SUMMARY
Stem/progenitors have been identified intrahepatically in canals of Hering and extrahepatically in glands of the biliary tree. Glands of the biliary tree (peribiliary glands: PBGs) are tubulo-alveolar glands with mucinous and serous acini, located deep within intrahepatic and extrahepatic bile ducts. We have shown that biliary tree stem/progenitors (BTSCs) are multipotent, giving rise in vitro and in vivo to hepatocytes, cholangiocytes or pancreatic islets. Cells with the phenotype of BTSCs are located at the bottom of the PBGs near the fibromuscular layer. They are phenotypically heterogeneous expressing transcription factors and surface and cytoplasmic markers for stem/progenitors of liver (e.g. SOX9/17), pancreas (e.g. PDX1) and endoderm (e.g. SOX17, EpCAM, NCAM, CXCR4, Lgr5, OCT4), but not for mature markers (e.g. albumin, secretin receptor, or insulin). Subpopulations co-expressing liver and pancreatic markers (e.g. PDX1+/SOX17+), are EpCAM±, and are assumed to be the most primitive of the BTSC subpopulations. They give rise to descendents undergoing a maturational lineage process from the interior to the surface of ducts and varying in mature cells generated: pancreatic cells in hepato-pancreatic ducts; liver cells in large intrahepatic bile ducts; and bile duct cells along most of the biliary tree. We hypothesize that there is ongoing organogenesis throughout life with BTSCs giving rise to hepatic stem cells in the canals of Hering and to committed progenitors within the pancreas. The BTSCs are likely to be central to normal tissue turnover and injury repair and to be key elements in the pathophysiology of liver, pancreas and biliary tree diseases including oncogenesis.
The purpose of this study was to compare the value of pelvic ultrasound with color Doppler and magnetic resonance imaging (MRI) in: (1) the diagnosis of placental adhesive disorders (PADs), (2) the definition of the degree of placenta invasiveness, (3) determining the topographic correlation between the diagnostic images and the surgical results. Fifty patients in the third trimester of pregnancy with a diagnosis of placenta previa and at least one previous caesarean section underwent color Doppler ultrasound (US) and MRI. The sonographic and MRI diagnoses were compared with the final pathologic or operative findings. Outcomes at delivery were as follows: normal placenta (n = 38) and PAD (n = 12). MR and US Doppler showed no statistically difference in identifying patients with PAD (P = 0.74), while MRI was statistically better than US Doppler in evaluating the depth of placenta infiltration (P < 0.001). MRI accurately characterized the topography of invasion in 12/12 (100%) of the cases, while US accurately characterized the topography of invasion in 9/12 (75%) of the cases. In conclusion, we confirmed that pelvic US is highly reliable to diagnose or exclude the presence of PAD and found MRI to be an excellent tool for the staging and topographic evaluation of PAD.
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