particles. One reviewer also commented that potential pitfalls were not outlined in detail. The reviewers praised the strong international collaboration established to carry out the proposed studies. Reviewers noted that the applicant is a clinical hematologist with project management skills, but lacks stem cell research experience and has a thin publication record. They appreciated the strong track records of many members of the research team, including experts in the areas of hematopoiesis, isolation of stem cells from amnion and placenta, and genomic profiling of stem cells. The research environment and resources were judged to be excellent. Overall, while the reviewers felt there is strong rationale for studying amnion, chorion and placenta as potential sources for therapeutic stem cells, they noted a lack of critical preliminary studies and in vivo work needed to demonstrate the capacity of these cells to expand in vitro and engraft in vivo. Without this data, it is not clear that the project is feasible or that it will have a significant impact on the field. Reviewers suggested that the project was at too early a stage of development to be considered for this RFA.