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).