Canalicular domain structure and function in matrix-free hepatic spheroids.

The liver performs essential metabolic and excretory functions. These processes depend on hepatocyte polarization and bile canaliculi formation. Standard 2D cell cultures fail to replicate these structures accurately. Primary hepatocytes lose function rapidly in culture. This limits the ability to study liver function in a physiological context. Researchers need models that preserve liver architecture. Matrix-free spheroids offer a promising alternative. However, detailed structural and functional analysis remains limited. This gap motivated the development of new imaging techniques.

The aim was to investigate bile canaliculi formation and function in a more physiological model. Researchers used a hepatoma-derived cell line to form matrix-free hepatic spheroids. These spheroids were analyzed for hepatocyte polarization and bile canaliculi activity. The study combined advanced imaging methods to capture structural details. The goal was to understand how canaliculi form and function in 3D. The researchers also aimed to compare apical and basal membrane dynamics. They sought to resolve the first structure of active bile canaliculi. This work addresses a key gap in liver cell culture research.

The team used a hepatoma-derived cell line to generate matrix-free hepatic spheroids. These spheroids were cultured under conditions promoting hepatocyte polarization. Light sheet fluorescence microscopy captured live dynamics of the spheroids. 3D electron microscopy provided ultrastructural details of bile canaliculi. Actin network dynamics were tracked in basal membranes. Apical structures were compared for stability and microvilli density. The combined approach allowed functional and structural analysis. This methodology enabled high-resolution imaging of active canaliculi.

Hepatocytes in spheroids polarized and formed active bile canaliculi. These structures excreted both organics and inorganics effectively. Live imaging showed dynamic actin networks in basal membranes. Apical membranes remained stable and rich in microvilli. The first structure of active bile canaliculi was resolved at nm resolution. Microvilli density was high across all cells forming the canaliculus. The canaliculi demonstrated physiological excretory function. These findings suggest spheroids replicate key liver functions.

The study demonstrates that matrix-free spheroids support hepatocyte polarization. Bile canaliculi in these spheroids function similarly to in vivo systems. The combination of imaging techniques revealed structural and functional details. Actin dynamics differ between apical and basal membranes. Microvilli density is a defining feature of active canaliculi. This work provides the first comprehensive analysis of bile canaliculi in 3D. The findings support the use of spheroids for liver research. These models offer a more physiological alternative to 2D cultures.