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.
Human neural stem cells (hNSCs) expressing CXCR4 have been found to migrate in vivo toward an infarcted area that are representative of central nervous system (CNS) injuries, where local reactive astrocytes and vascular endothelium up-regulate the SDF-1α secretion level and generate a concentration gradient. Exposure of hNSCs to SDF-1α and the consequent induction of CXCR4-mediated signaling triggers a series of intracellular processes associated with fundamental aspects of survival, proliferation and more importantly, proper lamination and migration during the early stages of brain development . To date, there is no crystal structure available for chemokine receptors [2, 3]. Structural and modeling studies of SDF-1α and D-(1~10)-L-(11~69)-vMIP-II in complexes with CXCR4 TM helical regions led us to a plausible “two-pocket” model for CXCR4 interaction with agonists or antagonists. [4-6] In this study, we extended the employment of this model into the novel design strategy for highly potent and selective CXCR4 agonist molecules, with potentials in activating CXCR4-mediated hNSC migration by mimicking a benign version of the proinflamatory signal triggered by SDF-1α. Successful verification of directed, extensive migration of hNSCs, both in vitro and in transplanted uninjured adult mouse brains, with the latter manifesting significant advantages over the natural CXCR4 agonist SDF-1α in terms of both distribution and stability in mouse brains, strongly supports the effectiveness and high potentials of these de novo designed CXCR4 agonist molecules in optimizing directed migration of transplanted human stem cells during the reparative therapeutics for a broad range of neurodegenerative diseases in a more foreseeable future.
Our final progress report is divided into 3 subsections, each addressing progress in the 3 fundamental areas of investigation for the successful completion of this project:
(1) De-novo design and synthesis of CXCR4-specific SDF-1α analogs.
(2) In vitro studies on validating biological potencies of molecules in (1) in activating CXCR4 down-stream signaling.
(3) In vivo studies on migration of transplanted neural precursor cells (NPCs) in co-administration of molecules with validated biological activities in (2).