Adult neurogenesis creates new neurons and glia from stem cells in the human brain throughout life. It is best understood in the dentate gyrus (DG) of the hippocampus and the subventricular zone (SVZ). Circadian rhythms have been identified in the hippocampus, but the role of any endogenous circadian oscillator cells in hippocampal neurogenesis and their importance in learning or memory remains unclear. Any study of stem cell regulation by intrinsic circadian timing within the DG is complicated by modulation from circadian clocks elsewhere in the brain. To examine circadian oscillators in greater isolation, neurosphere cultures were prepared from the DG of two knockout mouse lines that lack a functional circadian clock and from mPer1::luc mice to identify circadian oscillations in gene expression. Circadian mPer1 gene activity rhythms were recorded in neurospheres maintained in a culture medium that induces neurogenesis but not in one that maintains the stem cell state. Although the differentiating neural stem progenitor cells of spheres were rhythmic, evidence of any mature neurons was extremely sparse. The circadian timing signal originated in undifferentiated cells within the neurosphere. This conclusion was supported by immunocytochemistry for mPER1 protein that was localized to the inner, more stem cell-like neurosphere core. To test for effects of the circadian clock on neurogenesis, media conditions were altered to induce neurospheres from BMAL1 knockout mice to differentiate. These cultures displayed unusually high differentiation into glia rather than neurons according to GFAP and NeuN expression, respectively, and very few BetaIII tubulin-positive, immature neurons were observed. The knockout neurospheres also displayed areas visibly devoid of cells and had overall higher cell death. Neurospheres from arrhythmic mice lacking two other core clock genes, Cry1 and Cry2, showed significantly reduced growth and increased astrocyte proliferation during differentiation, but they generated normal percentages of neuronal cells. Neuronal fate commitment therefore appears to be controlled through a non-clock function of BMAL1. This study provides insight into how cell autonomous circadian clocks and clock genes regulate adult neural stem cells with implications for treating neurodegenerative disorders and impaired brain functions by manipulating neurogenesis.

Immune-mediated bile duct epithelial injury and toxicity of retained hydrophobic bile acids drive disease progression in fibrosing cholangiopathies such as biliary atresia or primary sclerosing cholangitis. Emerging therapies include pharmacological agonists to farnesoid X receptor (FXR), the master regulator of hepatic synthesis, excretion, and intestinal reuptake of bile acids. Unraveling the mechanisms of action of pharmacological FXR agonists in the treatment of sclerosing cholangitis (SC), we found that intestinally restricted FXR activation effectively reduced bile acid pool size but did not improve the SC phenotype in MDR2 ^−/− mice. In contrast, systemic FXR activation not only lowered bile acid synthesis but also suppressed proinflammatory cytokine production by liver-infiltrating inflammatory cells and blocked progression of hepatobiliary injury. The hepatoprotective activity was linked to suppressed production of IL1β and TNFα by hepatic macrophages and inhibition of T _H 1/T _H 17 lymphocyte polarization. Deletion of FXR in myeloid cells caused aberrant T _H 1 and T _H 17 lymphocyte responses in diethoxycarbonyl-1,4-dihydrocollidine–induced SC and rendered these mice resistant to the anti-inflammatory and liver protective effects of systemic FXR agonist treatment. Pharmacological FXR activation reduced IL1β and IFNγ production by liver- and blood-derived mononuclear cells from patients with fibrosing cholangiopathies. In conclusion, we demonstrate FXR to control the macrophage-T _H 1/17 axis, which is critically important for the progression of SC. Hepatic macrophages are cellular targets of systemic FXR agonist therapy for cholestatic liver disease.

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and a leading cause of death in the US and worldwide. HCC remains a global health problem and is highly aggressive with unfavorable prognosis. Even with surgical interventions and newer medical treatment regimens, patients with HCC have poor survival rates. These limited therapeutic strategies and mechanistic understandings of HCC immunopathogenesis urgently warrant non-palliative treatment measures. Irrespective of the multitude etiologies, the liver microenvironment in HCC is intricately associated with chronic necroinflammation, progressive fibrosis, and cirrhosis as precedent events along with dysregulated innate and adaptive immune responses. Central to these immunological networks is the complement cascade (CC), a fundamental defense system inherent to the liver which tightly regulates humoral and cellular responses to noxious stimuli. Importantly, the liver is the primary source for biosynthesis of >80% of complement components and expresses a variety of complement receptors. Recent studies implicate the complement system in liver inflammation, abnormal regenerative responses, fibrosis, carcinogenesis, and development of HCC. Although complement activation differentially promotes immunosuppressive, stimulant, and angiogenic microenvironments conducive to HCC development, it remains under-investigated. Here, we review derangement of specific complement proteins in HCC in the context of altered complement regulatory factors, immune-activating components, and their implications in disease pathogenesis. We also summarize how complement molecules regulate cancer stem cells (CSCs), interact with complement-coagulation cascades, and provide therapeutic opportunities for targeted intervention in HCC.

