Abstract
Purpose :
Fungal keratitis(FK) is one of the most common vision-threatening ocular diseases. Immune systems are effective host defense against fungus, but excessive immune response would accelerate the corneal perforation. This study was aiming at exploring the role of Th17 and Tregs in the pathogenesis process of fungal keratitis and the associating miRNA regulatory mechanisms modulating the inflammatory response in FK.
Methods :
A FK mouse model was generated through intrastromal injection of Aspergillus fumigatus spores and the severity of corneal damage was evaluated with clinical scoring and histological examination at 1, 3 and 5 days post-infection. Immune organs draining lymph nodes (DLN) and corneal infiltration of CD4+ T cell, Th17 and Treg cells were analyzed by flow cytometry. The mRNA,miRNA and protein expression levels of downstream inflammatory cytokines were determined by quantitative real-time PCR (qRT-PCR) and Mouse High Sensitivity T Cell Magnetic Bead Panel.
Results :
Clinical scores of FK mouse model illustrated that corneal disease progression mainly reached the peak on Day 3 and then declined on Day 5. Th17 cells continued infiltration in the cornea on day 5 though the disease progressed to a healing form (Th17: Day 1, 8.63%; Day 3, 11.4%; Day 5, 13.9%). However, the ratio of cell percentage of Th17 to Treg peaked on day 3, as the disease progressed to a more severe form, then declined on day 5(Th17/Treg: Day 1, 41.7 %; Day 3: 133.7%; Day 5: 76.5%).The frequency of Th17 and the ratio of cell population of Th17 to Treg in DLN revealed the same trend as in the infected cornea. Among18 inflammatory markers , IL-6, IL-17A, IL-1β, MCP-1, MIP-2 showed statistically significant decreases. Diverse with the proteins, the mRNA levels of inflammatory cytokines continuously increased after infection (p<0.005). The highly dysregulated miRNAs (miR-511-5p, miR-142-3p, miR-155-5p, miR144-3p, miR-21-5p, and miR-223-3p) may regulate wound healing in FK through specifically targeting inflammatory genes.
Conclusions :
Th17 and Treg, play key roles in host immune response during corneal Aspergillus fumigatus infection. The present data indicated that miRNA should inhibit the mRNA transcription of the inflammatory associated cytokines in the pathogenic process of fungal keratitis.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.