Tumor blood vessels are abnormal and differ from normal blood vessels in their morphology, gene expression, and functionality (Maishi et al. These vessels control the passage of oxygen and nutrients and supply them to the tumor cells. TECs line the insides of the vessels, and pericytes surround the vessels externally. Tumor blood vessels comprise tumor endothelial cells (TECs) or tumor-associated endothelial cells and pericytes (Maishi et al. Pathophysiological characteristics of tumor endothelial cells and tumor cells under hypoxia In addition, the therapeutics by the control of vascular abnormality are also discussed. In this review, we have focused on the role of pathological angiogenesis in tumors and organ diseases from a specific viewpoint of ECs as a key player of microenvironment. In particular, during inflammatory processes, the vascular responsibility is to be permeable to allow inflammatory mediators and immune cells infiltrate to the site of injury or stresses (Aguilar-Cazares et al. Cross talk between tissue microenvironment, such as parenchymal cells and vascular ECs as well as stromal cells and extracellular matrix, plays an important role in organ function and tumor progression (Belli et al. Emphasis on the tissue microenvironment as well as tumor microenvironment has been recently highlighted in the research of therapeutics (Bahrami et al. If this protective response becomes chronic, the inflammation is not resolved, and there is a resultant increase in the number of pathologies, including cancer (Taniguchi and Karin 2018). ![]() Acute inflammation is a critical protective response to insults by pathogens, toxins, and physical stresses. Inflammation is the primary and the most important reaction to tissues and cell damage. When physiological stress or pathological conditions exceed the capacity of the cells to react and disrupt homeostasis, the tissues experience injury. These tissue-specific ECs play a part of stem cell niches and role in tissue regeneration (Gomez-Salinero and Rafii 2018). This is owing to the specific signaling molecules, known as angiocrine factor, secreted from the tissue-specific ECs. Moreover, tissue repair and regeneration depend on local ECs. In the development, tissue-derived signals induce angiogenesis, and ECs release growth factors or directly control or contribute to organ morphogenesis (Ramasamy et al. 2018) and active contribution to the growth or maintenance of the homeostasis in tissue repair or regeneration in the surrounding tissue (Rafii et al. In addition to the conventional functions, increasing evidence has indicated that they perform other physiological functions, such as gatekeeping of immune responses (Shetty et al. Moreover, the vascular network has a well-established function of delivering oxygen, nutrients, hormones, metabolites, and cells as well as regulation of the coagulation processes. The formation of vasculature is optimized by the subsequent remodeling and comprises arteries, veins, and capillary beds. Most of the vascular growth is mediated by angiogenesis that is involved in EC proliferation, migration and maturation (Eelen et al. Furthermore, we suggest that the normalization strategy of pathological angiogenesis could be a promising therapeutic target for various diseases, including cancer.Įndothelial cells (ECs) that line the capillary blood vessels in the tissues form numerous networks in the body. Here, we review vascular contribution as a major factor in microenvironment homeostasis in the pathogenesis of normal as well as cancerous tissues. Therefore, vascular–organ interactions as a vascular microenvironment or tissue microenvironment under physiological and pathological conditions are gaining popularity as an interesting research topic. ![]() Moreover, inflammatory cytokines and signaling regulators activated upon exposure to infection or various stresses play crucial roles in the pathological function of parenchymal cells, peripheral immune cells, stromal cells, and cancer cells in tissues. Recently, vascular endothelial cells have been classified as a type of innate immune cells that are dependent on the pathological situations. Vascular–organ interaction is a key mechanism and a concept that enables an understanding of all biological phenomena and normal physiology that is essential for human survival under pathological conditions. The role of angiogenesis in the growth of organs and tumors is widely recognized.
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