Executive summary of the 14th HHT international scientific conference

Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant vascular disorder characterized by small, dilated clustered vessels (telangiectasias) and by larger visceral arteriovenous malformations (AVMs), which directly connect the feeding arteries with the draining veins. These lesions are fragile, prone to rupture, and lead to recurrent epistaxis and/or internal hemorrhage among other complications. Germline heterozygous loss-of-function (LOF) mutations in Bone Morphogenic Protein 9 (BMP9) and BMP10 signaling pathway genes (endoglin-ENG, activin like kinase 1 ACVRL1 aka ALK1, and SMAD4) cause different subtypes of HHT (HHT1, HHT2 and HHT-juvenile polyposis (JP)) and have a worldwide combined incidence of about 1:5000. Expert clinicians and international scientists gathered in Cascais, Portugal from September 29th to October 2nd, 2022 to present the latest scientific research in the HHT field and novel treatment strategies for people living with HHT. During the largest HHT scientific conference yet, participants included 293 in person and 46 virtually. An impressive 209 abstracts were accepted to the meeting and 59 were selected for oral presentations. The remaining 150 abstracts were presented during judged poster sessions. This review article summarizes the basic and clinical abstracts selected as oral presentations with their new observations and discoveries as well as surrounding discussion and debate. Two discussion-based workshops were also held during the conference, each focusing on mechanisms and clinical perspectives in either AVM formation and progression or current and future therapies for HHT. Our hope is that this paper will represent the current progress and the remaining unanswered questions surrounding HHT, in order to serve as an update for those within the field and an invitation to those scientists and clinicians as yet outside of the field of HHT.

Abstract 163: Potential Therapeutic Effects Of Angiopoietin-2 Inhibition On Rescuing Hereditary Hemorrhagic Telangiectasia Associated Cerebrovascular Defects

Introduction: Hereditary Hemorrhagic Telangiectasia (HHT) is a vascular disease characterized by arteriovenous malformations (AVMs), which are abnormal, enlarged connections between arteries and veins that are prone to hemorrhage. AVMs often form in the brain and can lead to stroke. Mutations in endoglin (Eng), activin receptor-like kinase 1 (Alk1) or smad-related protein 4 (Smad4) cause HHT. Endothelial cell (EC) specific knock out of Alk1, Eng, or Smad4 in mice mimics HHT vascular defects, including AVM formation. We showed that Smad4 directly repressed transcription of the critical pro-angiogenic factor Angiopoietin-2 (Ang2) in ECs and that in Smad4-HHT mice, Ang2 /ANG2 levels are robustly and ectopically increased in ECs. By inhibiting Ang2, we prevented and rescued AVMs and normalized retinal vasculature. Since Smad4 is a central transcription factor in the TGF-β signaling pathway and a downstream effector of the Eng and Alk1 co-receptors, we hypothesized that Ang2 inhibition may universally normalize HHT vascular phenotypes.

Methods: Blue latex dye perfusion methods were used to visualize and characterize cerebrovascular defects in HHT mouse models (n=5~7). RNA-seq was performed on isolated brain ECs (iBECs) to further define molecular phenotypic characteristics (n=5). In situ hybridization on brain slices (n=3) and ELISA on whole brain lysate (n=3~9) were performed to confirm elevated Ang2 RNA and protein levels. Ang2 inhibitor was delivered via intraperitoneal injection, followed by cerebrovascular assessments (n=5~9).

Results: We found that brain AVMs are present in Smad4-, Alk1-, and Eng-HHT mutants, with all models displaying elevated Ang2 levels. RNA-seq of iBECs in Smad4-, Alk1-, and Eng-HHT models reveals 5502, 5307, and 1659 differentially expressed genes in respective mutants compared to controls. Data set comparisons revealed common, increased pro-angiogenic genes, which helped to define the HHT-specific angiogenic profile. Moreover, Ang2 inhibition decreased Smad4-HHT’s brain vessel diameter and Alk1-HHT’s brain vessel density, and prevented brain AVM formation in Eng-HHT mice. In conclusion, Ang2 inhibition partially normalized cerebrovascular defects in Smad4- and Alk1-HHT mice, and completely in Eng-HHT mice.

Metabolic equivalents fail to indicate metabolic load in post-myocardial infarction patients during the modified Bruce treadmill walking test

AIM

To investigate the suitability of metabolic equivalents (METs) for determining exercise intensity in phase-IV post-myocardial infarction (MI) men during the modified Bruce treadmill walking test (MBWT).

