Telocyte Behaviour During Inflammation, Repair and Tumour Stroma Formation

Morphological and histochemical identification of telocytes in adult yak epididymis

Telocytes (TCs) are a newly discovered type of mesenchymal cell that are closely related to the tissue's internal environment. The study aimed to investigate the morphological identification of TCs in the epididymis of adult yak and their role in the local microenvironment. In this study, transmission electron microscopy (TEM), scanning electron microscopy, immunofluorescence, qRT-PCR, and western blotting were used to analyze the cell morphology of TCs. The results showed that there are two types of TCs in the epididymal stroma of yak by TEM; one type is distributed around the capillaries with full cell bodies, longer TPs, and a large number of secretory vesicles; the other is distributed outside the basement membrane with irregularly long, striped, large nuclei and short telopodes (TPs). In addition, these TCs formed complex TC cell networks through TPs with epididymal interstitial capillaries and basal fibroblasts. TCs often appear near the capillaries and basement membrane by special staining. The surface markers of TCs (CD34, vimentin, and CD117) were positively expressed in the epididymal stroma and epithelium by immunohistochemistry, and immunofluorescence co-expression of vimentin + CD34 and CD117 + CD34 was observed on the surface of TCs. The trends in the mRNA and protein expression of TCs surface markers revealed expression was highest in the caput epididymis. In summary, this is first report of TCs in the epididymis of yak, and two phenotypes of TCs were observed. The existence and distribution characteristics of TCs in the epididymis of plateau yaks provide important clues for further study of the adaptation to reproductive function in the plateau.

Comparison of the Behavior of Perivascular Cells (Pericytes and CD34+ Stromal Cell/Telocytes) in Sprouting and Intussusceptive Angiogenesis

Perivascular cells in the pericytic microvasculature, pericytes and CD34+ stromal cells/telocytes (CD34+SCs/TCs), have an important role in angiogenesis. We compare the behavior of these cells depending on whether the growth of endothelial cells (ECs) from the pre-existing microvasculature is toward the interstitium with vascular bud and neovessel formation (sprouting angiogenesis) or toward the vascular lumen with intravascular pillar development and vessel division (intussusceptive angiogenesis). Detachment from the vascular wall, mobilization, proliferation, recruitment, and differentiation of pericytes and CD34+SCs/TCs, as well as associated changes in vessel permeability and functionality, and modifications of the extracellular matrix are more intense, longer lasting over time, and with a greater energy cost in sprouting angiogenesis than in intussusceptive angiogenesis, in which some of the aforementioned events do not occur or are compensated for by others (e.g., sparse EC and pericyte proliferation by cell elongation and thinning). The governing mechanisms involve cell-cell contacts (e.g., peg-and-socket junctions between pericytes and ECs), multiple autocrine and paracrine signaling molecules and pathways (e.g., vascular endothelial growth factor, platelet-derived growth factor, angiopoietins, transforming growth factor B, ephrins, semaphorins, and metalloproteinases), and other factors (e.g., hypoxia, vascular patency, and blood flow). Pericytes participate in vessel development, stabilization, maturation and regression in sprouting angiogenesis, and in interstitial tissue structure formation of the pillar core in intussusceptive angiogenesis. In sprouting angiogenesis, proliferating perivascular CD34+SCs/TCs are an important source of stromal cells during repair through granulation tissue formation and of cancer-associated fibroblasts (CAFs) in tumors. Conversely, CD34+SCs/TCs have less participation as precursor cells in intussusceptive angiogenesis. The dysfunction of these mechanisms is involved in several diseases, including neoplasms, with therapeutic implications.

Altered Mucus Barrier Integrity and Increased Susceptibility to Colitis in Mice upon Loss of Telocyte Bone Morphogenetic Protein Signalling

FoxL1+-Telocytes (TCFoxL1+) are subepithelial cells that form a network underneath the epithelium. We have shown that without inflammatory stress, mice with loss of function in the BMP signalling pathway in TCFoxL1+ (BmpR1aΔFoxL1+) initiated colonic neoplasia. Although TCFoxL1+ are modulated in IBD patients, their specific role in this pathogenesis remains unclear. Thus, we investigated how the loss of BMP signalling in TCFoxL1+ influences the severity of inflammation and fosters epithelial recovery after inflammatory stress. BmpR1a was genetically ablated in mouse colonic TCFoxL1+. Experimental colitis was performed using a DSS challenge followed by recovery steps to assess wound healing. Physical barrier properties, including mucus composition and glycosylation, were assessed by alcian blue staining, immunofluorescences and RT-qPCR. We found that BmpR1aΔFoxL1+ mice had impaired mucus quality, and upon exposure to inflammatory challenges, they had increased susceptibility to experimental colitis and delayed healing. In addition, defective BMP signalling in TCFoxL1+ altered the functionality of goblet cells, thereby affecting mucosal structure and promoting bacterial invasion. Following inflammatory stress, TCFoxL1+ with impaired BMP signalling lose their homing signal for optimal distribution along the epithelium, which is critical in tissue regeneration after injury. Overall, our findings revealed key roles of BMP signalling in TCFoxL1+ in IBD pathogenesis.

