Angiosarcomas express mixed endothelial phenotypes of blood and lymphatic capillaries: podoplanin as a specific marker for lymphatic endothelium

Genetic and Molecular Determinants of Lymphatic Malformations: Potential Targets for Therapy

Lymphatic malformations are fluid-filled congenital defects of lymphatic channels occurring in 1 in 6000 to 16,000 patients. There are various types, and they often exist in conjunction with other congenital anomalies and vascular malformations. Great strides have been made in understanding these malformations in recent years. This review summarize known molecular and embryological precursors for lymphangiogenesis. Gene mutations and dysregulations implicated in pathogenesis of lymphatic malformations are discussed. Finally, we touch on current and developing therapies with special attention on targeted biotherapeutics.

Analyzing Lymphatic Vessel Patterning in Adult Tissue

Whole-mount immunostaining allows intact tissue to be surveyed in three dimensions, avoiding the more restricted fields of view provided by visualizing thin sections. This technique is particularly useful for imaging lymphatic and blood networks by high-resolution confocal microscopy, revealing how such vessels are spatially positioned, the subcellular arrangements of individual antigens, and interactions with individual cells within the interstitium or vessel lumen. The purpose of this chapter is to provide a practical guide for obtaining images of lymphatic vessels following immunofluorescence staining, primarily in mouse skin.

Spontaneous hemangiosarcoma in the spleen and liver of a young rat

Spontaneous hemangiosarcoma in young rats is rare. In this report, we describe a case of a spontaneous hemangiosarcoma in the spleen and liver of young rats. At necropsy, multiple pale red masses were observed in the spleen. Histopathologically, solid growth and haphazardly arranged neoplastic cells were observed, although no characteristic growth pattern was observed. In contrast, irregularly sized small slit-shaped spaces containing erythrocytes were found among the neoplastic cells. Reticular fibers incompletely surrounding the neoplastic cells were observed by silver staining. Immunohistochemistry revealed that the neoplastic cells were positive for vWF and CD34. Electron microscopic examination revealed that the neoplastic cells had erythrocytes in the lumen and Weibel-Palade bodies in the cytoplasm and were arranged along a discontinuous basal lamina. These features indicate that the tumor originated from vascular endothelial cells. Based on these results, the tumor was diagnosed as a hemangiosarcoma in the spleen and liver.

Lymphatic Endothelial Markers and Tumor Lymphangiogenesis Assessment in Human Breast Cancer

Metastasis via lymphatic vessels or blood vessels is the leading cause of death for breast cancer, and lymphangiogenesis and angiogenesis are critical prerequisites for the tumor invasion–metastasis cascade. The research progress for tumor lymphangiogenesis has tended to lag behind that for angiogenesis due to the lack of specific markers. With the discovery of lymphatic endothelial cell (LEC) markers, growing evidence demonstrates that the LEC plays an active role in lymphatic formation and remodeling, tumor cell growth, invasion and intravasation, tumor–microenvironment remodeling, and antitumor immunity. However, some studies have drawn controversial conclusions due to the variation in the LEC markers and lymphangiogenesis assessments used. In this study, we review recent findings on tumor lymphangiogenesis, the most commonly used LEC markers, and parameters for lymphangiogenesis assessments, such as the lymphatic vessel density and lymphatic vessel invasion in human breast cancer. An in-depth understanding of tumor lymphangiogenesis and LEC markers can help to illustrate the mechanisms and distinct roles of lymphangiogenesis in breast cancer progression, which will help in exploring novel potential predictive biomarkers and therapeutic targets for breast cancer.

Nicotine-mediated OTUD3 downregulation inhibits VEGF-C mRNA decay to promote lymphatic metastasis of human esophageal cancer

Nicotine addiction and the occurrence of lymph node spread are two major significant factors associated with esophageal cancer's poor prognosis; however, nicotine's role in inducing lymphatic metastasis of esophageal cancer remains unclear. Here we show that OTU domain-containing protein 3 (OTUD3) is downregulated by nicotine and correlates with poor prognosis in heavy-smoking esophageal cancer patients. OTUD3 directly interacts with ZFP36 ring finger protein (ZFP36) and stabilizes it by inhibiting FBXW7-mediated K48-linked polyubiquitination. ZFP36 binds with the VEGF-C 3-'UTR and recruits the RNA degrading complex to induce its rapid mRNA decay. Downregulation of OTUD3 and ZFP36 is essential for nicotine-induced VEGF-C production and lymphatic metastasis in esophageal cancer. This study establishes that the OTUD3/ZFP36/VEGF-C axis plays a vital role in nicotine addiction-induced lymphatic metastasis, suggesting that OTUD3 may serve as a prognostic marker, and induction of the VEGF-C mRNA decay might be a potential therapeutic strategy against human esophageal cancer.

Expression of podoplanin in various types of feline tumor tissues

Podoplanin is expressed in various human tumors where it promotes tumor progression, epithelial-mesenchymal transition, and distant metastasis. Podoplanin is also expressed in cancer-associated fibroblasts and induces tumor malignancy. The objective of this study was to evaluate podoplanin expression in various types of feline tumor tissues. Immunohistochemical analysis revealed that podoplanin was expressed in cells of 13/15 (87%) squamous cell carcinomas and 5/19 (26%) fibrosarcomas. Moreover, cancer-associated fibroblasts expressed podoplanin in most tumor types, including 18/21 (86%) mammary adenocarcinoma tissues. Our findings demonstrate that various types of feline tumor tissues expressed podoplanin, indicating the importance of the comparative aspects of podoplanin expression, which may be used as a novel research model for podoplanin biology.

New nomograms to predict overall and cancer-specific survival of angiosarcoma

Objective

This study was designed to establish and validate promising and reliable nomograms for predicting the survival of angiosarcoma (AS) patients.

Methods

The Surveillance, Epidemiology, and End Results database was queried to collect the clinical information of 785 AS patients between 2004 and 2015. Data were split into a training cohort (n = 549) and a validation cohort (n = 236) without any preference. Univariate Cox and multivariate Cox regression analyses were performed to analyze the clinical parameters. Independent prognostic factors were then identified. Two nomograms were constructed to predict overall survival (OS) and cancer‐specific survival (CSS) at 3 and 5 years. Finally, the models were evaluated using concordance indices (C‐indices), calibration plots, and decision curve analysis (DCA).

Results

Based on the inclusion and exclusion criteria, 785 individuals were included in this analysis. Univariate and multivariate Cox regression analyses revealed that age, tumor size, and stage were prognostic factors independently associated with the OS of AS. Tumor site, tumor size, and stage were associated with the CSS of AS. Based on the statistical results and clinical significance of variables, nomograms were built. The nomograms for OS and CSS had C‐indices of 0.666 and 0.654, respectively. The calibration curves showed good agreement between the predictive values and the actual values. DCA also indicated that the nomograms were clinically useful.

Conclusion

We established nomograms with good predictive ability that could provide clinicians with better predictions about the clinical outcomes of AS patients.

Podoplanin Drives Motility of Active Macrophage via Regulating Filamin C During Helicobacter pylori Infection

Podoplanin (Pdpn) is a mucin-type transmembrane protein that has been implicated in multiple physiological settings including lymphangiogenesis, platelet aggregation, and cancer metastasis. Here, we reported an absence of Pdpn transcript expression in the resting mouse monocytic macrophages, RAW264.7 cells; intriguingly, a substantial upregulation of Pdpn was observed in activated macrophages following Helicobacter pylori or lipopolysaccharide stimulation. Pdpn-knockout macrophages demonstrated intact phagocytic and intracellular bactericidal activities comparable to wild type but exhibited impaired migration due to attenuated filopodia formation. In contrast, an ectopic expression of Pdpn augmented filopodia protrusion in activated macrophages. NanoString analysis uncovered a close dependency of Filamin C gene on the presence of Pdpn, highlighting an involvement of Filamin C in modulation of actin polymerization activity, which controls cell filopodia formation and migration. In addition, interleukin-1β production was significantly declined in the absence of Pdpn, suggesting a role of Pdpn in orchestrating inflammation during H. pylori infection besides cellular migration. Together, our findings unravel the Pdpn network that modulates movement of active macrophages.

