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

Angiogenic T cell expansion correlates with severity of peripheral vascular damage in systemic sclerosis

The mechanisms underlying endothelial cell injury and defective vascular repair in systemic sclerosis (SSc) remain unclear. Since the recently discovered angiogenic T cells (Tang) may have an important role in the repair of damaged endothelium, this study aimed to analyze the Tang population in relation to disease-related peripheral vascular features in SSc patients. Tang (CD3+CD31+CXCR4+) were quantified by flow cytometry in peripheral blood samples from 39 SSc patients and 18 healthy controls (HC). Circulating levels of the CXCR4 ligand stromal cell-derived factor (SDF)-1α and proangiogenic factors were assessed in paired serum samples by immunoassay. Serial skin sections from SSc patients and HC were subjected to CD3/CD31 and CD3/CXCR4 double immunofluorescence. Circulating Tang were significantly increased in SSc patients with digital ulcers (DU) compared either with SSc patients without DU or with HC. Tang levels were significantly higher in SSc patients with late nailfold videocapillaroscopy (NVC) pattern than in those with early/active NVC patterns and in HC. No difference in circulating Tang was found when comparing either SSc patients without DU or patients with early/active NVC patterns and HC. In SSc peripheral blood, Tang percentage was inversely correlated to levels of SDF-1α and CD34+CD133+VEGFR-2+ endothelial progenitor cells (EPC), and positively correlated to levels of vascular endothelial growth factor and matrix metalloproteinase-9. Tang were frequently detected in SSc dermal perivascular inflammatory infiltrates. In summary, our findings demonstrate for the first time that Tang cells are selectively expanded in the circulation of SSc patients displaying severe peripheral vascular complications like DU. In SSc, Tang may represent a potentially useful biomarker reflecting peripheral vascular damage severity. Tang expansion may be an ineffective attempt to compensate the need for increased angiogenesis and EPC function. Further studies are required to clarify the function of Tang cells and investigate the mechanisms responsible for their change in 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

The contribution of mesenchymal transitions to the pathogenesis of systemic sclerosis

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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

Increased Circulating Soluble Junctional Adhesion Molecules in Systemic Sclerosis: Association with Peripheral Microvascular Impairment

Systemic sclerosis (SSc, scleroderma) is a severe disease characterized by peripheral microcirculation abnormalities manifesting with Raynaud’s phenomenon, nailfold videocapillaroscopic (NVC) changes, and even ischemic digital ulcers (DUs) that are often refractory to treatments. In the wake of previously described associations between the circulating levels of soluble junctional adhesion molecules (sJAMs) and SSc clinical features, here, we measured sJAM-A and sJAM-C levels by enzyme-linked immunosorbent assay in serum samples from a large case series of 110 SSc patients and 85 healthy controls, focusing on their possible association with peripheral vascular clinical features and their potential as biomarkers that are either diagnostic or mirror SSc-related microvasculopathy severity. Our data demonstrated that serum sJAM-A and sJAM-C are significantly increased in patients with SSc vs. healthy controls, especially in those featuring early/active NVC patterns and the presence of ischemic DUs. Moreover, circulating sJAM-C levels showed good diagnostic accuracy in discriminating between patients and controls, as assessed by receiver operator characteristics curve analysis. Finally, logistic regression revealed that, when comparing sJAM-A to sJAM-C, the latter might be better suited as a biomarker for SSc-related DUs. Our promising findings provide the necessary groundwork for longitudinal follow-up analyses of SSc patients aiming to assess whether circulating sJAM-C levels might be predictive for the development of new DUs, as well as DU recurrence and/or refractoriness to targeted therapies

Circulating Neurovascular Guidance Molecules and Their Relationship with Peripheral Microvascular Impairment in Systemic Sclerosis

Systemic sclerosis (SSc, scleroderma) is a complex connective tissue disease whose earliest clinical manifestations are microvascular tone dysregulation and peripheral microcirculatory abnormalities. Following previous evidence of an association between circulating neurovascular guidance molecules and SSc disturbed angiogenesis, here, we measured the levels of soluble neuropilin 1 (sNRP1), semaphorin 3E (Sema3E), and Slit2 by enzyme-linked immunosorbent assay in serum samples from a large case series of 166 SSc patients vs. 110 healthy controls. We focused on their possible correlation with vascular disease clinical features and applied logistic regression analysis to determine which of them could better reflect disease activity and severity. Our results demonstrate that, in SSc: (i) sNRP1 is significantly decreased, with lower sNRP1 serum levels correlating with the severity of nailfold videocapillaroscopy (NVC) abnormalities and the presence of ischemic digital ulcers (DUs); (ii) both Sema3E and Slit2 are increased, with Sema3E better reflecting early NVC abnormalities; and (iii) higher Sema3E correlates with the absence of DUs, while augmented Slit2 associates with the presence of DUs. Receiver operator characteristics curve analysis revealed that both circulating sNRP1 and Sema3E show a moderate diagnostic accuracy. Moreover, logistic regression analysis allowed to identify sNRP1 and Sema3E as more suitable independent biomarkers reflecting the activity and severity of SSc-related peripheral microvasculopathy

Decreased Serum Levels of SIRT1 and SIRT3 Correlate with Severity of Skin and Lung Fibrosis and Peripheral Microvasculopathy in Systemic Sclerosis

Systemic sclerosis (SSc, scleroderma) is a severe autoimmune connective tissue disease characterized by widespread peripheral microvasculopathy, and progressive cutaneous and visceral fibrosis, leading to significant organ dysfunction. Sirtuins (SIRTs) are a family of NAD-dependent protein deacetylases with pleiotropic effects on a variety of biological processes, including metabolism, cell survival, and aging. In the last decades, increasing studies have explored the contribution of SIRTs to the pathogenesis of SSc, highlighting a significant antifibrotic effect of both SIRT1 and SIRT3. On these bases, the aim of this study was to measure circulating SIRT1 and SIRT3 levels by enzyme-linked immune-sorbent assay in a well-characterized cohort of SSc patients (n = 80) and healthy controls (n = 71), focusing on their possible association with disease clinical features, and their potential as biomarkers reflecting SSc activity and severity. Significantly decreased serum levels of both SIRT1 and SIRT3 were found in SSc patients compared to controls. In SSc, the reduction in circulating SIRT1 and SIRT3 associated with a greater extent of cutaneous fibrosis, presence of interstitial lung disease, and worse pulmonary function. Serum SIRT1 and SIRT3 decrease also correlated with the severity of nailfold microvascular damage, with SIRT3 levels being additionally related to the occurrence of digital ulcers. The levels of these two proteins showed a direct correlation with one another in the circulation of SSc patients. Of the two SIRTs, serum SIRT3 was found to better reflect disease activity and severity in a logistic regression analysis model. Our findings suggest that serum SIRT1 and SIRT3 may represent novel potential biomarkers of increased risk for a more severe, life-threatening SSc disease course