Mast cells in human choroid and their role in age-related macular degeneration (AMD).

The role of mast cells in physiologic and pathological processes extends far beyond the allergy processes: they are involved in wound healing, chronic inflammation, and tumor growth. This short article emphasizes the role played by mast cells in age-related macular degeneration (AMD). Mast cells can induce angiogenesis and are present around Bruch's membrane during the early and late stages of choroidal neovascularization in AMD. Proteolytic enzymes released by mast cells lead to thinning of the choroid in AMD as well as degradation of vascular basement membranes and Bruch's membrane, which in turn could result in retinal pigment epithelial death and choriocapillaris degeneration in geographical atrophy and exudative AMD.

Aberrant tumor vasculature. Facts and pitfalls.

Endothelial cells form a single cell layer lining the inner walls of blood vessels and play critical roles in organ homeostasis and disease progression. Specifically, tumor endothelial cells are heterogenous, and highly permeable, because of specific interactions with the tumor tissue environment and through soluble factors and cell-cell interactions. This review article aims to analyze different aspects of endothelial cell heterogeneity in tumor vasculature, with particular emphasis on vascular normalization, vascular permeability, metabolism, endothelial-to-mesenchymal transition, resistance to therapy, and the interplay between endothelial cells and the immune system.

Mast cells in meningiomas.

Meningioma represents the most frequent tumor of the central nervous system (CNS). Correlations between the presence of mast cells (MCs) and grade or other histological features of meningioma are still debated. Our study aimed to better understand the relationship between mast cells and meningiomas and to compare our results based on specific histological subtypes and novel 2021 CNS WHO grading system. We observed some differences as regards the number of MCs and meningioma grade. In low-grade (grade 1) meningiomas, MCs were observed in 7/22 cases, while they were consistently present in all eight high-grade cases (grade 2 and grade  3). Among the grade 1 meningiomas, we observed two "low-positive", two "intermediate-positive", and three "high-positive" cases. Among the group of high-grade meningiomas, the six cases grade 2 were considered as "low-positive", while the two grade 3 cases showed a higher number of MCs and were included in the "intermediate-positive" group. Even though with no statistical significance, due to the low number of cases, our results seem to confirm a sort of relationship between meningioma grading and the number of MCs, as demonstrated by the higher percentage of high-grade meningiomas showing MCs infiltrates, compared to low-grade meningiomas.

New insights into the role of mast cells as a therapeutic target in cancer through the blockade of immune checkpoint inhibitors.

Mast cells release different anti-and pro-inflammatory agents changing their role from protective to pro-inflammatory cells involved in the progression of different pathological conditions, including autoimmune diseases and tumors. Different mediators released by mast cells are involved in their biological activities which may be anti-tumorigenic and/or pro-tumorigenic. For these reasons, tumor mast cells have been considered a novel therapeutic target to prevent tumor progression and metastatic process. Many different agents have been suggested and used in the past pre-clinical and clinical settings. Among the novel immunotherapeutic approaches to cancer treatment, different immune checkpoint inhibitors targeting PD-1/PDL-1 have been used in the treatment of many human tumors improving overall survival. In this context, inhibition of mast cell activity may be considered a novel strategy to improve the efficacy of anti-PD-1/PDL-1 therapy. The blockade of the PD-1/PD-L1 interaction may be suggested as a useful and novel therapeutic approach in the treatment of tumors in which mast cells are involved.

Macrophages and angiogenesis in human lymphomas.

A link exists between chronic inflammation and cancer and immune cells, angiogenesis, and tumor progression. In hematologic malignancies, tumor-associated macrophages (TAMs) are a significant part of the tumor microenvironment. Macrophages are classified into M1/classically activated and M2/alternatively activated. In tumors, TAMs are mainly constituted by M2 subtype, which promotes angiogenesis, lymphangiogenesis, repair, and remodeling, suppressing adaptive immunity, increasing tumor cell proliferation, drug resistance, histological malignancy, and poor clinical prognosis. The aim of our review article is to define the role of TAMs and their relationship with the angiogenesis in patients with lymphoma reporting both an analysis of main published data and those emerging from our studies. Finally, we have discussed the anti-angiogenic approach in the treatment of lymphomas.

