Abstract
Purpose :
Adrenaline is a sympathomimetic that is used in the irrigating solution to maintain pupil dilation during cataract surgery, and as a vasoconstrictor to decrease the risk of bleeding (Xylocaine- Adrenaline 0.0005%). It is less cytotoxic than Mitomycin-C and 5-Fluorouracil, which are currently used to prevent scarring in glaucoma surgery. We hypothesise that adrenaline could also have antifibrotic effects in glaucoma surgery.
Methods :
Adrenaline (0% to 0.05%) was tested in fibroblast-populated collagen contraction and cell viability assays. Human Tenon’s fibroblasts were treated with Adrenaline 0%, 0.0005%, 0.01% for 24 hours and mRNA was sequenced on the Illumina NextSeq 2000. FASTQ files were aligned to the human genome UCSC hg38 using RNA-STAR 2.5.2b. Differential expression was carried out using DESeq2. Adrenaline 0.05% (0.1 ml) was also injected subconjunctivally in 3 patients during trabeculectomy, Baerveldt tube and Microshunt surgeries, and the patients were monitored for ocular and systemic adverse effects. Two-tailed Student’s t-test was used for statistical analyses.
Results :
There was a dose-response decrease in fibroblast contractility: matrices decreased to 47.4% (p=0.0002) and 86.6% (p<0.0001) with Adrenaline 0.0005% and 0.01%, respectively, compared to control (0%) where matrices decreased to 25.2%. There was no significant decrease in cell viability even at high drug concentrations (p>0.05). High quality RNA was extracted (RIN≥ 9.4) and principal component analysis revealed tight clustering for each drug concentration. Adrenaline 0.01% significantly upregulated 25 G1/S genes and 11 S-phase genes, and downregulated 23 G2-phase and 17 M-phase genes (p<0.05) (Fig 1A). Adrenaline 0.05% also caused a significant decrease in conjunctival vascularity and there was no significant change in pupil size, pulse, blood pressure, and respiratory rate during glaucoma surgery (p>0.05) (Fig 1B).
Conclusions :
Adrenaline is a safe and cheap antifibrotic drug (£1 per vial) that significantly blocks key cell cycle genes when used at high concentrations. Adrenaline inhibits the proliferation of fibroblasts, which enter a period of growth arrest but do not die. Unless contraindicated, we recommend subconjunctival injections of Adrenaline 0.05% to 0.1% in all glaucoma surgeries. Future aim is to include adrenaline in clinical trials of new antifibrotic drugs.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.