Faculty Bibliography

Gastrointestinal (GI) symptoms of SARS-CoV-2/COVID-19 in the form of anorexia, nausea, vomiting, abdominal pain and diarrhea are usually preceded by respiratory manifestations and are associated with a poor prognosis. Hematochezia is an uncommon clinical presentation of COVID-19, and we hypothesize that older patients with significant comorbidities (obesity and cardiovascular) and prolonged hospitalization are susceptible to ischemic injury to the bowel. We reviewed the clinical course, key laboratory data including acute-phase reactants, and drug/medication history in 2 elderly male patients admitted for COVID-19 respiratory failure. Both patients had a complicated clinical course and suffered from hematochezia, acute blood loss, and anemia which led to hemodynamic instability requiring blood transfusion around day 40 of their hospitalization. Colonoscopic impressions were correlated with the histopathological findings in the colonic biopsies that included changes compatible with ischemia and nonspecific acute inflammation, edema, and increased eosinophils in the lamina propria. Both patients were hemodynamically stable, on prophylactic anticoagulants, multiple antibiotics, and antifungal agents due to respiratory infections at the time of lower GI bleeding. Hematochezia resolved spontaneously with supportive care. Both patients eventually recovered and were discharged. Elderly patients with significant comorbid conditions are uniquely at risk for ischemic injury to the bowel. This case report highlights hematochezia as an uncommon GI manifestation of spectrum of COVID-19 complications. The causes of bleeding in these COVID-19 associated cases are likely multifactorial and can be attributed to concomitant etiologies based on their age, multiple comorbid conditions, prolonged hospitalization compounded by lung injury, and hypoxia precipitated by the virus. We hypothesize that rather than a direct viral cytopathic effect, ischemia and hypoperfusion may be unleashed due to the cytokine storm orchestrated by the virus that leads to abnormal coagulation profile. Additional factors that may contribute to ischemic injury are prophylactic use of anticoagulants and polypharmacy. There were no other causes to explain the brisk lower GI bleeding. Presentation of hematochezia was followed by hemodynamic instability that may further increase the mortality and morbidity of COVID-19 patients, and prompt consultation and management by gastroenterology is therefore warranted.

The human brain functions at the center of a network of systems aimed at providing a structural and immunological layer of protection. The cerebrospinal fluid (CSF) maintains a physiological homeostasis that is of paramount importance to proper neurological activity. CSF is largely produced in the choroid plexus where it is continuous with the brain extracellular fluid and circulates through the ventricles. CSF movement through the central nervous system has been extensively explored. Across numerous animal species, the involvement of various drainage pathways in CSF, including arachnoid granulations, cranial nerves, perivascular pathways, and meningeal lymphatics, has been studied. Among these, there is a proposed CSF clearance route spanning the olfactory nerve and exiting the brain at the cribriform plate and entering lymphatics. While this pathway has been demonstrated in multiple animal species, evidence of a similar CSF egress mechanism involving the nasal cavity in humans remains poorly consolidated. This review will synthesize contemporary evidence surrounding CSF clearance at the nose-brain interface, examining across species this anatomical pathway, and its possible significance to human neurodegenerative disease. Our discussion of a bidirectional nasal pathway includes examination of the immune surveillance in the olfactory region protecting the brain. Overall, we expect that an expanded discussion of the brain-nose pathway and interactions with the environment will contribute to an improved understanding of neurodegenerative and infectious diseases, and potentially to novel prevention and treatment considerations.

PT150 is a clinical-stage molecule, taken orally, with a strong safety profile having completed Phase 1 and Phase 2 clinical trials for its original use as an antidepressant. It has an active IND for COVID-19. Antiviral activities have been found for PT150 and other members of its class in a variety of virus families; thus, it was now tested against SARS-CoV-2 in human bronchial epithelial lining cells and showed effective 90% inhibitory antiviral concentration (EC90) of 5.55 µM. PT150 is a member of an extended platform of novel glucocorticoid receptor (GR) and androgen receptor (AR) modulating molecules. In vivo, their predominant net effect is one of systemic glucocorticoid antagonism, but they also show direct downregulation of AR and minor GR agonism at the cellular level. We hypothesize that anti-SARS-CoV-2 activity depends in part on this AR downregulation through diminished TMPRSS2 expression and modulation of ACE2 activity. Given that hypercortisolemia is now suggested to be a significant co-factor for COVID-19 progression, we also postulate an additive role for its potent immunomodulatory effects through systemic antagonism of cortisol.