Tertiary lymphoid structures, a historical reappraisal.

Tertiary lymphoid structures (TLSs) are accumulations of lymphoid cells within non-lymphoid organs that share the cellular compartments, spatial organization, vasculature, chemokines, and function with secondary lymphoid organs, especially lymph nodes. TLSs are organized into a separate T cell and B cell compartments which contain germinal centers with follicular dendritic cells. In most cases, TLSs contain Peripheral Node addressin (PNAD) expressing high endothelial venules (HEVs). TLSs have been described in various mouse models of inflammation and are associated with a wide range of autoimmune diseases. Other than these, TLSs have been described in chronic allograft rejection and cancer.

Vascular co-option in resistance to anti-angiogenic therapy.

Three different mechanisms of neovascularization have been described in tumor growth, including sprouting angiogenesis, intussusceptive microvascular growth and glomeruloid vascular proliferation. Tumors can also grow by means of alternative mechanisms including vascular co-option, vasculogenic mimicry, angiotropism, and recruitment of endothelial precursor cells. Vascular co-option occurs in tumors independently of sprouting angiogenesis and the non-angiogenic cancer cells are described as exploiting pre-existing vessels. Vascular co-option is more frequently observed in tumors of densely vascularized organs, including the brain, lung and liver, and vascular co-option represents one of the main mechanisms involved in metastasis, as occurs in liver and lung, and resistance to anti-angiogenic therapy. The aim of this review article is to analyze the role of vascular co-option as mechanism through which tumors develop resistance to anti-angiogenic conventional therapeutic approaches and how blocking co-option can suppress tumor growth.

PTX3 shapes profibrotic immune cells and epithelial/fibroblast repair and regeneration in a murine model of pulmonary fibrosis.

The long pentraxin 3 (PTX3) is protective in different pathologies but was not analyzed in-depth in Idiopathic Pulmonary Fibrosis (IPF). Here, we have explored the influence of PTX3 in the bleomycin (BLM)-induced murine model of IPF by looking at immune cells (macrophages, mast cells, T cells) and stemness/regenerative markers of lung epithelium (SOX2) and fibro-blasts/myofibroblasts (CD44) at different time points that retrace the progression of the disease from onset at day 14, to full-blown disease at day 21, to incomplete regression at day 28. We took advantage of transgenic PTX3 overexpressing mice (Tie2-PTX3) and Ptx3 null ones (PTX3-KO) in which pulmonary fibrosis was induced. Our data have shown that PTX3 overexpression in Tie2-PTX3 compared to WT or PTX3-KO: reduced CD68+ and CD163+ macrophages and the Tryptase+ mast cells during the whole experimental time; on the contrary, CD4+ T cells are consistently present on day 14 and dramatically decreased on day 21; CD8+ T cells do not show significant differences on day 14, but are significantly reduced on day 21; SOX2 is reduced on days 14 and 21; CD44 is reduced on day 21. Therefore, PTX3 could act on the proimmune and fibrogenic microenvironment to prevent fibrosis in BLM-treated mice.

Bone angiocrine factors.

