The contribution of endothelial cells to tissue fibrosis.

PURPOSE OF REVIEW: Tissue fibrosis is an increasingly prevalent condition associated with various diseases and heavily impacting on global morbidity and mortality rates. Growing evidence indicates that common cellular and molecular mechanisms may drive fibrosis of diverse cause and affecting different organs. The scope of this review is to highlight recent findings in support for an important role of vascular endothelial cells in the pathogenesis of fibrosis, with a special focus on systemic sclerosis as a prototypic multisystem fibrotic disorder. RECENT FINDINGS: Although transition of fibroblasts to chronically activated myofibroblasts is widely considered the central profibrotic switch, the endothelial cell involvement in development and progression of fibrosis has been increasingly recognized over the last few years. Endothelial cells can contribute to the fibrotic process either directly by acting as source of myofibroblasts through endothelial-to-myofibroblast transition (EndMT) and concomitant microvascular rarefaction, or indirectly by becoming senescent and/or secreting a variety of profibrotic and proinflammatory mediators with consequent fibroblast activation and recruitment of inflammatory/immune cells that further promote fibrosis. SUMMARY: An in-depth understanding of the mechanisms underlying EndMT or the acquisition of a profibrotic secretory phenotype by endothelial cells will provide the rationale for novel endothelial cell reprogramming-based therapeutic approaches to prevent and/or treat fibrosis.

The differential crosstalk of the skin-gut microbiome axis as a new emerging actor in systemic sclerosis.

OBJECTIVES: We characterized the microbiota in SSc, focusing on the skin-oral-gut axis and the serum and faecal free fatty acid (FFA) profile. METHODS: Twenty-five SSc patients with ACA or anti-Scl70 autoantibodies were enrolled. The microbiota of faecal, saliva and superficial epidermal samples was assessed through next-generation sequencing analysis. GC-MS was used to quantify faecal and serum FFAs. Gastrointestinal symptoms were investigated with the University of California Los Angeles Scleroderma Clinical Trial Consortium Gastrointestinal Tract Instrument (UCLA GIT-2.0) questionnaire. RESULTS: The ACA+ and anti-Scl70+ groups displayed different cutaneous and faecal microbiota profiles. The classes of cutaneous Sphingobacteriia and Alphaproteobacteria, the faecal phylum Lentisphaerae, the levels of the classes Lentisphaeria and Opitutae, and the genus NA-Acidaminococcaceae were significantly higher in faecal samples from the ACA+ patients than in samples from the anti-Scl70+ patients. The cutaneous Sphingobacteria and the faecal Lentisphaerae were significantly correlated (rho = 0.42; P = 0.03). A significant increase in faecal propionic acid was observed in ACA+ patients. Moreover, all levels of faecal medium-chain FFAs and hexanoic acids were significantly higher in the ACA+ group than in the anti-Scl70+ group (P < 0.05 and P < 0.001, respectively). In the ACA+ group, the analysis of the serum FFA levels showed an increasing trend in valeric acid. CONCLUSION: Different microbiota signatures and FFA profiles were found for the two groups of patients. Despite being in different body districts, the cutaneous Sphingobacteria and faecal Lentisphaerae appear interdependent.

Extraosseous Ewing's sarcoma of the pancreas.

We present the clinical case of a 21-year-old male with abdominal pain in the left hypochondrium radiating to the ipsilateral lumbar area and a weight loss of 2kg over a month, secondary to a large palpable intra-abdominal mass in the examination. TAC revealed a large solid mass with necrotic-cystic component which depended of the pancreas, infiltrated the spleen, enveloped the celiac trunk and affected to the splenic vases. Inmunohistochemical and molecular study confirmed the diagnosis extraosseus Ewing sarcoma (EES).

Soluble guanylate cyclase stimulation fosters angiogenesis and blunts myofibroblast-like features of systemic sclerosis endothelial cells.