METHODS

Twenty phase-IV post-MI men (mean±SD, aged 64.4±5.8 years) and 20 healthy non-cardiac male controls (59.8±7.6 years) participated. Participants performed a MBWT. Throughout the participants' heart rate (HR), heart rhythm, expired air parameters and ratings of perceived exertion (RPEs) were measured. MET values were compared between groups and those currently ascribed to each stage of the MBWT.

RESULTS

General linear model analysis found no significant differences between groups during the MBWT for VO2, VCO2, HR, METs or RPEs (Borg 6-20 scale). Ascribed METs did not differ from mean METs of post-MIs or controls other than at stage 5 where post-MI METs were significantly lower. Irrespective, the post-MI group worked at a higher percentage of their anaerobic threshold (AT) (respiratory exchange ratio, RER=1.0) (F(2,5)=7.22, p<0.008), higher RER (F(2,5)=11.25, p<0.001) with increased breathing frequency (F(2,5)=7.22, p<0.001). Regression analysis revealed AT to be VO2 25.6 (mL/kg/min) for post-MI versus VO2 31.1 (mL/kg/min) for controls. Gross energy expenditure (kcal/min) was greater for the post-MI group compared with controls (F(2,5)=11.22, p<0.001). Throughout the MBWT, post-MI group worked at a higher %AT/MET than controls (F(2,196)=211.76, p<0.01). Body composition did not strongly influence %AT/MET, parameters of VO2, METs or RPE.

CONCLUSION

During the MBWT, post-MI men worked more anaerobically per MET (%AT/MET) than controls. Therefore, current METs based on non-cardiac individuals appear unsuitable in determining the full metabolic load of the exercise intensity for cardiac patients during the MBWT.

Alk2/ACVR1 and Alk3/BMPR1A Provide Essential Function for Bone Morphogenetic Protein-Induced Retinal Angiogenesis

OBJECTIVE

Increasing evidence suggests that bone morphogenetic protein (BMP) signaling regulates angiogenesis. Here, we aimed to define the function of BMP receptors in regulating early postnatal angiogenesis by analysis of inducible, endothelial-specific deletion of the BMP receptor components Bmpr2 (BMP type 2 receptor), Alk1 (activin receptor-like kinase 1), Alk2, and Alk3 in mouse retinal vessels.

APPROACH AND RESULTS

Expression analysis of several BMP ligands showed that proangiogenic BMP ligands are highly expressed in postnatal retinas. Consistently, BMP receptors are also strongly expressed in retina with a distinct pattern. To assess the function of BMP signaling in retinal angiogenesis, we first generated mice carrying an endothelial-specific inducible deletion of Bmpr2. Postnatal deletion of Bmpr2 in endothelial cells substantially decreased the number of angiogenic sprouts at the vascular front and branch points behind the front, leading to attenuated radial expansion. To identify critical BMPR1s (BMP type 1 receptors) associated with BMPR2 in retinal angiogenesis, we generated endothelial-specific inducible deletion of 3 BMPR1s abundantly expressed in endothelial cells and analyzed the respective phenotypes. Among these, endothelial-specific deletion of either Alk2/acvr1 or Alk3/Bmpr1a caused a delay in radial expansion, reminiscent of vascular defects associated with postnatal endothelial-specific deletion of BMPR2, suggesting that ALK2/ACVR1 and ALK3/BMPR1A are likely to be the critical BMPR1s necessary for proangiogenic BMP signaling in retinal vessels.

CONCLUSIONS

Our data identify BMP signaling mediated by coordination of ALK2/ACVR1, ALK3/BMPR1A, and BMPR2 as an essential proangiogenic cue for retinal vessels.

Coxiella burnetii seropositivity and associated risk factors in sheep in Ontario, Canada

Coxiella burnetii is a zoonotic bacterium that can cause abortion in sheep in late gestation, as well as the delivery of stillborn, and non-viable lambs (Rodolakis, 2006). A cross-sectional study was conducted in Ontario, Canada, to investigate C. burnetii exposure in sheep. Between August 2010 and January 2012, sera from 2363 reproductively active ewes from 72 farms were tested for C. burnetii specific antibodies using the CHEKIT Q fever ELISA Test kit (IDEXX Laboratories). Overall, exposure was common; sheep-level seroprevalence was 14.7% (347/2363, 95% CI: 13.3-16.2), and was higher in dairy sheep (24.3%, 181/744) than meat sheep (10.2%, 166/1619) (p<0.0001). At the farm-level, 48.6% (35/72, 95% CI: 37.2-60.1) of farms had at least one seropositive sheep. A mixed multivariable logistic model that controlled for farm-level clustering, identified risk factors associated (p<0.05) with sheep seropositivity. Increasing female flock size (logarithmic scale) was associated with increased odds of seropositivity. By way of illustration, increasing the female flock size from 100 to 200 increased the odds of seropositivity by 2.26 times (95% CI: 1.5-3.5). Sheep that lambed in an airspace separate from the flock had 11.3 times (95% CI: 2.9-43.6) the odds of seropositivity relative to other sheep. The practice of loaning sheep that returned to the farm increased odds of seropositivity by 8.1 times (95% CI: 1.8-33.6). Lambing pen hygiene practices also influenced odds of seropositivity. Relative to sheep from farms where all lambing pen hygiene measures were practiced after lambing (i.e., adding bedding, removing birth materials and disinfection), sheep from farms that only added bedding, or those that just added bedding and removed birthing materials had 5.9 times (95% CI: 1.1-32.1) and 9.0 times (95% CI: 2.2-36.9) the odds of seropositivity, respectively. These results can be used to inform prevention and control strategies with the aim of reducing C. burnetii exposure in sheep.

