This proposal describes a sharply-focused, timely, and rigorous effort to develop new therapies for the treatment of injuries of the Central Nervous System (CNS). The underlying hypothesis for this proposal is that chemokines and their receptors (particularly those involved in inflammatory cascades) actually play important roles in mediating the directed migration of human neural stem cells (hNSCs) to, as well as engagement and interaction with, sites of CNS injury, and that understanding and manipulating the molecular mechanism of chemokine-mediated stem cell homing and engagement will lead to new, better targeted, more specific, and more efficacious chemokine-mediated stem cell-based repair strategies for CNS injury. In recent preliminary studies, we have discovered and demonstrated the important role of chemokine SDF-1-alpha and its receptor CXCR4 in mediating the directed migration of hNSCs to sites of CNS injury. To manipulate this SDF-1-alpha/CXCR4 pathway in stem cell migration, we have developed Synthetically and Modularly Modified Chemokines (SMM-chemokines) as highly potent and specific therapeutic leads. Here in this renewal application we propose to extend our research into a new area of stem cell biology and medicine involving chemokine receptors such as CXCR4 and its ligand SDF-1. Specifically, we will design more potent and specific analogs of SDF-1-alpha to direct the migration of beneficial stem cells toward the injury sites for the repair process.
This proposal describes a sharply-focused, timely, and rigorous effort to develop new therapies for the treatment of injuries of the Central Nervous System (CNS). CNS injuries and related disorders such as stroke, traumatic brain injury and spinal cord injury are significant health issues in the nation including the state of California. The new stem cell-based therapies to be developed from this application will have important clinical application in patients with these diseases in California.
SYNOPSIS: This proposal will design and synthesize novel analogs of the chemokine SDG-1-alpha in aim 1. The most potent and specific of these 'Synthetically and Modularly Modified Chemokines'(“SMM-chemokine analogs”) are expected to help mobilize and direct human neural stem cells (hNSCs) toward sites of CNS injury – in this case, a hypoxic ischemic (HI) cerebral injury. In specific aim 2, in vitro assays of the analogs will be performed including biochemical binding of ligands to their receptors and in vitro migration (e.g. Boyden chambers) followed by an in vivo screen of the most promising analogs in a model of hypoxic-ischemic cerebral injury in conjunction with hESC-derived NSC.
INNOVATION AND SIGNIFICANCE: The idea of developing new potent and specific analogs of SDF-1 alpha to manipulate stem cell-host interactions is very innovative and potentially very important.
STRENGTHS: This is a reasonably well-written proposal to study an important molecular “homing factor” in hNSC migration and integration in the brain. This work builds on previous studies from the Snyder group showing that the SDF-1-alpha/CXCR4 chemokine axis is very important for directed migration of other NSCs. The idea of manipulating “the molecular mechanism of chemokine-mediated stem cell homing and engagement” for better stem cell homing and integration is a major strength of this proposal.
The PI is a productive and experienced investigator who has extensive experience with designing and using synthetic peptides to study the chemokine/receptor interactions and the actions of this chemokine pathway. There is an ongoing collaboration with Evan Snyder, an experienced stem cell biologist.
WEAKNESSES: The proposal is based on the hypothesis that “…chemokines and their receptors…play important roles in mediating the directed migration of human neural stem cells (hNSCs) to, as well as engagement and interaction with, sites of CNS injury…” We already know this is true.
The rationale for using hES cells is not terribly strong since many previous studies from this group have already used an adult neural stem cell line that might be more appropriate for the testing of new analogs and deriving hNSC from hESC represents an extra and unnecessary step.
Most daunting about this proposal is that is seems that many parts have been already done or written for another grant. For example, in the Methods the PI states that organtopyic explants will be used (out of nowhere, since the migration assays in previous sections don’t seem to address this approach) from “adult C57BL6 mice …WERE SUBJECTED to permanent middle cerebral artery occlusion…” In another example, the PI states in the Abstract that, “…Here in this renewal application we propose to extend our research into a new area of stem cell biology and medicine involving chemokine receptors such as CXCR4 and its ligand SDF-1”… This would be great, but this RFA is new and not associated with any “renewals”. It is not clear why new ligand analogs of SDF-1alpha will also be tested for their decreasing or inhibiting monocyte/lymphocyte migration. This also seems like a leftover from ongoing or previous studies of the PI’s.
This PI seems to have a great deal of committed percentage effort toward studying chemokines and heat shock protein-related factors for therapeutic development in cancer and infectious disease. It is not completely clear that the amount of work needed to perform the proposed studies can be fit into this exiting commitment.
DISCUSSION: This represents a bit of a change of field and direction for the PI who has been focusing much of his previous attention on chemokines, XIAP family molecules, and other factors involved in cancer and infectious disease. Many people are interested in SDF-1alpha but very little is known about the role of SDF-1a/CXCR4 in NSC. There will be interest in analogs generated, thus potential for impact on field. The proposed work could have potential clinical significance because will direct hNSC to given area.