Aims
To assess the feasibility of using voided urine samples to perform a DNA methylation study in females with interstitial cystitis/bladder pain syndrome (IC/BPS) as compared to age- and race-matched controls. A unique methylation profile could lead to a non-invasive, reproducible, and objective biomarker that would aid clinicians in the diagnosis of IC/BPS.
Methods
Nineteen IC/BPS patients and 17 controls were included. IC/BPS patients had an Interstitial Cystitis Symptom Index score of >8; controls had no bladder symptoms. DNA was extracted from pelleted urine sediment. Samples with >500 ng of genomic DNA underwent quantitative DNA methylation assessment using the Illumina Infinium MethylationEPIC BeadChip. Age- and race- matching was applied prior to analysis. Linear regression models were used to compare average methylation between IC/BPS cases and controls at each cytosine guanine dinucleotide site (loci where methylation can occur).
Results
16 participants (8 IC/BPS age- and race-matched to 8 controls) had adequate DNA for methylation analysis. The median age was 43.5 years (interquartile range 33.8, 65.0), the median BMI was 27.1 (IQR 22.7, 31.4), and 14 were Caucasian (87.5%). A total of 688,417 CpG sites were analyzed. In exploratory pathway analysis utilizing the top 1000 differentially methylated CpG sites, the mitogen-activated protein kinase (MAPK) pathway was overrepresented by member genes.
Conclusions
The results demonstrate the feasibility of using voided urine specimens from women with IC/BPS to perform DNA methylation assessments. Additionally, the data suggest genes within or downstream of the MAPK pathway exhibit altered methylation in IC/BPS.