Interleukin-2 Mediated Expansion of T-Regulatory Cells as an Ischemic Stroke Therapy

HomeStrokeVol. 55, No. 6Interleukin-2 Mediated Expansion of T-Regulatory Cells as an Ischemic Stroke Therapy Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBInterleukin-2 Mediated Expansion of T-Regulatory Cells as an Ischemic Stroke Therapy David A. Hurst and Farida Sohrabji David A. HurstDavid A. Hurst https://orcid.org/0000-0003-2462-0100 Department of Neuroscience and Experimental Therapeutics, Women's Health in Neuroscience Program, Texas A&M University School of Medicine, Bryan. and Farida SohrabjiFarida Sohrabji Correspondence to: Farida Sohrabji, PhD, Department of Neuroscience and Experimental Therapeutics, Women's Health in Neuroscience Program, Texas A&M University School of Medicine, 8447 Riverside Pkwy, Mail Stop 1359, Bryan, TX 77807. Email E-mail Address: [email protected] https://orcid.org/0000-0002-6960-3411 Department of Neuroscience and Experimental Therapeutics, Women's Health in Neuroscience Program, Texas A&M University School of Medicine, Bryan. Originally published24 May 2024https://doi.org/10.1161/STROKEAHA.124.047357Stroke. 2024;55:e159–e160The inflammatory cascade that ensues following an ischemic stroke has been increasingly recognized as a driving force in the long-term disability associated with the disease. This synopsis will highlight recent preclinical studies that aimed to promote a robust Treg (T-regulatory cell) response via interleukin-2 (IL-2) signaling following an experimental stroke.To elucidate the mechanism by which an expansion in Tregs following experimental ischemic injury promotes white matter integrity and functional recovery, Yuan et al (Regulatory T cell expansion promotes white matter repair after stroke. Neurobiol Dis. 2023;179:106063. doi: 10.1016/j.nbd.2023.106063) demonstrated that Treg augmentation via direct intravenous transfer of Tregs isolated from donor mice 2 hours after transient middle cerebral artery occlusion (tMCAO) resulted in improved white matter recovery when compared with splenocyte-treated mice poststroke. To determine whether promoting an endogenous Treg expansion poststroke would similarly result in a neuroprotective phenotype, wild-type mice were treated with either a consecutive intraperitoneal administration of IL-2/IL-2 antibody complexes (IL-2/IL-2Ab) or equal concentrations of isotype-matched antibody (IgG) at 6 hours, 1 day, 2 days, 3 days, 10 days, 20 days, and 30 days after stroke. At 14 days after stroke, IL-2/IL-2Ab mice displayed a significant increase in the CD25+CD4+Foxp3+ Treg cell population in the blood, spleen, and brain parenchyma when compared with IgG-treated controls. Importantly, IL-2/IL-2Ab treatment mitigated sensorimotor dysfunction at 35 days, but not at 7 days after stroke. To evaluate white matter integrity, longitudinal in vivo diffusion tensor imaging scans 14 and 28 days after tMCAO coupled with ex vivo diffusion tensor imaging scanning of brains 35 days after stroke were used to construct fractional anisotropy maps. Fractional anisotropy mapping showed that IL-2/IL-2Ab–treated mice exhibited improved white matter integrity at 28 and 35 days after stroke, indicating that Treg expansion promotes white matter integrity in the late phase of stroke. Delayed IL-2/IL-2Ab treatment remained protective even when administered as late as 5 days after stroke, as Luxol fast blue staining of coronal brain slices of treated mice showed increased myelin in the external capsule and striatum 21 days after tMCAO in IL-2/IL-2Ab–treated mice compared with IgG-treated mice.To determine a precise signaling mechanism through which Tregs promote long-term tissue repair following ischemic stroke, Shi et al (Treg cell-derived osteopontin promotes microglia-mediated white matter repair after ischemic stroke. Immunity. 2021;54:1527–1542.e8. doi: 10.1016/j.immuni.2021.04.022) utilized single-cell RNA sequencing and flow cytometry to verify that Tregs are among the immune cell populations that infiltrate the brain poststroke at 3, 5, 7, 14, and 35 days after stroke. To confirm their role in improving white matter integrity after stroke, Tregs were selectively depleted via diphtheria toxin (DT) injections in Foxp3DTR (DTR) transgenic mice that express the DT receptor under the control of the Foxp3 promoter. Treg depletion resulted in diminished functional recovery and drastically aggravated white matter lesions following an ischemic stroke. Comparative transcriptomic analysis of sorted CD4+CD25+Foxp3(GFP)+ Treg cells from the ischemic brain and blood of stroke and sham DTR mice identified differentially expressed genes between brain-infiltrating Treg cells and peripheral Treg cells; several genes upregulated in brain-infiltrating Treg cells encoded trophic factors known to stimulate oligodendrocyte precursor cell differentiation, such as Igf1, IL-1a, and Osm. Additionally, brain-infiltrating Treg cells displayed higher levels of transcripts encoding cytokines such as Spp1, Il1b, Il1a, and Il10, suggesting that