Multiplexed immunohistochemical techniques give insight into contextual cellular relationships by offering the ability to collect cell-specific data with spatial information from formalin-fixed, paraffin-embedded tissue sections. We established an automated sequential elution-stripping multiplex immunohistochemical assay to address two controversial scientific questions in the field of hepatopathology: 1) whether epithelial-to-mesenchymal transition or mesenchymal-to-epithelial transition occurs during liver injury and repair of a chronic liver disease and 2) if there is a stromal:epithelial relationship along the canals of Hering that would support the concept of this biliary structure being a stem/progenitor cell niche. Our 4-plex assay includes both epithelial and mesenchymal clinical immunohistochemical markers and was performed on clinical human liver specimens in patients with primary biliary cholangitis. The assay demonstrated that in each specimen, co-expression of epithelial and mesenchymal markers was observed in extraportal cholangiocytes. In regard to possible mesenchymal components in a stem cell niche, 82.3% ± 5.5% of extraportal cholangiocytes were intimately associated with a vimentin-positive cell. Co-expression of epithelial and mesenchymal markers by extraportal cholangiocytes is evidence for epithelial to mesenchymal transition in primary biliary cholangitis. Vimentin-positive stromal cells are frequently juxtaposed to extraportal cholangiocytes, supporting an epithelial:mesenchymal relationship within the hepatobiliary stem cell niche. Our automated sequential elution-stripping multiplex immunohistochemical assay is a cost-effective multiplexing technique that can be readily applied to a small series of clinical pathology samples in order to answer scientific questions involving cell:cell relationships and cellular antibody expression.

BACKGROUND & AIMS/OBJECTIVE:Progression of liver fibrosis still occurs in some patients with chronic hepatitis B virus (HBV) infection despite antiviral therapy. We aimed to identify risk factors for fibrosis progression in patients who received antiviral therapy. METHODS:We conducted a longitudinal study of patients with chronic HBV infection and liver biopsies collected before and after 78 weeks of anti-HBV therapy. Fibrosis progression was defined as Ishak stage increase ≥ 1 or as predominantly progressive classified by P-I-R system (Beijing Classification). Levels of HBV DNA and HBV RNA in blood samples were measured by real-time quantitative PCR. HBV RNA in liver tissue was detected by in situ hybridization. RESULTS:A total of 239 patients with chronic HBV infection with paired liver biopsies were included. Among the 163 patients with significant fibrosis at baseline (Ishak ≥ stage 3), fibrosis progressed in 22 patients (13%), was indeterminate in 24 patients (15%), and regressed in 117 patients (72%). Univariate and multivariate analyses revealed that independent risk factors for fibrosis progression were higher rate of detected HBV DNA at week 78 (odds ratio, 4.84; 95% CI, 1.30-17.98; P=.019) and alcohol intake (odds ratio, 23.84; 95% CI, 2.68-212.50; P=.004). HBV DNA was detected in blood samples from a significantly higher proportion of patients with fibrosis progression (50%) at week 78 than patients with fibrosis regression (19%) or indeterminate fibrosis (26%) (P=.015), despite low viremia (20-200 IU/mL) in all groups. The decrease of serum HBV RNA from baseline in the fibrosis regression group was larger than that in the fibrosis progression group. CONCLUSIONS:In a longitudinal study of patients with chronic HBV infection, we associated liver fibrosis progression at week 78 of treatment with higher rates of detected HBV DNA. We propose that a low level of residual HBV may still promote fibrosis progression, and that patients' levels of HBV DNA should be carefully monitored.

The autonomic nervous system plays a role in a variety of liver regenerative and metabolic functions, including modulating bile secretion and cholangiocyte and hepatobiliary progenitors of the canals of Hering. However, the nature and location of nerves which link to the proximal biliary tree have remained uncertain. We investigate the anatomic relationship of nerves to the proximal biliary tree including the putative stem/progenitor cell niche of the canal of Hering. Using double immunostaining (fluorescence, histochemistry) to highlight markers of cholangiocytes (biliary-type keratins), nerves (S100, neurofilament protein, PGP9.5, tyrosine hydroxylase), and stellate cells (CRBP-1), we examined sections from normal adult livers from autopsy or surgical resections. There is extensive contact between nerves and interlobular bile ducts, bile ductules, and canals of Hering (CoH). In multiple serial sections from 4 normal livers, biliary-nerve contacts were seen in all of these structures and were more common in the interlobular bile ducts (78/137; 57%) than in the ductules and CoH (95/294; 33%) (p < 0.001). Contacts appear to consist of nerves in juxtaposition to the biliary basement membrane, though crossing through basement membrane to interface directly with cholangiocytes is also present. These nerves are positive for tyrosine hydroxylase and are, thus, predominately adrenergic. Electron microscopy confirms nerves closely approximating ductules. Nerve fiber-hepatic stellate cell juxtaposition is observed but without stellate cell approximation to cholangiocytes. We present novel findings of biliary innervation, perhaps mediated in part, by direct cholangiocyte-nerve interactions. The implications of these findings are protean for studies of neuromodulation of biliary physiology and hepatic stem/progenitor cells.

