Tracking Fenestrae Dynamics in Live Murine Liver Sinusoidal Endothelial Cells

Zapotoczny, Bartłomiej; Szafranska, Karolina; Kuś, Edyta; Braet, Filip; Wisse, Eddie; Chłopicki, Stefan; Szymoński, Marek

doi:10.1002/hep.30232

Cited by 53 publications

(67 citation statements)

References 39 publications

(100 reference statements)

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“…Our recent work demonstrated that even better insight into the dynamics of the fenestra structure could be achieved using multimodal AFM imaging. Dynamically tracking the detailed structure and dynamics of the fenestrae in vitro for the first time in living (ie, nonfixed) LSECs, enabled us to obtain time‐dependent high‐resolution images of the actin cytoskeleton that supports the fenestrae, confirming the previously reported fenestrae‐associated cytoskeletal structures . We showed that some FACRs are closed, that is, filled with lipid membrane, while others are open .…”

Section: Introductionsupporting

confidence: 84%

“…Dynamically tracking the detailed structure and dynamics of the fenestrae in vitro for the first time in living (ie, nonfixed) LSECs, enabled us to obtain time‐dependent high‐resolution images of the actin cytoskeleton that supports the fenestrae, confirming the previously reported fenestrae‐associated cytoskeletal structures . We showed that some FACRs are closed, that is, filled with lipid membrane, while others are open . Those findings underlay the need for the coexistence of some structural proteins, other than actin, for maintaining and switching the fenestrae in an open vs closed state.…”

Section: Introductionsupporting

confidence: 84%

“…Subsequently, 4D‐AFM tracking on a single sieve plate area of a live LSEC revealed that individual fenestrae changed from the open to closed state and vice versa in a time window as small as 1 second, without altering the FACR structure (Figure and Supplementary Animation 1). Note that “regular” LSEC dynamics (for untreated cells) invokes the fenestrae with a mean lifetime of 18 minutes (with many closing in a few minutes time) . In contrast, after IAA treatment the switching occurred in a time period of seconds—one to two orders of magnitude faster.…”

Section: Resultsmentioning

confidence: 99%

“…The proposed spectrin‐actin scaffold structure can also explain the speed of alterations in the fenestrae number at the peripheral parts of LSECs. Rapid changes are typically observed in the first hours of culture during cell spreading on a glass slide in contrast to relatively stable fenestra structures in the area close to cell‐cell interconnections . One can reasonably postulate that during LSECs spreading, the cells rearrange their actin cytoskeletal filaments causing continuous rapture of the spectrin‐actin connections across the cell membrane.…”

Section: Discussionmentioning

confidence: 99%

“…Fenestrae, nanometer‐size transmembrane pores gathered in groups to form sieve plates, are unique morphological features of LSECs and a hallmark of their normal physiological state . Each fenestra is supported by a fenestrae‐associated cytoskeletal ring (FACR), whose protein composition remains unknown . To date, many studies have focused on the structural composition of the fenestrae.…”

Section: Introductionmentioning

confidence: 99%

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Actin‐spectrin scaffold supports open fenestrae in liver sinusoidal endothelial cells

Zapotoczny

Braet

Kuś

et al. 2019

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Fenestrae are open transmembrane pores that are a structural hallmark of healthy liver sinusoidal endothelial cells (LSECs). Their key role is the transport of solutes and macromolecular complexes between the sinusoidal lumen and the space of Disse. To date, the biochemical nature of the cytoskeleton elements that surround the fenestrae and sieve plates in LSECs remain largely elusive. Herein, we took advantage of the latest developments in atomic force imaging and super‐resolution fluorescence nanoscopy to define the organization of the supramolecular complex(es) that surround the fenestrae. Our data revealed that spectrin, together with actin, lines the inner cell membrane and provided direct structural support to the membrane‐bound pores. We conclusively demonstrated that diamide and iodoacetic acid (IAA) affect fenestrae number by destabilizing the LSEC actin‐spectrin scaffold. Furthermore, IAA induces rapid and repeatable switching between the open vs closed state of the fenestrae, indicating that the spectrin‐actin complex could play an important role in controlling the pore number. Our results suggest that spectrin functions as a key regulator in the structural preservation of the fenestrae, and as such, it might serve as a molecular target for altering transendothelial permeability.

