PTGIR and inflammatory bowel disease: The transcription of PTGIR can be increased in response to cellular differentiation, estrogen, and low serum cholesterol in the vasculature.38 To explore the underlying mechanism of upregulated PTGIR expression in the fibrostenotic intestine, we examined the effects of TGF-β, the master regulator of fibrosis, and TNF-α, the key proinflammatory cytokine in IBD, on PTGIR transcription in primary intestinal fibroblasts.