Chemical mutagenesis of a GPCR ligand: Detoxifying “inflammo-attraction” to direct therapeutic stem cell migration

Abstract

A transplanted stem cell’s engagement with a pathologic niche is the first step in its restoring homeostasis to that site. Inflammatory chemokines are constitutively produced in such a niche; their binding to receptors on the stem cell helps direct that cell’s “pathotropism.” Neural stem cells (NSCs), which express CXCR4, migrate to sites of CNS injury or degeneration in part because astrocytes and vasculature produce the inflammatory chemokine CXCL12. Binding of CXCL12 to CXCR4 (a G protein-coupled receptor, GPCR) triggers repair processes within the NSC. Although a tool directing NSCs to where needed has been long-sought, one would not inject this chemokine in vivo because undesirable inflammation also follows CXCL12–CXCR4 coupling. Alternatively, we chemically “mutated” CXCL12, creating a CXCR4 agonist that contained a strong pure binding motif linked to a signaling motif devoid of sequences responsible for synthetic functions. This synthetic dual-moity CXCR4 agonist not only elicited more extensive and persistent human NSC migration and distribution than did native CXCL 12, but induced no host inflammation (or other adverse effects); rather, there was predominantly reparative gene expression. When co-administered with transplanted human induced pluripotent stem cell-derived hNSCs in a mouse model of a prototypical neurodegenerative disease, the agonist enhanced migration, dissemination, and integration of donor-derived cells into the diseased cerebral cortex (including as electrophysiologically-active cortical neurons) where their secreted cross-corrective enzyme mediated a therapeutic impact unachieved by cells alone. Such a “designer” cytokine receptor-agonist peptide illustrates that treatments can be controlled and optimized by exploiting fundamental stem cell properties (e.g., “inflammo-attraction”).

Understanding Neural Stem Cell Regulation in Vivo and Applying the Insights to Cell Therapy for Strokes

“…Interestingly, to counter this side effect, one preclinical study implanted human NSC derived from human induced pluripotent stem cells (iPSC)-NSC (discussed in section: iPSC-NSC) in mouse brains pretreated with a mutated form of the SDF1 ligand (termed SDV1a) prior to implantation. Interestingly, the SDV1a pretreatment promoted the migration of transplanted NSC to the site of injury without promoting inflammation [41].…”

“…In contrast, the noncanonical Notch ligand, EGFL7 known as an inhibitor of JAG-1-induced Notch signaling, acts as a neurovascular regulator of SVZ-NSC controlling olfactory perception and behavior [25]. Another study conducted in middle cerebral artery occlusion stroke-induced mice, reported that stroke enhances the SVZ's BBB 'leakiness' to facilitate direct access to stroke-induced increased levels of VEGF-A 165 to niche cells [41]. Additionally, these authors reported that the increase in VEGF-A levels post stroke activates Notch signaling by a transient induction of the Notch ligand DLL4 mRNA levels to enhance SVZ neurogenesis post stroke [27].…”

Neural Stem Cells for Early Ischemic Stroke

“…NSCs can migrate to areas of injury and neurodegeneration in the CNS. Migration and engagement of NSCs with a pathologic niche is the first step in cell-mediated restoration of homeostasis to the injured region [ 18 , 76 , 77 , 78 , 79 ]. NSC pathotropism, which is the natural tendency of homing to the site of injury, is partly achieved by chemokine receptors on NSCs that respond to proinflammatory cytokines secreted from the pathologic region [ 80 , 81 , 82 , 83 , 84 , 85 , 86 ].…”

“…NSC pathotropism, which is the natural tendency of homing to the site of injury, is partly achieved by chemokine receptors on NSCs that respond to proinflammatory cytokines secreted from the pathologic region [ 80 , 81 , 82 , 83 , 84 , 85 , 86 ]. For example, chemokine stromal cell-derived factor-1α (SDF-1α/CXCL12) interacts with CXCR4 receptors on NSCs as a major step in directing NSCs to injured brain regions [ 74 , 76 , 83 , 87 ]. The role of SDF-1α in stem cell homing is also implicated in cardiovascular and renal disease [ 88 , 89 , 90 ].…”

“…The role of SDF-1α in stem cell homing is also implicated in cardiovascular and renal disease [ 88 , 89 , 90 ]. Further, in vitro transwell chemotaxis experiments demonstrated that NSCs preferentially migrate toward a higher SDF-1α concentration [ 76 , 91 ] and also synthetic SDF-1α [ 76 ]. SDF-1α is increased in stroke-affected brain tissue, and NSCs migrated toward the infarct area [ 92 ].…”