Oligodendrocyte progenitor cell-specific delivery of lipid nanoparticles loaded with Olig2 synthetically modified messenger RNA for ischemic stroke therapy

The transcription factor Olig2 is highly expressed throughout oligodendroglial development and is needed for the differentiation of oligodendrocyte progenitor cells (OPCs) into oligodendrocytes and remyelination. Although Olig2 overexpression in OPCs is a possible therapeutic target for enhancing myelin repair in ischemic stroke, achieving Olig2 overexpression in vivo remains a formidable technological challenge. To address this challenge, we employed lipid nanoparticle (LNP)-mediated delivery of Olig2 synthetically modified messenger RNA (mRNA) as a viable method for in vivo Olih2 protein overexpression. Specifically, we developed CD140a-targeted LNPs loaded with Olig2 mRNA (C-Olig2) to achieve targeted Olig2 protein expression within PDGFRα+ OPCs, with the goal of promoting remyelination for ischemic stroke therapy. We show that C-Olig2 promotes the differentiation of PDGFRα+ OPCs derived from mouse neural stem cells into mature oligodendrocytes in vitro, suggesting that mRNA-mediated Olig2 overexpression is a rational approach to promote oligodendrocyte differentiation and remyelination. Furthermore, when C-Olig2 was administered to a murine model of ischemic stroke, it led to improvements in blood‒brain barrier (BBB) integrity, enhanced remyelination, and rescued learning and cognitive deficits. Our comprehensive analysis, which included bulk RNA sequencing (RNA-seq) and single-nucleus RNA-seq (snRNA-seq), revealed upregulated biological processes related to learning and memory in the brains of mice treated with C-Olig2 compared to those receiving empty LNPs (Mock). Collectively, our findings highlight the therapeutic potential of multifunctional nanomedicine targeting mRNA expression for ischemic stroke and suggest that this approach holds promise for addressing various brain diseases. STATEMENT OF SIGNIFICANCE: While Olig2 overexpression in OPCs represents a promising therapeutic avenue for enhancing remyelination in ischemic stroke, in vivo strategies for achieving Olig2 expression pose considerable technological challenges. The delivery of mRNA via lipid nanoparticles is considered aa viable approach for in vivo protein expression. In this study, we engineered CD140a-targeted LNPs loaded with Olig2 mRNA (C-Olig2) with the aim of achieving specific Olig2 overexpression in mouse OPCs. Our findings demonstrate that C-Olig2 promotes the differentiation of OPCs into oligodendrocytes in vitro, providing evidence that mRNA-mediated Olig2 overexpression is a rational strategy to foster remyelination. Furthermore, the intravenous administration of C-Olig2 into a murine model of ischemic stroke not only improved blood-brain barrier integrity but also enhanced remyelination and mitigated learning and cognitive deficits. These results underscore the promising therapeutic potential of multifunctional nanomedicine targeting mRNA expression in the context of ischemic stroke.

Shh and Olig2 sequentially regulate oligodendrocyte differentiation from hiPSCs for the treatment of ischemic stroke

Rationale: Demyelination is a major component of white matter injury, characterized by oligodendrocyte (OL) death and myelin sheath loss, which result in memory loss and cognitive impairment in the context of ischemic stroke. Accumulating evidence has shown that OLs can be generated by the direct activation of defined transcription factors (TFs) in human induced pluripotent stem cells (hiPSCs); however, the rapid acquisition of single TF-induced OL progenitor cells (OPCs) as cell therapy for ischemic stroke remains to be thoroughly explored.

Methods: A stable, chemically defined protocol was used to generate a substantial number of transplantable and functional OLs through the partial inhibition of sonic hedgehog (Shh) activity by GANT61 during neural induction from hiPSCs and sequential induction of TF Olig2 overexpression. Transcriptome and metabolome analyses further revealed a novel molecular event in which Olig2 regulates OL differentiation from hiPSC-derived neural progenitor cells (NPCs). Olig2-induced NG2⁺ OPCs (Olig2-OPCs) were then evaluated for their therapeutic potential in cell-based therapy for ischemic stroke.

