Ileal S100A9 expression distinguishes Crohn's disease patients by age at diagnosis
Crohn's disease (CD) is a debilitating gastrointestinal disorder that can impact the entirety of the GI tract. While substantial progress has been made in the medical management of CD, it remains incurable, frequently relapses, and is a significant financial and medical burden. The pathophysiology of CD is not well understood, but it is thought to arise in genetically susceptible individuals upon an environmental insult. Further elucidation of the disease etiology promises to expose additional therapeutic avenues, with the hope of reducing the burden of CD. One approach to understanding disease pathophysiology is to identify clinically relevant molecular disease subsets using transcriptomics. In this report, we use hierarchical clustering of the ileal transcriptomes of 34 patients to identify two CD subsets. Clinically, these clusters differed in the age of the patients at CD diagnosis, suggesting that age of disease onset impacts the pathophysiology of the disease. We found that the ileal transcriptomes of the early diagnosis cluster are enriched in inflammatory transcripts, including S100A9, which encodes a calprotectin subunit. Furthermore, levels of S100A9 distinguished individuals diagnosed before the age of 30 from those diagnosed after 30. Together, these findings suggest that medical management of CD patients should consider their age at diagnosis and therapeutic blockade of calprotectin may be beneficial in patients diagnosed earlier in life. Overall design: Gene expression profiles from the surgically resected, diseased, ileal tissue of 34 Crohn's disease patients were generated by deep sequencing.