Unique Cell Type-Specific Junctional Complexes in Vascular Endothelium of Human and Rat Liver Sinusoids

Liver sinusoidal endothelium is strategically positioned to control access of fluids, macromolecules and cells to the liver parenchyma and to serve clearance functions upstream of the hepatocytes. While clearance of macromolecular debris from the peripheral blood is performed by liver sinusoidal endothelial cells (LSECs) using a delicate endocytic receptor system featuring stabilin-1 and -2, the mannose receptor and CD32b, vascular permeability and cell trafficking are controlled by transcellular pores, i.e. the fenestrae, and by intercellular junctional complexes. In contrast to blood vascular and lymphatic endothelial cells in other organs, the junctional complexes of LSECs have not yet been consistently characterized in molecular terms. In a comprehensive analysis, we here show that LSECs express the typical proteins found in endothelial adherens junctions (AJ), i.e. VE-cadherin as well as α-, β-, p120-catenin and plakoglobin. Tight junction (TJ) transmembrane proteins typical of endothelial cells, i.e. claudin-5 and occludin, were not expressed by rat LSECs while heterogenous immunreactivity for claudin-5 was detected in human LSECs. In contrast, junctional molecules preferentially associating with TJ such as JAM-A, B and C and zonula occludens proteins ZO-1 and ZO-2 were readily detected in LSECs. Remarkably, among the JAMs JAM-C was considerably over-expressed in LSECs as compared to lung microvascular endothelial cells. In conclusion, we show here that LSECs form a special kind of mixed-type intercellular junctions characterized by co-occurrence of endothelial AJ proteins, and of ZO-1 and -2, and JAMs. The distinct molecular architecture of the intercellular junctional complexes of LSECs corroborates previous ultrastructural findings and provides the molecular basis for further analyses of the endothelial barrier function of liver sinusoids under pathologic conditions ranging from hepatic inflammation to formation of liver metastasis

Spontaneous regression of primary cutaneous diffuse large B‐cell lymphoma, leg type: A case series and review of the literature

Abstract Primary cutaneous diffuse large B‐cell lymphoma, leg type (PCDLBCL, LT) is a subtype of cutaneous B‐cell lymphoma with unfavorable prognosis usually requiring aggressive polychemotherapy for disease control. Only single cases of spontaneous regression of PCDLBCL, LT are reported in the literature, peaking 3 months post‐biopsy following a clinical history of no longer than 1 year. Here, we report the first case of a spontaneously relapsing and remitting PCDLBCL, LT with complete regression after a clinical history of more than 9 years and thus an atypically indolent clinical course. The female patient presented with recurrent erythematous, non‐ulcerated, non‐raised plaques of the right lower leg for 6 years. Pathological workup and exclusion of a systemic disease confirmed the diagnosis of PCDLBCL, LT. Due to the history of repeated spontaneous remission, no therapy was initiated. Nine years after first occurrence the patient presented with complete clinical remission lasting for 64 months. We retrospectively identified four additional PCDLBCL, LT patients with spontaneous remission lasting up to 53 months. Our data provide evidence for a distinct PCDLBCL, LT patient subgroup that clinicians should be aware of and warrants a watch‐and‐wait treatment regime

α-Catenin and β-Catenin co-localize with VE-cadherin in human LSECs.

<p>Immunofluorescent co-staining of human liver cryosections with anti-VE-cadherin (A, B, green), anti-α-Catenin (A, red), and anti-β-catenin (B, red) antibodies. Images were acquired using laser scanning confocal microscopy. Bars 11.9 µm.</p

Expression of JAM-family members in liver sinusoidal endothelial cells.

<p>(A) Immunofluorescent co-staining of rat liver cryosections with anti-JAM-A (green), anti-VE-cadherin (red), and anti-Stabilin-2 (blue) antibodies. (B) Immunofluorescent co-staining of human liver cryosections with anti-JAM-A (green), anti-CD32b (red), and anti-Stabilin-2 (blue) antibodies. Images were acquired using laser scanning confocal microscopy. Bars 11.9 µm. (C) Quantitative reverse transcriptase-PCR with mRNA isolated from rat LSECs and rat LMECs (n indicates the number of samples analyzed, error bars represent SEM). Primers specific for JAM-A, JAM-B, JAM-C, and β-Actin as normalizer were used.</p

Primers used in the study.

<p>Primers used in the study.</p

VE-cadherin is expressed in liver sinusoidal endothelial cells in rats and humans.

<p>(A) Immunofluorescent co-staining of human liver cryosections with anti-VE-cadherin (green) and anti-CD32b (red) antibodies. (B) Immunofluorescent co-staining of rat liver cryosections with anti-VE-cadherin (green) and anti-LYVE-1 (red) antibodies. (C) Immunofluorescent co-staining of isolated rat LSECs with anti-VE-cadherin (green) and anti-Stabilin-2 (red) antibodies. Toto3 (blue) was used to counterstain the cell nuclei. Images were acquired using laser scanning confocal microscopy. Bars 11.9 µm (A, B), 14.14 µm (C). (D) Reverse transcriptase-PCR with mRNA isolated from rat hepatoma McA-RH7777 cell line (1), freshly isolated rat LMECs (2), and freshly isolated rat LSECs (3). Primers specific for VE-cadherin or β-actin were used.</p