Romil Saxena

Following a report of skeletal muscle regeneration from bone marrow cells, we investigated whether hepatocytes could also derive in vivo from bone marrow cells. A cohort of lethally irradiated B6D2F1 female mice received whole bone marrow transplants from age-matched male donors and were sacrificed at days 1, 3, 5, and 7 and months 2, 4, and 6 posttransplantation (n = 3 for each time point). Additionally, 2 archival female mice of the same strain who had previously been recipients of 200 male fluorescence-activated cell sorter (FACS)-sorted CD34(+)lin(-) cells were sacrificed 8 months posttransplantation under the same protocol. Fluorescence in situ hybridization (FISH) for the Y-chromosome was performed on liver tissue. Y-positive hepatocytes, up to 2.2% of total hepatocytes, were identified in 1 animal at 7 days posttransplantation and in all animals sacrificed 2 months or longer posttransplantation. Simultaneous FISH for the Y-chromosome and albumin messenger RNA (mRNA) confirmed male-derived cells were mature hepatocytes. These animals had received lethal doses of irradiation at the time of bone marrow transplantation, but this induced no overt, histologically demonstrable, acute hepatic injury, including inflammation, necrosis, oval cell proliferation, or scarring. We conclude that hepatocytes can derive from bone marrow cells after irradiation in the absence of severe acute injury. Also, the small subpopulation of CD34(+)lin(-) bone marrow cells is capable of such hepatic engraftment.

The work of liver stem cell biologists, largely carried out in rodent models, has now started to manifest in human investigations and applications. We can now recognize complex regenerative processes in tissue specimens that had only been suspected for decades, but we also struggle to describe what we see in human tissues in a way that takes into account the findings from the animal investigations, using a language derived from species not, in fact, so much like our own. This international group of liver pathologists and hepatologists, most of whom are actively engaged in both clinical work and scientific research, seeks to arrive at a consensus on nomenclature for normal human livers and human reactive lesions that can facilitate more rapid advancement of our field.

Small, extraportal, hepatic parenchymal cells, positive for biliary-type cytokeratins, may represent hepatic stem cells, canals of Hering (CoH), and/or ductal plate remnants. We evaluated these cells 3 dimensionally in normal human liver and massive necrosis. Tissues from normal human livers and from 1 liver with acetaminophen-induced massive necrosis were serially sectioned, immunostained for cytokeratin 19 (CK19), and sequentially photographed. Images were examined to determine 3-dimensional relationships among CK19-positive cells. Immunostains for other hepatocyte and progenitor cell markers were examined. In normal livers, intraparenchymal CK19-positive cells lined up as linear arrays in sequential levels. One hundred of 106 (94.3%) defined, complete arrays within levels examined, most having 1 terminus at a bile duct, the other in the lobule, beyond the limiting plate. In massive necrosis, there were 767 individual CK19-positive cells or clusters around a single portal tract, 747 (97.4%) of which were spatially related forming arborizing networks connected to the interlobular bile duct by single tributaries. C-kit was positive in normal CoH. CK19 co-expressed with HepPar1, c-kit, and alpha-fetoprotein (AFP) in parenchymal cells in massive necrosis. Small, extraportal, biliary-type parenchymal cells represent cross-sections of the CoH that radiate from the portal tract, usually extending past the limiting plate into the proximate third of the hepatic lobule. The 3-dimensional structure of ductular reactions in massive necrosis suggests that these reactions are proliferations of the cells lining the CoH. Therefore, the CoH consist of, or harbor, facultative hepatic stem cells in humans.

In Brief Objective: To determine whether patients who develop a pancreatic fistula after pancreatoduodenectomy are more likely to have pancreatic fat than matched controls. Background: Pancreatic fistula continues to be a major cause of postoperative morbidity and increased length of stay after pancreatoduodenectomy. Factors associated with postoperative pancreatic fistula include a soft pancreas, a small pancreatic duct, the underlying pancreatic pathology, the regional blood supply, and surgeon's experience. Fatty pancreas previously has not been considered as a contributing factor in the development of postoperative pancreatic fistula. Methods: Forty patients with and without a pancreatic fistula were identified from an Indiana University database of over 1000 patients undergoing pancreatoduodenectomy and matched for multiple parameters including age, gender, pancreatic pathology, surgeon, and type of operation. Surgical pathology specimens from the pancreatic neck were reviewed blindly for fat, fibrosis, vessel density, and inflammation. These parameters were scored (0–4+). Results: The pancreatic fistula patients were less likely (P < 0.05) to have diabetes but had significantly more intralobular (P < 0.001), interlobular (P < 0.05), and total pancreatic fat (P < 0.001). Fistula patients were more likely to have high pancreatic fat scores (50% vs. 13%, P < 0.001). Pancreatic fibrosis, vessel density, and duct size were lower (P < 0.001) in the fistula patients and negative correlations (P < 0.001) existed between fat and fibrosis (R = −0.40) and blood vessel density (R = −0.15). Conclusions: These data suggest that patients with postoperative pancreatic fistula have (1) increased pancreatic fat and (2) decreased pancreatic fibrosis, blood vessel density, and duct size. Therefore, we conclude that fatty pancreas is a risk factor for postoperative pancreatic fistula. Surgical pathology specimens from the pancreatic neck of patients with and without a pancreatic fistula after pancreatoduodenectomy were examined for fat, inflammation, fibrosis, and vessel density. Patients with a pancreatic fistula had significantly more fat (P < 0.001) at the resection margin. We conclude that fatty pancreas is a risk factor for postoperative pancreatic fistula.

Primary liver carcinomas with both hepatocytic and cholangiocytic differentiation have been referred to as "combined (or mixed) hepatocellular-cholangiocarcinoma." These tumors, although described over 100 years ago, have attracted greater attention recently because of interest in possible stem cell origin and perhaps because of greater frequency and clinical recognition. Currently, because of a lack of common terminology in the literature, effective treatment and predictable outcome data have been challenging to accrue. This article represents a consensus document from an international community of pathologists, radiologists, and clinicians who have studied and reported on these tumors and recommends a working terminology for diagnostic and research approaches for further study and evaluation. CONCLUSION: It is recommended that diagnosis is based on routine histopathology with hematoxylin and eosin (H&E); immunostains are supportive, but not essential for diagnosis. (Hepatology 2018;68:113-126).