Gene Expression Profiles of Inflamed Ileocolonic Biopsy Tissue in GI Symptomatic ASD Children Are Consistent with an Inflammatory Bowel Disease

Background:  Gastrointestinal symptoms are common in children with autism spectrum disorder (ASD) and are often associated with mucosal inflammatory infiltrates of the small and large intestine. Although distinct histologic and immunohistochemical properties of this inflammatory infiltrate have been previously described in this ASD^GI group, molecular characterization of these lesions has not been reported. Currently, it is not clear whether children with ASD and GI symptoms, coupled with non-specific mucosal infiltrates, have conventionally recognized forms of IBD, a novel IBD phenotype, or no disease at all.

 Objectives:  The purpose of this study was to compare gene expression profiles (differentially expressed transcripts - DETs) in both ileal and colonic tissues in GI symptomatic ASD children (ASD^GI) with histologic inflammatory infiltrates and a non-ASD control group (non-pathologic tissue). The hypothesis being tested is that DETs in ASD^GI distinguish this group from non-inflamed controls, and provide further evidence of an inflammatory bowel disease (IBD) in the former group.

Methods: Study tissue consisted of ileocolonic biopsies from two groups of children undergoing ileocolonoscopy for active gastrointestinal symptoms: (1) those with an ASD diagnosis and, (2) typically developing children. All tissue specimens were collected under appropriate IRB approval. For each ASD individual two biopsies (one from terminal ileum, one from colon) that demonstrated the histologic presence of ileal infiltrates (ileitis), colonic infiltrates (colitis) or both (ileocolitis) were used. Two histopathologically normal tissues from the identical locations were obtained from each control individual for comparison. Total RNA was isolated from the tissue biopsy specimens and used to query whole genome DNA microarrays. Pair-wise comparisons of gene expression were made between ASD^GI and control groups for each of the two tissues. Lists of DETs in ASD^GI were then evaluated for gene ontology and biological pathway involvement using the Ingenuity Pathway Analysis (IPA) software suite.  

Results: Pair-wise analyses between ileal mucosa from ASD^GI and non-inflamed control samples resulted in 2570 DETs.  Seventy-three percent (1862) of DET’s were down-regulated in the ASD group compared with the control group while the remainder were up-regulated (@ fold change ≥ 2; adjusted p ≤ 0.05). Analyses of inflamed colonic mucosa from ASD^GI children and non-inflamed controls resulted in 2393 DETs, 69% (1657) down-regulated in ASD^GI mucosa compared with those in the control group, while the remainder were up-regulated (@ fold change ≥ 2; adjusted p ≤ 0.05). Two of the most highly significant disease categories returned by IPA in these tissues were gastrointestinal disease (p = 1 x 10^-9 [TI] and p = 3 x 10^-13 [colon]) and inflammatory response (p = 1.7 x 10^-11 [TI]).

Conclusions:  Taken as a whole, the picture that emerges is one in which GI symptomatic children with ASD in whom cellular infiltrate is present in the ileum and colon have a distinct molecular signature that is consistent with the larger disease categories of gastrointestinal disease, and more specifically, overlaps with Crohn’s disease, ulcerative colitis, and autoimmunity.