OBJECTIVES: In SSc, angiogenesis impairment advances in parallel with the development of fibrosis orchestrated by myofibroblasts originating from different sources, including endothelial-to-mesenchymal transition (EndoMT). Soluble guanylate cyclase (sGC) stimulation has shown antifibrotic effects in SSc skin fibroblasts and mouse models. Here, we investigated the effects of pharmacological sGC stimulation on impaired angiogenesis and myofibroblast-like features of SSc dermal microvascular endothelial cells (SSc-MVECs). METHODS: To determine whether sGC stimulation affected cell viability/proliferation, SSc-MVECs and healthy dermal MVECs (H-MVECs) were challenged with the sGC stimulator (sGCS) MK-2947 and assayed by annexin V/propidium iodide flow cytometry and the water-soluble tetrazolium salt (WST-1) assay. To study angiogenesis and EndoMT, MK-2947-treated SSc-MVECs were subjected to wound healing and capillary morphogenesis assays and analysed for the expression of endothelial/myofibroblast markers and contractile ability. RESULTS: MK-2947 treatment did not affect H-MVEC viability/proliferation, while it significantly increased SSc-MVEC proliferation, wound healing capability and angiogenic performance. After MK-2947 treatment, SSc-MVECs exhibited significantly increased proangiogenic MMP9 and decreased antiangiogenic MMP12 and PTX3 gene expression. A significant increase in the expression of CD31 and vascular endothelial cadherin paralleled by a decrease in α-smooth muscle actin, S100A4, type I collagen and Snail1 mesenchymal markers was also found in MK-2947-treated SSc-MVECs. Furthermore, stimulation of sGC with MK-2947 significantly counteracted the intrinsic ability of SSc-MVECs to contract collagen gels and reduced phosphorylated-extracellular signal-regulated kinases 1 and 2 protein levels. CONCLUSION: These findings demonstrate for the first time that pharmacological sGC stimulation effectively ameliorates the angiogenic performance and blunts the myofibroblast-like profibrotic phenotype of SSc-MVECs, thus providing new evidence for repurposing sGCSs for SSc.

Current Trends in Vascular Biomarkers for Systemic Sclerosis: A Narrative Review.

Systemic sclerosis (SSc, scleroderma) is a multifaceted rare connective tissue disease whose pathogenesis is dominated by immune dysregulation, small vessel vasculopathy, impaired angiogenesis, and both cutaneous and visceral fibrosis. Microvascular impairment represents the initial event of the disease, preceding fibrosis by months or years and accounting for the main disabling and/or life-threatening clinical manifestations, including telangiectasias, pitting scars, periungual microvascular abnormalities (e.g., giant capillaries, hemorrhages, avascular areas, ramified/bushy capillaries) clinically detectable by nailfold videocapillaroscopy, ischemic digital ulcers, pulmonary arterial hypertension, and scleroderma renal crisis. Despite a variety of available treatment options, treatment of SSc-related vascular disease remains problematic, even considering SSc etherogenity and the quite narrow therapeutic window. In this context, plenty of studies have highlighted the great usefulness in clinical practice of vascular biomarkers allowing clinicians to assess the evolution of the pathological process affecting the vessels, as well as to predict the prognosis and the response to therapy. The current narrative review provides an up-to-date overview of the main candidate vascular biomarkers that have been proposed for SSc, focusing on their main reported associations with characteristic clinical vascular features of the disease.

Morphologic evidence of telocytes in human thyroid stromal tissue.

