Defining the Isoform-Specific Effects of Apolipoprotein E on the Development of iPS Cells into Functional Neurons in Vitro and in Vivo

Defining the Isoform-Specific Effects of Apolipoprotein E on the Development of iPS Cells into Functional Neurons in Vitro and in Vivo

Funding Type: 
New Faculty II
Grant Number: 
RN2-00952
Approved funds: 
$2,847,600
Disease Focus: 
Stroke
Neurological Disorders
Stem Cell Use: 
iPS Cell
Cell Line Generation: 
iPS Cell
Public Abstract: 
GOALS We propose to determine the effects of different forms of apoE on the development of induced pluripotent stem (iPS) cells into functional neurons. In Aim 1, iPS cells will be generated from skin cells of adult knock-in (KI) mice expressing different forms of human apoE and in humans with different apoE genotypes. In Aim 2, the development of the iPS cells into functional neurons in culture and in mouse brains will be compared. In Aim 3, the effects of different forms of apoE on the functional recovery of mice with acute brain injury treated with iPS cell–derived neural stem cells (NSCs) will be assessed. RATIONALE AND SIGNIFICANCE The central nervous system (CNS) has limited ability to regenerate and recover after injury. For this reason, recovery from acute and chronic neurological diseases, such as stroke and Alzheimer’s disease (AD), is often incomplete and disability results. Embryonic stem cells have great promise for treating or curing neurological diseases, but their therapeutic use is limited by ethical concerns and by rejection reactions after allogenic transplantation. The generation of iPS cells from somatic cells offers a way to potentially circumvent the ethical issues and to generate patient- and disease-specific stem cells for future therapy. In the CNS, apoE plays important roles in lipid homeostasis and in neuronal maintenance. However, apoE2, apoE3, and apoE4 differ in their ability to accomplish these tasks. ApoE4, the major genetic risk factor for AD, is associated with poor clinical outcome and more rapid progression or greater severity of head trauma, stroke, Parkinson’s disease, multiple sclerosis, and amyotrophic lateral sclerosis—all potential targets of stem cell therapy. This proposal builds on three novel findings in human apoE-KI mice. (1) NSCs express apoE. (2) ApoE plays a role in cell-fate determination (neuron vs astrocyte) of NSCs. (3) ApoE4 impairs the neuronal development of NSCs. Thus, we hypothesize that transplantation of iPS cells derived from apoE4 carriers (~20% of the general population and ~50% of AD patients) might not be beneficial or even detrimental for patients with neurological diseases. We propose in vitro and in vivo studies to assess the effects of different forms of apoE on the development of iPS cells into functional neurons and on the functional recovery of mice with acute brain injury treated with iPS cell-derived NSCs. These studies will shed light on the regulation of neuronal development of iPS cells and help to “optimize” future iPS cell therapy for neurological diseases. SPECIFIC AIMS Aim 1. To establish adult mouse and human iPS cell lines with different apoE genotypes. Aim 2. To determine the isoform-specific effects of apoE on the development of iPS cells into functional neurons in culture and in mouse brains. Aim 3. To assess the isoform-specific effects of apoE on the functional recovery of mice with acute (stroke) brain injury treated with iPS cell-derived NSCs.
Statement of Benefit to California: 
CONTRIBUTION TO THE CALFORNIA ECONOMY: A major goal of regenerative medicine is to repair damaged cells or tissue. My research focuses on (1) understanding the role of neuronal regeneration in central nervous system function and (2) developing stem cell therapy for acute and chronic neurological diseases, including stroke and Alzheimer's disease. Stroke and Alzheimer's disease are the leading causes of disability and dementia and are the fastest growing form of neurological diseases in California, in the USA, and worldwide. My research could benefit the California economy by creating jobs in the biomedical sector. Ultimately, this study could help reduce the adverse impact of neurological diseases. Thereby, I hope to increase the productivity and enhance the quality of life for Californians. The results of my studies will also help develop new technology that could contribute to the California biotechnology industry. The studies will characterize multiple lines of induced pluripotent stem (iPS) cells carrying apoE3, a protein protective to the brain, or apoE4, which is detrimental to the brain and is associated with increased risk of Alzheimer’s disease and other neurodegenerative disorders. These cell lines could be valuable for biotechnology companies and researchers who are screening for drug compounds targeting different neurological diseases. CONTRIBUTION TO THE HEALTH OF CALFORNIANS: The most important contribution of the studies will be to improve the health of Californians. Diseases that are the target of regenerative medicine, such as stroke and Alzheimer’s disease, are major causes of mortality and morbidity, resulting in billions of dollars in healthcare costs and lost productivity. As we continue our efforts in medical research, we hope to one day unlock the secrets of brain development and repair. This knowledge will help medical researchers develop beneficial therapies beyond what is currently available and potentially improve the quality of life and life expectancy of patients with neurological diseases, such as stroke and Alzheimer’s disease.
Progress Report: 