Sialoglycans on lymphatic endothelial cells augment interactions with Siglec-1 (CD169) of lymph node macrophages

Cellular interactions between endothelial cells and macrophages regulate macrophage localization and phenotype, but the mechanisms underlying these interactions are poorly understood. Here we explored the role of sialoglycans on lymphatic endothelial cells (LEC) in interactions with macrophage-expressed Siglec-1 (CD169). Lectin-binding assays and mass spectrometric analyses revealed that LEC from human skin express more sialylated glycans than the corresponding blood endothelial cells. Higher amounts of sialylated and/or sulfated glycans on LEC than BEC were consistently observed in murine skin, lung and lymph nodes. The floor LEC of the subcapsular sinus (SCS) in murine lymph nodes (LN) displayed sialylated glycans at particularly high densities. The sialoglycans of LN LEC were strongly bound by Siglec-1. Such binding plays an important role in the localization of Siglec-1⁺ LN-SCS macrophages, as their numbers are strongly reduced in mice expressing a Siglec-1 mutant that is defective in sialoglycan binding. The residual Siglec-1⁺ macrophages are less proliferative and have a more anti-inflammatory phenotype. We propose that the densely clustered, sialylated glycans on the SCS floor LEC are a key component of the macrophage niche, providing anchorage for the Siglec-1⁺ LN-SCS macrophages.

Neoadjuvant radiation for cutaneous and soft tissue angiosarcoma

BACKGROUND AND OBJECTIVES

Neoadjuvant radiation (NRT) is frequently utilized in soft tissue sarcomas to increase local control. Its utility in cutaneous and soft tissue angiosarcoma remains poorly defined.

METHODS

This retrospective cohort study was performed using the National Cancer Database (2004-2016) evaluating patients with clinically localized, surgically resected angiosarcomas. Factors associated with receipt of NRT in the overall cohort and margin positivity in treatment naïve patients were identified by univariate and multivariable logistic regression analyses. Survival was assessed using Kaplan-Meier analysis.

RESULTS

Of 597 patients, 27 (4.5%) received NRT. Increasing age (odds ratio [OR] 0.95, p = 0.025), tumor size more than or equal to 5 cm (OR 3.16, p = 0.02), and extremity tumor location (OR 3.99, p = 0.04) were associated with receipt of NRT. All patients who received NRT achieved an R0 resection (p = 0.03) compared with 17.9% of patients without NRT. Factors associated with risk of margin positivity included tumor size more than or equal to 5 cm (OR 1.85, p = 0.01), and head/neck location (OR 2.24, p = 0.006). NRT was not significantly associated with improved survival (p = 0.21).

CONCLUSIONS

NRT improves rates of R0 resection but is infrequently utilized in cutaneous and soft tissue angiosarcoma. Increased usage of NRT, particularly for patients with lesions more than or equal to 5 cm, or head and neck location, may help achieve complete resections.

Primary lymphoedema

Lymphoedema is the swelling of one or several parts of the body owing to lymph accumulation in the extracellular space. It is often chronic, worsens if untreated, predisposes to infections and causes an important reduction in quality of life. Primary lymphoedema (PLE) is thought to result from abnormal development and/or functioning of the lymphatic system, can present in isolation or as part of a syndrome, and can be present at birth or develop later in life. Mutations in numerous genes involved in the initial formation of lymphatic vessels (including valves) as well as in the growth and expansion of the lymphatic system and associated pathways have been identified in syndromic and non-syndromic forms of PLE. Thus, the current hypothesis is that most cases of PLE have a genetic origin, although a causative mutation is identified in only about one-third of affected individuals. Diagnosis relies on clinical presentation, imaging of the structure and functionality of the lymphatics, and in genetic analyses. Management aims at reducing or preventing swelling by compression therapy (with manual drainage, exercise and compressive garments) and, in carefully selected cases, by various surgical techniques. Individuals with PLE often have a reduced quality of life owing to the psychosocial and lifelong management burden associated with their chronic condition. Improved understanding of the underlying genetic origins of PLE will translate into more accurate diagnosis and prognosis and personalized treatment.

Aqueous outflow channels and its lymphatic association: A review

The human eye has a unique immune architecture and behavior. While the conjunctiva is known to have a well-defined lymphatic drainage system, the cornea, sclera, and uveal tissues were historically considered "alymphatic" and thought to be immune privileged. The very fact that the aqueous outflow channels carry a clear fluid (aqueous humor) along the outflow pathway makes it hard to ignore its lymphatic-like characteristics. The development of novel lymphatic lineage markers and expression of these markers in aqueous outflow channels and improved imaging capabilities has sparked a renewed interest in the study of ocular lymphatics. Ophthalmic lymphatic research has had a directional shift over the last decade, offering an exciting new physiological platform that needs further in-depth understanding. The evidence of a presence of distinct lymphatic channels in the human ciliary body is gaining significant traction. The uveolymphatic pathway is an alternative new route for aqueous outflow and adds a new dimension to pathophysiology and management of glaucoma. Developing novel animal models, markers, and non-invasive imaging tools to delineate the core anatomical structure and physiological functions may help pave some crucial pathways to understand disease pathophysiology and help develop novel targeted therapeutic approaches for glaucoma.

Retinal VEGF-A Overexpression Is Not Sufficient to Induce Lymphangiogenesis Regardless of VEGF-C Upregulation and Lyve1+ Macrophage Infiltration

Purpose

No lymphatic vessels have been identified in the retina. This study investigated whether pathological VEGF-A-overexpressing diabetic retina causes lymphangiogenesis.

Methods

Three genetic mouse models of diabetic retinopathy (DR) (Akita [Ins2+/-], Kimba [vegfa+/+], and Akimba [Akita × Kimba] mice) were used. Retinas were examined by fundus photography, fluorescence angiography (FA), and immunostaining to detect lymphangiogenesis or angiogenesis. Lyve1-GFP (Lyve1EGFP/Cre) mice were used to examine Lyve1-expressing cells by immunostaining. Lymphatic-related factors were investigated in mouse retina and vitreous fluid from proliferative diabetic retinopathy (PDR) patients by RT-PCR and ELISA, respectively. Aged Kimba and Akimba mice were used to examine the retinal phenotype at the late phase of VEGF overexpression.

Results

FA and immunostaining showed retinal neovascularization in Kimba and Akimba mice but not wild-type and Akita mice. Immunohistochemistry showed that lymphangiogenesis was not present in the retinas of Akita, Kimba, or Akimba mice despite the significant upregulation of lymphatic-related factors (Lyve1, podoplanin, VEGF-A, VEGF-C, VEGF-D, VEGFR2, and VEGFR3) in the retinas of Kimba and Akimba mice by RT-PCR (P < 0.005). Furthermore, lymphangiogenesis was not present in aged Kimba or Akimba mice. Significantly increased numbers of Lyve1-positive cells present in the retinas of Kimba and Akimba mice, especially in the peripheral areas, were CD11b positive, indicating a macrophage population (P < 0.005). VEGF-C in PDR vitreous with vitreous hemorrhage (VH) was higher than in PDR without VH or a macular hole.

Conclusions

Retinal VEGF-A overexpression did not cause typical lymphangiogenesis despite upregulated lymphatic-related factors and significant Lyve1-positive macrophage infiltration.

