Trauma Can Induce Telangiectases in Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia: from signaling insights to therapeutic advances

Hereditary hemorrhagic telangiectsia (HHT) is an inherited vascular disorder with highly variable expressivity, affecting up to 1 in 5,000 individuals. This disease is characterized by small arteriovenous malformations (AVMs) in mucocutaneous areas (telangiectases) and larger visceral AVMs in the lungs, liver, and brain. HHT is caused by loss-of-function mutations in the BMP9-10/ENG/ALK1/SMAD4 signaling pathway. This Review presents up-to-date insights on this mutated signaling pathway and its crosstalk with proangiogenic pathways, in particular the VEGF pathway, that has allowed the repurposing of new drugs for HHT treatment. However, despite the substantial benefits of these new treatments in terms of alleviating symptom severity, this not-so-uncommon bleeding disorder still currently lacks any FDA- or European Medicines Agency-approved (EMA-approved) therapies.

Nonfunctional TGF-β/ALK1/ENG signaling pathway supports neutrophil proangiogenic activity in hereditary hemorrhagic telangiectasia

The transforming growth factor β (TGF-β)/ALK1/ENG signaling pathway maintains quiescent state of endothelial cells, but at the same time, it regulates neutrophil functions. Importantly, mutations of this pathway lead to a rare autosomal disorder called hereditary hemorrhagic telangiectasia (HHT), characterized with abnormal blood vessel formation (angiogenesis). As neutrophils are potent regulators of angiogenesis, we investigated how disturbed TGF-β/ALK1/ENG signaling influences angiogenic properties of these cells in HHT. We could show for the first time that not only endothelial cells, but also neutrophils isolated from such patients are ENG/ALK1 deficient. This deficiency obviously stimulates proangiogenic switch of such neutrophils. Elevated proangiogenic activity of HHT neutrophils is mediated by the increased spontaneous degranulation of gelatinase granules, resulting in high release of matrix-degrading matrix metalloproteinase 9 (MMP9). In agreement, therapeutic disturbance of this process using Src tyrosine kinase inhibitors impaired proangiogenic capacity of such neutrophils. Similarly, inhibition of MMP9 activity resulted in significant impairment of neutrophil-mediated angiogenesis. All in all, deficiency in TGF-β/ALK1/ENG signaling in HHT neutrophils results in their proangiogenic activation and disease progression. Therapeutic strategies targeting neutrophil degranulation and MMP9 release and activity may serve as a potential therapeutic option for HHT.

Generation of a Syngeneic Heterozygous ACVRL1(wt/mut) Knockout iPS Cell Line for the In Vitro Study of HHT2-Associated Angiogenesis

Hereditary hemorrhagic telangiectasia (HHT) type 2 is an autosomal dominant disease in which one allele of the ACVRL1 gene is mutated. Patients exhibit disturbances in TGF-beta/BMP-dependent angiogenesis and, clinically, often present with severe nosebleeds as well as a reduced quality of life. The aim of our study was to use CRISPR/Cas9 to knockout ACVRL1 in normal induced pluripotent stem cells (iPSCs) and evaluate the effects on TGF-beta- and BMP-related gene expression as well as angiogenesis. The CRISPR/Cas9 knockout of the ACVRL1 gene was carried out in previously characterized wild-type (ACVRL1^wt/wt) iPSCs. An HHT type 2 iPS cell line was generated via a single-allele knockout (ACVRL1^wt/mut) in wild-type (ACVRL1^wt/wt) iPSCs, resulting in a heterozygous 17 bp frameshift deletion in the ACVRL1 gene [NG_009549.1:g.13707_13723del; NM_000020.3:c.1137_1153del]. After the generation of embryoid bodies (EBs), endothelial differentiation was induced via adding 4 ng/mL BMP4, 2% B27, and 10 ng/mL VEGF. Endothelial differentiation was monitored via immunocytochemistry. An analysis of 151 TGF-beta/BMP-related genes was performed via RT-qPCR through the use of mRNA derived from single iPS cell cultures as well as endothelial cells derived from EBs after endothelial differentiation. Differential TGF-beta/BMP gene expression was observed between ACVRL1^wt/wt and ACVRL1^wt/mut iPSCs as well as endothelial cells. EBs derived from CRISPR/Cas9-designed ACVRL1 mutant HHT type 2 iPSCs, together with their isogenic wild-type iPSC counterparts, can serve as valuable resources for HHT type 2 in vitro studies.

A Comparative Study on Adipose-Derived Mesenchymal Stem Cells Secretome Delivery Using Microneedling and Fractional CO2 Laser for Facial Skin Rejuvenation

Background

The efficacy of adipose-derived mesenchymal stem cells (ADMSCs) secretome for skin aging has been established, yet no studies hitherto directly investigated the best administration method for such purpose.

Purpose

We aimed to compare microneedling (MN) versus fractional CO₂ laser (FL) as methods of delivery for ADMSCs secretome in the treatment of aging skin.

Patients and Methods

A single-blind, randomized split-face clinical trial was conducted on 30 Indonesian women (aged 35-59 years old) with signs of facial cutaneous senescence. Their initial aging status was assessed by dermoscopy photoaging scale (DPAS) and Janus-III measurement system. In the second and fourth weeks, all participants were treated with both MN and FL, followed by the application of a four-fold concentrated ADMSC secretome. The assignment of which side of the face received MN or FL was done by computer-based randomization. Skin parameters were reevaluated on the fourth and sixth weeks, along with patient satisfaction, level of comfort, preference for administration techniques, and also adverse events experienced during the study. Appropriate statistical analyses were subsequently performed at a significance level of 0.05.