Bone morphogenetic protein 2 signaling negatively modulates lymphatic development in vertebrate embryos

RATIONALE

The emergence of lymphatic endothelial cells (LECs) seems to be highly regulated during development. Although several factors that promote the differentiation of LECs in embryonic development have been identified, those that negatively regulate this process are largely unknown.

OBJECTIVE

Our aim was to delineate the role of bone morphogenetic protein (BMP) 2 signaling in lymphatic development.

METHODS AND RESULTS

BMP2 signaling negatively regulates the formation of LECs. Developing LECs lack any detectable BMP signaling activity in both zebrafish and mouse embryos, and excess BMP2 signaling in zebrafish embryos and mouse embryonic stem cell-derived embryoid bodies substantially decrease the emergence of LECs. Mechanistically, BMP2 signaling induces expression of miR-31 and miR-181a in a SMAD-dependent mechanism, which in turn results in attenuated expression of prospero homeobox protein 1 during development.

CONCLUSIONS

Our data identify BMP2 as a key negative regulator for the emergence of the lymphatic lineage during vertebrate development.

The timing of educational investment: a neuroscientific perspective

Economic models of investment in human capital sometimes refer to neuroscience as a means to support their underlying assumptions regarding human development. These assumptions have a crucial influence on the policy implications the models generate. We review the extent to which the neuroscience of development can be used to support a "learning begets learning" principle of human capital accumulation. We conclude that, although early neural development can be considered as foundational, it cannot be considered as a unitary phenomenon that proceeds in continuous fashion. Furthermore, the concept of the sensitive period, which is often used associated with the principle, suggests benefits of investment depend upon an individual's circumstances and developmental history, and particularly whether this can be classified as normal. A more recent model of investment has involved two different types of abilities, with outcomes demonstrating the value of including more sophisticated assumptions about human development. We conclude that, while current discussions of policy would benefit from a more careful interpretation of existing models, the potential for future work combining modern neuroscientific understanding with economic theory is considerable.

Investigation of the potential utility of a linomide analogue for treatment of choroidal neovascularization

The aim of this study was to test the selectivity, in-vivo effectiveness, and potential mechanism of action of a linomide analogue (N-phenyl-1,2-dihydro-4-hydroxyl-2-oxo-quinoline-3-carboxamide, Lin05) for inhibition of choroidal neovascularization. The selectivity of Lin05 was tested in cell proliferation assays with human umbilical vein endothelial cells (HUVEC) and a retinal pigmented epithelial cell line(ARPE-19). In-vivo anti-angiogenic effect of Lin05 was investigated utilizing an experimental laser-induced choroidal neovascularization (ECNV) model in adult Brown Norway rats. Western blot and/or reverse transcriptase-PCR was used to test the effect of Lin05 on potential targets. Our results indicate that Lin05 is at least an 8-fold more selective inhibitor of endothelial cell proliferation compared to RPE cells. Systemic administration of Lin05 in an ECNV model was associated with a significant decrease in both vascular leakage on fluorescein angiography and lesion size by histopathology (p = 0.02). No systemic toxicity was detected for Lin05 in major organs such as the liver, lung and kidneys. Lin05 did not inhibit VEGF-induced VEGFR2 (KDR) phosphorylation in HUVEC nor was associated with decreased VEGF gene expression. Also it did not inhibit insulin-like growth factor (IGF-1) and Epidermal Growth Factor (EGF) induced activation of p42/p44 MAPK activation. It inhibited both PDGF- and bFGF-induced p42/p44 MAPK phosphorylation. However, the effect on PDGF was variable in different HUVEC cells. In conclusion, Lin05 is a potential anti-angiogenic agent for the treatment of eye diseases associated with pathological neovascularization. The anti-angiogenic effect of Lin05 is likely through inhibition of bFGF but not through inhibition of the VEGF/KDR pathway.