Development and physiological functions of the lymphatic system: insights from human genetic studies of primary lymphedema

Primary lymphedema is a long-term (chronic) condition characterized by tissue lymph retention and swelling that can affect any part of the body, although it usually develops in the arms or legs. Due to the relevant contribution of the lymphatic system to human physiology, while this review mainly focuses on the clinical and physiological aspects related to the regulation of fluid homeostasis and edema, clinicians need to know that the impact of lymphatic dysfunction with a genetic origin can be wide ranging. Lymphatic dysfunction can affect immune function so leading to infection; it can influence cancer development and spread, and it can determine fat transport so impacting on nutrition and obesity. Genetic studies and the development of imaging techniques for the assessment of lymphatic function have enabled the recognition of primary lymphedema as a heterogenic condition in terms of genetic causes and disease mechanisms. In this review, the known biological functions of several genes crucial to the development and function of the lymphatic system are used as a basis for understanding normal lymphatic biology. The disease conditions originating from mutations in these genes are discussed together with a detailed clinical description of the phenotype and the up-to-date knowledge in terms of disease mechanisms acquired from in vitro and in vivo research models.

CD147 Promotes Tumor Lymphangiogenesis in Melanoma via PROX-1

Simple Summary

Melanoma is one of the most aggressive skin cancers, characterized by metastasis to the lymph nodes and a high capacity to develop drug resistance. There is a lack of knowledge on the mechanisms contributing to lymphatic vessel formation and metastasis regulation in malignant melanoma. We previously reported the involvement of CD147, a transmembrane glycoprotein overexpressed in melanoma, in the regulation of the tumor microenvironment and angiogenesis. The aim of our study was to further determine how CD147 is involved in lymphangiogenesis regulation. Our results revealed that high CD147 expression is correlated with the number of lymphatic vessels in the human melanoma lymph nodes and that paracrine CD147 upregulates lymphangiogenesis through lymphangiogenic mediators in vitro and in vivo, suggesting that CD147 could be a promising target for melanoma-associated lymphangiogenesis inhibition.

Abstract

Malignant melanoma is one of the most aggressive skin cancers and is characterized by early lymph node metastasis and the capacity to develop resistance to therapies. Hence, understanding the regulation of lymphangiogenesis through mechanisms contributing to lymphatic vessel formation represents a treatment strategy for metastatic cancer. We have previously shown that CD147, a transmembrane glycoprotein overexpressed in melanoma, regulates the angiogenic process in endothelial cells. In this study, we show a correlation between high CD147 expression levels and the number of lymphatic vessels expressing LYVE-1, Podoplanin, and VEGFR-3 in human melanoma lymph nodes. CD147 upregulates in vitro lymphangiogenesis and its related mediators through the PROX-1 transcription factor. In vivo studies in a melanoma model confirmed that CD147 is involved in metastasis through a similar mechanism as in vitro. This study, demonstrating the paracrine role of CD147 in the lymphangiogenesis process, suggests that CD147 could be a promising target for the inhibition of melanoma-associated lymphangiogenesis.

The lymphatic vasculature: An active and dynamic player in cancer progression

The lymphatic vasculature has been widely described and explored for its key functions in fluid homeostasis and in the organization and modulation of the immune response. Besides transporting immune cells, lymphatic vessels play relevant roles in tumor growth and tumor cell dissemination. Cancer cells that have invaded into afferent lymphatics are propagated to tumor‐draining lymph nodes (LNs), which represent an important hub for metastatic cell arrest and growth, immune modulation, and secondary dissemination to distant sites. In recent years many studies have reported new mechanisms by which the lymphatic vasculature affects cancer progression, ranging from induction of lymphangiogenesis to metastatic niche preconditioning or immune modulation. In this review, we provide an up‐to‐date description of lymphatic organization and function in peripheral tissues and in LNs and the changes induced to this system by tumor growth and progression. We will specifically focus on the reported interactions that occur between tumor cells and lymphatic endothelial cells (LECs), as well as on interactions between immune cells and LECs, both in the tumor microenvironment and in tumor‐draining LNs. Moreover, the most recent prognostic and therapeutic implications of lymphatics in cancer will be reported and discussed in light of the new immune‐modulatory roles that have been ascribed to LECs.

Isolation and Culture of Mouse Lymphatic Endothelial Cells from Lung Tissue

There is increasing interest in the study of the mammalian lymphatic system, including the lymphatic endothelial cells (LECs) that make up lymphatic vessels. The ability to isolate primary LECs from tissue of normal and genetically modified mice permits detailed analysis of this unique cell type. Here, we describe a robust protocol for the isolation and in vitro expansion of LECs from mouse lung by antibody-based magnetic separation.

Development of Core-Fucose-Deficient Humanized and Chimeric Anti-Human Podoplanin Antibodies

Podoplanin (PDPN), a 36-kDa type I transmembrane O-glycoprotein, is expressed in normal cells, including renal epithelial cells (podocytes), lymphatic endothelial cells, and pulmonary type I alveolar cells, and in cancer cells, including brain tumors and squamous cell lung carcinomas. PDPN activates platelet aggregation by binding to C-type lectin-like receptor-2 (CLEC-2) on platelets, and PDPN/CLEC-2 interaction facilitates blood/lymphatic vessel separation. We previously produced an anti-human PDPN monoclonal antibody (mAb), clone NZ-1 (rat IgG_2a, lambda) and its rat-human chimeric mAbs (NZ-8/NZ-12), which neutralize PDPN/CLEC-2 interactions and inhibit platelet aggregation and cancer metastasis. In this study, we first developed a humanized anti-human PDPN mAb, named as NZ-27. We further produced a core-fucose-deficient version of NZ-27, named as P1027 and a core-fucose-deficient version of NZ-12, named as NZ-12f. We investigated the binding affinity, antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and antitumor activity of P1027 and NZ-12f. We demonstrated that the binding affinities of P1027 and NZ-12f against LN319 (a human glioblastoma cell line) are 1.1 × 10^-8 and 3.9 × 10^-9 M, respectively. ADCC reporter assays demonstrated that NZ-12f shows 1.5 times higher luminescence than P1027. Furthermore, NZ-12f showed 2.2 times higher ADCC than P1027, whereas both P1027 and NZ-12f showed high CDC activities against LN319 cells. Using LN319 xenograft models, P1027 and NZ-12f significantly reduced tumor development in an LN319 xenograft model compared with control human IgG. Treatment with P1027 and NZ-12f may be a useful therapy for patients with PDPN-expressing cancers.

Characterization and visualization of murine coagulation factor VIII-producing cells in vivo

Coagulation factors are produced from hepatocytes, whereas production of coagulation factor VIII (FVIII) from primary tissues and cell species is still controversial. Here, we tried to characterize primary FVIII-producing organ and cell species using genetically engineered mice, in which enhanced green fluorescent protein (EGFP) was expressed instead of the F8 gene. EGFP-positive FVIII-producing cells existed only in thin sinusoidal layer of the liver and characterized as CD31^high, CD146^high, and lymphatic vascular endothelial hyaluronan receptor 1 (Lyve1)⁺. EGFP-positive cells can be clearly distinguished from lymphatic endothelial cells in the expression profile of the podoplanin⁻ and C-type lectin-like receptor-2 (CLEC-2)⁺. In embryogenesis, EGFP-positive cells began to emerge at E14.5 and subsequently increased according to liver maturation. Furthermore, plasma FVIII could be abolished by crossing F8 conditional deficient mice with Lyve1-Cre mice. In conclusion, in mice, FVIII is only produced from endothelial cells exhibiting CD31^high, CD146^high, Lyve1⁺, CLEC-2⁺, and podoplanin⁻ in liver sinusoidal endothelial cells.

