Increased Frequency and Vasculogenic Potential of Endothelial Colony-Forming Cells in Patients with Kaposi’s Sarcoma

The vascular phenotype of BPD: new basic science insights-new precision medicine approaches

Bronchopulmonary dysplasia (BPD) is the most common complication of preterm birth. Up to 1/3 of children with BPD develop pulmonary hypertension (PH). PH increases mortality, the risk of adverse neurodevelopmental outcome and lacks effective treatment. Current vasodilator therapies address symptoms, but not the underlying arrested vascular development. Recent insights into placental biology and novel technological advances enabling the study of normal and impaired lung development at the single cell level support the concept of a vascular phenotype of BPD. Dysregulation of growth factor pathways results in depletion and dysfunction of putative distal pulmonary endothelial progenitor cells including Cap1, Cap2, and endothelial colony-forming cells (ECFCs), a subset of vascular progenitor cells with self-renewal and de novo angiogenic capacity. Preclinical data demonstrate effectiveness of ECFCs and ECFC-derived particles including extracellular vesicles (EVs) in promoting lung vascular growth and reversing PH, but the mechanism is unknown. The lack of engraftment suggests a paracrine mode of action mediated by EVs that contain miRNA. Aberrant miRNA signaling contributes to arrested pulmonary vascular development, hence using EV- and miRNA-based therapies is a promising strategy to prevent the development of BPD-PH. More needs to be learned about disrupted pathways, timing of intervention, and mode of delivery. IMPACT: Single-cell RNA sequencing studies provide new in-depth view of developmental endothelial depletion underlying BPD-PH. Aberrant miRNA expression is a major cause of arrested pulmonary development. EV- and miRNA-based therapies are very promising therapeutic strategies to improve prognosis in BPD-PH.

Development of Personalized Thrombogenesis and Thrombin Generation Assays to Assess Endothelial Dysfunction in Cardiovascular Diseases

The study of endothelial dysfunction (ED) is crucial to identify the pathogenetic mechanism(s) and provide indications for patient management in cardiovascular diseases. It is currently hindered by the limited availability of patient-specific primary endothelial cells (ECs). Endothelial colony-forming cells (ECFCs) represent an optimal non-invasive tool to overcome this issue. Therefore, we investigated the use of ECFCs as a substrate in thrombogenesis and thrombin generation assay (TGA) to assess ED. Both assays were set up on human umbilical vein endothelial cells (HUVECs) and then tested on ECFCs obtained from healthy donors. To prove the ability of the assays to detect endothelial activation, ECs stimulated with TNFα were compared with unstimulated ECs. EC activation was confirmed by the upregulation of VCAM-1 and Tissue Factor expression. Both assays discriminated between unstimulated and activated HUVECs and ECFCs, as significantly higher platelet deposition and fibrin formation in thrombogenesis assay, and thrombin generation in TGA, were observed when TNFα-activated ECs were used as a substrate. The amount of fibrin and thrombin measured in the two assays were directly correlated. Our results support the combined use of a thrombogenesis assay and TGA performed on patient-derived ECFCs to provide a personalized global assessment of ED relevant to the patient's hemostatic profile.

Koebner Phenomenon in Kaposi's Sarcoma: A Large Single-Center Case Series and Review of Current Knowledge

BACKGROUND

occasional case reports have described the appearance of Kaposi's sarcoma (KS) on previously unaffected skin after incidental or accidental injury, but the association is probably under-reported.

OBJECTIVES

to present a large case series of patients suffering from Koebner phenomenon (KP) in KS and describe their main epidemiological, clinical, and therapeutic features.

METHODS

we have retrospectively analyzed our clinical and photographic records of 524 patients who had been diagnosed with KS between 2009 and 2021.

RESULTS

31 of 524 (6%) KS patients developed KP. Among these 31 patients, 24 (77%) had KS lesions after surgery, 4 (13%) after electrochemotherapy, laser therapy and cryotherapy, and 3 (10%) on areas affected by bullous diseases.

CONCLUSIONS

trauma, including surgery or other medical procedures, can trigger KS, underlying the importance of treatment options which cause the least injury to the skin.