Despite the evidence accumulated over the past decade that telocytes (TCs) are a distinctive, though long neglected, cell entity of the stromal microenvironment of several organs of the human body, to date their localization in the endocrine glands remains almost unexplored. This study was therefore undertaken to examine the presence and characteristics of TCs in normal human thyroid stromal tissue through an integrated morphologic approach featuring light microscopy and ultrastructural analysis. TCs were first identified by immunohistochemistry that revealed the existence of an intricate network of CD34+ stromal cells spread throughout the thyroid interfollicular connective tissue. Double immunofluorescence allowed to clearly differentiate CD34+ stromal cells lacking CD31 immunoreactivity from neighbour CD31+ microvascular structures, and the evidence that these stromal cells coexpressed CD34 and platelet-derived growth factor receptor α further strengthened their identification as TCs. Transmission electron microscopy confirmed the presence of stromal cells ultrastructurally identifiable as TCs projecting their characteristic cytoplasmic processes (i.e., telopodes) into the narrow interstitium between thyroid follicles and blood microvessels, where telopodes intimately surrounded the basement membrane of thyrocytes. Collectively, these morphologic findings provide the first comprehensive demonstration that TCs are main constituents of the human thyroid stroma and lay the necessary groundwork for further in-depth studies aimed at clarifying their putative implications in glandular homeostasis and pathophysiology.

A candidate gene study reveals association between a variant of the SRp55 splicing factor gene and systemic sclerosis.

OBJECTIVES: To examine the possible implication of the mRNA-binding protein serine/arginine protein 55 (SRp55, also known as SRSF6) rs2235611 single nucleotide polymorphism (SNP) in the genetic predisposition to systemic sclerosis (SSc) susceptibility and clinical phenotype. METHODS: A total population of 872 white Italian individuals (414 SSc patients, 458 controls) was studied. SSc patients were assessed for limited and diffuse cutaneous subsets and the presence of autoantibodies, interstitial lung disease (ILD), and nailfold videocapillaroscopy (NVC) abnormalities. The SRp55 rs2235611 SNP was genotyped by TaqMan real-time PCR. RESULTS: SRp55 rs2235611 genotype distribution and allele frequency were similar in SSc and healthy controls, though a trend toward significance was observed for genotype distribution (p=0.07). The SRp55 rs2235611 AA genotype significantly influenced the predisposition to SSc (p= 0.03). The SRp55 rs2235611 A minor allele and AA genotype showed a significant risk association with susceptibility to SSc-related ILD (A allele: p=0.046; AA genotype: p=0.007). A significant association of the AA genotype with SSc late NVC pattern was also found (p=0.006). After Bonferroni correction for multiple comparisons, the risk association of the SRp55 rs2235611 AA genotype with SSc-related ILD and late NVC pattern remained significant (padj=0.049 and padj=0.042, respectively). CONCLUSIONS: The SRp55 rs2235611 AA genotype significantly influences the susceptibility to SSc, and specifically associates with the presence of SSc-related ILD and late NVC pattern. Further in-depth studies on the SRp55 gene locus will hopefully contribute to extend our knowledge of the genetic predisposition to major SSc-related manifestations such as pulmonary fibrosis and peripheral microvasculopathy.

The Soluble Guanylate Cyclase Stimulator BAY 41-2272 Attenuates Transforming Growth Factor ß1-Induced Myofibroblast Differentiation of Human Corneal Keratocytes.

Corneal transparency, necessary for vision and depending on the high organization of stromal extracellular matrix, is maintained by keratocytes. Severe or continuous corneal injuries determine exaggerated healing responses resulting in the formation of irreversible fibrotic scars and vision impairment. Soluble guanylate cyclase (sGC) stimulation demonstrated antifibrotic effects in both experimental fibrosis and human lung and skin fibroblasts. Here, we assessed whether sGC stimulation with BAY 41-2272 could attenuate transforming growth factor ß1 (TGFß1)-induced myofibroblast differentiation of human corneal keratocytes. Cells were challenged with TGFß1, with/without BAY 41-2272 preincubation, and subsequently assessed for viability, proliferation, migration, chemoinvasion, as well for the expression of myofibroblast/fibroblast activation markers and contractile abilities. Treatment with BAY 41-2272 did not affect keratocyte viability, while preincubation of cells with the sGC stimulator was able to inhibit TGFß1-induced proliferation, wound healing capacity, and invasiveness. BAY 41-2272 was also able to attenuate TGFß1-induced myofibroblast-like profibrotic phenotype of keratocytes, as demonstrated by the significant decrease in ACTA2, COL1A1, COL1A2, FN1 and PDPN gene expression, as well as in α-smooth muscle actin, α-1 chain of type I collagen, podoplanin, vimentin and N-cadherin protein expression. Finally, BAY 41-2272 significantly counteracted the TGFß1-induced myofibroblast-like ability of keratocytes to contract collagen gels, reduced phosphorylated Smad3 protein levels, and attenuated gene expression of proinflammatory cytokines. Collectively, our data show for the first time that BAY 41-2272 is effective in counteracting keratocyte-to-myofibroblast transition, thus providing the rationale for the development of sGC stimulators as novel promising modulators of corneal scarring and fibrosis.