Epitope Mapping of the Anti-California Sea Lion Podoplanin Monoclonal Antibody PMab-269 Using Alanine-Scanning Mutagenesis and ELISA

Podoplanin (PDPN) plays a pivotal role in platelet aggregation, embryo development, and tumor progression. PDPN is universally expressed in many mammalian species, and is considered a typical lymphatic endothelial cell marker. We have previously developed the mouse anti-California sea lion (Zalophus californianus) PDPN (seaPDPN) monoclonal antibody (mAb), clone PMab-269, which is suitable for different experimental applications, including flow cytometry, Western blotting, and immunohistochemistry. In this study, we identified the PMab-269 epitope of the seaPDPN by enzyme-linked immunosorbent assay using deletion mutants and point mutants generated for seaPDPN. Our results demonstrated that PMab-269 recognized the peptide, corresponding to the amino acids 63-82 of seaPDPN. Furthermore, the reactions of PMab-269 to seven alanine-substituted peptides, such as P68A, D76A, F77A, H78A, L79A, E80A, and D81A, were abolished among 20 alanine-substituted peptides. We identified the seven amino acids (Pro68, Asp76, Phe77, His78, Leu79, Glu80, and Asp81) as the critical epitope targeted by PMab-269. The successful identification of the PMab-269 epitope might contribute to the pathophysiological investigations of seaPDPN.

Ferret Podoplanin Is Detected by PMab-241 in Immunohistochemistry

Podoplanin (PDPN) plays an important role in the development of many normal tissues and is expressed in various cancers. We have previously developed multiple monoclonal antibodies (mAbs) against PDPNs from a variety of animal species and characterized each of these PDPNs using the anti-PDPN mAbs. In this study, we evaluated whether these anti-PDPN mAbs possess cross-reactivity with ferret PDPN (ferPDPN) using flow cytometry. Comprehensive analysis using 17 differing anti-PDPN mAbs available for immunohistochemistry use, demonstrated that the anti-bear PDPN mAb (clone PMab-241) strongly cross-reacts with ferPDPN-overexpressed Chinese hamster ovary-K1 (CHO/ferPDPN) cells. Immunohistochemistry analysis demonstrated intense PMab-241 staining within Bowman's capsules and glomeruli of the ferret kidney, and lymphatic endothelial cells of the ferret lung. These results demonstrate that PMab-241 is suitable for the detection of PDPN in ferret tissues.

The heterogeneity of cancer endothelium: The relevance of angiogenesis and endothelial progenitor cells in cancer microenvironment

Tumor-associated vessels constitution is the result of angiogenesis, the hallmark of cancer essential for tumor to develop in dimension and to spread throughout the organism. Tumor endothelium is configured as an active functioning organ capable of determine interaction with the immune response and all the other components of the variegate cancer microenvironment, determining reciprocal influence. Angiogenesis is here analyzed in its molecular and cellular mechanisms, multiple mediators and principal players, represented by Endothelial Cells. It is discussed the striking heterogeneity of cancer endothelium, due to morphological and molecular aberrations that it often presents and its multiple origin. Among the cells that participate to the composition of tumor vasculature, Endothelial Progenitor Cells represent an important source for physical sustain and paracrine signaling in the process of angiogenesis. Treatment options are reviewed, with particular focus on novel therapeutic strategies for overcoming tumor resistance to anti-angiogenic agents.

Development of Monoclonal Antibody PMab-269 Against California Sea Lion Podoplanin

The development of protein-specific antibodies is essential for understanding a wide variety of biological phenomena. Parasitic and viral infections and cancers are known to occur within California sea lion (Zalophus californianus) populations. However, sensitive and specific monoclonal antibodies (mAbs) for the pathophysiological analysis of California sea lion tissues have not yet been developed. A type I transmembrane glycoprotein, podoplanin (PDPN), is a known diagnostic marker of lymphatic endothelial cells. We have previously developed several anti-PDPN mAbs in various mammalian species, with applications in flow cytometry, Western blotting, and immunohistochemistry. In this study, we established a novel mAb against California sea lion PDPN (seaPDPN), clone PMab-269 (mouse IgG₁, kappa), using a Cell-Based Immunization and Screening method. PMab-269 is specifically detected in seaPDPN-overexpressed Chinese hamster ovary (CHO)-K1 cells using flow cytometry and Western blotting. Moreover, PMab-269 clearly identified pulmonary type I alveolar cells, renal podocytes, and colon lymphatic endothelial cells in California sea lion tissues using immunohistochemistry. These findings demonstrate the usefulness of PMab-269 for the pathophysiological analysis of lung, kidney, and lymphatic tissues of the California sea lion.

Structure and Immune Function of Afferent Lymphatics and Their Mechanistic Contribution to Dendritic Cell and T Cell Trafficking

Afferent lymphatic vessels (LVs) mediate the transport of antigen and leukocytes to draining lymph nodes (dLNs), thereby serving as immunologic communication highways between peripheral tissues and LNs. The main cell types migrating via this route are antigen-presenting dendritic cells (DCs) and antigen-experienced T cells. While DC migration is important for maintenance of tolerance and for induction of protective immunity, T cell migration through afferent LVs contributes to immune surveillance. In recent years, great progress has been made in elucidating the mechanisms of lymphatic migration. Specifically, time-lapse imaging has revealed that, upon entry into capillaries, both DCs and T cells are not simply flushed away with the lymph flow, but actively crawl and patrol and even interact with each other in this compartment. Detachment and passive transport to the dLN only takes place once the cells have reached the downstream, contracting collecting vessel segments. In this review, we describe how the anatomy of the lymphatic network supports leukocyte trafficking and provide updated knowledge regarding the cellular and molecular mechanisms responsible for lymphatic migration of DCs and T cells. In addition, we discuss the relevance of DC and T cell migration through afferent LVs and its presumed implications on immunity.

To be or not to be: endothelial cell plasticity in development, repair, and disease

Endothelial cells display an extraordinary plasticity both during development and throughout adult life. During early development, endothelial cells assume arterial, venous, or lymphatic identity, while selected endothelial cells undergo additional fate changes to become hematopoietic progenitor, cardiac valve, and other cell types. Adult endothelial cells are some of the longest-lived cells in the body and their participation as stable components of the vascular wall is critical for the proper function of both the circulatory and lymphatic systems, yet these cells also display a remarkable capacity to undergo changes in their differentiated identity during injury, disease, and even normal physiological changes in the vasculature. Here, we discuss how endothelial cells become specified during development as arterial, venous, or lymphatic endothelial cells or convert into hematopoietic stem and progenitor cells or cardiac valve cells. We compare findings from in vitro and in vivo studies with a focus on the zebrafish as a valuable model for exploring the signaling pathways and environmental cues that drive these transitions. We also discuss how endothelial plasticity can aid in revascularization and repair of tissue after damage- but may have detrimental consequences under disease conditions. By better understanding endothelial plasticity and the mechanisms underlying endothelial fate transitions, we can begin to explore new therapeutic avenues.

CNS-Draining Meningeal Lymphatic Vasculature: Roles, Conundrums and Future Challenges

A genuine and functional lymphatic vascular system is found in the meninges that sheath the central nervous system (CNS). This unexpected (re)discovery led to a reevaluation of CNS fluid and solute drainage mechanisms, neuroimmune interactions and the involvement of meningeal lymphatics in the initiation and progression of neurological disorders. In this manuscript, we provide an overview of the development, morphology and unique functional features of meningeal lymphatics. An outline of the different factors that affect meningeal lymphatic function, such as growth factor signaling and aging, and their impact on the continuous drainage of brain-derived molecules and meningeal immune cells into the cervical lymph nodes is also provided. We also highlight the most recent discoveries about the roles of the CNS-draining lymphatic vasculature in different pathologies that have a strong neuroinflammatory component, including brain trauma, tumors, and aging-associated neurodegenerative diseases like Alzheimer’s and Parkinson’s. Lastly, we provide a critical appraisal of the conundrums, challenges and exciting questions involving the meningeal lymphatic system that ought to be investigated in years to come.

