Intestinal interstitial fluid isolation provides novel insight into the human host-microbiome interface

Area of Science:

• Gastroenterology and Microbiology
• Human Physiology
• Biotechnology

Background:

• The gastrointestinal (GI) tract's distinct regions have unique microbial communities and physiological features.
• Gut microbes act as an endocrine organ, producing metabolites that influence host immunity and cardiovascular health.
• Understanding the segment-specific mucosal microenvironment, reflected in interstitial fluid (IF), is crucial but challenging due to limited tools.

Purpose of the Study:

• To develop and validate novel methods for collecting intestinal interstitial fluid (IF) from specific GI segments.
• To enable direct quantification of microbiota-derived metabolites, cytokines, and proteins within the IF.
• To investigate segment-specific differences in the gut mucosal microenvironment in rodents and humans.

Main Methods:

• Developed tissue centrifugation and elution techniques to isolate IF from different intestinal segments.
• Validated these methods in rodent models (rats and mice).
• Translated the tissue elution method for human sample collection and analysis.

Main Results:

• Quantified microbiota-derived metabolites, cytokines, and proteins directly within the IF.
• Observed enrichment of short-chain fatty acids in colonic IF.
• Detected segment-specific differential abundances of metabolites and cytokines in IF, often higher than in plasma.
• Proteomics identified site-specific extracellular proteins in IF.
• Demonstrated higher ileal IL-1β levels in IF compared to plasma following lipopolysaccharide challenge in rats.

Conclusions:

• Novel methods allow direct IF collection and mediator measurement from defined intestinal segments.
• This approach bypasses limitations of indirect analyses (fecal/serum samples).
• Provides direct insights into the understudied gut interstitial fluid compartment and its role in host-microbe interactions.