Intussusceptive angiogenesis and its counterpart intussusceptive lymphangiogenesis

Intussusceptive angiogenesis (IA) is currently considered an important alternative and complementary form of sprouting angiogenesis (SA). Conversely, intussusceptive lymphangiogenesis (IL) is in an initial phase of study. We compare their morphofunctional characteristics, since many can be shared by both processes. To that end, the following aspects are considered: A) The concept of IA and IL as the mechanism by which blood and lymphatic vessels split, expand and remodel through transluminal pillar formations (hallmarks of intussusception). B) Terminology and historical background, with particular reference to the group of Burri, including Djonov and Patan, who initiated and developed the vessel intussusceptive concept in blood vessels. C) Incidence in normal (e.g. in the sinuses of developing lymph nodes) and pathologic conditions, above all in vessel diseases, such as dilated veins in hemorrhoidal disease, intravascular papillary endothelial hyperplasia (IPEH), sinusoidal hemangioma, lobular capillary hemangioma, lymphangiomas/lymphatic malformations and vascular transformation of lymph nodes. D) Differences and complementarity between vessel sprouting and intussusception. E) Characteristics of the cover (endothelial cells) and core (connective tissue components) of pillars and requirements for pillar identification. F) Structures involved in pillar formation, including endothelial contacts of opposite vessel walls, interendothelial bridges, merged adjacent capillaries, vessel loops and spilt pillars. G) Structures resulting from pillars with intussusceptive microvascular growth, arborization, remodeling and segmentation (compartmentalization). H) Influence of intussusception in the morphogenesis of vessel tumors/ pseudotumors; and I) Hemodynamic and molecular control of vessel intussusception, including VEGF, PDGF BB, Hypoxia, Notch, Endoglobin and Nitric oxide.

IQGAP1, AmotL2, and FKBP51 Scaffoldins in the Glioblastoma Microenvironment

Glioblastoma (GB) is the most frequently occurring and aggressive primary brain tumor. Glioma stem cells (GSCs) and astrocytoma cells are the predominant malignant cells occurring in GB besides a highly heterogeneous population of migrating, neovascularizing and infiltrating myeloid cells that forms a complex tumor microenvironment (TME). Cross talk between the TME cells is pivotal in the biology of this tumor and, consequently, adaptor proteins at critical junctions of signaling pathways may be crucial. Scaffold proteins (scaffolins or scaffoldins) integrate external and internal stimuli to regulate various signaling pathways, interacting simultaneously with multiple proteins involved. We investigated by double and triple immunofluorescence the localization of IQGAP1, AmotL2, and FKBP51, three closely related scaffoldins, in malignant cells and TME of human GB tumors. We found that IQGAP1 is preferentially expressed in astrocytoma cells, AmotL2 in GSCs, and FKBP51 in white blood cells in human GB tumors. As GSCs are specially the target for novel therapies, we will investigate in further studies whether AmotL2 inhibition is effective in the treatment of GB.

The molecular phenotypes of ureteral telocytes are layer-specific

Telocytes (TC) are the delicate interstitial (stromal) cells defined by their long, thin and moniliform processes termed telopodes. Numerous studies determined that different subsets of telocytes populate almost all tissues and attempted to relate these subsets to various functions, from cell signaling to tissue repair and regeneration. Extremely few studies addressed the urinary tract though few data on the molecular pattern of the urinary TCs actually exist. We therefore hypothesized that subsets of urinary TCs co-localize within the human ureter and we aimed at performing an immunohistochemical study to evaluate the tissue-specific molecular pattern of TCs. On sample tissues of proximal ureter drawn from ten human adult patients during surgery were applied primary antibodies against CD34, CD105, von Willebrand Factor, the heavy chain of smooth muscle myosin (SMM) and c-erbB-2. The molecular pattern indicated three different subsets of ureteral TCs which are neither endothelial nor epithelial in nature: (a) type I: the CD34-/CD105+ TCs of the superficial layer of lamina propria; (b) type II: the CD34+/CD105± myoid TCs of the deep layer of lamina propria and (c) type III: the CD34+/CD105+ perivascular TCs. Although apparently different, all these subsets of TCs could belong to the stem/progenitor niche of the ureter.

Adaptive changes of telocytes in the urinary bladder of patients affected by neurogenic detrusor overactivity

Urinary bladder activity involves central and autonomic nervous systems and bladder wall. Studies on the pathogenesis of voiding disorders such as the neurogenic detrusor overactivity (NDO) due to suprasacral spinal cord lesions have emphasized the importance of an abnormal handling of the afferent signals from urothelium and lamina propria (LP). In the LP (and detrusor), three types of telocytes (TC) are present and form a 3D-network. TC are stromal cells able to form the scaffold that contains and organizes the connective components, to serve as guide for tissue (re)-modelling, to produce trophic and/or regulatory molecules, to share privileged contacts with the immune cells. Specimens of full thickness bladder wall from NDO patients were collected with the aim to investigate possible changes of the three TC types using histology, immunohistochemistry and transmission electron microscopy. The results show that NDO causes several morphological TC changes without cell loss or network interruption. With the exception of those underlying the urothelium, all the TC display signs of activation (increase in Caveolin1 and caveolae, αSMA and thin filaments, Calreticulin and amount of cisternae of the rough endoplasmic reticulum, CD34, euchromatic nuclei and large nucleoli). In all the specimens, a cell infiltrate, mainly consisting in plasma cells located in the vicinity or taking contacts with the TC, is present. In conclusion, our findings show that NDO causes significant changes of all the TC. Notably, these changes can be interpreted as TC adaptability to the pathological condition likely preserving each of their peculiar functions.