Primary Small Intestinal Epithelia Are Physiological Alternatives to the Caco-2 Lymphatic Transport Model

Area of Science:

• Pharmacokinetics and Drug Delivery
• Gastroenterology and Hepatology
• Cell Biology and Biochemistry

Background:

• Highly lipophilic drugs (logP > 5) exhibit poor oral bioavailability due to absorption challenges.
• Chylomicron (CM)-mediated lymphatic transport is a key pathway for delivering lipophilic drugs and bypassing first-pass metabolism.
• Existing in vitro models, like Caco-2 cells, inadequately replicate the specialized lipoprotein synthesis in the small intestine.

Purpose of the Study:

• To investigate the response of primary human duodenum (hDuo) and murine ileum (mIle) enteroid monolayers to lipid digestion products.
• To assess lipoprotein secretion, re-esterification enzyme expression, and CM transport of model lipophilic drugs (halofantrine and navitoclax).
• To evaluate primary enteroid monolayers as a New Approach Methodology (NAM) for studying intestinal lymphatic drug transport.

Main Methods:

• Utilized a pulse-chase approach with differentiated primary hDuo and mIle enteroid monolayers.
• Stimulated monolayers with oleic acid (OA) and 2-monoolein (2-MO) mixed micelles.
• Analyzed lipoprotein secretion (apoB-48), re-esterification enzyme expression (MTTP, MGAT2), and drug incorporation into CMs.

Main Results:

• Primary enteroids exhibited basal-polarized apoB-48 secretion, distinct from Caco-2 cells.
• 2-MO stimulation significantly increased triglyceride-rich lipoprotein secretion (mass and diameter) in primary monolayers.
• Primary monolayers showed higher drug transport via CMs for halofantrine (4.6-fold) and navitoclax (14.9-fold) compared to Caco-2 cells.

Conclusions:

• Primary enteroid monolayers accurately recapitulate intestinal lipoprotein synthesis and CM assembly.
• This model demonstrates superior lymphatic transport of lipophilic drugs compared to Caco-2 cell lines.
• Pulse-chase studies in primary enteroid cultures represent a promising NAM for assessing intestinal lymphatic transport of lipid-formulated drugs.