Neuroinflammatory reactive astrocyte formation correlates with adverse outcomes in perinatal white matter injury.

Perinatal white matter injury (WMI) is the leading cause of long-term neurological morbidity in infants born preterm. Neuroinflammation during a critical window of early brain development plays a key role in WMI disease pathogenesis. The mechanisms linking inflammation with the long-term myelination failure that characterizes WMI, however, remain unknown. Here, we investigate the role of astrocyte reactivity in WMI. In an experimental mouse model of WMI, we demonstrate that WMI disease outcomes are improved in mutant mice lacking secretion of inflammatory molecules TNF-α, IL-1α, and C1q known, in addition to other roles, to induce the formation of a neuroinflammatory reactive astrocyte substate. We show that astrocytes express molecular signatures of the neuroinflammatory reactive astrocyte substate in both our WMI mouse model and human tissue affected by WMI, and that this gene expression pattern is dampened in injured mutant mice. Our data provide evidence that a neuroinflammatory reactive astrocyte substate correlates with adverse WMI disease outcomes, thus highlighting the need for further investigation of these cells as potential causal players in WMI pathology.

All but Small: miRNAs from Wharton's Jelly-Mesenchymal Stromal Cell Small Extracellular Vesicles Rescue Premature White Matter Injury after Intranasal Administration.

White matter injury (WMI) is a common neurological issue in premature-born neonates, often causing long-term disabilities. We recently demonstrated a key beneficial role of Wharton's jelly mesenchymal stromal cell-derived small extracellular vesicles (WJ-MSC-sEVs) microRNAs (miRNAs) in WMI-related processes in vitro. Here, we studied the functions of WJ-MSC-sEV miRNAs in vivo using a preclinical rat model of premature WMI. Premature WMI was induced in rat pups through inflammation and hypoxia-ischemia. Small EVs were purified from the culture supernatant of human WJ-MSCs. The capacity of WJ-MSC-sEV-derived miRNAs to decrease microglia activation and promote oligodendrocyte maturation was evaluated by knocking down (k.d) DROSHA in WJ-MSCs, releasing sEVs containing significantly less mature miRNAs. Wharton's jelly MSC-sEVs intranasally administrated 24 h upon injury reached the brain within 1 h, remained detectable for at least 24 h, significantly reduced microglial activation, and promoted oligodendrocyte maturation. The DROSHA k.d in WJ-MSCs lowered the therapeutic capabilities of sEVs in experimental premature WMI. Our results strongly indicate the relevance of miRNAs in the therapeutic abilities of WJ-MSC-sEVs in premature WMI in vivo, opening the path to clinical application.

MicroRNA Cargo in Wharton's Jelly MSC Small Extracellular Vesicles: Key Functionality to In Vitro Prevention and Treatment of Premature White Matter Injury.

Preterm birth is the leading cause of childhood morbidity and mortality and can result in white matter injury (WMI), leading to long-term neurological disabilities with global health burden. Mesenchymal stromal cell-derived small extracellular vesicles (MSC-sEV) are a promising therapeutic agent for treating perinatal neurological injury. They carry microRNAs (miRNAs) predicted to be involved in the onset of premature WMI. We hypothesize that miRNAs have a key function in the beneficial effects of MSC-sEV. We isolated MSC from umbilical cord tissue, the Wharton's jelly (WJ), and purified small extracellular vesicles (sEV) from WJ-MSC culture supernatant by ultracentrifugation and size exclusion chromatography. The miRNA content was quantified by real-time polymerase chain reaction. A luciferase gene assay validated silencing of TP53 and TAOK1, which we previously identified as predicted target genes of MSC-sEV miRNAs by Next Generation Sequencing and pathway enrichment analysis. The impact of sEV miRNAs on oligodendroglial maturation and neuronal apoptosis was evaluated using an in vitro oxygen-glucose deprivation model (OGD/R) by knocking-down DROSHA in WJ-MSC, which initiates miRNA processing. WJ-MSC-sEV contained miRNAs involved in WMI, namely hsa-miR-22-3p, hsa-miR-21-5p, hsa-miR-27b-3p, and the hsa-let-7 family. The luciferase assay strongly indicated an inhibitory effect of sEV miRNAs on the gene expression of TP53 and TAOK1. Small EV initiated oligodendrocyte maturation and reduced OGD/R-mediated neuronal apoptosis. Knocking-down DROSHA in WJ-MSC reduced the expression of sEV miRNAs and led to the loss of their beneficial effects. Our in vitro study strongly indicates the key function of miRNAs in the therapeutic potential of WJ-MSC-sEV in premature WMI.