PF-127 Hydrogel-Delivered hUCMSC-Exosomes Attenuate Endometrial Injury by Inhibiting Epithelial-Mesenchymal Transition.

BACKGROUND: Endometrial injury, often resulting from iatrogenic procedures or infections, can lead to fibrosis, adhesions, and infertility. Current therapies are inadequate for reversing fibrosis or restoring normal function. Mesenchymal stem cell-derived exosomes (MSC-exos) present therapeutic potential; however, their rapid clearance poses a challenge. The purpose of this study was to develop a thermosensitive Pluronic F-127 (PF-127) hydrogel for sustained intrauterine delivery of human umbilical cord MSC-derived exosomes (PF-127-hUCMSC-exos) and to evaluate its efficacy and underlying mechanisms in a rat model of ethanol-induced endometrial injury. METHODS: A thermosensitive PF-127 hydrogel loaded with hUCMSC-exos was developed. Its retention and therapeutic effects were evaluated in a rat model of ethanol-induced endometrial injury. Comparisons were made among control, model, hydrogel treatment alone, and PF-127-hUCMSC-exos treatment. Mechanistic assessments included histological analysis, collagen deposition measurement, fertility testing, expression analysis of epithelial-mesenchymal transition (EMT) markers (E-cadherin, vimentin, β-catenin), transcriptomic analysis of exosome-treated primary rat endometrial stromal cells, and measurement of early growth response 2 (EGR2) mRNA and protein levels. RESULTS: PF-127-hUCMSC-exos were detectable in the uterine cavity up to day 12, and this treatment significantly improved endometrial morphology, increased thickness and gland number, reduced collagen deposition, and partially restored fertility. Mechanistically, exosomes inhibited EMT by upregulating E-cadherin and downregulating vimentin and β-catenin. RNA-seq of exosome-treated rESCs identified 1173 differentially expressed genes, with enrichment in EMT-related pathways. EGR2, a pro-fibrotic transcription factor, was significantly downregulated at both mRNA and protein levels. EGR2 overexpression promoted cell migration, which was reversed by exosome treatment. CONCLUSIONS: PF-127-hUCMSC-exos hydrogel effectively repairs endometrial injury and restores fertility by inhibiting EMT, potentially via EGR2 downregulation. This cell-free strategy offers a promising approach for endometrial regeneration.