In a new study, researchers report that they have found epigenetic methylation markers on 15 genes that appear to foreshadow psoriatic arthritis (PsA), a development that could bring scientists closer to developing a DNA test to predict which patients with psoriasis will develop the condition.
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While no predictive test is in sight yet, the findings published in Arthritis & Rheumatology mark an important step, study lead author Omar F. Cruz-Correa, PhD, of the Psoriatic Arthritis Research Program in the University Health Network, Toronto, said in an interview. “In the future, markers like these could be measured by dermatologists and even general practitioners to help identify new psoriasis patients at a high risk of developing PsA,” he said. “Then both the health care team and the patients themselves could be more aware of their increased risk and the pressing need of closer monitoring for musculoskeletal symptoms. Once the first symptoms appear, treatment can be initiated early on, helping to prevent permanent joint damage.”
An estimated 30% of patients with psoriasis will develop PsA, too, putting them at higher risk of disability and death. According to Dr. Cruz-Correa, “one of the more pressing matters in PsA is the lack of means of predicting which psoriasis patients will develop PsA.”
DNA methylation, the topic of the new study, has already been linked to psoriasis and PsA. It’s “relatively easy to measure and helps regulate gene expression in response to environmental effects,” Dr. Cruz-Correa said. “DNA methylation is also appealing because it serves as an intermediary between environment and genetic factors as it’s transmitted between generations of cells and influenced by external factors.”
For the new study, researchers examined the DNA of 117 patients with psoriasis – 58 who went on to develop PsA (“converters”) and another 59 who were matched to converters but did not develop PsA (“nonconverters”). The patients were in a larger group of 700 patients with psoriasis who had the disease for a mean of about 17 years at the time of blood sampling.
Samples from converters were taken an average of 5.16 years (± 12.77 years) before PsA set in.
The researchers report that they found “36 highly relevant methylation markers … across 15 genes and several intergenic regions. A classification model relying on these markers identified converters and nonconverters with an area under the ROC curve of 0.9644.”
Statistically, this number is high and means that “the DNA methylation markers are really good at identifying psoriasis patients who will develop PsA and those that will not,” at least in this specific patient group, Dr. Cruz-Correa said.
At this point, the number of markers is a bit too high to develop a feasible DNA test to predict PsA, he said. “However, the results from our study have also pointed us toward some interesting metabolic pathways that may warrant further study.”
What’s next?
The first step forward “is the validation of these predictive DNA methylation markers in a wider population of patients with varied clinical and demographic characteristics. This would help assess the potential for generalization of such a test,” Dr. Cruz-Correa said. “A second step is to assess the potential impact of these methylation markers on disease activity and treatment response, which are clinical outcomes of great importance to patients.”
Meanwhile, he said, “there are ongoing efforts to shed light into how DNA methylation integrates with other epigenetic mechanisms like micro-RNAs to regulate gene expression in concert with one another. An integrative look into these mechanisms may be able to give insight into the pathogenesis of psoriatic disease in a way that has not been possible before.”
In an interview, Johann E. Gudjonsson, MD, PhD, professor of skin molecular immunology at the University of Michigan, Ann Arbor, said the study “is interesting and important as it indicates that there are changes in the blood that occur before the development of psoriatic arthritis. However, it does not provide much in terms of novel insights into the mechanisms involved and is still a long way away from being useful as a clinical predictor or biomarker.”
The National Psoriasis Foundation, Krembil Foundation, and Canadian Institutes of Health Research provided support for the study. Dr. Cruz-Correa reports support from the National Psoriasis Foundation and the Arthritis Society. Dr. Gudjonsson has no relevant financial relationships.