Pathologic up-regulation of TNFSF15–TNFRSF25 axis sustains endothelial dysfunction in unprovoked venous thromboembolism

Aims

The pathogenetic mechanisms underlying unprovoked venous thromboembolism (uVTE) are largely unknown. In this study, we investigated the molecular mechanisms involved in uVTE pathogenesis by using ex vivo expanded endothelial colony-forming cells (ECFCs), which represent a valuable non-invasive tool for the assessment of endothelial function.

Methods and results

We isolated and expanded ECFCs from the peripheral blood of uVTE patients and observed that these cells underwent earlier senescence and showed lower growth rate compared with ECFCs obtained from healthy donors. Through microarray expression profiling, we demonstrated that 2905 genes were differentially expressed between patients and controls. Among them, the anti-angiogenic cytokine TNF superfamily member 15 (TNFSF15) and its death-receptor TNFRSF25 were up-regulated in uVTE ECFCs, and this finding was validated by RT-qPCR. TNFSF15 up-regulation was confirmed at the protein level in ECFC supernatants, and the in vivo relevance of these findings was further corroborated by demonstrating that also the plasmatic levels of TNFSF15 are increased in uVTE patients. After proving that exogenous TNFSF15 exerts pro-apoptotic and anti-proliferative activity on control ECFCs, we demonstrated through blocking experiments that TNFSF15 up-regulation contributes to impaired survival and proliferation of uVTE ECFCs.

Conclusion

By providing evidence that TNFSF15 impairs ECFC functions crucial to endothelial repair, and that uVTE patients have increased TNFSF15 levels both ex vivo and in vivo, the results of this study suggest that pathologic up-regulation of TNFSF15–TNFRSF25 axis may contribute to uVTE pathogenesis, and may represent the target for novel therapeutic strategies aimed at preventing recurrences in uVTE patients.

Enhanced phosphorylation of sphingosine and ceramide sustains the exuberant proliferation of endothelial progenitors in Kaposi sarcoma

Endothelial colony-forming cells (ECFCs), a unique endothelial stem cell population, are highly increased in the blood of Kaposi sarcoma (KS) patients. KS-derived ECFCs (KS-ECFCs) are also endowed with increased proliferative and vasculogenic potential, thus suggesting that they may be precursors of KS spindle cells. However, the mechanisms underlying the increased proliferative activity of KS-ECFCs remain poorly understood. Sphingosine-1-phosphate (S1P) and ceramide-1-phosphate (C1P) are metabolically interconnected sphingoid mediators crucial to cell proliferation. Here, we investigated the metabolism, release, and proliferative effects of S1P and C1P in KS-ECFCs compared with control ECFCs (Ct-ECFCs). Metabolic studies by cell labeling, chromatographic analyses, and digital autoradiography revealed that S1P and C1P biosynthesis and S1P secretion are all efficient processes in KS-ECFCs, more efficient in KS-ECFCs than Ct-ECFCs. Quantitative PCR analyses demonstrated a significantly higher ceramide kinase and sphingosine kinase-2 expression in KS-ECFCs. Notably, also the expression of S1P1 and S1P3 receptors was augmented in KS-ECFCs. Accordingly, treatment with exogenous C1P or S1P induced a significant, concentration-dependent stimulation of KS-ECFC proliferation, but was almost completely ineffective in Ct-ECFCs. Hence, we identified C1P and S1P as autocrine/paracrine proliferative signals in KS-ECFCs. A better understanding of the mechanisms that enhance S1P/C1P formation in KS-ECFCs may yield effective therapeutic modalities.

Kaposi's sarcoma herpesvirus-induced endothelial cell reprogramming supports viral persistence and contributes to Kaposi's sarcoma tumorigenesis

Kaposi's sarcoma (KS) is an endothelial tumor causally linked to Kaposi's sarcoma herpesvirus (KSHV) infection. At early stages of KS, inflammation and aberrant neoangiogenesis are predominant, while at late stages the disease is characterized by the proliferation of KSHV-infected spindle cells (SC). Since KSHV infection modifies the endothelial cell (EC) identity, the origin of SCs remains elusive. Yet, pieces of evidence indicate the lymphatic origin. KSHV-infected ECs display increased proliferative, angiogenic and migratory capacities which account for KS oncogenesis. Here we propose a model in which KSHV reprograms the EC identity, induces DNA damage and establishes a dysregulated gene expression program involving interplay of latent and lytic genes allowing continuous reinfection of ECs attracted to the tumor by the secretion of virus-induced cellular factors.