Effects of Photobiomodulation in Patients Presenting with Reticular Pseudodrusen: A Retrospective Observational Case Series Study.

Background and Objectives: The purpose of this study is to describe the effects of photobiomodulation on drusen regression with patients presenting with reticular pseudodrusen (RPD). Materials and Methods: This study is a retrospective observational case series study including patients presenting with RPD who underwent treatment by photobiomodulation. All patients underwent a complete ophthalmic examination and multimodal imaging prior to treatment, including spectral-domain optical coherence tomography (SD-OCT). Eyes were treated two times per week for six consecutive weeks. Best corrected-visual acuity (BVCA) was measured prior and after treatment for all patients. The number of RPD on the SD-OCT scans centered on the macula and stages of RPD was noted at baseline and 6 months after the first treatment session. Results: Five eyes of five patients were included in the study. Mean BCVA did not change 6 months after treatment compared to baseline. Mean number of RPD per eye was 112.60 +/- 48.33 RPD at baseline and 111.6 +/- 49.29 in the same area 6 months after treatment. Changes in RPD distribution according to RPD classification were observed before and after treatment with photobiomodulation. Changes in distribution mostly concerned stages 1 and 3 RPD: Total number of stage 1 RPD was 289 and increased to 324 after treatment. Total number of stage 3 RPD was 97 at baseline and decreased to 67 6 months after treatment. Percentage of stage 1 RPD increased from 46% to 56% after treatment. Percentage of stage 3 RPD decreased from 20% to 13% after treatment. Conclusions: Changes in RPD distribution were observed before and after treatment with photobiomodulation. The number of stage 3 reticular pseudodrusen decreased while number of stage 1 reticular pseudodrusen increased after treatment.

Impairment in the telocyte/CD34+ stromal cell network in human rheumatoid arthritis synovium.

Telocytes (TCs)/CD34+ stromal cells have recently emerged as peculiar interstitial cells detectable in a variety of organs throughout the human body. TCs are typically arranged in networks establishing unique spatial relationships with neighbour cells and likely contributing to the maintenance of tissue homeostasis by both cell-to-cell contacts and releasing extracellular vesicles. Hence, TC defects are being increasingly reported in different pathologies, such as chronic inflammatory and fibrotic conditions. In this regard, TCs/CD34+ stromal cells have been shown to constitute an intricate interstitial network in the subintimal area of the normal human synovial membrane, but whether they are altered in chronic synovitis has yet to be explored. We therefore undertook a morphologic study to compare the distribution of TCs/CD34+ stromal cells between normal synovium and chronically inflamed synovium from patients with rheumatoid arthritis (RA) by using CD34 immunohistochemistry and CD31/CD34 double immunofluorescence. CD34 immunostaining revealed that, at variance with normal synovium, the inflamed and hyperplastic RA synovial tissue was nearly or even completely devoid of TCs/CD34+ stromal cells. Double immunofluorescence confirmed that almost all CD34+ tissue components detectable in RA synovium were blood vessels coexpressing CD31, while a widespread network of CD31- /CD34+ TCs was clearly evident in the whole sublining layer of normal synovium. In the context of the emerging diverse roles of TCs/CD34+ stromal cells in the regulation of tissue homeostasis and structure, the remarkable impairment in their networks herein uncovered in RA synovium may suggest important pathophysiologic implications that will be worth investigating further.

