Evaluation of corneal graft survival in mice model

Pro-inflammatory role of NLRP3 inflammasome in experimental sterile corneal inflammation

We evaluated the role of NLR family pyrin domain containing 3 (NLRP3) inflammasome in sterile corneal inflammation caused by lipopolysaccharide (LPS) or alkali burns in C57BL6 mice or NLRP3 KO (Nlrp3^−/−) mice. Various molecules related to the NLRP3 inflammasome were upregulated in C57BL6 mice after both alkali burn injury and LPS treatment. After alkali burn injury, the corneal opacity grade was significantly reduced in Nlrp3^−/− mice compared with C57BL6 mice. In Nlrp3^−/− mice, Gr-1 immunoreactivity and MMP-9 mRNA expression in the corneal stroma were significantly reduced by both LPS treatment and alkali burn injury. Quantitative PCR and immunohistochemistry revealed that IL-1β and MMP-9 expression in the corneal stroma were down-regulated in Nlrp3^−/− mice with both alkali burn injury and LPS treatment. These findings suggest that the NLRP3 inflammasome has a pro-inflammatory effect in the cornea by recruiting neutrophils to sites of inflammation.

The Balance of Th1/Th2 and LAP+Tregs/Th17 Cells Is Crucial for Graft Survival in Allogeneic Corneal Transplantation

Purpose

CD4+LAP+ T cells are newly discovered regulatory T cells (Tregs). The aim of this study is to investigate the balance of Th1/Th2 and LAP+Tregs/Th17 in mice after allogeneic corneal transplantation.

Methods

A total of 65 mice received orthotopic penetrating transplantation. According to the survival scores of the grafts, the mice were divided into the rejection group and the survival group 3 weeks after transplantation. Th1, Th2, Th17, and regulatory T cells in the ipsilateral drainage lymph nodes and spleens were measured with flow cytometry. The related cytokines in aqueous humor were also analyzed.

Results

The frequencies of Foxp3+Tregs, GARP+Tregs, and LAP+Tregs in the survival group were significantly higher than those in the rejection group. And the expression trend of CD4+LAP+ T cells and CD4+GARP+ T cells was consistent. The level of IFN-γ, TNF, IL-6, and IL-17A markedly increased in aqueous humor during corneal allograft rejection. The ratio of Th1/Th2 and Th17/LAP+Tregs significantly increased in the rejection group at the 3rd week after corneal transplantation.

Conclusion

LAP+Tregs might be regarded as substitute for Foxp3+Tregs. The balance of Th1/Th2 and LAP+Tregs/Th17 is crucial for corneal allograft survival.

Optimizing rejection readouts in a corneal allograft transplantation model

PURPOSE

To evaluate the feasibility of anterior segment spectral domain optic coherence tomography (ASOCT) as rejection readout in a keratoplasty mouse model and to compare ASOCT against the current standard (i.e., a clinical score system). Furthermore, to compare both approaches with respect to intra- and inter-individual observer variability and to calculate a critical point that distinguishes between rejection and non-rejection in ASOCT analysis.

METHODS

Allogeneic penetrating keratoplasties (PKs) were performed using C3H/He donor mice and BALB/c recipient mice; syngeneic transplantations served as controls using BALB/c donors and recipients. Corneal graft rejection was determined with a clinical score. ASOCT was used to determine the central thickness of the corneal grafts in the same animals. The rejection status was corroborated with histopathological examination.

RESULTS

The median survival time (MST) of the corneal allografts in the wild-type BALB/c mice was 12 days. Allogeneic transplantation led to a 100% rejection rate, whereas signs of rejection after syngeneic transplantation appeared in up to 20% of the mice. Central corneal thickness (CCT) determination via customized software revealed a direct correlation with the clinical score. Receiver operating curve (ROC) analysis confirmed CCT as a valid surrogate for rejection. Calculation of the area under the curve (AUC) revealed a value of 0.88 with an optimal cut-off at 267 pixels.

CONCLUSIONS

An increase in the CCT during acute allogeneic corneal graft rejection significantly correlated with the clinical surrogate parameter "corneal opacity." ASOCT not only generates source data, but also analysis of the ASOCT data shows lower readout variability and fewer interpreter variations than the clinical score commonly used to define the time point of graft rejection in mice.