Results: GANT61 treatment resulted in a motor neuron (MN)-OL fate switch during neural induction, and induced overexpression of Olig2 accelerated oligodendroglial lineage cell specification. Olig2-OPCs expressed typical oligodendroglial lineage marker genes, including NKX2.2, CSPG4, and ST8SIA1, and displayed superior ability to differentiate into mature OLs in vitro. Mechanistically, Olig2-OPCs showed increased gene expression of the peroxisome proliferator-activated receptor γ (PPARγ) signaling pathway, and activated CEPT1-mediated phospholipogenesis. Functionally, inhibiting PPARγ and knocking down CEPT1 further compromised the terminal differentiation of Olig2-OPCs. Most importantly, when transplanted into a rat model of transient middle cerebral artery occlusion (tMCAO), Olig2-OPCs efficiently promoted neurological functional recovery by reducing neuronal death, promoting remyelination, and rescuing spatial memory decline.

Conclusions: We developed a stable, chemically defined protocol to generate OPCs/OLs with partial inhibition of Shh activity by GANT61 from hiPSCs and sequentially induced the expression of the single TF Olig2. Olig2-OPC transplantation may be an ideal alternative approach for ischemic stroke rehabilitation therapy.

The Stem Cell Factor Sox2 Is a Positive Timer of Oligodendrocyte Development in the Postnatal Murine Spinal Cord

Myelination in the central nervous system takes place predominantly during the postnatal development of humans and rodents by myelinating oligodendrocytes (OLs), which are differentiated from oligodendrocyte progenitor cells (OPCs). We recently reported that Sox2 is essential for developmental myelination in the murine brain and spinal cord. It is still controversial regarding the role of Sox2 in oligodendroglial lineage progression in the postnatal murine spinal cord. Analyses of a series of cell- and stage-specific Sox2 mutants reveal that Sox2 plays a biphasic role in regulating oligodendroglial lineage progression in the postnatal murine spinal cord. Sox2 controls the number of OPCs for subsequent differentiation through regulating their proliferation. In addition, Sox2 regulates the timing of OL differentiation and modulates the rate of oligodendrogenesis. Our experimental data prove that Sox2 is an intrinsic positive timer of oligodendroglial lineage progression and suggest that interventions affecting oligodendroglial Sox2 expression may be therapeutic for overcoming OPC differentiation arrest in dysmyelinating and demyelinating disorders.

Interleukin-1β impedes oligodendrocyte progenitor cell recruitment and white matter repair following chronic cerebral hypoperfusion

Subcortical ischemic vascular dementia (SIVD) caused by chronic cerebral hypoperfusion exhibits progressive white matter and cognitive impairments. However, its pathogenetic mechanisms are poorly understood. We investigated the role of interleukin-1β (IL-1β) and its receptor IL-1 receptor type 1 (IL-1R1) in an experimental SIVD model generated via right unilateral common carotid arteries occlusion (rUCCAO) in mice. We found that IL-1β expression was elevated in the corpus callosum at the early stages after rUCCAO. IL-1 receptor antagonist (IL-1Ra), when delivered at an early stage, as well as IL-1R1 knockout, rescued the downregulation of myelin basic protein (MBP) and improved remyelination at the later stage after rUCCAO. Our data suggest that the recruitment of OPCs, but not the proliferation or differentiation of OPCs, is the only compromised step of remyelination following chronic cerebral ischemia. IL-1Ra treatment and IL-1R1 knockout had no effect on the oligodendrocyte progenitor cell (OPC) proliferation, but did promote the recruitment of newly generated OPCs to the corpus callosum, which can be reversed by compensatory expression of IL-1R1 in the SVZ of IL-1R1 knockout mice. Further, we found that recruited OPCs contribute to oligodendrocyte regeneration and functional recovery. In transwell assays, IL-1β inhibited OPC migration through IL-1R1. Moreover, KdPT which can enter the brain to block IL-1R1 also showed comparable protection when intraperitoneally delivered. Our results suggest that IL-1β during the early stages following chronic cerebral hypoperfusion impedes OPC recruitment via IL-1R1, which inhibits white matter repair and functional recovery. IL-1R1 inhibitors may have potential uses in the treatment of SIVD.