Good morning, everybody. Good morning. It's great to see so many of you here, and I'd like to wish you a warm welcome to the debrief session that we have this morning. We have five excellent speakers who are going to cover the various topics that have been highlights for them for the meeting, and we're going to cover basic science, viral hepatitis, muscle hypertension, cholestatic liver diseases, and finally, we're going to finish with muscle D. It's with my delight that I introduce our first speaker, Professor Rebecca Wells. She's professor of medicine at the University of Pennsylvania, and she's going to give us her highlights of basic science from the meeting. Thank you. Dr. Shawcross, Dr. Kim, ladies and gentlemen, as we approach the twilight of the 2023 liver meeting in Boston, I'm honored to give the basic science debrief. There have been many basic science sessions at this meeting, including the basic science symposium on bile acids and the gut liver and brain liver axes, the basic research workshop on humanized models as tools and host of meet the expert sessions, SIG programs, named lectures and other special programs. Nonetheless, the peer reviewed abstracts presented in plenary, parallel and poster sessions are the heart and soul of basic science at this meeting. In my presentation, I will highlight what I believe are some of the most important and impactful themes and abstracts. There are nine debriefs, and while much of what I miss will be covered in the eight topic debriefs to follow, this was a meeting filled with exciting, rigorous, forward thinking and clinically relevant basic science, and I acknowledge that any 30 minute selection will miss much high quality work. I would like to divide this debrief into five sections as noted on this slide. There were multiple abstracts that addressed this first topic, that of gut liver crosstalk. The four I highlight identified new mechanisms to explain the function and dysfunction of the gut, thank you, of the gut epithelium and its role in liver disease from ALD or Masold. The first abstract is from Noemi Cabre from Bern Schnabel's lab at UC San Diego on intestinal endogenous retroviruses which promote ethanol induced liver disease in mice. In two models of alcohol feeding in mice, as seen in the bars in red at the top here, this group showed that alcohol led to increases in two retroviral markers in the intestine. The group then showed that the intestinal protein ZBP1, which is an endogenous retrovirus sensor and mediator, was increased, an increase in the intestines of ethanol fed mice and ethanol treated intestinal organoids. I'm sorry, I was reading the wrong slide. This group used stool from people with or without evidence of retroviruses to humanize the microbiota of germ free mice, showing that the presence of the retroviruses led to liver disease and that antiretroviral treatment of these humanized mice led to decreases in liver damage when ERVs were present. Then they showed that in ZBP1 knockout mice, there is a similar decrease in alcohol induced liver injury. They reached the novel conclusion that ethanol leads to increased ERVs and ZBP1, which leads to increased liver disease, likely due to increased intestinal permeability and bacterial translocation. Treating the ERV ZBP1 axis may be a viable therapeutic strategy. In the second abstract, Carbonda and colleagues from the University of Nebraska studied the S-adenosylmethionine and S-adenosylhomocysteine ratio, which has been previously shown to be important in alcohol associated liver injury. In this case, they looked at it in the intestine. They showed that alcohol feeding led to altered ratios in the intestine of SAM and SAH, with a significant loss of occludin, including indicating barrier dysfunction due to tight junctions, and that's seen here on this part of the, in these images. Betaine, a methyl donor, was protective. The alcohol induced tight junction disruption was accompanied by, sorry, was accompanied by increased permeability. In a third abstract, Ming Song and the McLean Lab at the University of Louisville studied HIF-1-alpha, a master transcriptional factor in hypoxia, which plays a critical role in the gut barrier function. The investigators used an inducible, intestine-specific HIF-1-alpha overexpression system, and then treated animals with either a high fructose or a high fructose, high fat diet. You can see the experimental design here. They demonstrated that intestine-specific HIF-1-alpha overexpression attenuated Western diet-induced steatosis. It also improved glucose tolerance on the diet, and the similar things were seen with pharmacological inhibition. Notably, this was primarily in males, suggesting that intestine-specific HIF-1-alpha overexpression can be used as a treatment for mazald, although sex differences need to be considered. So like the previous abstracts, the mechanism outlined here was aimed at barrier function, though notably the effects were seen primarily in males. The next abstract is from Han and Nieto and colleagues at the University of Chicago, looking at intestinal epithelial cell osteopontin, and they noted that it protects animals against mash through changes in the gut microbiome and the bile acids. You can see here that osteopontin is lost from intestinal epithelial cells in mash. This is an animal model of mash, suggesting a potential protective effect, which they then investigated by generating