Bleeding associated with angiodysplasia is a common, often intractable complication in patients with von Willebrand disease (VWD). Von Willebrand factor (VWF), the protein deficient or defective in VWD, is a negative regulator of angiogenesis, which may explain the pathologic blood vessel growth in VWD. OBJECTIVE This study explores the normal range of angiogenesis in blood outgrowth endothelial cells (BOECs) derived from healthy donors and compares this to angiogenesis in BOECs from VWD patients of all types and subtypes. METHODS BOECs were assessed for VWF and angiopoietin-2 (Ang-2) gene expression, secretion, and storage. To explore angiogenic potential we characterized cellular proliferation, matrix protein adhesion, migration, and tubule formation. RESULTS We found great angiogenic variability in VWD BOECs with respect to each of the angiogenesis parameters. However, type 1 and 3 VWD BOECs had higher Ang-2 secretion associated with impaired endothelial cell migration velocity and enhanced directionality. Type 2A and 2B BOECs were the most proliferative and multiple VWD BOECs had impaired tubule formation in Matrigel. CONCLUSION This study highlights the angiogenic variability in BOECs derived from VWD patients. Abnormal cell proliferation, migration, and increased Ang-2 secretion are common features of VWD BOECs. Despite the many abnormalities of VWD BOECs, significant heterogeneity amongst individual VWD phenotypes precludes a simple description of relationship between VWD type and in vitro surrogates for angiodysplasia.

This study contributes to the growing body of work aimed at optimizing management of bleeding disorder patients through pregnancy and the postpartum period, showing patients are at a higher risk of PPH as they age. Risk factors such as low third trimester VWF:RCo have been identified. Treatment with tranexamic acid in the postpartum period is associated with a reduced incidence of abnormal postpartum bleeding.

Circulating NK cells are known to convert to a type 1 innate lymphoid cell (ILC1)-like phenotype in response to TGF-b exposure. However, the precise cellular changes defining this process as well as the downstream signaling pathways guiding it remain poorly defined, particularly in humans. We used mass cytometry by time-of-flight (CyTOF) to model this phenotypic shift in vitro and identify a synergistic activity of TGF-b and IL-15 in this cellular conversion. CyTOF profiling identified substantial heterogeneity in the propensity of NK cells to adopt an ILC1-like phenotype in culture, characterized by the step-wise acquisition of various markers, including CD69, CD9, CD103, and CD49a. Activating and inhibitory receptors, including NKG2A, NKG2D, KIR2DL1, KIR3DL1, NKp30, NKp44, and NKp46, were all found to be upregulated exclusively on the cellular subsets that converted most readily in response to TGF-b. An assessment of downstream TGF-b signaling identified TAK1-mediated activation of p38 MAPK as the critical pathway driving conversion. IL-15 enhanced TGF-b-mediated conversion through Ras:RAC1 signaling as well as via the activation of MEK/ERK. Interestingly, the adoption of an ILC1-like phenotype was independent of the effect of IL-15 or TGF-b on mTOR, as the culture of NK cells in the presence of mTOR inhibitors, such as rapamycin or torin1, had minimal impact on the degree of conversion. In conclusion, we have used in vitro human culture systems and CyTOF to define the conversion of circulating NK cells to an ILC1-like phenotype and have clarified the pathways responsible for this process.

Objective: Pulmonary arterial hypertension is a disease of proliferative vascular occlusion that is strongly linked to mutations in BMPR2 —the gene encoding the BMPR-II (BMP [bone morphogenetic protein] type II receptor). The endothelial-selective BMPR-II ligand, BMP9, reverses disease in animal models of pulmonary arterial hypertension and suppresses the proliferation of healthy endothelial cells. However, the impact of BMPR2 loss on the antiproliferative actions of BMP9 has yet to be assessed. Approach and Results: BMP9 suppressed proliferation in blood outgrowth endothelial cells from healthy control subjects but increased proliferation in blood outgrowth endothelial cells from pulmonary arterial hypertension patients with BMPR2 mutations. This shift from growth suppression to enhanced proliferation was recapitulated in control human pulmonary artery endothelial cells following siRNA-mediated BMPR2 silencing, as well as in mouse pulmonary endothelial cells isolated from endothelial-conditional Bmpr2 knockout mice ( Bmpr2 EC −/ − ). BMP9-induced proliferation was not attributable to altered metabolic activity or elevated TGFβ (transforming growth factor beta) signaling but was linked to the prolonged induction of the canonical BMP target ID1 in the context of BMPR2 loss. In vivo, daily BMP9 administration to neonatal mice impaired both retinal and lung vascular patterning in control mice ( Bmpr2 EC+/+ ) but had no measurable effect on mice bearing a heterozygous endothelial Bmpr2 deletion ( Bmpr2 EC+/− ) and caused excessive angiogenesis in both vascular beds for Bmpr2 EC −/− mice. Conclusions: BMPR2 loss reverses the endothelial response to BMP9, causing enhanced proliferation. This finding has potential implications for the proposed translation of BMP9 as a treatment for pulmonary arterial hypertension and suggests the need for focused patient selection in clinical trials.

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