Case Reports1. A Late Presentation of Loeys-Dietz Syndrome: Beware of TGFβ Receptor Mutations in Benign Joint Hypermobility

Background: Thoracic aortic aneurysms (TAA) and dissections are not uncommon causes of sudden death in young adults. Loeys-Dietz syndrome (LDS) is a rare, recently described, autosomal dominant, connective tissue disease characterized by aggressive arterial aneurysms, resulting from mutations in the transforming growth factor beta (TGFβ) receptor genes TGFBR1 and TGFBR2. Mean age at death is 26.1 years, most often due to aortic dissection. We report an unusually late presentation of LDS, diagnosed following elective surgery in a female with a long history of joint hypermobility. Methods: A 51-year-old Caucasian lady complained of chest pain and headache following a dural leak from spinal anaesthesia for an elective ankle arthroscopy. CT scan and echocardiography demonstrated a dilated aortic root and significant aortic regurgitation. MRA demonstrated aortic tortuosity, an infrarenal aortic aneurysm and aneurysms in the left renal and right internal mammary arteries. She underwent aortic root repair and aortic valve replacement. She had a background of long-standing joint pains secondary to hypermobility, easy bruising, unusual fracture susceptibility and mild bronchiectasis. She had one healthy child age 32, after which she suffered a uterine prolapse. Examination revealed mild Marfanoid features. Uvula, skin and ophthalmological examination was normal. Results: Fibrillin-1 testing for Marfan syndrome (MFS) was negative. Detection of a c.1270G > C (p.Gly424Arg) TGFBR2 mutation confirmed the diagnosis of LDS. Losartan was started for vascular protection. Conclusions: LDS is a severe inherited vasculopathy that usually presents in childhood. It is characterized by aortic root dilatation and ascending aneurysms. There is a higher risk of aortic dissection compared with MFS. Clinical features overlap with MFS and Ehlers Danlos syndrome Type IV, but differentiating dysmorphogenic features include ocular hypertelorism, bifid uvula and cleft palate. Echocardiography and MRA or CT scanning from head to pelvis is recommended to establish the extent of vascular involvement. Management involves early surgical intervention, including early valve-sparing aortic root replacement, genetic counselling and close monitoring in pregnancy. Despite being caused by loss of function mutations in either TGFβ receptor, paradoxical activation of TGFβ signalling is seen, suggesting that TGFβ antagonism may confer disease modifying effects similar to those observed in MFS. TGFβ antagonism can be achieved with angiotensin antagonists, such as Losartan, which is able to delay aortic aneurysm development in preclinical models and in patients with MFS. Our case emphasizes the importance of timely recognition of vasculopathy syndromes in patients with hypermobility and the need for early surgical intervention. It also highlights their heterogeneity and the potential for late presentation. Disclosures: The authors have declared no conflicts of interes

Involvement of the estrogen receptor and aryl hydrocarbon receptor in 4-vinylcyclohexene diepoxide-induced ovotoxicity in F344 rats

