This study aimed to investigate the therapeutic potential and molecular mechanism of human umbilical cord MSC-derived exosomes (hUC-MSC-EVs) in treating SLE-related cognitive impairment.

Cognitive function of MRL/lpr spontaneous lupus mice was assessed using cognitive-related behavioral tests, including the Morris water maze, Y-maze, and novel object recognition tests. Transcriptome sequencing, qRT-PCR, Western blot, and immunofluorescence were used to analyze the senescence level in the brain tissue of lupus mice. hUC-MSC-EVs were isolated by ultracentrifugation and identified, then co-cultured with BV2 microglial cells in vitro to detect their effects on senescence-related indicators of BV2 cells. In vivo, MRL/lpr mice were treated with intravenous infusion of hUC-MSC-EVs, and their cognitive improvement was evaluated by behavioral tests. The effect of EV intervention on brain senescence in MRL/lpr mice was assessed using SA-β-gal staining, immunofluorescence for p16INK4a and γ-H2AX, and quantitative analysis of senescence-associated secretory phenotype (SASP) factors. Finally, small RNA sequencing was performed on hUC-MSC-EVs and plasma samples of SLE patients before and after MSC infusion to screen key miRNAs. Functional verification was conducted by stereotaxic injection of antago-miRNA into the brains of MRL/lpr mice in vivo. In vitro, miRNA mimic and inhibitor experiments, combined with dual-luciferase reporter gene assays, were used to clarify the regulatory relationship between the key miRNA and its target genes.

This study obtained the following key findings: First, MRL/lpr mice exhibited cognitive behavioral abnormalities and senescent phenotypes in the hippocampal region of the brain; treatment with the senolytic drug combination (dasatinib plus quercetin) significantly improved cognitive impairment in MRL/lpr mice. Second, after tail vein injection of hUC-MSC-EVs, cognitive impairment in MRL/lpr mice was significantly alleviated. Meanwhile, MRL/lpr mice showed obvious microglial senescence characteristics in the hippocampus, including increased SA-β-gal activity, upregulated expression of p16INK4a and γ-H2AX, and enhanced secretion of SASP factors, which were effectively reversed by hUC-MSC-EV treatment. Third, integrated miRNA sequencing and bioinformatics analysis identified miR-27b-3p as the most significantly enriched miRNA in hUC-MSC-EVs and the most obviously upregulated miRNA in the plasma of SLE patients after MSC infusion. Functional studies showed that miR-27b-3p inhibitor in vitro abolished the anti-senescence effect of hUC-MSC-EVs, while intracerebral administration of antagomiR-27b-3p reversed the cognitive improvement effect of hUC-MSC-EVs in vivo. Fourth, mechanistic studies confirmed that MAPK14 (p38α) is a direct target of miR-27b-3p; delivery of miR-27b-3p mediated by hUC-MSC-EVs significantly inhibited MAPK14 expression.

hUC-MSC-EVs improve SLE-related cognitive impairment by delivering miR-27b-3p to microglia, which targets and inhibits the MAPK14/p38 signaling pathway, thereby suppressing microglial senescence and subsequent neuroinflammation. This study establishes microglial senescence as a key pathological mechanism in NPSLE and identifies miR-27b-3p as a critical therapeutic mediator in hUC-MSC-EVs.