Bone Marrow-Mesenchymal Stromal Cell Secretome as Conditioned Medium Relieves Experimental Skeletal Muscle Damage Induced by Ex Vivo Eccentric Contraction.

Bone marrow-mesenchymal stem/stromal cells (MSCs) may offer promise for skeletal muscle repair/regeneration. Growing evidence suggests that the mechanisms underpinning the beneficial effects of such cells in muscle tissue reside in their ability to secrete bioactive molecules (secretome) with multiple actions. Hence, we examined the effects of MSC secretome as conditioned medium (MSC-CM) on ex vivo murine extensor digitorum longus muscle injured by forced eccentric contraction (EC). By combining morphological (light and confocal laser scanning microscopies) and electrophysiological analyses we demonstrated the capability of MSC-CM to attenuate EC-induced tissue structural damages and sarcolemnic functional properties' modifications. MSC-CM was effective in protecting myofibers from apoptosis, as suggested by a reduced expression of pro-apoptotic markers, cytochrome c and activated caspase-3, along with an increase in the expression of pro-survival AKT factor. Notably, MSC-CM also reduced the EC-induced tissue redistribution and extension of telocytes/CD34+ stromal cells, distinctive cells proposed to play a "nursing" role for the muscle resident myogenic satellite cells (SCs), regarded as the main players of regeneration. Moreover, it affected SC functionality likely contributing to replenishment of the SC reservoir. This study provides the necessary groundwork for further investigation of the effects of MSC secretome in the setting of skeletal muscle injury and regenerative medicine.

Scleroderma-like Impairment in the Network of Telocytes/CD34+ Stromal Cells in the Experimental Mouse Model of Bleomycin-Induced Dermal Fibrosis.

Considerable evidence accumulated over the past decade supports that telocytes (TCs)/CD34+ stromal cells represent an exclusive type of interstitial cells identifiable by transmission electron microscopy (TEM) or immunohistochemistry in various organs of the human body, including the skin. By means of their characteristic cellular extensions (telopodes), dermal TCs are arranged in networks intermingled with a multitude of neighboring cells and, hence, they are thought to contribute to skin homeostasis through both intercellular contacts and releasing extracellular vesicles. In this context, fibrotic skin lesions from patients with systemic sclerosis (SSc, scleroderma) appear to be characterized by a disruption of the dermal network of TCs, which has been ascribed to either cell degenerative processes or possible transformation into profibrotic myofibroblasts. In the present study, we utilized the well-established mouse model of bleomycin-induced scleroderma to gain further insights into the TC alterations found in cutaneous fibrosis. CD34 immunofluorescence revealed a severe impairment in the dermal network of TCs/CD34+ stromal cells in bleomycin-treated mice. CD31/CD34 double immunofluorescence confirmed that CD31-/CD34+ TC counts were greatly reduced in the skin of bleomycin-treated mice compared with control mice. Ultrastructural signs of TC injury were detected in the skin of bleomycin-treated mice by TEM. The analyses of skin samples from mice treated with bleomycin for different times by either TEM or double immunostaining and immunoblotting for the CD34/α-SMA antigens collectively suggested that, although a few TCs may transition to α-SMA+ myofibroblasts in the early disease stage, most of these cells rather undergo degeneration, and then are lost. Taken together, our data demonstrate that TC changes in the skin of bleomycin-treated mice mimic very closely those observed in human SSc skin, which makes this experimental model a suitable tool to (i) unravel the pathological mechanisms underlying TC damage and (ii) clarify the possible contribution of the TC loss to the development/progression of dermal fibrosis. In perspective, these findings may have important implications in the field of skin regenerative medicine.

Targeting anticoagulant protein S to improve hemostasis in hemophilia.