Women are born with a finite number of primordial follicles, the smallest follicles in the ovary. Once these follicles are destroyed, they cannot be replaced and after extensive loss, ovarian failure (menopause) can occur. The industrial chemical 4-vinylcyclohexene diepoxide (VCD) induces depletion of these follicles and causes premature ovarian failure in rats. VCD-induced ovotoxicity has been found to accelerate a natural process in the ovary, atresia, which occurs via apoptosis. The mechanism(s) by which VCD enhances follicular atresia are unknown; however, it has been shown to alter the expression of several genes and proteins associated with apoptosis. While downstream signaling events of VCD are becoming identified, the early signaling events of this pathway have not yet been determined, but may involve a receptor-mediated cascade. Therefore, these studies tested the hypothesis that VCD-induced ovotoxicity involves a nuclear receptor-mediated pathway that leads to increased atresia. Concurrent treatment of rats with VCD and estradiol selectively protected primary follicles from loss by an estrogen receptor-mediated mechanism via a reduction of caspase-3-induced apoptosis. VCD does not alter ER number, affinity, circulating estradiol levels, or directly bind ERbeta. Concurrent dosing of rats with VCD and an AhR antagonist prevented primordial and primary follicle loss via a reduction in caspase-3-induced apoptosis. Repeated dosing with VCD was shown to up-regulate expression of AhR mRNA; however, VCD did not alter expression of AhR-mediated genes glutathione-S-transferase Ya1 or Ya2 nor CYP 1A1 protein. AhR-deficient mice were still susceptible to VCD-induced follicle loss. Repeated dosing with VCD reduced Heat Shock Protein (HSP) 90 expression in small primary follicles. Analogs of the ER and AhR did not alter HSP90 protein, nor did a loss of HSP90 function induce follicle loss or potentiate VCD-induced follicle depletion. While the ER, AhR, and HSP90 are all co-localized in the oocyte nucleus of primordial and primary follicles, no evidence was seen to support that these proteins are interacting. Taken together, the ER is able to prevent VCD-induced ovotoxicity in primary follicles, the AhR is not required for VCD-induced follicle loss, and HSP90 does not appear to play a central role in follicle depletion caused by VCD

Potential seminal transport of pharmaceuticals to the conceptus

Small molecule pharmaceutical products are assumed to reach concentrations in semen similar to those in blood plasma. Exposure modeling for these small-molecule products assumes a daily dose of 5 mL of semen and 100% absorption from the vagina with distribution to the conceptus through the maternal systemic circulation. Monoclonal antibody drugs are present in semen at concentrations about 2% or less of those in blood, and the modeling used for small molecules will over-estimate the possibility of conceptus exposure to immunoglobulins. It is not known whether peptide products reach semen, but peptide medications are destroyed by vaginal peptidases, and conceptus exposure is predicted to be minimal. Theoretical exposure routes to pharmaceuticals that might result in exposure of the conceptus greater than that of maternal systemic exposures include direct access through the cervical canal, adsorption to sperm for carriage into the oocyte, and direct delivery from the vaginal veins or lymphatics to the uterine artery. There is some evidence for direct access to the uterus for progesterone, terbutaline, and danazol, but the evidence does not involve exposures during pregnancy in most instances. Studies in mice, rats, rabbits, and monkeys do not suggest that exposure to small molecule pharmaceuticals in semen imposes risks to the conceptus beyond those that can be predicted using modeling of systemic maternal exposure. Monoclonal antibody and peptide exposure in semen does not pose a risk to the conceptus

Rethinking developmental toxicity testing: Evolution or revolution?

BACKGROUND: Current developmental toxicity testing adheres largely to protocols suggested in 1966 involving the administration of test compound to pregnant laboratory animals. After more than 50 years of embryo-fetal development testing, are we ready to consider a different approach to human developmental toxicity testing? METHODS: A workshop was held under the auspices of the Developmental and Reproductive Toxicology Technical Committee of the ILSI Health and Environmental Sciences Institute to consider how we might design developmental toxicity testing if we started over with 21st century knowledge and techniques (revolution). We first consider what changes to the current protocols might be recommended to make them more predictive for human risk (evolution). RESULTS: The evolutionary approach includes modifications of existing protocols and can include humanized models, disease models, more accurate assessment and testing of metabolites, and informed approaches to dose selection. The revolution could start with hypothesis-driven testing where we take what we know about a compound or close analog and answer specific questions using targeted experimental techniques rather than a one-protocol-fits-all approach. Central to the idea of hypothesis-driven testing is the concept that testing can be done at the level of mode of action. It might be feasible to identify a small number of key events at a molecular or cellular level that predict an adverse outcome and for which testing could be performed in vitro or in silico or, rarely, using limited in vivo models. Techniques for evaluating these key events exist today or are in development. DISCUSSION: Opportunities exist for refining and then replacing current developmental toxicity testing protocols using techniques that have already been developed or are within reach