osteopontin intestinal epithelial cell-specific knock-in and knock-out mice. And note that osteopontin is encoded by the SPP1 gene, and that's how it's referred to in these slides. They induced mash by dietary means for six months. And they found that osteopontin IEC-specific knock-in mice are protected from mash. Note that in the images and in the table that's shown that measures of mash in the liver were much less severe in the knock-in. Animals lacking osteopontin in the intestinal epithelial cells, shown in this slide, showed abnormal intestinal epithelial cell turnover and loss, as can be seen on the right-hand side of the slide. And liver damage was much more severe in the diet model in the osteopontin knock-outs. And there was significantly increased inflammation, injury, and fibrosis, as you can see in this histology. So the authors go on to provide extensive mechanistic studies that I'm not going to go through, but they show that osteopontin is associated with changes in the gut microbiome and the bile acids. There is less bile acid deconjugation. And they noted increased levels of conjugated bile acids in the portal system. They additionally noted hepatocyte injury and macrophage activation. So they conclude that intestinal osteopontin protects from mash through changes in the microbiome and bile acids. So in this section, I presented four different stories of gut-liver crosstalk, all related to intestinal permeability and liver damage, but all with completely different mechanisms and therapeutic implications, highlighting both the complexity of the gut-liver crosstalk and also the varied relationships between the intestinal microbiota, the intestinal epithelium, and the liver. I will now switch to fibrosis and highlight three abstracts that I believe add new mechanisms as well as layers of complexity to understanding the progression and regression of fibrosis. The first is from Enes Castellari at the Mayo Clinic. And she, in abstract 23 and also in a related poster, showed that stellate cell glycolysis amplifies liver fibrosis. Activated hepatic stellate cells have high energy needs. And given that hexokinase 2, the rate-limiting enzyme in glycolysis, is increased in fibrogenic hepatic stellate cells, she and her group asked whether glycolysis could play a role in fibrosis. So they first showed, as shown here in the first graph, that fibrogenic hepatic stellate cells in a carbon tetrachloride model are pericentral. And they made use of this in the future, in the next experiment, taking advantage of the zonation information. They showed that cells lacking the rate-limiting glycolysis enzyme hexokinase 2, which they were able to delete, specifically in stellate cells, are protected from fibrosis and that glycolysis is stimulated by expression of PDGF, which is very important in fibrosis, and leads to secretion of extracellular vesicles, thus leading to the conclusion that glycolysis worsens fibrosis and causes extracellular vesicle release, and raising the question of whether extracellular vesicles are pro-fibrogenic. And they, in fact, were able to show this in a really exciting and elegant mix-and-match study with extracellular vesicles and fibrosis. They were able to show that EVs from glycolysis-competent hepatic stellate cells caused fibrosis, whereas those from animals with hexokinase 2 depletion had less fibrosis. So this is an exciting and novel mechanism linking hepatic stellate cell energetics, PDGF, extracellular vesicles, and fibrosis. In a second highlighted abstract, Jessica Myers and colleagues from Indiana University School of Medicine studied the role of ER-associated degradation, or ERAD, in hepatic fibrogenesis. So misfolded proteins, ER proteins, are targeted for proteasomal degradation by ERAD, as shown in this cartoon. And Myers and colleagues further showed that ERAD components are increased in activated hepatic stellate cells, as shown in these graphs. These are all just different components of the ERAD system. They then showed that ERAD inhibition increases collagen 1 deposition and secretion. So that led to a decrease in intracellular collagen, but an increase in secretion, suggesting that there was upregulation of trafficking to relieve stress within the ER. However, this group also noted that there was a long-term decrease in fibrogenesis, suggesting that there's a complex but potentially targetable role for ERAD in fibrosis. In the third fibrosis presentation, Ganguly and Darr from University of California at San Diego analyzed macrophages from a hyperphagic mouse-mash model and looked specifically at macrophage populations in the setting of fibrosis regression. And they found five different populations, which were related, as shown on the UMAP plot on the left, and found specifically that macrophages associated with regression clustered with macrophages associated with mash, suggesting a relationship between them. Two of the populations, which they call MOKC and LAM, were called restorative macrophages and seemed to be associated with and necessary for regression. And they highly expressed TREM2, a cell surface protein with varied functions. This group, after doing this initial work, looking at the various macrophage populations, took the same hyperphagic mash model with a regression component and knocked out TREM2 in specific cells. They found that resolution of both fibrosis and steatosis was impaired and that collagen