isolation-of-rat-portal-fibroblasts-by-in-situ-liver-perfusion

Isolation of Rat Portal Fibroblasts by <em>In situ</em> Liver Perfusion

Liver fibrosis is defined  by the excessive deposition of extracellular matrix by activated  myofibroblasts. There are multiple precursors of hepatic ...

measuring-constipation-in-a-drosophila-model-of-parkinson-s-disease

Measuring Constipation in a <em>Drosophila</em> Model of Parkinson's Disease

Non-motor symptoms in Parkinson's disease (PD) are common, difficult to treat, and significantly impair quality of life. One prevalent non-motor symptom ...

University of Pennsylvania 

University of Pittsburgh

Embryonic stem (ES) cells exhibit the remarkable capacity to become virtually any differentiated tissue upon appropriate manipulation in culture, a property that has been beneficial for studies of hematopoiesis. Until recently, the majority of this work used murine ES cells for basic research to elucidate fundamental properties of blood-cell development and establish methods to derive specific mature lineages. Now, the advent of human ES cells sets the stage for more applied pursuits to generate transplantable cells for treating blood disorders. Current efforts are directed toward adapting in vitro hematopoietic differentiation methods developed for murine ES cells to human lines, identifying the key interspecies differences in biologic properties of ES cells, and generating ES cell-derived hematopoietic stem cells that are competent to repopulate adult hosts. The ultimate medical goal is to create patient-specific and generic ES cell lines that can be expanded in vitro, genetically altered, and differentiated into cell types that can be used to treat hematopoietic diseases.

Designer blood: creating hematopoietic lineages from embryonic stem cells.

The myofibroblastic differentiation of hepatic stellate cells (HSC) is a critical event in liver fibrosis and is part of the final common pathway to cirrhosis in chronic liver disease from all causes. The molecular mechanisms driving HSC differentiation are not fully understood. Because macroscopic tissue stiffening is a feature of fibrotic disease, we hypothesized that mechanical properties of the underlying matrix are a principal determinant of HSC activation. Primary rat HSC were cultured on inert polyacrylamide supports of variable but precisely defined shear modulus (stiffness) coated with different extracellular matrix proteins or poly-L-lysine. HSC differentiation was determined by cell morphology, immunofluorescence staining, and gene expression. HSC became progressively myofibroblastic as substrate stiffness increased on all coating matrices, including Matrigel. The degree rather than speed of HSC activation correlated with substrate stiffness, with cells cultured on supports of intermediate stiffness adopting stable intermediate phenotypes. Quiescent cells on soft supports were able to undergo myofibroblastic differentiation with exposure to stiff supports. Stiffness-dependent differentiation required adhesion to matrix proteins and the generation of mechanical tension. Transforming growth factor-β treatment enhanced differentiation on stiff supports, but was not required. HSC differentiate to myofibroblasts in vitro primarily as a function of the physical rather than the chemical properties of the substrate. HSC require a mechanically stiff substrate, with adhesion to matrix proteins and the generation of mechanical tension, to differentiate. These findings suggest that alterations in liver stiffness are a key factor driving the progression of fibrosis.

Hepatic stellate cells require a stiff environment for myofibroblastic differentiation.

Aging is characterized by extensive metabolic reprogramming. To identify metabolic pathways associated with aging, we analyzed age-dependent changes in the metabolomes of long-lived . Among the metabolites that changed, levels of tyrosine were increased with age in long-lived flies. We demonstrate that the levels of enzymes in the tyrosine degradation pathway increase with age in wild-type flies. Whole-body and neuronal-specific downregulation of enzymes in the tyrosine degradation pathway significantly extends  lifespan, causes alterations of metabolites associated with increased lifespan, and upregulates the levels of tyrosine-derived neuromediators. Moreover, feeding wild-type flies with tyrosine increased their lifespan. Mechanistically, we show that suppression of ETC complex I drives the upregulation of enzymes in the tyrosine degradation pathway, an effect that can be rescued by tigecycline, an FDA-approved drug that specifically suppresses mitochondrial translation. In addition, tyrosine supplementation partially rescued lifespan of flies with ETC complex I suppression. Altogether, our study highlights the tyrosine degradation pathway as a regulator of longevity.

ArticleTotal : 2	Year
Publication title Cited by 22	2012
Publication title Cited by 1	2023

Article	Year
Designer blood: creating hematopoietic lineages from embryonic stem cells. Blood\| PubMed ID: 16254136	2006
Hepatic stellate cells require a stiff environment for myofibroblastic differentiation. American journal of physiology. Gastrointestinal and liver physiology\| PubMed ID: 21527725	2011
Human vaccines\| PubMed ID: 22108033	2011
Gastroenterology\| PubMed ID: 22202457	2012
Downregulation of the tyrosine degradation pathway extends lifespan. eLife\| PubMed ID: 33319750	2020

Abby L. Olsen

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