Genome-wide study of aging and oxidative stress response in Drosophila melanogaster

Aging is a universal but poorly understood biological process. Free radicals accumulate with age and have been proposed to be a major cause of aging. We measured genome-wide changes in transcript levels as a function of age in Drosophila melanogaster and compared these changes with those caused by paraquat, a free-radical generator. A number of genes exhibited changes in transcript levels with both age and paraquat treatment. We also found genes whose transcript levels changed with age but not with paraquat treatment. This study suggests that free radicals play an important role in regulating transcript levels in aging but that they are not the only factors. This genome-wide survey also identifies candidates for molecular markers of aging.

Failure of endometrial cup development in the donkey-in-horse model of equine abortion

The mature preinvasive chorionic girdles of horse, mule, donkey and extraspecies donkey-in-horse conceptuses, and the very young endometrial cups on d 37 of gestation in mares carrying horse, mule and transferred donkey-in-horse conceptuses, were compared histologically and ultrastructurally to determine possible mechanisms underlying failure of endometrial cup development in the donkey-in-horse model of equine abortion. The progenitor chorionic girdle from the failing donkey-in-house pregnancy was similar in size to the normal donkey chorionic girdle but the trophoblast cells within the former were smaller, less organised and showed definite signs of degeneration and pyknosis. In the 37 d endometrial cups both in the horse and mule pregnancies, the recently invaded, differentiated and enlarging endometrial cup cells had penetrated deeply into the endometrial stroma and were becoming tightly packed between the persisting endometrial glands. In the donkey-in-horse pregnancy, on the other hand, relatively few donkey chorionic girdle cells had begun the invasion process and the majority of these, having penetrated and dislodged the horse luminal epithelium, did not penetrate the basement membrane beneath. Very few cells had reached the endometrial stroma and these had already attracted considerable numbers of lymphocytes to the area. It is concluded that unknown factors in the horse uterus affect adversely all phases of the development, attachment and invasion of donkey chorionic girdle cells, thereby leading to very little or no endometrial cup development and equine chorionic gonadotropin secretion in the extraspecific donkey-in-horse pregnancy created by embryo transfer.

Religious issues in the capacity evaluation

The authors explore the difficulties present in the capacity evaluation of patients with strong religious beliefs. The article reviews the legal protection for treatment refusal on religious grounds as well as psychiatry's approach to religion. Clinical cases encountered in an urban hospital are presented to highlight how the conflicts among psychiatric, religious, and legal issues can be resolved. Suggestions are made for incorporating an exploration of religious values into the capacity assessment.

Local pay determination

Discusses the building blocks required for National Health Trusts in the UK to move effectively towards local pay determination as part of an overall coherent reward strategy. Concludes that the current preoccupation with purely the pay part of the reward strategy, combined with the absence of many of the other required building blocks, may well result in an extremely patchwork approach to reward and will leave the National Health Service in the position where it has lost the advantages of a national system, while failing to achieve the benefits of local pay determination.

Medical staffing--the Calman Report: implications and costs

Introduces the 1993 Calman Report on specialist medical training, summarizing the report's recommendations and then exploring its implications for service purchasers and providers. Illustrates these using discussions within University College London Hospitals NHS Trust and The Royal Hospitals NHS Trust.

The modified Insall-Salvati ratio for assessment of patellar height

The Insall-Salvati ratio for the assessment of patellar height was the first widely used index to be relatively independent of knee flexion. Despite the subsequent publication of other indices, it remains the most widely used index. The Insall-Salvati ratio nevertheless has drawbacks, one of which has received little attention: the ratio lacks sensitivity to patellar morphology. Unusual patellar shapes can lead to misleading values of the Install-Salvati ratio. In particular, the authors have found a significant number of inaccurate readings for patellar height in patients whose patella exhibits a long distal (nonarticulating) facet. A modified Insall-Salvati ratio is described which, when applied in conjunction with the traditional ratio, significantly reduces these errors. The cutoff point between normal and alta for this modified Insall-Salvati ratio is 2. One half of the cases of patella alta in this study were missed by the traditional ratio, yet identified by the modified index.

Residential placement of individuals with mental retardation: factors influencing court decisions

Pennsylvania law mandates that involuntary commitment of persons with mental retardation be reviewed by the court system in order to assure due process. Fifty such cases in Philadelphia were reviewed in court over a period of one year and subsequently examined to determine current court trends toward institutional placement. Factors evaluated included characteristics of the individual, the presiding court, the impact of a court-appointed Child Advocate or Public Defender, and availability of residential alternatives. Results indicate that children were committed to institutional settings less frequently than adults. Other critical factors were prior placement, recommendations of advocates, and availability of alternative services.