Dynamics of the vascular profile of the finer branches of the biliary tree in normal and diseased human livers.

Background/aims: Results of our previous studies supported the concept that in the human liver, the smallest ramification of the biliary tree, the bile ductules, might contain hepatic progenitor cells. An insufficient proliferative response and loss of bile ductules preceded bile duct loss whereas preservation of bile ductules mitigated bile duct loss.

Methods: Presently we investigated the vascular profile of the bile ductules in diseased human livers and livers showing normal histological features as controls, using CD34, CK7 and alphaSMA antibodies in a double immunolabeling technique. VEGF-A expression was also studied. In control livers bile ductules traversed the boundaries of the portal tract into the lobule as ductular-vascular units, in a pattern outlining the classic hexagonal lobule, following the vascular septa. The latter are thought to be extensions of portal veins. In diseased states the two structures reacted in unison. Increased or decreased numbers of ductules were consistently accompanied by similar changes of accompanying microvessels. Increased numbers of ductules and microvessels were paralleled by increased ductular expression of VEGF-A.

Results: Our data support the concept that the smallest branches of the biliary tree might have their own vascular supply and that the ductules might in turn maintain their vasculature during regenerative processes.