Angiogenesis in the bone is unique and involves distinctive signals. Whether they are created through intramembranous ossification or endochondral ossification, bones are highly vascularized tissues. Long bones undergo a sequence of processes known as endochondral osteogenesis. Angiogenesis occurs during the creation of endochondral bone and is mediated by a variety of cells and factors. An initially avascular cartilage template is invaded by blood vessels from the nearby subchondral bone thanks to the secreted angiogenic chemicals by hypertrophic chondrocytes. Vascular endothelial growth factor (VEGF), one of several angiogenic molecules, is a significant regulator of blood vessel invasion, cartilage remodeling, and ossification of freshly created bone matrix; chondrocyte proliferation and hypertrophy are facilitated by the production of VEGFA and VEGF receptor-2 (VEGFR-2), which is stimulated by fibroblast growth factors (FGFs). NOTCH signaling controls blood capillaries formation during bone maturation and regeneration, while hypoxia-inducible factor 1 alpha (HIF1-a) promotes chondrocyte development by switching to anaerobic metabolism. To control skeletal remodeling and repair, osteogenic cells release angiogenic factors, whereas endothelial cells secrete angiocrine factors. One of the better instances of functional blood vessels specialization for certain organs is the skeletal system. A subpopulation of capillary endothelial cells in the bone regulate the activity of osteoprogenitor cells, which in turn affects bone formation during development and adult homeostasis. Angiogenesis and osteogenesis are strictly connected, and their crosstalk is essential to guarantee bone formation and to maintain bone homeostasis. Additionally, pathological processes including inflammation, cancer, and aging include both bone endothelial cells and angiocrine factors. Therefore, the study and understanding of these mechanisms is fundamental, because molecules and factors involved may represent key targets for novel and advanced therapies.

Different patterns of mast cell distribution in B-cell non-Hodgkin lymphomas.

Tumor growth, progression, and metastatic capability in non-Hodgkin lymphomas (NHLs) are influenced by different component of tumor microenvironment, including inflammatory cells. Among these latter, mast cells play a crucial role. The spatial distribution of mast cells inside the tumor stroma of different types of B-cell NHLs has not yet been investigated. The aim of this study is to analyze the pattern of distribution of mast cells in biopsy samples obtained from three different types of B-cell NHLs by utilizing an image analysis system and a mathematical model to allow a quantitative estimation to characterize their spatial distribution. As concerns the spatial distributions exhibited by mast cells in diffuse large B cell lymphoma (DLBCL), some clustering was detected in both activated B-like (ABC) and germinal center B-like (GBC) groups. In follicular lymphoma (FL), mast cell spatial distribution tends to uniformly fill the tissue space as far as the grade of the pathology increases. Finally, in marginal lymphoma tissue (MALT) lymphoma, mast cells maintain a significantly clustered spatial distribution, suggesting a lower tendency of the cells to fill the tissue space in this pathological condition. Overall, the data of this study confirm that the analysis of the spatial distribution of the tumor cells is of particular significance for the knowledge of the biological processes occurring in tumor stroma and for the development of parameters to characterize the morphologic organization of the cellular patterns in different types of tumors.

Hematopoiesis and Mast Cell Development.

Hematopoietic stem cells (HSCs) are defined based on their capacity to replenish themselves (self-renewal) and give rise to all mature hematopoietic cell types (multi-lineage differentiation) over their lifetime. HSCs are mainly distributed in the bone marrow during adult life, harboring HSC populations and a hierarchy of different kinds of cells contributing to the "niche" that supports HSC regulation, myelopoiesis, and lymphopoiesis. In addition, HSC-like progenitors, innate immune cell precursors such as macrophages, mast cells, natural killer cells, innate lymphoid cells, and megakaryocytes and erythrocyte progenitor cells are connected by a series of complex ontogenic relationships. The first source of mast cells is the extraembryonic yolk sac, on embryonic day 7. Mast cell progenitors circulate and enter peripheral tissues where they complete their differentiation. Embryonic mast cell populations are gradually replaced by definitive stem cell-derived progenitor cells. Thereafter, mast cells originate from the bone marrow, developing from the hematopoietic stem cells via multipotent progenitors, common myeloid progenitors, and granulocyte/monocyte progenitors. In this review article, we summarize the knowledge on mast cell sources, particularly focusing on the complex and multifaceted mechanisms intervening between the hematopoietic process and the development of mast cells.

Vascular Growth in Lymphomas: Angiogenesis and Alternative Ways.

