Biology subjects

Pietila, R.

Publications and source records attributed to Pietila, R..

3 recordsLinked to original sources

bioRxiv2025

A comprehensive molecular atlas of the cell types in the mouse liver

The liver plays a crucial role in essential physiological processes, and its impaired function due to liver fibrosis from various causes is an increasingly significant health issue. The livers functionality relies on the precise arrangement of its cellular structures, yet the molecular architecture of these units remains only partially understood. We created a comprehensive molecular atlas detailing all the major cell types present in the adult mouse liver through deep single-cell RNA sequencing. Our analysis offers new insights into hepatic endothelial and mesenchymal cells, specifically highlighting the differences between the cells of the periportal microvasculature, the sinusoids, and the portal vein, the latter exhibiting a mixed arterio-venous phenotype. We identified distinct subpopulations of hepatic stellate cells, fibroblasts, and vascular mural cells located in different anatomical regions. Comparisons with transcriptomic data from disease models indicate that a previously unrecognized capsular population of hepatic stellate cells expands in response to fibrotic disease. Our findings reveal that various fibroblast subpopulations respond differently to pathological insults. This data resource will be invaluable for advancing therapeutic interventions targeting hepatic diseases.

cell biology↗

bioRxiv2020

Pericyte-specific vascular expression of SARS-CoV-2 receptor ACE2 - implications for microvascular inflammation and hypercoagulopathy in COVID-19 patients

Accumulating clinical observations implicate vascular inflammation as an underlying cause of coagulopathy in severely ill COVID-19 patients and it was recently suggested that SARS-CoV-2 virus particles infect endothelial cells. Here, we show that endothelial cells do not express angiotensin-converting enzyme-2 (ACE2), the SARS-CoV-2 receptor. Instead, pericytes and microvascular smooth muscle cells express ACE2 in an organotypic manner. Pericyte deficiency leads to increased endothelial expression and release of Von Willebrand factor and intravascular platelet and fibrin aggregation, suggesting that pericytes limit endothelial pro-thrombotic responses. That pericytes and not endothelial cells express ACE2 may provide important clues to the pathology of COVID-19, as pericytes are normally shielded behind an endothelial barrier and may get infected only when this barrier is compromised by COVID-19 risk factors.

pathology↗

bioRxiv2020

Paladin is a PI(4,5)P2 phosphoinositide phosphatase that regulates endosomal signaling and angiogenesis

Cell signaling governs cellular behavior and is therefore subject to tight spatiotemporal regulation. Signaling output is regulated by specialized cell membranes and vesicles which contain unique combinations of lipids and proteins. The phospholipid phosphatidylinositol 4,5-bisphosphate, (PI(4,5)P2), an important component of the plasma membrane as well as other subcellular membranes, is involved in multiple processes, including signaling. However, which enzymes drive the formation and degradation of non-plasma membrane PI(4,5)P2, and their impact on cell signaling and function at the organismal level are unknown. Here we show in a mouse model that Paladin is a vascular PI(4,5)P2 phosphatase that regulates endosomal signaling and angiogenesis. Paladin was localized to the endosomal and Golgi compartments, and interacted with vascular endothelial growth factor receptor 2 (VEGFR2) in vitro and in vivo. Loss of Paladin resulted in increased internalization of the receptor, over-activation of extracellular regulated kinase, and hypersprouting of endothelial cells in the developing retina of mice. These findings suggest that inhibition of Paladin, or other endosomal PI(4,5)P2 phosphatases, could be exploited to modulate VEGFR2 signaling and angiogenesis, when direct and full inhibition of the receptor is not desirable.

cell biology↗