It is well known that the precipitation of solid

It is well-known that the precipitation of solid cholesterol monohydrate crystals from supersaturated bile is the first irreversible physical-chemical step in gallstone formation. To study the characteristics, metastable intermediates, and kinetics in the phase transitions of bile, a series of phase diagrams that consist of cholesterol, phospholipids, and bile acids are generated for investigating the regions wherein different sequences of metastable intermediates, such as cholesterol crystallization sequences, occur. Five distinct crystallization pathways A to E have been identified in cholesterol-phospholipid-mixed bile jak inhibitor model bile systems, with each of these cholesterol crystallization pathways illustrating a different sequence of phase transitions. These phase transitions include an anhydrous cholesterol pathway and a liquid crystalline pathway to the formation of classical solid plate-like cholesterol monohydrate crystals. Furthermore, five crystallization pathways in model bile systems are carefully investigated as a function of total lipid concentration, CSI value, bile acid composition (hydrophilic-hydrophobic index), cholesterol to phospholipid ratio, cholesterol to bile acid ratio, bile acid to phospholipid ratio, and temperature. These cholesterol crystallization pathways found in model bile systems have been confirmed in native human and mouse gallbladder bile. The growth of solid cholesterol crystals starts as soon as cholesterol nucleation and crystallization occurs and this process is greatly accelerated by mucin gel, a potent pro-nucleating agent. Fig. 6 shows three modes of solid cholesterol crystal growth habits as observed by phase contrast and polarizing light microscopy in supersaturated gallbladder bile during the early stage of cholesterol gallstone formation in mice fed the lithogenic diet. The first mode of solid cholesterol crystal growth habits is the proportional enlargement patterns that lead to solid cholesterol crystals larger in one direction, length, or width. The second mode is the spiral dislocation growth in which the pyramidal surface contains numerous growth spirals nucleated and crystallized by a screw dislocation. The third mode is the twin crystal growth in which the crystals grow upright and perpendicular to the surface. These solid cholesterol crystal growth habits are found not only in native mouse gallbladder bile, but also in model bile systems. Obviously, these crystal growth modes enlarge solid cholesterol crystals in size and promote the development and evolution of solid cholesterol crystals to microlithiasis and eventually to macroscopic stones. More importantly, in the presence of a heterogeneous pro-nucleating agent, such as mucin gel, higher CSI values promotes more rapid precipitation of solid plate-like cholesterol monohydrate crystals from a phase-separated liquid-crystalline phase in gallbladder bile, followed by growth and agglomeration of these solid cholesterol crystals into mature and macroscopic stones. When CSI values are higher in bile, this process is faster. These findings in mice provide clear evidence showing that these three modes of solid cholesterol crystal growth habits closely recapitulate the early events of cholesterol gallstone formation in humans.
Conclusion and future research Many new findings from physical-chemical, biochemical, genetic, and molecular biological studies of gallstones in humans and animals have clearly demonstrated that interactions of five primary defects lead to the formation of cholesterol gallstones. A novel concept has been established that cholesterol gallstone disease is determined by multiple Lith genes, which is a dominant trait. However, no mode of inheritance fitting to the Mendelian pattern is found in most cases. Although hepatic hypersecretion of biliary cholesterol is the primary pathogenic defect, other defects also play a critical role in the pathogenesis of cholesterol gallstone formation, which include unphysiological supersaturation with cholesterol (such as high CSI values in gallbladder bile), accelerated cholesterol nucleation and crystallization, rapid solid cholesterol crystal growth, impaired gallbladder motility, and increased amounts of the absorbed cholesterol delivered to the liver from the small intestine. Obviously, rapid growth and agglomeration of solid cholesterol crystals to form microlithiasis and macroscopic stones is a consequence of both gallbladder mucin hypersecretion and gel formation with impaired gallbladder emptying, leading to the formation of biliary sludge, the precursor of gallstones.