The formation of new blood vessels is a critical process for tumor growth and may be achieved through different mechanisms. Angiogenesis represents the first described and most studied mode of vessel formation, but tumors may also use alternative ways to secure blood supply and eventually acquire resistance to anti-angiogenic treatments. These non-angiogenic mechanisms have been described more recently, including intussusceptive microvascular growth (IMG), vascular co-option, and vasculogenic mimicry. Like solid tumors, angiogenic and non-angiogenic pathways in lymphomas play a fundamental role in tumor growth and progression. In view of the relevant prognostic and therapeutic implications, a comprehensive understanding of these mechanisms is of paramount importance for improving the efficacy of treatment in patients with lymphoma. In this review, we summarize the current knowledge on angiogenic and non-angiogenic mechanisms involved in the formation of new blood vessels in Hodgkin's and non-Hodgkin's lymphomas.

The Tumor Microenvironment in Classic Hodgkin's Lymphoma in Responder and No-Responder Patients to First Line ABVD Therapy.

Although classical Hodgkin lymphoma (CHL) is typically curable, 15-25% of individuals eventually experience a relapse and pass away from their disease. In CHL, the cellular microenvironment is constituted by few percent of H/RS (Hodgkin/Reed-Sternberg) tumor cells surrounded from a heterogeneous infiltration of inflammatory cells. The interplay of H/RS cells with other immune cells in the microenvironment may provide novel strategies for targeted immunotherapies. In this paper we analyzed the microenvironment content in CHL patients with responsive disease (RESP) and patients with relapsed/refractory disease to treatment (REL). Our results indicate the increase of CD68+ and CD163+ macrophages, the increase of PDL-1+ cells and of CD34+ microvessels in REL patients respective to RESP patients. In contrast we also found the decrease of CD3+ and of CD8+ lymphocytes in REL patients respective to RESP patients. Finally, in REL patients our results show the positive correlation between CD68+ macrophages and PDL-1+ cells as well as a negative correlation between CD163+ and CD3+.

Mast Cells and Resistance to Immunotherapy in Cancer.

Mast cells are involved in tumor growth and their mediators exert both pro- and anti-tumorigenic roles in different human cancers. The identification of defined immunosuppressive pathways that are present in the tumor microenvironment has pointed therapeutic strategies that may promote inflammation and/or innate immune activation in this context. Mast cells can contribute to the immune suppressive tumor microenvironment and may also enhance anti-tumor responses. This review article is focused on the analysis of the mechanisms of the role of mast cells in resistance to immunotherapy in cancer.

Overlapping between Wound Healing Occurring in Tumor Growth and in Central Nervous System Neurodegenerative Diseases.

Wound healing is characterized by the formation of a granulation tissue consisting of inflammatory cells, newly formed blood vessels, and fibroblasts embedded in a loose collagenous extracellular matrix. Tumors behave as wounds that fail to heal. Neuronal loss in neurodegenerative disease is associated with the synthesis and release of new components of the extracellular matrix by activated fibroblasts and astrocytes. This condition is responsible for a perpetuation of the wound healing state and constitutes a condition very similar to that which occurs during tumor progression. The aim of this article is to emphasize and compare the role of wound healing in two different pathological conditions, namely tumor growth and central nervous system neurodegenerative diseases. Both are conditions in which wounds fail to heal, as occurs in physiological conditions.

Chick embryo area vasculosa as an in vivo assay for the screening of angiogenic and anti-angiogenic molecules.

The chick embryo area vasculosa is an extraembryonic membrane that is commonly used in vivo to study both angiogenesis and anti-angiogenesis. This review article analyzes the possibility to use the area vasculosa as an in vivo assay for the screening of putative angiogenic and anti-angiogenic molecules in alternative to the chorioallantoic membrane, more useful to study tumor growth, angiogenesis, and metastasis, and the angiogenic activity of acellular scaffolds and organoids.

Nasal cytology and histology in CRSwNP: Two sides of the same coin.

