Background: The prevalence of inflammatory bowel disease (IBD) is increasing worldwide, and anemia, one of the most prevalent extraintestinal manifestations of IBD, is still often underdiagnosed and undertreated. Aims: To analyze the correlations of clinical factors with anemia in patients with ulcerative colitis (UC). Methods: A retrospective analysis was conducted in 60 cases of UC admitted from September 2019 to May 2020 at the Second Affiliated Hospital of Zhengzhou University. Sixty healthy subjects were served as controls. Data of fasting venous blood sample analysis on admission were collected, and the correlations of indicators for anemia with the clinical factors were analyzed. Results: The indicators for anemia, including red blood cell (RBC) count, hemoglobin (Hb), hematocrit (HCT), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) etc. were significantly decreased in UC patients than in healthy controls (all P<0.05). RBC was lower in females than in males (P<0.05); RBC and HCT were lower in patients with pancolitis than in those with proctitis or left hemi-colon colitis (all P<0.05); RBC, Hb and HCT were lower in severe active UC than in mild active UC (all P<0.05). RBC, Hb, HCT and MCH were negatively correlated with two disease activity indicators for IBD, C-reactive protein (CRP) and/or erythrocyte sedimentation rate (ESR) (all P<0.05). Conclusions: Gender, as well as the disease extent, activity and severity are important clinical factors for anemia in patients with UC.

Exosomes are extracellular vesicles with a diameter of 30-150 nm, which exist in multi-vesicular bodies in the form of intraluminal vesicles. Exosomes can be secreted by a variety of immune cells. Studies have shown that exosomes might play an important role in IBD through their components, such as annexin-A1 (ANXA1), the miRNAs and lipids. As a carrier of antigen presentation, it can affect the signaling pathways related to IBD, regulate the immune response and intestinal homeostasis. This article reviewed the relationship between exosomes and IBD.

MicroRNAs (miRNAs) are a group of short non-coding RNAs consisting of about 22 nucleotides that downregulate gene expression at posttranscriptional level through binding to the 3'-untranslated region (3'-UTR) of target mRNAs. With the increase in research about miRNAs, it is found that miRNAs could modulate the differentiation and secretion of immunocytes as well as the function of intestinal mucosal barrier. Besides, miRNAs could regulate the composition of intestinal microbiome, and could be used as crucial biomarkers for the diagnosis of inflammatory bowel disease (IBD). In this paper, the roles of miRNAs in the pathogenesis of IBD were reviewed through intestinal immunity and barrier function.