TLR3-overexpressing umbilical cord mesenchymal stromal cells suppress immune responses to attenuate high-risk corneal transplantation rejection.

Background: The success rates of high-risk corneal transplantation are significantly hindered by immunological rejection. Umbilical cord mesenchymal stem cells (UC-MSCs) have emerged as a potential solution to improve graft outcomes. Toll-like receptors (TLRs) play pivotal roles in the immune response, however, their specific functions in UC-MSC-based treatments for corneal graft rejection requires further investigation.

Methods: New Zealand rabbits that underwent high-risk corneal transplantation were treated with UC-MSC-coated contact lenses (MSCohi-O), while blank lenses and untreated grafts served as controls. Clinical manifestations related to rejection were assessed. RNA-seq was performed on the grafts. GSEA, CIBERSORT, and flow cytometry analyses were performed to investigate the activation of signaling pathways and immune changes. The microarray dataset GSE68610, which contains transcriptome data for normal human UC-MSCs and UC-MSCs treated with cytokines, was analyzed to evaluate TLR expression and identify the key factors involved in the anti-inflammatory effect of UC-MSCs. Overexpression and knockout of TLR3 were performed in UC-MSCs, and the therapeutic effects of TLR3-activated and -inactivated UC-MSCs were compared in a high-risk corneal transplantation model.

Results: MSCohi-O treatment alleviated corneal opacity and edema, inhibited neovascularization, promoted epithelialization, and prolonged the survival time of corneal grafts (all p < 0.05). GSEA revealed that the allograft rejection pathway was upregulated in untreated grafts and downregulated in UC-MSC-treated grafts. Increased numbers of Tregs and decreased numbers of Th17 cells were observed in UC-MSC-treated corneas. An analysis of the GSE68610 dataset revealed that TLR3 expression was upregulated in cytokine-activated UC-MSCs, suggesting that TLR3 is a potential regulator of the immunosuppression function of UC-MSCs. TLR3-overexpressing UC-MSCs exhibited enhanced suppression of rejection in high-risk corneal transplants, whereas TLR3 knockdown diminished these effects.

Conclusions: This study shows that the localized application of UC-MSC-coated contact lenses is capable of inhibiting rejection in high-risk corneal transplantation. TLR3-overexpressing UC-MSCs have enhanced antirejection and immunomodulatory effects. This research could offer a safer and more effective therapeutic strategy to prevent corneal transplant rejection.