Knowledge of chronic rhinosinusitis with nasal polyps (CRSwNP) has increased rapidly over the past decade. However, the study of the histological features of nasal polyps has not gone hand in hand with the study of the inflammatory mechanisms underlying CRSwNP. Indeed, precisely because they are benign neoformations, nasal polyps have not attracted the attention of pathologists over the years. Nasal cytology has shown that CRSwNP, generally defined as a Type-2 disease, is characterized not only by eosinophilic but also mast cell inflammation and, in particular, the most severe forms of CRSwNP are precisely characterized by a mixed eosinophilic-mast cell inflammation. Interestingly, mast cells cannot be visualized by histology due to limitations in staining and magnification, and therefore are not commonly described in histological reports of nasal polyps. However, immunohistochemistry can highlight these latter cells and specifically this technique has recently demonstrated that mast cells are located in the lamina propria of almost all types of polyps and in the epithelial level of the most severe forms. Unfortunately, the latter technique is not commonly carried out in clinical practice by virtue of the high cost and time burden. On the other hand, nasal cytology is an easy-to-apply and economic diagnostic tool, commonly practiced in rhinological setting, which can effectively fill the gap between histology and immunohistochemistry, allowing to non-invasively establish the endotype of nasal polyps and to highlight all cytotypes, including mast cells, that cannot be visualized by the other two techniques. The recent demonstration of the close correlation between mast cell intraepithelial infiltrate and CRSwNP severity paves the way for new therapeutic possibilities aimed at reducing not only eosinophilic infiltration but also mast cell infiltration.

MUC1 Expression Affects the Immunoflogosis in Renal Cell Carcinoma Microenvironment through Complement System Activation and Immune Infiltrate Modulation.

Mucin1 (MUC1), a glycoprotein associated with an aggressive cancer phenotype and chemoresistance, is aberrantly overexpressed in a subset of clear cell renal cell carcinoma (ccRCC). Recent studies suggest that MUC1 plays a role in modulating cancer cell metabolism, but its role in regulating immunoflogosis in the tumor microenvironment remains poorly understood. In a previous study, we showed that pentraxin-3 (PTX3) can affect the immunoflogosis in the ccRCC microenvironment by activating the classical pathway of the complement system (C1q) and releasing proangiogenic factors (C3a, C5a). In this scenario, we evaluated the PTX3 expression and analyzed the potential role of complement system activation on tumor site and immune microenvironment modulation, stratifying samples in tumors with high (MUC1H) versus tumors with low MUC1 expression (MUC1L). We found that PTX3 tissue expression was significantly higher in MUC1H ccRCC. In addition, C1q deposition and the expressions of CD59, C3aR, and C5aR were extensively present in MUC1H ccRCC tissue samples and colocalized with PTX3. Finally, MUC1 expression was associated with an increased number of infiltrating mast cells, M2-macrophage, and IDO1+ cells, and a reduced number of CD8+ T cells. Taken together, our results suggest that expression of MUC1 can modulate the immunoflogosis in the ccRCC microenvironment by activating the classical pathway of the complement system and regulating the immune infiltrate, promoting an immune-silent microenvironment.

The chick embryo chorioallantoic membrane patient-derived xenograft (PDX) model.

The chick embryo chorioallantoic membrane (CAM) CAM is an extraembryonic membrane generated by the fusion of the chorion with the vascularized allantoic membrane. It performs multiple functions during embryonic development, including respiration, calcium transport from the eggshell, acid-base homeostasis, and ion/water reabsorption from the allantoic fluid. The CAM is a widely used model for the study of angiogenesis, anti-angiogenesis, tumor growth, and metastasis as well as drug efficacy. Ethical approval is omitted if experiments are terminated at embryonic day 14 in most countries, facilitating screenings of pharmacological or physics-based therapies with high reproducibility at large scales supporting the 3Rs principle. Being naturally immunodeficient, the chick embryo accepts transplantation from various tissues and species without immune response. This review article is focused on the analysis of the literature and personal data concerning the effects of patient-derived xenografts (PDX) on the CAM.