Improved treatments are needed for hemophilia A and B, bleeding disorders affecting 400 000 people worldwide. We investigated whether targeting protein S could promote hemostasis in hemophilia by rebalancing coagulation. Protein S (PS) is an anticoagulant acting as cofactor for activated protein C and tissue factor pathway inhibitor (TFPI). This dual role makes PS a key regulator of thrombin generation. Here, we report that targeting PS rebalances coagulation in hemophilia. PS gene targeting in hemophilic mice protected them against bleeding, especially when intra-articular. Mechanistically, these mice displayed increased thrombin generation, resistance to activated protein C and TFPI, and improved fibrin network. Blocking PS in plasma of hemophilia patients normalized in vitro thrombin generation. Both PS and TFPIα were detected in hemophilic mice joints. PS and TFPI expression was stronger in the joints of hemophilia A patients than in those of hemophilia B patients when receiving on-demand therapy, for example, during a bleeding episode. In contrast, PS and TFPI expression was decreased in hemophilia A patients receiving prophylaxis with coagulation factor concentrates, comparable to osteoarthritis patients. These results establish PS inhibition as both controller of coagulation and potential therapeutic target in hemophilia. The murine PS silencing RNA approach that we successfully used in hemophilic mice might constitute a new therapeutic concept for hemophilic patients.

REAL-COLOR VERSUS PSEUDO-COLOR IMAGING OF FIBROTIC SCARS IN EXUDATIVE AGE-RELATED MACULAR DEGENERATION.

PURPOSE: To compare the morphological characteristics of subretinal fibrosis in late age-related macular degeneration using multicolor (MC) imaging, color fundus photography (CFP), and ultra-widefield CFP (UWFCFP). METHODS: Thirty-two eyes of 31 patients diagnosed with subretinal fibrosis complicating exudative age-related macular degeneration were included. Included eyes were imaged by MC, CFP, and UWFCFP. The overall ability to visualize fibrosis, its margins, and dissimilarity with surrounding atrophy was graded using a score (0: not visible, 1: barely visible, 2: mostly visible, and 3: fully visible) by two readers. Area of fibrosis was calculated. Scaling, lesion colocalization on all three imaging techniques, and area measurements were performed using ImageJ. RESULTS: Ninety-six images of 32 eyes were graded. The average area of fibrosis was 14.59 ± 8.94 mm for MC, 13.84 ± 8.56 mm for CFP, and 13.76 ± 8.79 mm for UWFCFP. Fibrosis was fully visible in 87.5% of cases using MC and 50% using CFP and UWFCFP. Fibrosis' margins were sharply defined in 40.6% of eyes with MC, 15.6% and 9.4% with CFP and UWFCFP, respectively. Multicolor imaging provided superior distinction between fibrosis and atrophy (100% for MC vs. 13.4% for CFP and 33.3% for UWFCFP). The inter- and intra-reader agreement was high for all measurements (P < 0.0001). CONCLUSION: Multicolor technology allows for improved visualization and analysis of subretinal fibrosis when compared with CFP and UWFCFP, especially when surrounding atrophy is present.

New onset severe right ventricular failure associated with COVID-19 in a young infant without previous heart disease.

We present our recent experience with a 6-month-old infant with a personal history of short bowel syndrome that presented with fever, cyanosis, and cardiogenic shock secondary to severe pulmonary hypertension and right ventricular failure without pulmonary thromboembolism. He did not present signs of toxin-mediated disease or Kawasaki disease. He was finally diagnosed with SARS-CoV-2 infection. If this presentation is confirmed in future research, the severe cardiovascular impairment in children with COVID-19 could be also attributable to the primary pulmonary infection, not only to a multisystem inflammatory syndrome but also in children without heart disease.

A Two-Step Immunomagnetic Microbead-Based Method for the Isolation of Human Primary Skin Telocytes/CD34+ Stromal Cells.

