Multipotent stem cells and renal progenitors derived from amniotic fluid as potential tools for chronic kidney disease therapies
Early Translational I
A great deal of attention has recently been focused in the area of stem cell technology as a possible alternative modality of treatment for a variety of diseases. End stage renal disease (ESRD) has reached epidemic proportions in the United States. An estimated 390,000 US residents are in treatment for ESRD and just last year more than 56,000 individuals were awaiting a kidney transplant. Currently, dialysis or kidney transplantation remain the only viable treatments despite significant limitations of both treatments. This situation along with an increasing shortage of donor organs has heightened interest in developing novel methods of therapy for kidney replacement. In this research we propose to study Alport Syndrome as a model leading to ESRD. Alport Syndrome is a hereditary glomerulonephritis estimated to affect at least 1 in 20,000 people. It is a chronic kidney disease caused by genetic defects in one of the proteins (type IV collagen) that make up the Glomerular Basement Membrane (GBM), an important component of the filter that allows the kidney to clean the blood. It has been shown that mesenchymal stem cells derived from bone marrow may contribute to kidney repair in acute models of kidney disease as well as slowing down the progression of kidney disease in mice that suffer from chronic kidney injury. Herein we focus on the application of stem cells (AFSC) and kidney-specific progenitors (AFKPC) derived from mouse and human amniotic fluid. We have successfully demonstrated that these cells have the potential to differentiate into multiple cell types in vitro and when injected into experimental animals they can restore the functionality of multiple organs such as the kidney, lung, and pancreas. In particular, when injected in an in vivo model of Acute Tubular Necrosis, AFSC survive, integrate, differentiate into tubular-like cells and restore renal function. Major advantages of AFSC are that they can be easily retrieved through amniocentesis with no injury to the embryo and that they do not form tumors (teratomas) in vivo. We have also identified and characterized specific kidney progenitor cells within the total cell suspension present in the amniotic fluid. We hypothesize that AFSC or AFKPC could represent a readily available source of ethically acceptable, biologically unmodified stem cells that may prove useful as a novel alternative to current stem cell therapeutic techniques in regenerative medicine for chronic kidney disease.
Statement of Benefit to California:
The State of California is home to some of the nation's best organ transplant and treatment centers and becomes acuity aware of the growing shortage of organs for our patients and of the need for good alternative therapies in the field of regenerative medicine. In particular we focused our attention on chronic kidney disease that ultimately leads to ESRD. The need for donor organs continues to rise every year and emerging technologies such as those offered by stem cell research may assist our child patients as well as the adult citizens of California with alternative technologies that perhaps can make a significant impact in this field. Although human embryonic stem cells show the capacity for differentiation into multiple cell types, they also have an inherent propensity to form teratomas (tumors) which may limit their clinical usefulness in future therapies. However, a novel population of pluripotent stem cell exists within amniotic fluid, which can be easily obtained, stored, and possibly used for future regenerative medicine or clinical purposes without some of the same concerns over clinical compatibility as embryonic stem cells. In addition to stem cells, within the amniotic fluid there is a very heterogeneous cell population. In particular we have focused our attention on progenitor cells with specific renal characteristics. These could represent a new tool to ameliorate or cure various kidney diseases, because of their commitment toward kidney cell types. We intend to characterize the potential of these cells in kidney regeneration as preliminary studies to their possible use one day in the clinic. CIRM funding will ensure a competitive advantage for California in this innovative direction.
This application is focused on a development candidate and describes studies to investigate the potential of amniotic fluid-derived stem cells (AFSCs) and amniotic fluid kidney progenitor cells (AFKPCs) to mediate kidney repair in animal models of Alport’s syndrome, and to develop human AFSC’s or AFKPCs for clinical use. Currently, dialysis and kidney transplantation remain the only viable treatments for end-stage renal disease, and significant complications are associated with both therapies. Stem cells are, then, attractive and rational potential therapeutic tools. The applicant intends to determine whether different treatment regimens, specifically early versus later treatment and single versus multiple treatments of stem cells, can improve renal outcome. Safety and efficacy of AFSC/AFKPC in the Alport animal model will be examined. To facilitate progress toward the early clinical development phases for AFSCs and AFKPCs, the applicant proposes to fulfill all of the requirements for scalability under Good Manufacturing Practice (GMP) conditions as a prerequisite to testing the safety and activity of the stem cells in human phase I trials. The principal investigator has chosen an important health care problem to address, one that has not been seriously impacted by stem cell biology--deterioration of kidney function that leads to kidney failure. If stem cells of any type could home to the kidney and replace or augment the function of the injured or dysfunctional cells, kidney failure might be potentially slowed, thus improving the lives of many patients and saving billions of dollars in health care costs. The use of AFSCs as opposed to embryonic stem cells has several potential advantages, since AFSCs do not rely on embryonic sources for isolation, and are considered less likely to generate teratomas. Thus, the development candidate(s) could address an unmet medical need and potentially have significant impact. However, a lack of consideration of issues of immunogenicity relating to the use of allogeneic stem cells limits the potential of this approach, and reviewers were surprised that extensive discussion of this issue was missing from the application. There was no consideration of the fact that human AFSC’s or AFKPCs from allogeneic donors have potential to elicit an immune response, especially upon differentiation into renal lineage cells. The preliminary data were obtained in either syngeneic models or immunodeficient mice, although little detail was provided. In Alport’s syndrome, podocytes (part of the glomerular filtration apparatus) fail to make the appropriate collagen IV network, which leads to glomerular injury, decreased renal perfusion, and kidney failure. If the defective podocytes could be replaced with genetically normal cells, they may synthesize the correct collagen IV network, leading to a halt in disease progression. One reviewer stated that the dependence of Aim 2 on Aim 1’s success was a drawback, as the applicant acknowledges that Aim 1 may consume considerable amounts of time and that alternative approaches may be required as the applicant works through the disease model. In short, reviewers felt there was a disproportionate reliance in the proposed work on the mouse model. Although there were good preliminary data to suggest the model would be useful, reviewers were concerned that potential pitfalls and alternatives to the mouse work were not adequately addressed. In addition, there was a lack of detail for reviewers in the description of purification of the bone marrow stem cells, which is the control cell population. Finally, one reviewer felt that interpretation of some figures in the proposal was unconvincing and not clearly aligned with the hypothesis. In addition, reviewers interpreted the data as showing only few AFSCs in the glomeruli of treated animals, which may suggest that regenerative processes may be insufficient to restore sufficient collagen to address functional glomerular rescue. The principal applicant is an internationally recognized researcher with an outstanding publication and funding track record. The assembled team of investigators is outstanding, and covers expertise in kidney physiology and in isolation and handling of human stem cells. Thus, the expertise is in place to carry out these studies, with the exception of immunology where the team lacks domain expertise. The budget proposed by the principal applicant is extremely high for the work proposed. The amount of work is no more than proposed in a typical R01, as a benchmark. Inflated FTEs, travel ($5000 per year for each individual paid from the grant), mouse, microarray charges, etc. appeared inflated. Given the risky nature of the work and the lack of consideration to important immunologic issues, a more modest budget is appropriate especially for the first two years of proposed work. In summary, this application focuses on creation of a development candidate to address Alport Syndrome as a model kidney disease, using stem cells from the amniotic fluid and kidney progenitor cells from the amniotic fluid as therapies. Although the reviewers praised the rationale and the enormous need for new approaches to end-stage renal disease, this application had several issues that detracted from its appeal, most importantly the lack of sufficient consideration of thorny immunological issues. Enthusiasm for the proposal was also dampened by vague and unconvincing presentation of some preliminary data, and major concerns over construction of the budget.