degradation was decreased. So overall, this is a significant contribution to understanding the complexity of macrophages in fibrosis, suggesting that two of the macrophage cell types are restorative and that they were able to show that these cell types are highly enriched in antifibrotic and anti-inflammatory pathways, highlighting the multiple macrophage subpopulations involved in regression, but also suggesting that TREM2 is a critical mediator of these macrophages and that regression. So next, I would like to highlight three IPSC-based models with potentially important research implications. The first is from Robert Schwartz at Cornell in Columbia, who developed a multicellular human hepatic spheroid system to study hepatitis B infection. This was, I think, somewhat of a tour de force. The goal was to develop a model of HBV infection with normal human hepatocytes and to study HBV hepatocyte crosstalk and recapitulate all aspects of the HBV viral lifecycle. Dr. Schwartz and colleagues developed a platform that enabled maintenance of hepatocyte function and HBV in culture, which has been in the past extremely difficult to do. And they personalized it using IPSCs, which were differentiated to hepatocyte-like cells. And these cells functioned extremely well with very similar function to primary human hepatocytes. And the system is shown, and the differentiation, as well as the high hepatocyte function are shown in the graphic at the bottom. And these cells, interestingly enough, were able to support hepatitis B surface antigen, HBV 3.5 expression, and high copy numbers of CCC HBV DNA. And this is much, much better than traditional cell culture. The group then made multicellular spheroids using IPSC technology to include non-parenchymal cells, including LCECs and Kupfer cells. And they found that the hepatocytes were even healthier. These multicellular spheroids supported HBV infection. And they demonstrated that Kupfer cells altered infection kinetics and that IL-6 plays a role. And this really was surprising. It's not yet understood. But it suggests that this system is of enormous potential use in dissecting infection and HBV liver cell crosstalk. So it will be extremely useful for the field for hepatitis B in the future. The next abstract is from Florentino and colleagues at the University of Pittsburgh, who applied IPSC technology to a different problem, namely to studying a devastating pediatric disease, which results from abnormalities in the flipase PFIC-1, which flips phosphatidylserine and phosphatidylethanolamine from the ectoplasm to the apical membrane of hepatocytes. This group established a validated patient IPSCs from a number of patients, corrected them, and carried out hepatocyte-like differentiation. And they saw very similar molecular signatures and disease phenotypes as the primary hepatocytes from patients with this disease. So this will have enormous potential in dissecting the mechanism of the disease, which is not well known in spite of the well-established genetic defect. Finally, Lugilu and colleagues, including in Dr. Marr's lab at UCSF, carried out a comparative analysis of IPSCs from NAFLD patients, comparing them with healthy controls. And they were able to show that there was, looking at the NAFLD cells compared to the IPSC-like hepatocytes differentiated from normal control patients, they were able to show higher maximal mitochondrial oxygen consumption under glucose deprivation, higher triglyceride content, higher maximal fatty acid oxidation, and increased oxidative stress, overall pointing to mitochondrial dysfunction. And so this is, I think, quite an important advance, suggesting that you can take IPSCs from NAFLD patients and you can actually use them to study hepatocyte dysfunction. So overall, this section has highlighted three IPSC models that have the potential as tools to dramatically alter the study of three different diseases, HPV infection, PFICC1, and NAFLD, in personalized and highly mechanistic ways. So there were several other abstracts that introduced new tools with the potential to significantly impact basic research in the field. The first is from Cafe and Mahal from Yale. This group used a combination of human cord blood stem cells and human hepatocytes with an FAH null mouse, and this is shown in the diagram below on the left, to generate fully humanized mouse livers that included hepatocytes and non-parenchymal cells and add human functionality and zonation. They were able to show in these humanized mice, or mice with humanized livers, that alcohol feeding caused steatosis, cholestasis, and fibrosis, but there was minimal disease from alcohol feeding in the control mice. And I just want to comment that this, as well, will be an incredibly important tool. They show remarkable liver responses to alcohol. The features of human disease, similar to human disease, are remarkable, and they'll be very useful to study, really, the full range of alcohol-associated liver disease. So the next tool abstract is from Muller and colleagues in Glasgow, and they introduced a valuable resource for studying hepatocellular carcinoma. There is a need, and there has been a need for non-chemical models of human-relevant HCC. This has been a problem with mouse studies and rodent studies of HCC. And so this group used AAV-CRE technology to generate more than 30 genetically-engineered mouse models of HCC, all with human-relevant mutations. And