In Sickness and in Health: The Immunological Roles of the Lymphatic System

The lymphatic system plays crucial roles in immunity far beyond those of simply providing conduits for leukocytes and antigens in lymph fluid. Endothelial cells within this vasculature are distinct and highly specialized to perform roles based upon their location. Afferent lymphatic capillaries have unique intercellular junctions for efficient uptake of fluid and macromolecules, while expressing chemotactic and adhesion molecules that permit selective trafficking of specific immune cell subsets. Moreover, in response to events within peripheral tissue such as inflammation or infection, soluble factors from lymphatic endothelial cells exert “remote control” to modulate leukocyte migration across high endothelial venules from the blood to lymph nodes draining the tissue. These immune hubs are highly organized and perfectly arrayed to survey antigens from peripheral tissue while optimizing encounters between antigen-presenting cells and cognate lymphocytes. Furthermore, subsets of lymphatic endothelial cells exhibit differences in gene expression relating to specific functions and locality within the lymph node, facilitating both innate and acquired immune responses through antigen presentation, lymph node remodeling and regulation of leukocyte entry and exit. This review details the immune cell subsets in afferent and efferent lymph, and explores the mechanisms by which endothelial cells of the lymphatic system regulate such trafficking, for immune surveillance and tolerance during steady-state conditions, and in response to infection, acute and chronic inflammation, and subsequent resolution.

Case Report: ANXA2 Associated Life-Threatening Coagulopathy With Hyperfibrinolysis in a Patient With Non-APL Acute Myeloid Leukemia

Patients with acute promyelocytic leukemia (APL) often present with potentially life-threatening hemorrhagic diathesis. The underlying pathomechanisms of APL-associated coagulopathy are complex. However, two pathways considered to be APL-specific had been identified: 1) annexin A2 (ANXA2)-associated hyperfibrinolysis and 2) podoplanin (PDPN)-mediated platelet activation and aggregation. In contrast, since disseminated intravascular coagulation (DIC) is far less frequent in patients with non-APL acute myeloid leukemia (AML), the pathophysiology of AML-associated hemorrhagic disorders is not well understood. Furthermore, the potential threat of coagulopathy in non-APL AML patients may be underestimated. Herein, we report a patient with non-APL AML presenting with severe coagulopathy with hyperfibrinolysis. Since his clinical course resembled a prototypical APL-associated hemorrhagic disorder, we hypothesized pathophysiological similarities. Performing multiparametric flow cytometry (MFC) and immunofluorescence imaging (IF) studies, we found the patient’s bone-marrow mononuclear cells (BM-MNC) to express ANXA2 - a biomarker previously thought to be APL-specific. In addition, whole-exome sequencing (WES) on sorted BM-MNC (leukemia-associated immunophenotype (LAIP)1: ANXA^lo, LAIP2: ANXA^hi) demonstrated high intra-tumor heterogeneity. Since ANXA2 regulation is not well understood, further research to determine the coagulopathy-initiating events in AML and APL is indicated. Moreover, ANXA2 and PDPN MFC assessment as a tool to determine the risk of life-threatening DIC in AML and APL patients should be evaluated.

Macrophage-Mediated Tissue Vascularization: Similarities and Differences Between Cornea and Skin

Macrophages are critical mediators of tissue vascularization both in health and disease. In multiple tissues, macrophages have been identified as important regulators of both blood and lymphatic vessel growth, specifically following tissue injury and in pathological inflammatory responses. In development, macrophages have also been implicated in limiting vascular growth. Hence, macrophages provide an important therapeutic target to modulate tissue vascularization in the clinic. However, the molecular mechanisms how macrophages mediate tissue vascularization are still not entirely resolved. Furthermore, mechanisms might also vary among different tissues. Here we review the role of macrophages in tissue vascularization with a focus on their role in blood and lymphatic vessel formation in the barrier tissues cornea and skin. Comparing mechanisms of macrophage-mediated hem- and lymphangiogenesis in the angiogenically privileged cornea and the physiologically vascularized skin provides an opportunity to highlight similarities but also tissue-specific differences, and to understand how macrophage-mediated hem- and lymphangiogenesis can be exploited for the treatment of disease, including corneal wound healing after injury, graft rejection after corneal transplantation or pathological vascularization of the skin.

CD31 and D2-40 Contribute to Peritoneal Metastasis of Colorectal Cancer by Promoting Epithelial-Mesenchymal Transition

Background/Aims

Colorectal cancer (CRC) patients often exhibit peritoneal metastasis, which negatively impacts their prognosis. CD31 and D2-40 have recently been suggested to be predictors of breast cancer prognosis, but their role in colorectal peritoneal metastasis (CRPM) remains unknown.

Methods

The expression profiles of CD31 and D2-40 were analyzed in CRC patients with or without CRPM and in CRC cell lines with increasing metastatic potential. Overexpression and short hairpin RNA knockdown assays were performed in CRC cells, and the effects of these alterations on epithelial-mesenchymal transition (EMT) in vitro, growth of xenograft tumors in vivo, and peritoneal metastasis potential in a mouse model of CRPM were examined.

Results

The expressions of CD31 and D2-40 were upregulated in CRC tumor tissues and was elevated further in tumor tissues from patients with CRPM. CD31 and D2-40 expression levels exhibited increasing trends parallel to the EMT potential of CRC cells. CD31 and D2-40 are essential for CRC cell EMT in vitro as well as for xenograft tumor growth and peritoneal metastasis in vivo.

Conclusions

CD31 and D2-40 contribute to CRPM by promoting EMT and may serve as prognostic markers and therapeutic targets for CRC, particularly in patients with peritoneal metastasis.

Specialized Pro-Resolving Mediators and the Lymphatic System

Diminished lymphatic function and abnormal morphology are common in chronic inflammatory diseases. Recent studies are investigating whether it is possible to target chronic inflammation by promoting resolution of inflammation, in order to enhance lymphatic function and attenuate disease. Resolution of inflammation is an active process regulated by bioactive lipids known as specialized pro-resolving mediators (SPMs). SPMs can modulate leukocyte migration and function, alter cytokine/chemokine release, modify autophagy, among other immune-related activities. Here, we summarize the role of the lymphatics in resolution of inflammation and lymphatic impairment in chronic inflammatory diseases. Furthermore, we discuss the current literature describing the connection between SPMs and the lymphatics, and the possibility of targeting the lymphatics with innovative SPM therapy to promote resolution of inflammation and mitigate disease.

Characterising cancer-associated fibroblast heterogeneity in non-small cell lung cancer: a systematic review and meta-analysis

Cancer-associated fibroblasts (CAFs) are a key component of the tumour microenvironment with evidence suggesting they represent a heterogeneous population. This study summarises the prognostic role of all proteins characterised in CAFs with immunohistochemistry in non-small cell lung cancer thus far. The functions of these proteins in cellular processes crucial to CAFs are also analysed. Five databases were searched to extract survival outcomes from published studies and statistical techniques, including a novel method, used to capture missing values from the literature. A total of 26 proteins were identified, 21 of which were combined into 7 common cellular processes key to CAFs. Quality assessments for sensitivity analyses were carried out for each study using the REMARK criteria whilst publication bias was assessed using funnel plots. Random effects models consistently identified the expression of podoplanin (Overall Survival (OS)/Disease-specific Survival (DSS), univariate analysis HR 2.25, 95% CIs 1.80-2.82) and α-SMA (OS/DSS, univariate analysis HR 2.11, 95% CIs 1.18-3.77) in CAFs as highly prognostic regardless of outcome measure or analysis method. Moreover, proteins involved in maintaining and generating the CAF phenotype (α-SMA, TGF-β and p-Smad2) proved highly significant after sensitivity analysis (HR 2.74, 95% CIs 1.74-4.33) supporting attempts at targeting this pathway for therapeutic benefit.