Treg cell-mediated white matter repair may rely on immunomodulatory signals and cell-cell interactions. Treg-derived osteopontin was identified as a potential signaling molecule driving microglial-mediated white matter repair, as protein-protein interaction enrichment analysis via STRING (Search Tool for the Retrieval of Interacting Genes/Proteins) identified interactions between Spp1, which encodes osteopontin, and Itgb1, Itga5, and Itgav, which encode the integrin subunits of the osteopontin receptor on microglia. To confirm the role of osteopontin signaling in vivo, Treg cells derived from wild-type or Spp1−/− mice into DTR+DT mice 6 hours after tMCAO, and myelination was assessed via Luxol fast blue staining. Importantly, Spp1−/− Treg cell-treated mice displayed a reduction in myelination when compared with wild-type Treg cell-treated mice. Lastly, this study showed that IL-2/IL-2Ab treatment boosted the number of osteopontin+ Treg cells in the ischemic brain 3 days after tMCAO, improved sensorimotor function, spatial learning, and mitigated white matter injury (fractional anisotropy mapping and dual staining for myelin basic protein).Observing the capacity of IL-2 to drive Treg recruitment and infiltration into the brain following stroke resulting in improved functional recovery and white matter repair, Yshii et al (Astrocyte-targeted gene delivery of interleukin 2 specifically increases brain-resident regulatory T cell numbers and protects against pathological neuroinflammation. Nat Immunol. 2022;23:878–891. doi: 10.1038/s41590-022-01208-z) aimed to develop and validate a central nervous system–specific therapeutic strategy. The adeno-associated virus–based therapeutic delivery system detailed in this study utilized the GFAP (glial fibrillary acidic protein) promoter to drive IL-2 expression in astrocytes specifically while simultaneously avoiding expression in both the peripheral immune systems and astrocytes. The ability of the delivery system to drive astrocyte-specific expression of IL-2 and increase recruit of Tregs to the central nervous system was validated using ELISA, flow cytometry, immunofluorescent staining, and single-cell RNA-seq. The efficacy of the gene delivery was evaluated in various models of central nervous system injury, such as the controlled cortical impact model for traumatic brain injury, a distal middle cerebral artery occlusion model, the photothrombotic model stroke, and the experimental autoimmune encephalomyelitis model of multiple sclerosis. Cognitive recovery was then assessed 15 days after injury using the Morris water maze test and the novel object recognition test. Comparative assessments of tissue injury and lesion size were conducted using immunofluorescence staining of the cortical tissue and MRI 14 days after injury. Importantly, PHP.GFAP-IL-2 treatment before injury mitigated neuroinflammation and improved functional recovery in all models of central nervous system injury, including traumatic brain injury, stroke, and multiple sclerosis, and did not impact the peripheral immune system.While preclinical studies have shown promising results in the use of IL-2 to amplify Tregs to mitigate white matter injury following ischemic stroke, the application of this method in clinical settings remains sparse. One major hurdle in applying IL-2–mediated Treg expansion in clinical trials is to do so without inadvertently activating other immune cells or causing broader side effects that come with IL-2 treatments.ARTICLE INFORMATIONSources of FundingNone.FootnotesFor Sources of Funding and Disclosures, see page e160.Correspondence to: Farida Sohrabji, PhD, Department of Neuroscience and Experimental Therapeutics, Women's Health in Neuroscience Program, Texas A&M University School of Medicine, 8447 Riverside Pkwy, Mail Stop 1359, Bryan, TX 77807. Email f-sohrabji@tamu.edu eLetters(0)eLetters should relate to an article recently published in the journal and are not a forum for providing unpublished data. Comments are reviewed for appropriate use of tone and language. Comments are not peer-reviewed. Acceptable comments are posted to the journal website only. Comments are not published in an issue and are not indexed in PubMed. Comments should be no longer than 500 words and will only be posted online. References are limited to 10. Authors of the article cited in the comment will be invited to reply, as appropriate.Comments and feedback on AHA/ASA Scientific Statements and Guidelines should be directed to the AHA/ASA Manuscript Oversight Committee via its Correspondence page.Sign In to Submit a Response to This Article Previous Back to top Next FiguresReferencesRelatedDetails June 2024Vol 55, Issue 6 Advertisement Article InformationMetrics © 2024 American Heart Association, Inc.https://doi.org/10.1161/STROKEAHA.124.047357PMID: 38787931 Originally publishedMay 24, 2024 Keywordsinterleukin-2immunoglobulin GstrokeT-lymphocytes, regulatorywhite matterPDF download Advertisement SubjectsAnimal Models of Human DiseaseBasic Science ResearchInflammation