Imaging supramolecular aggregates in bile models and human bile

Area of Science:

• Biochemistry
• Materials Science
• Microscopy

Background:

• Gallstone formation is intrinsically linked to cholesterol crystallization.
• Prior research indicates various pre-crystalline aggregates precede classical cholesterol monohydrate crystal formation.
• Understanding these microstructural pathways is key to preventing gallstones.

Purpose of the Study:

• To investigate microstructural pathways of cholesterol crystallization in simplified bile models and native bile.
• To determine if polymorphism observed in native bile also occurs in simplified model systems.
• To correlate findings from cryo-transmission electron microscopy (cryo-TEM) and video-enhanced light microscopy (VELM).

Main Methods:

• Utilized cryo-transmission electron microscopy (cryo-TEM) for nanoscale observations.
• Employed video-enhanced light microscopy with Nomarski optics (VELM) for micron-scale observations.
• Diluted concentrated bile model solutions (cholesterol, lecithin, taurocholate) to induce supersaturation and observe microstructural evolution.

Main Results:

• Observed initial spheroidal micelles by cryo-TEM, followed by uni-, oligo-, and multilamellar vesicles.
• Identified filaments, tubular, helical microstructures, and plate-like crystals during dynamic crystallization.
• Found that crystallization in simplified models closely resembles that in native human bile.

Conclusions:

• Polymorphic microstructural evolution occurs in simplified bile models, not just complex native bile.
• Combined cryo-TEM and VELM effectively characterize the full range of microstructures in cholesterol crystallization.
• Simplified bile models are applicable for studying microstructural aspects of nucleating human bile.