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Section: Introductionsupporting

confidence: 84%

Section: Introductionsupporting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Actin‐spectrin scaffold supports open fenestrae in liver sinusoidal endothelial cells

Zapotoczny

Braet

Kuś

et al. 2019

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Alcohol‐associated capillarization of sinusoids: A critique since the discovery by Schaffner and Popper in 1963

Mak

Kee

Shin

2021

The Anatomical Record

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This article reviews the literature on capillarization of hepatic sinusoids since its discovery in 1963. Liver sinusoidal endothelial cells are uniquely fenestrated and lack an underlying basement membrane. In chronic liver disease, the sinusoids capillarize and transform into systemic capillaries, a process termed capillarization of sinusoids. The histopathology is marked by defenestration, basement membrane formation, and space of Disse fibrogenesis. Capillarized sinusoids compromise the bidirectional exchange of materials between sinusoids and hepatocytes, leading to hepatocellular dysfunction. Sinusoidal capillarization was first described in active cirrhosis of alcoholics in 1963. Since then, it has been found in early and progressive stages of alcoholic hepatic fibrosis before the onset of cirrhosis. The sinusoidal structure is not altered in alcoholic steatosis without fibrosis. Defenestration impairs the ability of the endothelium to filter chylomicron remnants from sinusoids into the Disse's space, contributing to alcohol‐induced postprandial hyperlipidemia and possibly atherosclerosis. Ethanol also modulates the fenestration dynamics in animals. In baboons, chronic alcohol consumption diminishes endothelial porosity in concomitance with hepatic fibrogenesis and in rats defenestrates the endothelium in the absence of fibrosis, and sometimes capillarizes the sinusoids. Acute ethanol ingestion enlarges fenestrations in rats and contracts fenestrations in rabbits. In sinusoidal endothelial cell culture, ethanol elicits fenestration dilation, which is likely related to its interaction with fenestration‐associated cytoskeleton. Ethanol potentiates sinusoidal injury caused by cocaine, acetaminophen or lipopolysaccharide in mice and rats. Understanding ethanol's mechanisms on pathogenesis of sinusoidal capillarization and fenestration dynamics will lead to development of methods to prevent risks for atherosclerosis in alcoholism.

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Actin Depolymerization in Dedifferentiated Liver Sinusoidal Endothelial Cells Promotes Fenestrae Re‐Formation

et al. 2018

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Liver sinusoidal endothelial cells (LSECs) possess fenestrae, which are key for the exchange between blood and hepatocytes. Alterations in their number or diameter have important implications for hepatic function in liver diseases. They are lost early in the development of hepatic fibrosis through a process called capillarization. In this study, we aimed to demonstrate whether in vitro dedifferentiated LSECs that have lost fenestrae are able to re‐form these structures. Using stimulated emission depletion super‐resolution microscopy in combination with transmission electron microscopy, we analyzed fenestrae formation in a model mimicking the capillarization process in vitro. Actin is known to be involved in fenestrae regulation in differentiated LSECs. Using cytochalasin D, an actin‐depolymerizing agent, we demonstrated that dedifferentiated LSECs remain capable of forming fenestrae. Conclusion: We provide a new insight into the complex role of actin in fenestrae formation and in the control of their size and show that LSEC fenestrae re‐formation is possible, suggesting that this process could be used during fibrosis regression to try to restore exchanges and hepatocyte functions.

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Tracking Fenestrae Dynamics in Live Murine Liver Sinusoidal Endothelial Cells

Cited by 53 publications

References 39 publications

Actin‐spectrin scaffold supports open fenestrae in liver sinusoidal endothelial cells

Actin‐spectrin scaffold supports open fenestrae in liver sinusoidal endothelial cells

Alcohol‐associated capillarization of sinusoids: A critique since the discovery by Schaffner and Popper in 1963

Actin Depolymerization in Dedifferentiated Liver Sinusoidal Endothelial Cells Promotes Fenestrae Re‐Formation

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