Sickle cell anemia (SCA) results from an abnormal sickle hemoglobin (HbS). HbS polymerizes upon deoxygenation, resulting in red blood cell (RBC) sickling and membrane damage that cause vaso-occlusions and hemolysis. Sickle RBCs contain less adenosine triphosphate and more 2,3-diphosphoglycerate than normal RBCs, which allosterically reduces hemoglobin (Hb) oxygen (O2) affinity (ie, increases the partial pressure of oxygen at which hemoglobin is 50% saturated with oxygen [P50]), potentiating HbS polymerization. Herein, we tested the effect of investigational agent FT-4202, an RBC pyruvate kinase (PKR) activator, on RBC sickling and membrane damage by administering it to Berkeley SCA mice. Two-week oral FT-4202 administration was well tolerated, decreasing HbS P50 to levels similar to HbA and demonstrating beneficial biological effects. In FT-4202–treated animals, there was reduced sickling in vivo, demonstrated by fewer irreversibly sickled cells, and improved RBC deformability, assessed at varying shear stress. Controlled deoxygenation followed by reoxygenation of RBCs obtained from the blood of FT-4202–treated mice showed a shift in the point of sickling to a lower partial pressure of oxygen (pO2). This led to a nearly 30% increase in RBC survival and a 1.7g/dL increase in Hb level in the FT-4202–treated SCA mice. Overall, our results in SCA mice suggest that FT-4202 might be a potentially useful oral antisickling agent that warrants investigation in patients with SCA.

Circadian rhythms are common in many cell types but are reported to be lacking in embryonic stem cells. Recent studies have described possible interactions between the molecular mechanism of circadian clocks and the signaling pathways that regulate stem cell differentiation. Circadian rhythms have not been examined well in neural stem cells and progenitor cells that produce new neurons and glial cells during adult neurogenesis. To evaluate circadian timing abilities of cells undergoing neural differentiation, neurospheres were prepared from the mouse subventricular zone (SVZ), a rich source of adult neural stem cells. Circadian rhythms in mPer1 gene expression were recorded in individual spheres, and cell types were characterized by confocal immunofluorescence microscopy at early and late developmental stages in vitro. Circadian rhythms were observed in neurospheres induced to differentiate into neurons or glia, and rhythms emerged within 3–4 days as differentiation proceeded, suggesting that the neural stem cell state suppresses the functioning of the circadian clock. Evidence was also provided that neural stem progenitor cells derived from the SVZ of adult mice are self-sufficient clock cells capable of producing a circadian rhythm without input from known circadian pacemakers of the organism. Expression of mPer1 occurred in high frequency oscillations before circadian rhythms were detected, which may represent a role for this circadian clock gene in the fast cycling of gene expression responsible for early cell differentiation.

Biliary atresia (BA) is a rare but severe fibroinflammatory disease of the extrahepatic and the intrahepatic bile ducts. Without prompt interventions, BA has fatal outcomes and is the most common indicator for pediatric liver transplantation (LTx). While the mainstay of treatment involves surgically correcting the extrahepatic biliary obstruction via Kasai hepato-portoenterostomy (KHPE), activation of a multitude of biological pathways and yet-to-be-determined etiology in BA continue to foster liver inflammation, cirrhosis and need for LTx. However, important caveats still exist in our understandings of the biliary pathophysiology, the rapidity of liver fibrosis and progression to liver failure, largely due to limited knowledge of the triggers of biliary injury and the inability to accurately model human BA. Although inconclusive, a large body of existing literature points to a potential viral infection in the early peri- or postnatal period as triggers of epithelial injury that perpetuates the downstream biliary disease. Further confounding this issue, are the lack of in-vivo and in-vitro models to efficiently recapitulate the cardinal features of BA, primarily liver fibrosis. To overcome these barriers in BA research, new directions in recent years have enabled (I) identification of additional triggers of biliary injury linked mostly to environmental toxins, (II) development of models to investigate liver fibrogenesis, and (III) translational research using patient-derived organoids. Here, we discuss recent advances that undoubtedly will stimulate future efforts investigating these new and exciting avenues towards mechanistic and drug discovery efforts and disease-preventive measures. The implications of these emerging scientific investigations and disease modeling in severe fibrosing cholangiopathies like BA are enormous and contribute substantially in our understandings of this rare but deadly disease. These findings are also expected to facilitate expeditious identification of translationally targetable pathways and bring us one step closer in treating an infant with BA, a population highly vulnerable to life-long liver related complications.