Endothelial Cells as Tools to Model Tissue Microenvironment in Hypoxia-Dependent Pathologies

Endothelial cells (ECs) lining the blood vessels are important players in many biological phenomena but are crucial in hypoxia-dependent diseases where their deregulation contributes to pathology. On the other hand, processes mediated by ECs, such as angiogenesis, vessel permeability, interactions with cells and factors circulating in the blood, maintain homeostasis of the organism. Understanding the diversity and heterogeneity of ECs in different tissues and during various biological processes is crucial in biomedical research to properly develop our knowledge on many diseases, including cancer. Here, we review the most important aspects related to ECs’ heterogeneity and list the available in vitro tools to study different angiogenesis-related pathologies. We focus on the relationship between functions of ECs and their organo-specificity but also point to how the microenvironment, mainly hypoxia, shapes their activity. We believe that taking into account the specific features of ECs that are relevant to the object of the study (organ or disease state), especially in a simplified in vitro setting, is important to truly depict the biology of endothelium and its consequences. This is possible in many instances with the use of proper in vitro tools as alternative methods to animal testing.

Overcoming challenges in developing small molecule inhibitors for GPVI and CLEC-2

GPVI and CLEC-2 have emerged as promising targets for long-term prevention of both arterial thrombosis and thrombo-inflammation with a decreased bleeding risk relative to current drugs. However, while there are potent blocking antibodies of both receptors, their protein nature comes with decreased bioavailability, making formulation for oral medication challenging. Small molecules are able to overcome these limitations, but there are many challenges in developing antagonists of nanomolar potency, which is necessary when considering the structural features that underlie the interaction of CLEC-2 and GPVI with their protein ligands. In this review, we describe current small-molecule inhibitors for both receptors and strategies to overcome such limitations, including considerations when it comes to in silico drug design and the importance of complex compound library selection.

Absence of lymphatic vessels in non-functioning bleb capsules of glaucoma drainage devices

PURPOSE

To evaluate the presence and appearance of blood and lymphatic vessels in non-functioning bleb capsules of glaucoma drainage devices (GDD).

MATERIALS AND METHODS

Non-functioning (n=14) GDD-bleb capsules of 12 patients were analyzed by immunohistochemistry for blood vessels (CD31, vascular endothelium), lymphatic vessels (lymphatic vessel endothelial hyaluronan receptor-1 [LYVE-1] and podoplanin) and macrophages (CD68).

RESULTS

CD31+++ blood vessels and CD68+ macrophages were detected in the outer layer of all specimens. LYVE-1 immunoreactivity was registered in single non-endothelial cells in 8 out of 14 (57%) bleb capsule specimens. Podoplanin-immunoreactivity was detected in all cases, located in cells and profiles of the collagen tissue network of the outer and/or the inner capsule layer. However, a colocalization of LYVE-1 and podoplanin as evidence for lymphatic vessels was not detected.

CONCLUSIONS

We demonstrate the presence of blood-vessels but absence of lymphatic vessels in non-functioning bleb capsules after GDD-implantation. While the absence of lymphatic vessels might indicate a possible reason for drainage device failure, this needs to be confirmed in upcoming studies, including animal experiments.

Expression of Calretinin, Marker of Mesothelial Differentiation, in Pancreatic Ductal Adenocarcinoma: A Potential Diagnostic Pitfall

OBJECTIVE

Pancreatic ductal adenocarcinoma is one of the most common causes of "peritoneal carcinomatosis" and has an insidious growth pattern. Thus, it falls into the differential diagnosis of other peritoneal malignancies including malignant mesothelioma. Recently, we have encountered an undifferentiated pancreatic carcinoma presenting with peritoneal disease and exhibiting immunoreactivity to calretinin, mimicking mesothelioma. In this study, we explored the incidence of calretinin expression in pancreatic ductal adenocarcinoma.

MATERIALS AND METHODS

Calretinin immunohistochemical staining was performed on the tissue microarrays (TMAs), which were created using three 0.6 mm diameter punches per tumor (n=113). Distribution and intensity of expression were evaluated.

RESULTS

The TMAs contained 86 well/moderately differentiated and 27 poorly differentiated/undifferentiated carcinomas. Calretinin was positive in nine tumors (8%); six with diffuse and strong staining, three with focal and/or weak staining. The incidence of calretinin expression was 15% in poorly differentiated/undifferentiated carcinomas (vs. 6% in well/moderately differentiated carcinomas, p=0.03).

CONCLUSIONS

Pancreatic ductal adenocarcinomas, especially when poorly differentiated/undifferentiated, may be diffusely and strongly positive for calretinin creating a potential diagnostic challenge with malignant mesothelioma. Therefore, caution should be exercised when using this marker to explore a diagnosis of malignant mesothelioma. Tumors expressing calretinin without other mesothelial markers should prompt a careful evaluation of the morphologic and immunohistochemical features to exclude other malignancies. If the diagnosis of pancreatic ductal adenocarcinoma is considered, ductal differentiation can be demonstrated by using additional immunohistochemical markers such as mucin-related glycoproteins (MUC1, MUC5AC) and/or oncoproteins (CEA, B72.3, CA125).

The YAP signaling pathway promotes the progression of lymphatic malformations through the activation of lymphatic endothelial cells

BACKGROUND

To investigate whether the YAP/TAZ (Yes-associated protein/transcriptional coactivator with PDZ binding motif) pathway contributes to the pathogenesis of lymphatic malformations (LMs).

METHODS

YAP, TAZ, CTGF (connective tissue growth factor), and Ki-67 were detected in LMs by immunohistochemistry. The colocalization of YAP and Ki-67 was analyzed by double immunofluorescence. Pearson's correlation and cluster analyses were performed to analyze the relationships between these proteins. Human dermal lymphatic endothelial cells (HDLECs) were used for mechanistic investigation. Rat models of LMs were established to investigate the role of the YAP pathway in LM development.

RESULTS

Compared with those in normal skin, the expression levels of YAP, TAZ, CTGF, and Ki-67 were significantly upregulated in lymphatic endothelial cells (LECs) of LMs. Interestingly, YAP and CTGF presented much higher expression levels in infected LMs. In experiments in vitro, lipopolysaccharide (LPS) enhanced the expression of YAP in a concentration- and time-dependent manner via the increased phosphorylation of Erk1/2 (extracellular signal-regulated kinase 1/2). Moreover, the proliferation, invasion, and tubule formation of HDLECs increased significantly in accordance with the activation of the YAP signaling pathway. Furthermore, LM rat models validated that LPS facilitated the development of LMs, which was dependent on the activation of YAP.

CONCLUSIONS

The data reveal that activation of the YAP signaling pathway in LECs may play a crucial role in the progression of LMs.

IMPACT

Compared with that in normal skin, the YAP signaling pathway was activated in LECs of LMs. Inhibiting the YAP signaling pathway attenuated the proliferation, invasion, and tubule formation of HDLECs. Additionally, the activation of the YAP signaling pathway could promote LM development in a rat model. Activation of the YAP signaling pathway in LECs may play a crucial role in the progression of LMs. The YAP signaling pathway was activated in LMs. Inhibition of the YAP signaling pathway could promote regression of the lesions.

