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Cham, C. M.

Publications and source records attributed to Cham, C. M..

4 recordsLinked to original sources

Epithelial-Intrinsic Alterations and Maladaptation to Luminal Metabolites Underlie Persistent Crohn's Disease Pathogenesis

In patients with Crohns disease, the noninflamed intestinal epithelium exhibits inflammation-like transcriptional signatures that persist even during clinical remission. However, it is unclear whether this signature is due to sustained environmental triggers or to the epitheliums intrinsic immunological adaptions. To disentangle environmental and cell-intrinsic effects on disease signatures, we used noninflamed intestinal tissue biopsies from patients with active and inactive Crohns disease, as well as control donors, to generate donor-matched organoids enriched for intestinal epithelial cells. We collected single-cell RNA-seq and single-cell ATAC-seq data from intestinal tissues, and from their matched organoids before and after stimulation with luminal metabolites of patients. This approach allowed us to distinguish between the effects of extrinsic factors and the intrinsic alterations that persist when cells are removed from their local environment. We found that organoid cells retained epithelial-autonomous disease phenotypes, even when derived from patients in remission, whereas signatures from tissue cells showed evidence of immune- and microbial-epithelial crosstalk. In contrast to healthy control organoids, organoids from Crohns disease patients exhibited selective activation of disease-associated transcriptional changes and environment-responsive inflammatory chromatin remodeling after exposure to patient-derived luminal metabolites. Overall, our study suggests that disease-associated epithelial states are shaped by both cell-intrinsic dysregulation and microenvironmental cues.

immunology↗

Untangling the Role of Pathobionts from Bacteroides Species in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) arise from a convergence of underlying genetic susceptibility, environmental factors, and shifts in gut microbiota function and membership. Although the latter may trigger and contribute to IBD, there is little consensus on a specific causative pathogen. In this study, we demonstrate that commensal Bacteroides fragilis strains from ulcerative colitis (UC) patients before and during the development of ileal pouchitis engraft and promote colitis in specific pathogen free (SPF) IL-10 deficient (IL-10-/-) mice, but not in wild type SPF mice or when mono-associated in germ free mice. The colitis in IL-10-/- mice was also associated with significant alterations in commensal microbiota potentially important for maintaining intestinal and immune homeostasis. UC pouchitis B. fragilis also engrafts in DSS-induced colitis in WT SPF mice, indicating a fitness advantage under conditions of mucosal inflammation over other commensals in the gut microbiota. These findings show that gut inflammation promotes the expansion and fitness of UC-derived Bacteroides species that is associated with changes in the SPF gut microbiota and may be promote colitis in genetically susceptible hosts. ImportanceThis study supports the notion that human inflammatory bowel diseases arise from the emergence of indigenous pathobionts in genetically-prone subjects. Colitis-promoting pathobionts are well-suited to establish themselves in the host inflammatory environment and outcompete endogenous microbiota. Once engrafted, the pathobiont can further aggravate inflammation in a genetically-susceptible host. Such complex interplay among several factors creates a vicious pro-inflammatory cycle and promotes disease development. These findings are consistent with our previous clinical observation that B. fragilis, an otherwise low-abundance commensal species, expands prior to the development of UC pouchitis. We believe these findings are relevant to the pathogenesis of UC pouchitis and possibly human inflammatory bowel diseases in general, underscoring the role of commensal to pathobiont transitions, rather than classical pathogens, in promoting and exacerbating the onset of human IBD.

microbiology↗

Intestinal Epithelial Heat Shock Protein 25/27 integrates host and microbial drivers of mucosal restitution following inflammatory injury

Mucosal healing following inflammatory injury is poorly understood and often neglected, despite being the best indicator of long-term outcomes in inflammatory bowel diseases. We report here that the enigmatic small molecular weight heat shock protein, Hsp25 (the human form is Hsp27), plays a vital role in converging microbial and host factors to promote pSTAT3-mediated mucosal healing. In wild type mice, the proximal-to-distal gradient of intestinal epithelial cell (IEC) Hsp25 expression is dependent on microbial cues. Patients with left-sided ulcerative colitis, however, show reduced levels of Hsp27 expression in both uninvolved and involved areas compared to normal colons of non-IBD patients. In mice with global or IEC-specific Hsp25 gene-targeted deletion, impaired mucosal healing with development of hallmarks of chronic disease are observed following DSS-induced or TNBS-induced colitis, whereas mucosal restitution is accelerated in IEC-specific overexpressing Hsp25 transgenic mice. In colonic IECs derived from these murine lines, Hsp25 binds and stabilizes a phospho-STAT3/YAP nuclear complex stimulated by IL-22 to sustain its wound healing gene programming. Thus, our findings provide insight into the mechanism of action of IEC Hsp25/27 in integrating host and microbial drivers of mucosal restitution, which can be leveraged to develop novel approaches for achieving and maintaining remission in complex immune disorders like IBD.

pathology↗

Peptide YY: a novel Paneth cell antimicrobial peptide that maintains fungal commensalism

Perturbed interactions between the intestinal microbes and host correlate with emergence of fungal virulence. Here we report a previously unknown role for peptide YY (PYY), a described endocrine molecule, as an antimicrobial peptide (AMP) expressed by gut immune epithelial Paneth Cells (PC). PC-PYY differs from other AMPs, including lysozyme, because of limited antibacterial activity, packaging in discrete secretory granules, and selective antifungal activity to virulent hyphae, but not yeast forms of Candida albicans. The latter action is through binding of cationic PC-PYY to the anionic hyphal surface, resulting in membrane disruption and killing. PC-PYY is compartmentalized to surface mucus, which optimizes activity and prevents conversion to endocrine PYY by dipeptidyl peptidase-IV (DPP-IV). We conclude PC-PYY is a unique AMP with selective antifungal activity that maintains gut fungal commensalism. Compromised PC-PYY action from PC dysfunction and/or mucus depletion in ileal Crohns disease may initiate or contribute to disease via fungal pathogenesis. Highlights Paneth Cell PYY (PC-PYY) is an antimicrobial peptide that differs from endocrine-PYY PC-PYY is a selective anti-fungal peptide, targeting the virulent form of C. albicans PC-PYY is separately packaged, retained by mucus, and released by C. albicans hyphae PC-PYY is proposed as essential for maintenance of fungal commensalism in the gut Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY Model for Paneth cell (PC) PYY action and regulation of fungal commensalisms and potential role in the pathogenesis of ileal Crohns Disease (iCD) (A) In a healthy ileum, commensal yeast reside and do not stimulate PYY1-36 release from PCs. (B) Increased virulent hyphae (purple hyphae) results in PYY1-36 release from crypt PCs into the mucus. Hyphae are targeted by PYY1-36 and killed (red hyphae) to manage the increased fungi community in gut. (C) In a diseased ileum such as iCD, hyphal load induces immune activation and increased inflammation through PC dysfunction (gray PCs) and decreased PYY1-36 release or mucus depletion and PC dysfunction. C_FIG_DISPLAY

molecular biology↗