High-throughput Optimization of Stem Cell Microenvironment in 3D

Funding Type: 
Basic Biology II
Grant Number: 
RB2-01637
ICOC Funds Committed: 
$0
Disease Focus: 
Alzheimer's Disease
Neurological Disorders
Stem Cell Use: 
Embryonic Stem Cell
iPS Cell
Public Abstract: 
Human pluripotent stem cells (hPSCs), including human embryonic stem cells (hESCs) and recently developed human induced pluripotent stem cells (iPSCs), hold great promise as attractive cell sources for tissue regeneration. Unlike other types of cells, hPSCs can self-renew indefinitely and possess the potential to differentiate into any type of cells in our body. Before hPSCs can be used for therapeutic purposes, methods must be developed to control their differentiation into functional mature cell types. Stem cells reside in a highly complex niche in vivo where they constantly respond to microenvironmental cues including soluble factors, extracellular matrix, adjacent cells and mechanical signals. To fully realize the therapeutic potential of hPSCs, it is critical to understand the mechanisms by which they receive information from microenvironment and how such interactions alter hPSC functions. While the effect of individual type of microenvironmental cues on stem cell behavior has been studied in great depth, little is known about how the complex interplay of multiple types of microenvironmental cues would influence stem cell behavior. In addition, conventional iterative approach typically requires large amounts of cells and materials, and is slow an inefficient in discovery. To address these limitations, high-throughput screening has emerged as a novel approach to achieve rapid discovery with reduced materials and costs. However, most high-throughput studies on cell-material interactions to date have been performed on two-dimensional environments, while the architecture of the stem cell niche itself is three-dimensional. Recent research have clearly emphasized dimensionality as a critical determinant for regulating cell behavior, and systematic evaluation of stem cell responses to complex 3D signaling environment remains challenging. Through working at the interface of biology, material science, and engineering, here we propose to develop novel 3D combinatorial systems to understand how microenvironmental signals influences stem cells fate decision in 3D, and to rapidly optimize stem cell niche using high-throughput strategies. Such studies can greatly accelerate the clinical applications of hPSCs by elucidating the mechanisms underlying the control of hPSC differentiation. The outcome of proposed work can also aid in the synthesis of culture microenvironments that emulate stem cell niche in vivo, and would have broad applications in areas such as tissue regeneration and drug delivery.
Statement of Benefit to California: 
California is the most populated State in the US and many Californians suffer from diseases and injuries that lead to tissue loss and organ failure. With the rise of average life expectancy in our population, the number of Californians that suffer from devastating diseases will continue to increase. Human pluripotent stem cells (hPSCs) represent a promising candidate as cell sources for tissue repair and regenerative medicine. However, before they can be broadly used for therapeutic purposes, methods must be developed to control their differentiation into functional mature cell types. This proposal aims to elucidate the fundamental mechanisms by which hPSCs respond to the complex microenvironmental cues, and the outcomes of the proposed work will greatly accelerate the clinical translation of hPSCs for treating many Californian patients. Furthermore, the discovery from the proposed work will strengthen the leadership role of California in stem cell research. Our findings could also provide outstanding opportunities to stimulate the growth of biotechnology and pharmaceutical industries within the State as well as creating new job opportunities.
Progress Report: 
  • We are interested in identifying soluble protein factors in blood which can either promote or inhibit stem cell activity in the brain. Through a previous aging study and the transfer of blood from young to old mice and vice versa we had identified several proteins which correlated with reduced stem cell function and neurogenesis in young mice exposed to old blood. Over the past year we studied two factors, CCL11/eotaxin and beta2-microglobulin in more detail in tissue culture and in mice. We could demonstrate that both factors administered into the systemic environment of mice reduce neurogenesis in a brain region involved in learning and memory. We have also begun to test the effect of these factors on human neural stem cells and we started experiments to try to identify protein factors which can enhance neurogenesis.