Water intake accelerates ATP release from myofibroblast cells in rats: ATP-mediated podoplanin-dependent control for physiological function and immunity

We previously demonstrated that water intake increased mesenteric lymph flow and the total flux of IL-22 in rat jejunum. The drained water and the higher permeability of albumin in the jejunal microcirculation contributed to increase the lymph flow and IL-22 transport via the activation of great bulk flow in the jejunal villi. To address the effects of water intake-mediated great bulk flow-dependent mechanical force on jejunal physiological function and immunological regulation of innate lymphoid cells (ILC)-3, we examined the effects of shear stress stimulation on cultured rat myofibroblast cells. Next, we investigated the effects of water intake on podoplanin and IL-22 expressions in cultured human intestinal epithelial cells and rat in vivo jejunal preparations, respectively. Shear stress stimulation of the myofibroblast cells induced ATP release via an activation of cell surface F₁/F₀ ATP synthase. ATP produced podoplanin expression in the intestinal epithelial cells. Water intake accelerated immunohistochemical expressions of podoplanin and IL-22 in the interepithelial layers and lamina propria of the jejunum. ATP dose-dependently increased IL-22 mRNA expression in ILC-3, which are housed in the lamina propria. Water intake also increased immunohistochemical and mRNA expressions of ecto-nucleoside triphosphate diphosphohydrolases 2 and 5 in jejunal villi. In conclusion, water intake-mediated shear stress stimulation-dependent ATP release from myofibroblast cells maintains higher tissue colloid osmotic pressure in the jejunal microcirculation through podoplanin upregulation in the interepithelial layers. ATP induces IL-22 mRNA expression in ILC-3 in jejunal villi, which may contribute to regulation of mucosal immunity in small intestine.NEW & NOTEWORTHY We investigated effects of shear stress stimulation on cultured myofibroblast cells and water intake on podoplanin and IL-22 expressions in rat jejunal villi. The stimulation induced ATP release from the cells. Water intake accelerated podoplanin and IL-22 expression levels. ATP increased IL-22 mRNA expression in innate lymphoid cells (ILC)-3. Hence, water intake maintains higher osmotic pressure in the jejunal villi through ATP release and podoplanin upregulation. Water intake may regulate the mucosal immunity.

Comprehensive phenotyping of endothelial cells using flow cytometry 2: Human

In vascular research, clinical samples and samples from animal models are often used together to foster translation of preclinical findings to humans. General concepts of endothelia and murine-specific endothelial phenotypes were discussed in part 1 of this two part series. Here, in part 2, we present a comprehensive overview of human-specific endothelial phenotypes. Pan-endothelial cell markers, organ specific endothelial antigens, and flow cytometric immunophenotyping of blood-borne endothelial cells are reviewed.

The Detection of Plasma Soluble Podoplanin of Patients with Breast Cancer and Its Clinical Signification

Background

Podoplanin (PDPN) is a type-1 membrane sialoglycoprotein that is expressed in many cancer tumors including breast cancer; nonetheless, its roles in tumor occurrence, development, and metastasis are unclear. In this study, we aimed to investigate the clinical significance of plasma soluble PDPN (sPDPN) levels in patients with breast cancer and its significance in the diagnosis and metastasis.

Materials and Methods

Blood samples from healthy controls (CTL), patients with fibroadenomas of breast (FOB), and breast cancer (pathological type: invasive ductal carcinoma, IDC) were collected. sPDPN levels in the plasma of CTL and patients with FOB and IDC were measured by the ELISA.

Results

The plasma sPDPN levels in IDC patients (159 cases, 22.59±3.70 ng/mL) were higher than those in FOB patients (50 cases, 8.29±1.09 ng/mL; P<0.05) and CTL (100 cases, 1.21±0.12 ng/mL; P<0.0001). The sPDPN levels in patients at stage III and stage IV (30.08±4.66 ng/mL) were higher than in patients at stage I and stage II (11.84±1.12 ng/mL; P=0.005). The sPDPN levels in patients with high-moderate and moderate differentiation (17.50±3.02 ng/mL) were lower than those in patients with moderately low and low differentiation (35.73±4.26 ng/mL; P=0.026). The sPDPN levels in patients with metastasis (30.60±4.27 ng/mL) were much higher than those in patients without metastasis (13.02±1.30 ng/mL; P=0.017).

Conclusion

Plasma sPDPN may be used as a new marker for the determination of the clinical stage, differentiation degree, and metastasis status of breast cancer.

Crystal structure of an anti-podoplanin antibody bound to a disialylated O-linked glycopeptide

Podoplanin (PDPN) is a highly O-glycosylated glycoprotein that is utilized as a specific lymphatic endothelial marker under pathophysiological conditions. We previously developed an anti-human PDPN (hPDPN) monoclonal antibody (mAb), clone LpMab-3, which recognizes the epitope, including both the peptides and the attached disialy-core-l (NeuAcα2-3Galβl-3 [NeuAcα2-6]GalNAcαl-O-Thr) structure at the Thr76 residue in hPDPN. However, it is unclear if the mAb binds directly to both the peptides and glycans. In this study, we synthesized the binding epitope region of LpMab-3 that includes the peptide (-₆₇LVATSVNSV-T-GIRIEDLP₈₄-) possessing a disialyl-core-1 O-glycan at Thr76, and we determined the crystal structure of the LpMab-3 Fab fragment that was bound to the synthesized glycopeptide at a 2.8 Å resolution. The six amino acid residues and two sialic acid residues are directly associated with four complementarity-determining regions (CDRs; H1, H2, H3, and L3) and four CDRs (H2, H3, L1, and L3), respectively. These results suggest that IgG is advantageous for generating binders against spacious epitopes such as glycoconjugates.

Modeling Drug Absorption from the Dermis after an Injection

A dermal absorption model for small and macromolecules was previously proposed by Ibrahim et al. This model estimated absorption of therapeutics from the dermal tissue based on their molecular size and protein binding through blood and lymphatics. Blood absorption followed a two-pore theory and the lymphatic absorption was limited by the constant lymphatic flow rate. Current work builds on this steady-state concept by modeling the absorption from the dermis immediately after an injection is given (unsteady state). An injection in the dermis creates a localized pressure gradient which resolves itself over time. This phenomenon is captured in the model to estimate the impact of injection volume on the absorption rate constant. Blood absorption follows the two-pore theory but is time-dependent and the lymphatic absorption is determined based on valve opening and pressure driven convective flow, returning to steady-state as the molecule is absorbed. A direct comparison of the steady-state analysis, experimental data and the current model is made. The results indicate that accounting for the localized time-varying pressure can better predict the experimental absorption rate constants. This work significantly improves the existing understanding of macromolecule uptake from the interstitial fluid following intradermal injection.

Network patterning, morphogenesis and growth in lymphatic vascular development

The lymphatic vasculature is a vital component of the vertebrate vascular system that mediates tissue fluid homeostasis, lipid uptake and immune surveillance. The development of the lymphatic vasculature starts in the early vertebrate embryo, when a subset of blood vascular endothelial cells of the cardinal veins acquires lymphatic endothelial cell fate. These cells sprout from the veins, migrate, proliferate and organize to give rise to a highly structured and unique vascular network. Cellular cross-talk, cell-cell communication and the interpretation of signals from surrounding tissues are all essential for coordinating these processes. In this chapter, we highlight new findings and review research progress with a particular focus on LEC migration and guidance, expansion of the LEC lineage, network remodeling and morphogenesis of the lymphatic vasculature.