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer death in the world. Although most cases occur in stiff, cirrhotic livers, and stiffness is a significant risk factor, HCC can also arise in non-cirrhotic livers in the setting of non-alcoholic fatty liver disease (NAFLD). We hypothesized that lipid droplets in NAFLD might apply mechanical forces to the nucleus, functioning as mechanical stressors akin to stiffness. We investigated the effect of lipid droplets on cellular mechanosensing and found that primary human hepatocytes loaded with the fatty acids oleate and linoleate exhibited decreased stiffness-induced cell spreading and disrupted focal adhesions and stress fibers. The presence of large lipid droplets in hepatocytes resulted in increased nuclear localization of the mechano-sensor Yes-associated protein (YAP). In cirrhotic livers from patients with NAFLD, hepatocytes filled with large lipid droplets showed significantly higher nuclear localization of YAP as compared to cells with small lipid droplets. This work suggests that lipid droplets induce a mechanical signal that disrupts the ability of the hepatocyte to sense its underlying matrix stiffness, and that the presence of lipid droplets can induce intracellular mechanical stresses.

The origin and initiating features of PBC remain obscure despite decades of study. However, recent papers have demonstrated loss of canals of Hering (CoH) to be the earliest histologic change in liver biopsy specimens from patients with primary biliary cholangitis (PBC). We posit that CoH loss prior to significant inflammation or evidence of bile duct injury might be a very early, perhaps even an initiating lesion of PBC. As a potential target of inflammatory or toxic injury, CoH loss may initiate rather than follow the cascade of events leading to duct injury and loss and their sequelae. Toxins may be exogenous in origin, such as environmental toxins or drug exposures, or endogenous, resulting from genetic or epigenetic alterations in canalicular bile transporters upstream from the CoH. In turn, this hypothesis suggests that loss of CoH would lead to altered bile flow and composition injurious to downstream bile ducts, because bile composition has not been modulated by normal CoH physiologic functions or because, in the absence of CoH, canalicular fluid flow into the biliary tree is disrupted interfering with soluble trophic factors important for bile duct integrity. Regardless of the pathogenic mechanism causing CoH loss, only following such loss would the characteristic diagnostic findings of PBC become evident: damage to downstream interlobular and sub-lobular bile ducts. To the extent that the causal mechanisms for CoH loss can be identified, clinical identification (as through early identification of CoH loss) and intervention (depending on the inciting cause) may offer promise for treatment of this enigmatic disease.

Background: Fibroconnective tissues of the body are traditionally conceived as layers of densely compacted collagen. Recent in vivo microscopy, however, demonstrates that at least some, including visceral submucosae, dermis, fascia, adventitia and perineurium, are actually a reticular network of fluid-filled sinuses supported by a complex scaffold of thick collagen bundles (Benias et al Sci Rep 2018: 8). The interstitial fluid is rich in hyaluronic acid (HA). Whether these large scale interstitial spaces are continuous between tissues/organs or separate is unclear. Continuity was investigated by two methods: 1. movement of non-biological pigment (tattoo pigment, colloidal silver) in colon and skin specimens; 2. localization of HA by IHC.
Design(s): H&E-stained sections of FFPE tissues from resected colons following endoscopic submucosal tattoo for malignant polyps (n=5) and from skin biopsies with either cosmetic tattoos (n=3) or colloidal silver (n=2) were examined. Location of particles was assessed. The slides were then scanned, decolorized, and stained by multiplex chromogenic IHC assay (Discovery Ultra, Ventana) for HA-binding protein (brown), vimentin (magenta) and CD34 (teal) to label interstitial lining cells.
Result(s): Tattoo pigment and colloidal silver within the interstitial spaces was identified in the dermis (Fig. 1) and colonic submucosa and in the dependent mesenteric and subcutaneous fascias. In all colon specimens HA IHC highlighted the spatial continuity of all layers of the colon from lamina propria through muscularis mucosae to submucosa (Fig. 2A), then through the muscularis propria into mesenteric fascia (Fig. 2B, C). Continuity between these spaces and perivascular stroma/adventitia and perineurium in the bowel wall was also evident. Continuity of HA-filled spaces is also demonstrated from papillary to reticular dermis and then to subcutaneous fascia interface. (Figure presented)
Conclusion(s): Interstitial spaces are neither virtual nor a result of processing artifact, but are filled with physiologically relevant fluid rich in HA. Their continuity across tissue compartments is demonstrated by movement of non-biological pigments and by spatial continuity of HA. The implications of such multisystem continuity are protean, but may particularly explain commonly observed modes of discontinuous cancer spread through tissue planes, such as mesenteric tumor deposits in colon cancer and subcutaneous in-transit melanoma metastasis, and spread of infection (e.g. necrotizing fasciitis)