  • While age-related cognitive dysfunction and dementia in humans are clearly distinct entities and affect different brain regions, the aging brain shows the telltale molecular and cellular changes that characterize most neurodegenerative diseases. Remarkably, the aging brain remains plastic and exercise or dietary changes can increase cognitive function in humans and animals, with animal brains showing a reversal of some of the aforementioned biological changes associated with aging. We showed recently that blood-borne factors coming outside the brain can inhibit or promote adult neurogenesis in an age-dependent fashion in mice. Accordingly, exposing an old mouse to a young systemic environment or to plasma from young mice increased neurogenesis, synaptic plasticity, and improved contextual fear conditioning and spatial learning and memory. Preliminary proteomic studies show several proteins with stem cell activity increase in old “rejuvenated” mice supporting the notion that young blood may contain increased levels of beneficial factors with regenerative capacity. We believe we have identified some of these factors now and tested them on cultured mouse and human neural stem cell derived cells. Preliminary data suggest that these factors have beneficial effects and we will test whether these effects hold true in living mice.
  • Cognitive function in humans declines in essentially all domains starting around age 50-60 and neurodegeneration and Alzheimer’s disease seems to be inevitable in all but a few who survive to very old age. Mice with a fraction of the human lifespan show similar cognitive deterioration indicating that specific biological processes rather than time alone are responsible for brain aging. While age-related cognitive dysfunction and dementia in humans are clearly distinct entities the aging brain shows the telltale molecular and cellular changes that characterize most neurodegenerative diseases including synaptic loss, dysfunctional autophagy, increased inflammation, and protein aggregation. Remarkably, the aging brain remains plastic and exercise or dietary changes can increase cognitive function in humans and animals. Using heterochronic parabiosis or systemic application of plasma we showed recently that blood-borne factors present in the systemic milieu can rejuvenate brains of old mice. Accordingly, exposing an old mouse to a young systemic environment or to plasma from young mice increased neurogenesis, synaptic plasticity, and improved contextual fear conditioning and spatial learning and memory. Unbiased genome-wide transcriptome studies from our lab show that hippocampi from old “rejuvenated” mice display increased expression of a synaptic plasticity network which includes increases in c-fos, egr-1, and several ion channels. In our most recent studies, plasma from young but not old humans reduced neuroinflammation in brains of immunodeficient mice (these mice allow us to avoid an immune response against human plasma). Together, these studies lend strong support to the existence of factors with beneficial, “rejuvenating” activity in young plasma and they offer the opportunity to try to identify such factors.
  • Cognitive function in humans declines in essentially all domains starting around age 50-60 and neurodegeneration and dementia seem to be inevitable in all but a few who survive to very old age. Mice with a fraction of the human lifespan show similar cognitive deterioration indicating that specific biological processes rather than time alone are responsible for brain aging. While age-related cognitive dysfunction and dementia in humans are clearly distinct entities and affect different brain regions the aging brain shows the telltale molecular and cellular changes that characterize most neurodegenerative diseases including synaptic loss, dysfunctional autophagy, increased inflammation, and protein aggregation. Remarkably, the aging brain remains plastic and exercise or dietary changes can increase cognitive function in humans and animals, with animal brains showing a reversal of some of the aforementioned biological changes associated with aging. Using heterochronic parabiosis we showed recently that blood-borne factors present in the systemic milieu can inhibit or promote adult neurogenesis in an age-dependent fashion in mice. Accordingly, exposing an old mouse to a young systemic environment or to plasma from young mice increased neurogenesis, synaptic plasticity, and improved contextual fear conditioning and spatial learning and memory. Over the past three years we discovered that factors in blood can actively change the number of new neurons that are being generated in the brain and that local cells in areas were neurons are generated respond to cues from the blood. We have started to identify some of these factors and hope they will allow us to regulate the activity of neural stem cells in the brain and hopefully improve cognition in diseases such as Alzheimer's.

© 2013 California Institute for Regenerative Medicine