A New Clarification Method to Visualize Biliary Degeneration During Liver Metamorphosis in Sea Lamprey (<i>Petromyzon marinus</i>)

Abstract

Biliary atresia is a rare disease of infancy, with an estimated 1 in 15,000 frequency in the southeast United States, but more common in East Asian countries, with a reported frequency of 1 in 5,000 in Taiwan. Although much is known about the management of biliary atresia, its pathogenesis is still elusive. The sea lamprey (Petromyzon marinus) provides a unique opportunity to examine the mechanism and progression of biliary degeneration. Sea lamprey develop through three distinct life stages: larval, parasitic, and adult. During the transition from larvae to parasitic juvenile, sea lamprey undergo metamorphosis with dramatic reorganization and remodeling in external morphology and internal organs. In the liver, the entire biliary system is lost, including the gall bladder and the biliary tree. A newly-developed method called "CLARITY" was modified to clarify the entire liver and the junction with the intestine in metamorphic sea lamprey. The process of biliary degeneration was visualized and discerned during sea lamprey metamorphosis by using laser scanning confocal microscopy. This method provides a powerful tool to study biliary atresia in a unique animal model. Video LinkThe video component of this article can be found at

TGF‐β Signaling Plays a Pivotal Role During Developmental Biliary Atresia in Sea Lamprey (Petromyzon marinus)

“…An additional 30 M2 larvae were injected with vehicle (3.3% lipofectamine), 0.3 mM TGF‐β1 siRNA, or TGF‐βRII siRNA intraperitoneally (n = 10 for each group). Liver samples were collected 2 weeks after treatment and fixed in hydrogel for CLARITY and immunofluorescent confocal microscopy imaging . Two‐week treatment was chosen because it took 1 to 2 weeks for M2 larvae to progress to M3 .…”

Advances in Ex Situ Tissue Optical Clearing

“…This evident difference might be due to: 1) very high liver blood flow, which under physiological conditions accounts for ≈30% of the resting cardiac output and likely enhances the effect of perfusion‐based clearing, 2) the size of the liver, which is the biggest solid organ of mice, with relatively low surface‐area‐to‐volume ratio, or 3) combination of both. Nonetheless, a few studies did establish and utilized TOC methods for the enhanced, 3D imaging of liver, with the main formula being BABB . Such approaches allowed for precise macroscopic visualization of the whole architecture of the mouse biliary tree ( Figure a,b) during both disease and development, when ingeniously combined with carbon ink .…”

Translational Research in Biliary Atresia: News from Mice and Men

“…23 Sea lampreys react to this process with a unique mechanism: de novo synthesis and section of bile salts in the intestine with a reduction of bile salt synthesis in the liver. 26,27 Suchy criticized the terminology in this discussion, as atresia is defined as a congenital absence or pathological closure of an opening, while in the case of the sea lamprey, we have to speak of a programmed loss of the biliary system. 28 This critique leads us to the main problem of observations in animals: despite the fact that BA-like diseases were reported, the etiology (if known) and the process of these conditions, and even the response strategies, are different than in BA in humans.…”