Results

Significant improvements in total DPAS and wrinkles were found in the MN and FL groups at the end of the trial. In contrast, no statistical differences in all parameters were observed between groups in the fourth and sixth weeks. FL scored higher than MN for satisfaction and preference, but lower in terms of comfort. Pain, burning sensation, and itch were the side effects experienced by subjects upon treatment. Two patients had prolonged reddish skin succeeding FL treatment, which relieved with moisturizer application.

Conclusion

Both MN and FL yielded comparable results for improving several skin aging features. However, subjective preference for ADMSCs secretome administration method may differ when considering satisfaction, comfort, and possible adverse events.

Efficacy and Safety of Tacrolimus as Treatment for Bleeding Caused by Hereditary Hemorrhagic Telangiectasia: An Open-Label, Pilot Study

Haploinsufficiency for Endoglin (ENG) and activin A receptor type II-like I (ACVRL1/ALK1) lead to the formation of weak and abnormal vessels in hereditary hemorrhagic telangiectasia (HHT). These cause epistaxis (nosebleeds) and/or gastrointestinal blood loss. In vitro in cultured endothelial cells, tacrolimus has been shown to increase ENG and ALK1 expression. It is, therefore, a potential treatment option. We report here a proof-of-concept study in patients with HHT and severe epistaxis and/or gastrointestinal bleeding who were treated daily with orally-administered tacrolimus for twenty weeks. Twenty-five patients with HHT (11 females (44%)) and median age of 59 years were enrolled. Five patients (20%) stopped the trial prematurely-four due to (serious) adverse events ((S)AE). Twenty patients were included in further analyses. Hemoglobin levels increased during tacrolimus treatment from 6.1 (IQR 5.2–6.9) mmol/L at baseline (9.8 g/dL) to 6.7 (6.5–7.1) mmol/L (10.8 g/dL), p = 0.003. The number of blood transfusions over the twenty weeks decreased from a mean of 5.0 (±9.2) to 1.9 (±3.5), p = 0.04. In 64% of the patients, at least one AE occurred. Oral tacrolimus, thus, significantly increased hemoglobin levels and decreased blood transfusion needs, epistaxis and/or gastrointestinal bleeding in patients with HHT. However, side-effects were common. Further investigation of the potential therapeutic benefit is justified by the outcome of the study.

Systemic Antiangiogenic Therapies for Bleeding in Hereditary Hemorrhagic Telangiectasia: A Practical, Evidence-Based Guide for Clinicians

Management of bleeding in hereditary hemorrhagic telangiectasia (HHT), the second most common hereditary bleeding disorder in the world, is currently undergoing a paradigm shift. Disease-modifying antiangiogenic therapies capable of achieving durable hemostasis via inducing telangiectasia regression have emerged as a highly effective and safe modality to treat epistaxis and gastrointestinal bleeding in HHT. While evidence to date is incomplete and additional studies are ongoing, patients presently in need are being treated with antiangiogenic agents off-label. Intravenous bevacizumab, oral pazopanib, and oral thalidomide are the three targeted primary angiogenesis inhibitors, with multiple studies describing both reassuring safety and impressive effectiveness in the treatment of moderate-to-severe HHT-associated bleeding. However, at present there is a paucity of guidance in the literature, including the published HHT guidelines, addressing the practical aspects of antiangiogenic therapy for HHT in clinical practice. This review article and practical evidence-based guide aims to fill this unaddressed need, synthesizing published data on the use of antiangiogenic agents in HHT, relevant data for their use outside of HHT, and expert guidance where evidence is lacking. After a brief review of principles of bleeding therapy in HHT, guidance on hematologic support with iron and blood products, and alternatives to antiangiogenic therapy, this article examines each of the aforementioned antiangiogenic agents in detail, including patient selection, initiation, monitoring, toxicity management, and discontinuation. With proper, educated use of antiangiogenic therapies in HHT, patients with even the most severe bleeding manifestations can achieve durable hemostasis with minimal side-effects, dramatically improving health-related quality of life and potentially altering the disease course.

[Epistaxis-overview and current aspects]

Nosebleeds (epistaxis) are usually minor. Medical intervention is only necessary in about 6% of cases. The source of bleeding is frequently located in the anterior region of the nose (Kiesselbach's plexus). The estimated lifetime prevalence of epistaxis is 60%. Diffuse epistaxis is often a manifestation of systemic disease. Epistaxis is the leading symptom of Rendu-Osler-Weber disease (hereditary hemorrhagic telangiectasia, HHT). If intervention is required, the first-choice of treatment is bidigital compression for several minutes. Common therapeutic measures include local hemostasis using electrocoagulation or chemical agents, e.g., silver nitrate. Resorbable anterior nasal tampons or tampons with a smooth surface are also frequently employed. In case of failed surgical closure of the sphenopalatine artery, angiographic embolization is the method of choice.

Potential Second-Hits in Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant genetic disorder that presents with telangiectases in skin and mucosae, and arteriovenous malformations (AVMs) in internal organs such as lungs, liver, and brain. Mutations in ENG (endoglin), ACVRL1 (ALK1), and MADH4 (Smad4) genes account for over 95% of HHT. Localized telangiectases and AVMs are present in different organs, with frequencies which differ among affected individuals. By itself, HHT gene heterozygosity does not account for the focal nature and varying presentation of the vascular lesions leading to the hypothesis of a “second-hit” that triggers the lesions. Accumulating research has identified a variety of triggers that may synergize with HHT gene heterozygosity to generate the vascular lesions. Among the postulated second-hits are: mechanical trauma, light, inflammation, vascular injury, angiogenic stimuli, shear stress, modifier genes, and somatic mutations in the wildtype HHT gene allele. The aim of this review is to summarize these triggers, as well as the functional mechanisms involved.