Bidirectional CRISPR screens decode a GLIS3-dependent fibrotic cell circuit.

Area of Science:

• Immunology
• Gastroenterology
• Cell Biology

Background:

• Stromal cells coordinate immune responses and tissue homeostasis.
• Chronic inflammation can lead to fibrosis, a common complication in inflammatory bowel disease (IBD).
• Fibrosis and treatment-refractory disease in IBD are linked to stromal fibroblasts, but their activation mechanisms are unclear.

Purpose of the Study:

• To elucidate the mechanisms of stromal fibroblast activation in inflammatory bowel disease.
• To identify key regulators of the inflammation-fibrosis cycle in the intestine.
• To explore the potential of targeting this pathway for therapeutic benefit.

Main Methods:

• Integrative single-cell and spatial profiling of intestinal tissues from IBD patients.
• Genome-wide CRISPR screens (knockout and activation) to identify regulatory networks.
• Analysis of GLIS3 gene expression in patient biopsies and fibroblast-specific Glis3 deletion in mouse models of colitis.

Main Results:

• A pathological cell nexus centered on inflammation-associated fibroblasts was identified.
• These fibroblasts are induced by proinflammatory macrophages and produce the profibrotic cytokine IL-11.
• The transcription factor GLIS3 was identified as a key regulator of inflammatory and fibrotic gene expression.
• GLIS3 expression levels correlate with ulcerative colitis disease severity.
• Fibroblast-specific Glis3 deletion in mice ameliorated chronic colitis pathology.

Conclusions:

• A critical immune-stromal cell circuit, involving GLIS3-regulated fibroblasts, drives the inflammation-fibrosis cycle in IBD.
• This pathway represents a potential therapeutic target for inflammatory bowel disease and associated fibrosis.
• GLIS3 serves as a biomarker for disease severity in ulcerative colitis.