Year 1

The goal of this proposal is to determine the isoform-specific effects of apolipoprotein (apo) E on the development of induced pluripotent stem (iPS) cells into functional neurons both in vitro and in mice. Toward this goal, we have made significant progress in Aims 1 and 2. First, we further demonstrated that neural stem cells (NSCs) express apoE. ApoE-KO mice had significantly less hippocampal neurogenesis, but significantly more astrogenesis, than wildtype mice due to decreased Noggin expression in NSCs. In contrast, neuronal maturation in apoE4 knock-in (apoE4-KI) mice was impaired due to reduced survival and function of GABAergic interneurons in the hilus of the hippocampus, and a GABAA receptor potentiator rescued the apoE4-associated decrease in hippocampal neurogenesis. Thus, apoE plays an important role in hippocampal neurogenesis, and the apoE4 isoform impairs GABAergic input to newborn neurons, leading to decreased neurogenesis. A paper describing these data was published in Cell Stem Cell (Li G. et al. 2009, 5:634-645), which evidently is the 400th publication of CIRM-funded projects. Second, we established mouse iPS cell lines from adult mouse fibroblasts of wildtype, apoE knockout (apoE-KO), human apoE2-KI, human apoE3-KI, and human apoE4-KI mice. Finally, we developed NSC lines from mouse iPS cells with different apoE genotypes (wildtype mouse apoE, apoE-KO, apoE2, apoE3, and apoE4). These cell lines will be used to study the effects of apoE isoforms on neuronal development in vitro in culture and in vivo in mouse models.

Year 2

The goal of this proposal is to determine the isoform-specific effects of apolipoprotein (apo) E on the development of induced pluripotent stem (iPS) cells into functional neurons both in vitro and in mice. Toward this goal, we have made significant progress in the past year, as summarized below. First, We developed human iPS cells from skin fibroblasts of individuals with different apoE genotypes. We are fully characterizing these human iPS cell lines. Second, We are establishing neural stem cell (NSC) lines from human iPS cells with different apoE genotypes. Some of the NSCs have been maintained in monolayer cultures for many generations. These NSCs will be used to study the effects of apoE isoforms on neuronal development in vitro in cultures and in vivo in mice. Finally, we demonstrated that mouse apoE4-NSCs generated significantly fewer total neurons and fewer GABAergic interneurons than mouse apoE3-NSCs in culture. Thus, the detrimental effects of apoE4 on neurogenesis and GABAergic interneuron survival, as we observed in vivo in apoE4 knock-in mice (Li G. et al. Cell Stem Cell, 2009, 5:634-645), are recapitulated in cultures of mouse iPS cell–derived NSCs in vitro.

Year 3

The goal of this proposal is to determine the isoform-specific effects of apolipoprotein (apo) E on the development of induced pluripotent stem (iPS) cells into functional neurons both in vitro and in mice. Toward this goal, we have made significant progress in all three aims in the past year, as summarized below. 1) We have fully characterized two apoE3/3-hiPS cell lines and two apoE4/4-iPS cell lines. 2) We have established NSC lines from human iPS cells with an apoE3/3 or apoE4/4 genotype. The hNSCs have been maintained in suspension or monolayer culture for multiple passages. 3) We demonstrated that apoE4-hNSCs generated ~50% fewer GABAergic interneurons than apoE3-hNSCs in culture. Thus, the detrimental effects of apoE4 on GABAergic interneuron survival, as we observed in vivo in apoE4 knock-in mice (Li G. et al. Cell Stem Cell, 2009, 5:634-645), are recapitulated in cultures of human iPS cell-derived NSCs in vitro. 4) We established protocols in our lab to differentiate human iPS cell-derived NSCs into different types of neurons in cultures.

Year 4

The goal of this proposal is to determine the isoform-specific effects of apolipoprotein (apo) E on the development of induced pluripotent stem (iPS) cells into functional neurons both in vitro and in mice. Toward this goal, we have made significant progress in all three aims in the past year, as summarized below. 1) We demonstrated that apoE4-miPSC-derived mNSCs had a greater “age-dependent (passage-dependent)” decrease in generation and/or survival of MAP2-positive neurons in cultures. 2) We also demonstrated that apoE4-miPSC-derived mNSCs had an even greater “age-dependent (passage-dependent)” decrease in generation and/or survival of GAD67-positive GABAergic neurons, as seen in vivo in apoE4 knock-in mice (Li et al., Cell Stem Cell, 2009, 5:634–645). 3) We expanded the pilot study reported last year and confirmed the detrimental effect of apoE4 on GABAergic interneuron development/survival of hiPS cell-derived hNSCs. ApoE4 also increased tau phosphorylation, one of the pathological hallmarks of Alzheimer’s disease, in neurons derived from apoE4-hiPS cells. 4) We established a protocol to transplant apoE-miPS cell-derived mNSCs into mouse brains. The transplanted apoE-mNSCs developed into neurons and astrocytes and integrated into the neural circuitry.

Year 5

The goal of this proposal is to determine the isoform-specific effects of apolipoprotein (apo) E on the development of pluripotent stem cells into functional neurons in vitro in culture and in vivo in mice for potential cell replacement therapy. Toward this goal, we have made significant progress in all three aims in the past year, as summarized below. 1) We demonstrated that mouse GABAergic progenitors transplanted into the hilus of apoE3-KI and apoE4-KI mice developed into mature interneurons and functionally integrated into the hippocampal circuitry. 2) We also demonstrated that transplantation of mouse GABAergic progenitors into the hilus of apoE4-KI mice rescued learning and memory deficits. 3) Transplantation of mouse GABAergic progenitors into the hilus of hippocampus also rescued learning and memory deficits in apoE4-KI mice expressing Alzheimer’s disease-causing APP mutations.

© 2013 California Institute for Regenerative Medicine