The Effects of Old Age on Hepatic Stellate Cells

Aging is associated with marked changes in the hepatic sinusoid, yet the effect of old age on hepatic stellate cells (HSC) has not been well described. Transmission electron microscopy and immunohistochemistry were used to study the effects of aging on HSC in livers from rats (3-4 mths versus 24–27 mths) and mice (2-3 mths versus 20–22 mths). Desmin-positive HSC doubled in old age in both mice and rats. Alpha-smooth muscle actin- (αSMA-) positive cells did not increase significantly and remained only a small percentage of desmin-positive cells. Electron microscopy revealed that old age is associated with HSC that have a substantial increase in the number of lipid droplets which are larger in diameter. There was also a marked increase of HSC that protruded into the sinusoidal lumen in old mice. In conclusion, old age is associated with hyperplasia of HSC that are not activated and are engorged with lipid droplets

Ischemia/reperfusion injury in the aged liver: The importance of the sinusoidal endothelium in developing therapeutic strategies for the elderly.

The liver endothelium plays a key role in the progression and resolution of liver diseases in young and adult individuals. However, its role in older people remains unknown. We have herein evaluated the importance of the sinusoidal endothelium in the pathophysiology of acute liver injury, and investigated the applicability of simvastatin, in aged animals.18 months old male Wistar rats underwent 60 min of partial warm ischemia followed by 2h of reperfusion (WIR). A group of aged rats received simvastatin for 3 days before WIR. Endothelial phenotype, parenchymal injury, oxidative and nitrosative stress, and fenestrae dynamics were analysed. The effects of WIR and simvastatin were investigated in primary LSEC from aged animals.The results of this study demonstrated that WIR significantly damages the liver endothelium and its effects are markedly worse in old animals. WIR-aged livers exhibited reduced vasodilation and sinusoidal capillarization, associated with liver damage and cellular stress. Simvastatin prevented the detrimental effects of WIR in aged livers.In conclusion, the liver sinusoidal endothelium of old animals is highly vulnerable to acute insult, thus targeted protection is especially relevant in preventing liver damage. Simvastatin represents a useful therapeutic strategy in aging

In vitro models for the study of liver biology and diseases - advances and limitations.

In vitro models of liver (patho)physiology, new technologies and experimental approaches are progressing rapidly. Based on cell lines, induced pluripotent stem cells (iPSCs) or primary cells derived from mouse or human liver as well as whole tissue (slices), such in vitro single- and multi-cellular models, including complex microfluidic organ-on-a-chip systems, provide tools to functionally understand mechanisms of liver health and disease. The International Society of Hepatic Sinusoidal Research (ISHSR) commissioned this working group to review the currently available in vitro liver models and describe the advantages and disadvantages of each in the context of evaluating their use for the study of liver functionality, disease modelling, therapeutic discovery and clinical applicability

Cost-efficient nanoscopy reveals nanoscale architecture of liver cells and platelets

Single-molecule localization microscopy (SMLM) provides a powerful toolkit to specifically resolve intracellular structures on the nanometer scale, even approaching resolution classically reserved for electron microscopy (EM). Although instruments for SMLM are technically simple to implement, researchers tend to stick to commercial microscopes for SMLM implementations. Here we report the construction and use of a “custom-built” multi-color channel SMLM system to study liver sinusoidal endothelial cells (LSECs) and platelets, which costs significantly less than a commercial system. This microscope allows the introduction of highly affordable and low-maintenance SMLM hardware and methods to laboratories that, for example, lack access to core facilities housing high-end commercial microscopes for SMLM and EM. Using our custom-built microscope and freely available software from image acquisition to analysis, we image LSECs and platelets with lateral resolution down to about 50 nm. Furthermore, we use this microscope to examine the effect of drugs and toxins on cellular morphology

Sucrose and starch intake contribute to reduced alveolar bone height in a rodent model of naturally occurring periodontitis

Funding: This research project was funded in part by the Strategic Research Excellence Initiative 2020 (SREI2020), University of Sydney to JE and the University of Sydney HMR + Implementation Funding Grant to VC, DLC and SS.Peer reviewedPublisher PD

Osteoblasts mediate the adverse effects of glucocorticoids on fuel metabolism

Long-term glucocorticoid treatment is associated with numerous adverse outcomes, including weight gain, insulin resistance, and diabetes; however, the pathogenesis of these side effects remains obscure. Glucocorticoids also suppress osteoblast function, including osteocalcin synthesis. Osteocalcin is an osteoblast-specific peptide that is reported to be involved in normal murine fuel metabolism. We now demonstrate that osteoblasts play a pivotal role in the pathogenesis of glucocorticoid-induced dysmetabolism. Osteoblast-targeted disruption of glucocorticoid signaling significantly attenuated the suppression of osteocalcin synthesis and prevented the development of insulin resistance, glucose intolerance, and abnormal weight gain in corticosterone-treated mice. Nearly identical effects were observed in glucocorticoid-treated animals following heterotopic (hepatic) expression of both carboxylated and uncarboxylated osteocalcin through gene therapy, which additionally led to a reduction in hepatic lipid deposition and improved phosphorylation of the insulin receptor. These data suggest that the effects of exogenous high-dose glucocorticoids on insulin target tissues and systemic energy metabolism are mediated, at least in part, through the skeleton.NHMRC Grants 402462 and 63281

Liver specification of human iPSC-derived endothelial cells transplanted into mouse liver

Background & Aims: Liver sinusoidal endothelial cells (LSECs) are important in liver development, regeneration, and pathophysiology, but the differentiation process underlying their tissue-specific phenotype is poorly understood and difficult to study because primary human cells are scarce. The aim of this study was to use human induced pluripotent stem cell (hiPSC)-derived LSEC-like cells to investigate the differentiation process of LSECs. Methods: hiPSC-derived endothelial cells (iECs) were transplanted into the livers of Fah−/−/Rag2−/−/Il2rg−/− mice and assessed over a 12-week period. Lineage tracing, immunofluorescence, flow cytometry, plasma human factor VIII measurement, and bulk and single cell transcriptomic analysis were used to assess the molecular and functional changes that occurred following transplantation. Results: Progressive and long-term repopulation of the liver vasculature occurred as iECs expanded along the sinusoids between hepatocytes and increasingly produced human factor VIII, indicating differentiation into LSEC-like cells. To chart the developmental profile associated with LSEC specification, the bulk transcriptomes of transplanted cells between 1 and 12 weeks after transplantation were compared against primary human adult LSECs. This demonstrated a chronological increase in LSEC markers, LSEC differentiation pathways, and zonation. Bulk transcriptome analysis suggested that the transcription factors NOTCH1, GATA4, and FOS have a central role in LSEC specification, interacting with a network of 27 transcription factors. Novel markers associated with this process included EMCN and CLEC14A. Additionally, single cell transcriptomic analysis demonstrated that transplanted iECs at 4 weeks contained zonal subpopulations with a region-specific phenotype. Conclusions: Collectively, this study confirms that hiPSCs can adopt LSEC-like features and provides insight into LSEC specification. This humanised xenograft system can be applied to further interrogate LSEC developmental biology and pathophysiology, bypassing current logistical obstacles associated with primary human LSECs. Impact and implications: Liver sinusoidal endothelial cells (LSECs) are important cells for liver biology, but better model systems are required to study them. We present a pluripotent stem cell xenografting model that produces human LSEC-like cells. A detailed and longitudinal transcriptomic analysis of the development of LSEC-like cells is included, which will guide future studies to interrogate LSEC biology and produce LSEC-like cells that could be used for regenerative medicine