Biology subjects

Boon, R.

Publications and source records attributed to Boon, R..

5 recordsLinked to original sources

bioRxiv2023

Osmolar modulation drives reversible cell cycle exit and human pluripotent cell differentiation via NF-κB and WNT signaling

Terminally differentiated cells are regarded as the most stable and common cell state in adult organisms as they reside in growth arrest and carry out their cellular function. Improving our understanding of the mechanisms involved in promoting cell cycle exit would facilitate our ability to manipulate pluripotent cells into mature tissues for both pharmacological and therapeutic use. Here, we demonstrated that a hyperosmolar environment enforced a protective p53-independent quiescent state in dedifferentiated hepatoma cells and pluripotent stem cells (PSCs)-derived models of human hepatocytes and endothelial cells, representing the endodermal and mesodermal lineages. Prolonged culture in hyperosmolar conditions stimulated transcriptional and functional cell maturation. Interestingly, hyperosmolar conditions did not only trigger cell cycle exit and cellular maturation but were also necessary to maintain this maturated state, as switching back to plasma osmolarity caused the loss of maturation markers and the gain of proliferative markers. Transcriptome analysis revealed activation of NF-{kappa}[V] and repression of WNT signaling as the two main pathways downstream of osmolarity-regulated growth arrest and cell maturation, respectively. This study revealed that increased osmolarity serves as a biochemical signal to promote long-term growth arrest, transcriptional changes, and maturation into different lineages, serving as a practical method to generate differentiated hiPSCs that resemble their mature counterpart more closely.

developmental biology↗

bioRxiv2022

The circular RNA Ataxia-telangiectasia mutated (cATM) regulates oxidative stress in smooth muscle cells in expanding abdominal aortic aneurysms

An abdominal aortic aneurysm (AAA) is a pathological widening of the aortic wall characterized by loss of smooth muscle cells (SMCs), extracellular matrix degradation, and local inflammation. This condition is often asymptomatic until rupture occurs, leading to high morbidity and mortality rates. Diagnosis is often accidental, and for now, the only available treatment option remains surgical intervention. Circular RNAs (circRNAs) are RNA loops that originated from backsplicing, which have received increasing attention as a novel class of functional non-coding RNAs contributing to cardiovascular physiology and disease. Their high structural stability, combined with a remarkable enrichment in body fluids, make circRNAs promising disease biomarkers. We aimed to investigate the contribution of circRNAs to AAA pathogenesis and their potential application as biomarkers for AAA diagnosis. Combined circRNA array and quantitative real-time PCR analysis revealed the presence of differentially expressed circular transcripts stemming from AAA-relevant gene loci. Among these, the circRNA to the Ataxia-telangiectasia mutated gene (cATM) was upregulated in human AAA tissue specimens, in AAA patient-derived SMCs, and serum samples collected from aneurysm patients. In control primary aortic SMCs, cATM increased upon angiotensin II stimulation, while its silencing triggered apoptosis. Furthermore, doxorubicin could induce cATM expression, supporting a link with acute stress response in SMCs. Constitutively higher cATM expressing AAA patient-derived SMCs were less vulnerable to oxidative stress-induced cell death and survival pathways enriched when compared to control SMCs. Taken together, this data supports the role of cATM in adapting SMCs to oxidative stress in the vascular AAA micromilieu. This molecular signature provides an additional parameter to be included in procedures for AAA screening in combination with already established practices.

molecular biology↗

bioRxiv2022

The glutathione S-transferase Gstt1 is a robust driver of survival and dissemination in metastases

Identifying adaptive mechanisms of metastatic cancer cells remains an elusive question in the treatment of metastatic disease, particularly in pancreatic cancer (PDA), where the majority of patients present with metastatic lesions at the time of diagnosis. A loss-of-function shRNA targeted screen in metastatic-derived cells identified Gstt1, a member of the glutathione S-transferase superfamily, as uniquely required for metastasis and dissemination however dispensable for primary tumor growth. Gstt1 is expressed in early disseminated tumor cells (DTCs), is retained within a subpopulation of slow-cycling cells within established metastases and its inhibition led to a regression of macrometastatic lesions. This distinct Gstt1high population is highly metastatic and retains slow-cycling phenotypes, EMT features, and DTC characteristics compared to the Gstt1low population. Mechanistic studies indicate that in this subset of cells, Gstt1 maintains metastases by binding to and modifying intracellular fibronectin, regulating Fibronectin secretion from cancer cells and deposition into the metastatic microenvironment. We identified Gstt1 as a novel mediator of metastasis, highlighting the importance of metastatic heterogeneity and its influence on the metastatic tumor microenvironment.

cancer biology↗

bioRxiv2020

A fully defined pluripotent stem cell derived multi-liver-cell model for steatohepatitis and fibrosis

Chronic liver injury, as observed in non-alcoholic steatohepatitis (NASH), progressive fibrosis, and cirrhosis, remains poorly treatable. Steatohepatitis causes hepatocyte loss in part by a direct lipotoxic insult, which is amplified by derangements in the non-parenchymal cellular (NPC) interactive network wherein hepatocytes reside, including, hepatic stellate cells, liver sinusoidal endothelial cells and liver macrophages. To create an in vitro culture model encompassing all these cells that allows studying liver steatosis, inflammation and fibrosis caused by NASH, we here developed a fully defined hydrogel microenvironment, termed hepatocyte maturation (HepMat) gel, that supports maturation and maintenance of pluripotent stem cell (PSC)-derived hepatocyte- and NPC-like cells for at least one month. The HepMat-based co-culture system modeled key molecular and functional features of TGF{beta}-induced liver fibrosis and fatty-acid induced inflammation and fibrosis better than monocultures its constituent cell populations. The novel co-culture system should open new avenues for studying mechanisms underlying liver steatosis, inflammation and fibrosis as well as for assessing drugs counteracting these effects.

bioengineering↗

bioRxiv2020

PU.1 drives specification of pluripotent stem cell-derived endothelial cells to LSEC-like cells

To date there is no representative in vitro model for liver sinusoidal endothelial cells (LSECs), as primary LSECs dedifferentiate very fast in culture and no combination of cytokines or growth factors can induce an LSEC fate in (pluripotent stem cell-derived) endothelial cells (ECs). Furthermore, the transcriptional programs driving an LSEC fate have not yet been described. Here, we first present a computational workflow (CenTFinder) that can identify transcription factors (TFs) that are crucial for modulating pathways involved in cell lineage specification. Using CenTFinder, we identified several novel LSEC-specific protein markers such as FCN2 and FCN3, which were validated by analysis of previously published single-cell RNAseq data. We also identified PU.1 (encoded by the SPI1 gene) as a major regulator of LSEC-specific immune functions. We show that SPI1 overexpression (combined with the general EC transcription factor ETV2) in human pluripotent stem cells (PSCs) induces ECs with an LSEC-like phenotype. The ETV2-SPI1-ECs display increased expression of LSEC markers such as CD32B and MRC1 as well as several of the proposed novel markers. More importantly, ETV2-SPI1-ECs acquire LSEC functions, including uptake of FSA-FITC as well as labelled IgG. In conclusion, we present the CenTFinder computational tool to identify key regulatory TFs within specific pathways, in this work pathways of lineage specification, and we demonstrate its use by the identification and validation of PU.1 as a master regulator for LSEC fating.

developmental biology↗