Telocytes (TCs), commonly referred to as TCs/CD34+ stromal cells, are a peculiar type of interstitial cells with distinctive morphologic traits that are supposed to exert several biological functions, including tissue homeostasis regulation, cell-to-cell signaling, immune surveillance, and reparative/regenerative effects. At present, the majority of studies investigating these cells are mainly descriptive and focus only on their morphology, with a consequent paucity of functional data. To gain relevant insight into the possible functions of TCs, in vitro analyses are clearly required, but currently, the protocols for TC isolation are only at the early stages and not fully standardized. In the present in vitro study, we describe a novel methodology for the purification of human primary skin TCs through a two-step immunomagnetic microbead-based cell separation (i.e., negative selection for CD31 followed by positive selection for CD34) capable of discriminating these cells from other connective tissue-resident cells on the basis of their different immunophenotypic features. Our experiments clearly demonstrated that the proposed method allows a selective purification of cells exhibiting the peculiar TC morphology. Isolated TCs displayed very long cytoplasmic extensions with a moniliform silhouette (telopodes) and presented an immunophenotypic profile (CD31-/CD34+/PDGFRα+/vimentin+) that unequivocally differentiates them from endothelial cells (CD31+/CD34+/PDGFRα-/vimentin+) and fibroblasts (CD31-/CD34-/PDGFRα+/vimentin+). This novel methodology for the isolation of TCs lays the groundwork for further research aimed at elucidating their functional properties and possible translational applications, especially in the field of regenerative medicine.

A new avenue in the pathogenesis of systemic sclerosis: the molecular interface between the endothelial and the nervous systems.

Systemic sclerosis (SSc) is a connective tissue disorder characterised by immune dysregulation, endothelial cell dysfunction followed by defective vascular repair and neovascularization and progressive tissue fibrosis of the skin and internal organs, whose pathophysiology remains to be fully elucidated. Perturbed neuroendothelial control mechanisms comprising either endothelial cell or peripheral nerve fiber impairment are supposed to play an important role in the onset of Raynaud's phenomenon and development of microvascular abnormalities which are the earliest events and key features of SSc. Such pathogenic neuroendothelial mechanisms may trigger both the early endothelial cell damage and the subsequent loss of peripheral microvascular integrity characterised by the lack of compensatory angiogenesis. Of note, the vascular and nervous systems have several anatomical similarities that extend to molecular level, and the molecular mechanisms of nerve regulation are shared by the vascular system. In this context, increasing evidence demonstrated that endothelial cells express receptors for axon guidance molecules, including Ephrin family receptor tyrosine kinases, Neuropilins, Plexins, Robos, and UNC5B that are able to respond to their soluble neuroendothelial trophic ligands, such as Semaphorins and Slits, to guide the sprouting of endothelial tip cells. Here, we first provide a historical view of neuroendothelial control mechanism alterations in the pathogenesis of SSc, and then discuss the emerging role of a class of molecules sharing neurogenic and angiogenic properties, such as members of Semaphorin/Plexin/Neuropilin and Slit/Roundabout families, in SSc-related peripheral microvasculopathy.

Systemic Sclerosis Serum Significantly Impairs the Multi-Step Lymphangiogenic Process: in Vitro Evidence.