they were able to show with these models that HCC occurs, it progresses, and it can metastasize. And these tumors can be taken and used to form tumoroids that can have the potential for high-throughput screening. This is a demonstration of one example of high-throughput screening, looking at the response of different tumor cells to various chemotherapeutics. And the hope is that this technology in the future will be useful for subtype-specific identification of therapies for HCC. Finally, Miner and Brenner and colleagues in a poster presentation have used 3D bioprinting to study the interactions and roles of specific non-parenchymal cell populations in NASH. And I use the terminology that's been used in the posters and presentations themselves. The system, which is shown here on the left, where you have printing of hepatocytes surrounded by non-parenchymal cells, allows the selective mixing of different combinations of healthy and diseased non-parenchymal cells in different ratios. And it's all bioprinted. And what this group was able to show is that diseased stellate and endothelial cells taken from NASH patients can lead to increased collagen production, which I think is a fairly provocative result, but suggests that this technology will be incredibly useful in the future in understanding the roles of different cell types. This just shows you what it looks like, what these little bioprinted livers look like. And this will additionally be useful for drug testing and identification of new therapeutics. So the final set of abstracts I'd like to cover highlights topics that arguably, and at least I would argue, deserve considerably more attention than they actually get. In other words, they're under the radar, but they shouldn't be. So the first is a series of three abstracts that highlight really the critical and underappreciated role of environmental toxins in liver disease. First, at the top, from Beyer and colleagues, this is a group that has, for many years, studied the impact of low-dose final chloride, which is widely present in the environment on the liver. And in this case, they looked at the response of mice, the mitochondrial liver response to low-dose final chloride. And they are able to show that this exposure increased indices of liver injury and oxidative stress. It dysregulated hepatic glucose homeostasis, decreased mitochondrial respiration and membrane potential, and in other ways, altered mitochondrial function. And so I think this is potentially important in the future and probably deserves more attention than it gets. There were two abstracts on microplastics and their impact on the liver. The first from Adil and Cave and colleagues from the University of Louisville showed that microplastics, and these are tiny, tiny beads of plastics in the environment. Exposure is generally via an oral mechanism, that they cause marked disruption of hepatic metabolism in response to microplastics, in particular, cholesterol metabolism. And then the next abstract from Bake and colleagues from Korea showed that microplastics migrated to liver, spleen, and brain, causing steatosis of the liver in the setting of alcohol feeding. And that was because the alcohol feeding led to disruption of the intestinal barrier, which then led to uptake of these microplastics. And given what the previous group had shown, it suggests that this is potentially highly impactful on liver disease. So I look forward to more such work in the future and felt it was very important to highlight this work here. So finally, last but not least, there is a lovely set of work, a lovely abstract and parallel presentation following up on other work from Yasuko Iwakiri's group and Jane Jiang, who was the presenter, looking at lymphatics in liver fibrosis and cirrhosis. Lymphatics have been very, very poorly studied otherwise in the liver. And I felt, again, this is a topic that didn't get enough attention. So this group showed that lymphatic vessel area increases in early stages of cirrhosis, namely compensated cirrhosis, but decreased at late stage or decompensated cirrhosis. And you can see here lymphatics are shown in red. And you can see that as these animals become cirrhotic after a bile duct ligation, you see more and more of these lymphatic vessels. But interestingly enough, they suggested that they saw that there was a decrease in lymphatic vessel area as cirrhosis progressed from compensated to decompensated. And they suggested that this decrease in lymphatic area was actually promoted the progression from compensated to decompensated. And they did a very elegant study where they used VEGF overexpression to increase lymphangiogenesis in the liver. And what they were able to find was that it significantly improved lymphatic drainage function. And this is, at least somewhere down the line, is a potential therapeutic. But I think it highlights the power of considering this generally underappreciated population of vessels. So shockingly, I'm on time, which is actually early. Probably a first in my life. But with this, I want to thank you. And I hope that you do, as do I, look forward to the exciting additional impactful work that will result from all of these findings that I've highlighted, and really from all of the basic science at this meeting. Thank you very much. Thank you.

liver meeting

basic science

viral hepatitis

muscle hypertension

cholestatic liver diseases

fibrosis progression