Characterization of weaning-induced breast involution in women: implications for young women's breast cancer

In rodents, weaning-induced mammary gland involution supports increased mammary tumor incidence, growth, and progression to metastasis. Further, the protumor attributes of gland involution are COX-2 dependent and mitigated by short-duration non-steroidal anti-inflammatory drugs (NSAIDs), suggesting a potential prevention strategy. However, the transition from lactation to postweaning breast involution has not been rigorously evaluated in healthy women. Here we queried breast biopsies from healthy women (n = 112) obtained at nulliparity, lactation, and multiple postweaning time points using quantitative immunohistochemistry. We found that mammary remodeling programs observed in rodents are mirrored in the human breast. Specifically, lactation associates with the expansion of large, secretory mammary lobules and weaning associates with lobule loss concurrent with epithelial cell death and stromal hallmarks of wound healing, including COX-2 upregulation. Altogether, our data demonstrate that weaning-induced breast involution occurs rapidly, concurrent with protumor-like attributes, and is a potential target for NSAID-based breast cancer prevention.

Vascular tumors of the mediastinum

Vascular tumors represent only a sliver of all tumors affecting the mediastinum, but they pose diagnostic challenges due to significant overlap among entities, ever-evolving classification schemes, and the exquisite rarity of some of the entities not only in the mediastinum but in pathology practice as a whole. Most of the vascular tumors are better known to the practice of soft tissue pathology, from which some of the knowledge of clinical behavior can be extrapolated. For example, the stratification of epithelioid hemangioendothelioma (EHE) into two biologically separate categories has effectively translated from the somatic soft tissues to the thorax. For other entities, the effective validation of soft tissue parameters is hindered by the small numbers of reported mediastinal cases. Many of the treatment modalities have also transferred over, with the key differences resting on the difficulty in achieving complete surgical resection for mediastinal tumors as opposed to those in the somatic soft tissues. Accordingly, systemic drug therapies have emerged as attractive options for some of the mediastinal vascular tumors, such as kaposiform hemangioendothelioma (KHE) and Kaposi sarcoma (KS). The categories presented herein mirror the classification scheme set forth by the 5th Edition WHO Classification of Soft Tissue and Bone Tumors. This review focuses on the biologically aggressive vascular neoplasms while limiting discussion of the benign entities to relevant comparisons in the differential diagnoses. While distinguishing among the benign entities has academic importance, in practice, the stakes are far higher for diagnosing the biologically aggressive tumors given their marked heterogeneity in clinical outcomes. Practical advice for problem areas in pathology will be reviewed alongside tumor pathobiology, including the latest in molecular diagnostics.

Cellular Origins of the Lymphatic Endothelium: Implications for Cancer Lymphangiogenesis

The lymphatic system plays important roles in physiological and pathological conditions. During cancer progression in particular, lymphangiogenesis can exert both positive and negative effects. While the formation of tumor associated lymphatic vessels correlates with metastatic dissemination, increased severity and poor patient prognosis, the presence of functional lymphatics is regarded as beneficial for anti-tumor immunity and cancer immunotherapy delivery. Therefore, a profound understanding of the cellular origins of tumor lymphatics and the molecular mechanisms controlling their formation is required in order to improve current strategies to control malignant spread. Data accumulated over the last decades have led to a controversy regarding the cellular sources of tumor-associated lymphatic vessels and the putative contribution of non-endothelial cells to this process. Although it is widely accepted that lymphatic endothelial cells (LECs) arise mainly from pre-existing lymphatic vessels, additional contribution from bone marrow-derived cells, myeloid precursors and terminally differentiated macrophages, has also been claimed. Here, we review recent findings describing new origins of LECs during embryonic development and discuss their relevance to cancer lymphangiogenesis.

Primary Cystic Lymphangioma of the Spleen in an Adult Dog

Proliferative disorders of lymphatic origin in animals are mostly congenital or occur within the first few months of life. Involvement of internal organs is extremely infrequent. A seven-year-old entire female mixed-breed dog was presented with apathy and poor appetite. Abdominal ultrasonography revealed a focally enlarged spleen with an anechoic round lesion. Splenectomy was performed and pathological examination demonstrated a sponge-like, compressible tumour composed of endothelium-lined vascular cystic spaces filled with eosinophilic proteinaceous material lacking erythrocytes. Immunohistochemical stains showed that cyst-lining cells were strongly positive for CD31 and factor VIII and focally positive for lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1). Based on these findings, the lesion was identified as splenic cystic lymphangioma. To the best of our knowledge, this is the first description of solitary lymphangioma of the spleen in animals.

New Insights into the Pathophysiology of Primary and Secondary Lymphedema: Histopathological Studies on Human Lymphatic Collecting Vessels

Background: Lymphedema is characterized by an accumulation of interstitial fluids due to inefficient lymphatic drainage. Primary lymphedema is a rare condition, including congenital and idiopathic forms. Secondary lymphedema is a common complication of lymph node ablation in cancer treatment. Previous studies on secondary lymphedema lymphatic vessels have shown that after an initial phase of ectasia, worsening of the disease is associated with wall thickening accompanied by a progressive loss of the endothelial marker podoplanin. Methods and Results: We enrolled 17 patients with primary and 29 patients with secondary lymphedema who underwent lymphaticovenous anastomoses surgery. Histological sections were stained with Masson's trichrome, and immunohistochemistry was performed with antibodies to podoplanin, smooth muscle α-actin (α-SMA), and myosin heavy chain 11 (MyH11). In secondary lymphedema, we found ectasis, contraction, and sclerosis vessel types. In primary lymphedema, the majority of vessels were of the sclerosis type, with no contraction vessels. In both primary and secondary lymphedema, not all α-SMA-positive cells were also positive for MyH11, suggesting transformation into myofibroblasts. The endothelial marker podoplanin had a variable expression unrelatedly with the morphological vessel type. Conclusions: Secondary lymphedema collecting vessels included all the three types described in literature, that is, ectasis, contraction, and sclerosis, whereas in primary lymphedema, we found the ectasis and the sclerosis but not the contraction type. Some cells in the media stained positively for α-SMA but not for MyH11. These cells, possibly myofibroblasts, may contribute to collagen deposition.

Development and Characterization of Anti-Sheep Podoplanin Monoclonal Antibodies PMab-253 and PMab-260

Anti-podoplanin (PDPN) monoclonal antibodies (mAbs) are needed as markers for lymphatic endothelial cells or type I alveolar cells in immunohistochemical analyses. We have developed anti-PDPN mAbs for many species, including humans, mice, rats, rabbits, dogs, cats, bovines, pigs, Tasmanian devils, alpacas, tigers, whales, goats, horses, and bears. This study develops and characterizes anti-sheep PDPN (sPDPN) mAbs using Cell-Based Immunization and Screening (CBIS) method. A RAP14 tag was added to the N-terminus of sPDPN, and an anti-RAP14 tag mAb (PMab-2) was used to measure the expression level of sPDPN in flow cytometry and Western blots. We immunized mice with sPDPN-overexpressing Chinese hamster ovary (CHO)-K1 (CHO/sPDPN) cells and screened mAbs against sPDPN using flow cytometry. Two of the mAbs, PMab-253 (immunoglobulin M [IgM], kappa) and PMab-260 (IgM, kappa), detected CHO/sPDPN cells specifically using flow cytometry and Western blots. Both PMab-253 and PMab-260 stained the renal glomerulus and Bowman's capsule, lymphatic endothelial cells of the lung and colon, and type I alveolar cells of the lung, suggesting PMab-253 and PMab-260, which were developed by CBIS method, can be applied to functional analyses of sPDPN. We also determined the binding epitope of PMab-253 and PMab-260 using flow cytometry. Analysis of sPDPN deletion mutants revealed that the N-terminus of the PMab-253 and PMab-260 epitope exists between amino acids 110 and 115 of sPDPN. Analysis of sPDPN point mutations revealed that the critical epitope of PMab-253 and PMab-260 includes Thr112 and Ser113 of sPDPN, indicating that the PMab-253 and PMab-260 epitope are independent of the platelet aggregation-stimulating (PLAG) domain or the PLAG-like domain of sPDPN.