In systemic sclerosis (SSc), the possible involvement of lymphatic microcirculation and lymphangiogenesis has traditionally been overshadowed by the greater emphasis placed on dysfunctional blood vascular system and angiogenesis. In the present in vitro study, we explore for the first time whether the SSc microenvironment may interfere with lymphangiogenesis, a complex, multi-step process in which lymphatic microvascular endothelial cells (LMVECs) sprout, migrate, and proliferate to generate new lymphatic capillaries. Normal human adult dermal LMVECs from three donors were treated with serum from SSc patients (n = 8), serum from healthy individuals (n = 8), or recombinant human vascular endothelial growth factor (VEGF)-C as a positive control for lymphangiogenesis. Cell proliferation, Boyden chamber Matrigel chemoinvasion, wound healing capacity, and lymphatic capillary morphogenesis on Geltrex were assayed. VEGF-C serum levels were measured by enzyme-linked immunosorbent assay. Gene and protein expression levels of the lymphangiogenic orchestrators VEGF receptor-3 (VEGFR-3)/Flt-4 and neuropilin-2 (NRP-2) were determined by real-time PCR and Western blotting, respectively. Conditioning with SSc serum significantly inhibited LMVEC proliferation, Matrigel invasion, and wound healing capacity with respect to healthy serum. The ability of LMVECs to form lymphatic tubes on Geltrex was also severely compromised in the presence of SSc serum. VEGF-C levels were comparable in SSc and healthy sera. Treatment with SSc serum resulted in a significant downregulation of both VEGFR-3/Flt-4 and NRP-2 mRNA and protein levels. In SSc, the pathologic environment severely hampers every lymphangiogenesis step, likely through the reduction of pro-lymphangiogenic VEGFR-3/NRP-2 co-receptor signaling. The impairment of the lymphangiogenic process opens a new scenario underlying SSc vascular pathophysiology, which is worth investigating further.

Telocyte implications in human pathology: An overview.

Telocytes are a recently described interstitial cell population widely distributed in the stromal compartment of many organs in vertebrates, including humans. Owing to their close spatial relationship with multiple cell types, telocytes are universally considered as 'connecting cells' mostly committed to intercellular signaling by converting the interstitium into an integrated system that drives organ development and contributes to the maintenance of local tissue homeostasis. Increasing evidence indicates that telocytes may cooperate with tissue-resident stem cells to foster organ repair and regeneration, and that telocyte damage and dysfunction may occur in several disorders. The goal of this review is to provide an overview of the most recent findings concerning the implication of telocytes in a variety of pathologic conditions in humans, including heart disease, chronic inflammation and multiorgan fibrosis. Based on recent promising experimental data, there is realistic hope that by targeting telocytes alone or in tandem with stem cells, we might be able to promote organ regeneration and/or prevent irreversible end-stage organ damage in different pathologies.

Slit2/Robo4 axis may contribute to endothelial cell dysfunction and angiogenesis disturbance in systemic sclerosis.

OBJECTIVE: In systemic sclerosis (SSc), early microvascular injury is followed by impaired angiogenesis and peripheral capillary loss. Here, we investigated the possible contribution of the neurovascular guidance molecule Slit2 and its Roundabout (Robo) receptors to SSc-related endothelial cell dysfunction. METHODS: Circulating Slit2 levels were measured in patients with SSc and healthy controls. Slit2, Robo1 and Robo4 expression was investigated in SSc and healthy skin biopsies and explanted dermal microvascular endothelial cells (MVECs). Slit2/Robo4 function in MVEC angiogenesis was studied by cell viability, wound healing and capillary-like tube formation assays. RESULTS: Circulating Slit2 was significantly increased in either SSc or patients with a very early diagnosis of SSc (VEDOSS) compared with controls. Interestingly, serum Slit2 levels were raised in patients with VEDOSS with nailfold videocapillaroscopy (NVC) abnormalities, while they were similar in VEDOSS with normal NVC and controls. In SSc, Slit2 and Robo4 expression was upregulated in clinically affected skin and explanted MVECs in respect to controls. The angiogenic performance of healthy MVECs was significantly reduced after challenge with recombinant human Slit2 or SSc sera. These inhibitory effects were significantly attenuated when SSc sera were preincubated with an anti-Slit2 blocking antibody. In vitro angiogenesis was severely compromised in SSc-MVECs and could be significantly ameliorated by Slit2 neutralisation or ROBO4 gene silencing. Slit2/Robo4 axis interfered with angiogenesis through the inhibition of Src kinase phosphorylation. CONCLUSIONS: In SSc, increased circulating levels of Slit2 and activation of the Slit2/Robo4 antiangiogenic axis may contribute to peripheral microangiopathy since the very early phase of the disease.