Comparative therapeutic strategies for preventing aortic rupture in a mouse model of vascular Ehlers-Danlos syndrome.

Vascular Ehlers-Danlos syndrome is a rare inherited disorder caused by genetic variants in type III collagen. Its prognosis is especially hampered by unpredictable arterial ruptures and there is no therapeutic consensus. We created a knock-in Col3a1+/G182R mouse model and performed a complete genetic, molecular and biochemical characterization. Several therapeutic strategies were also tested. Col3a1+/G182R mice showed a spontaneous mortality caused by thoracic aortic rupture that recapitulates the vascular Ehlers-Danlos syndrome with a lower survival rate in males, thin non-inflammatory arteries and an altered arterial collagen. Transcriptomic analysis of aortas showed upregulation of genes related to inflammation and cell stress response. Compared to water, survival rate of Col3a1+/G182R mice was not affected by beta-blockers (propranolol or celiprolol). Two other vasodilating anti-hypertensive agents (hydralazine, amlodipine) gave opposite results on aortic rupture and mortality rate. There was a spectacular beneficial effect of losartan, reversed by the cessation of its administration, and a marked deleterious effect of exogenous angiotensin II. These results suggest that blockade of the renin angiotensin system should be tested as a first-line medical therapy in patients with vascular Ehlers-Danlos syndrome.

Silodosin improves functional consequences of lower urinary tract obstruction secondary to benign prostate hypertrophy, a proof of concept study in the spontaneously hypertensive rat supplemented with testosterone.

BACKGROUND: The main purpose of this study is to investigate the effect of silodosin on the urodynamic consequences in a previously established model of lower urinary tract symptoms associated with benign prostate hyperplasia, the spontaneously hypertensive rats (SHR) supplemented with testosterone. METHODS: Three groups of animals (8-week-old; n = 10/group) were considered: Wistar Kyoto (control) rats (WKY), SHR supplemented with testosterone at 3 mg/kg/day and treated with either vehicle (SHR-T, n = 10) or silodosin at 0.1 mg/kg/day (SHR-T + silodosin, n = 10) by oral gavage for 6 weeks. Cystometry experiments were performed. The bladder was harvested, weighed and paraffin-embedded for morphometric analysis. The prostate was also harvested and weighed. RESULTS: The number of animals included in the analysis were n = 10/10 for WKY and n = 7-8/10 for each SHR rats supplemented with testosterone group. SHR-T displayed a significant decrease in the intercontraction interval, infused volume and mean flow rate whereas the frequency of non-voiding contractions was increased. Silodosin improved the voiding behavior of SHR-T by significantly increasing the intercontraction interval, the infused volume and the mean flow rate and decreasing the number of non-voiding contractions. SHR-T displayed a significant increase in prostate and bladder weights and a 15% increase in the detrusor wall area compared to WKY. CONCLUSIONS: Chronic silodosin treatment relieved storage symptoms in SHR supplemented with testosterone and decreased the frequency of non-voiding detrusor contractions during the filling phase.

Angiotensin II promotes thoracic aortic dissections and ruptures in Col3a1 haploinsufficient mice.

Vascular Ehlers-Danlos syndrome is a dramatic inherited disease caused by mutations of type III collagen (COL3A1) gene, associated with early-onset occurrence of arterial ruptures. Col3a1(+/-) heterozygous mice, the only vascular Ehlers-Danlos syndrome model available to date, have no spontaneous early vascular phenotype. Our objective was to determine the susceptibility of Col3a1(+/-) mice to develop arterial ruptures under high blood pressure (BP) conditions induced by a 4-week infusion of angiotensin II (AngII). AngII (1 µg/kg per minute) significantly and comparably increased systolic BP in Col3a1(+/-) and Col3a1(+/+) mice but led to a higher premature mortality rate in Col3a1(+/-) mice compared with Col3a1(+/+) mice (73% versus 36%; P=0.03), particularly during the first-week infusion (55% versus 0%). Echocardiography and histological analysis evidenced that early deaths were caused by thoracic aortic ruptures preceded by dissections and associated with low aortic collagen fibrils content. Remarkably, lowering the dose of AngII (0.5 µg/kg per minute) rescued the first-week premature deaths of Col3a1(+/-) mice while decreasing the rises in systolic BP (P=0.05 compared with the high-dose AngII), resulting in similar mortality rates in both groups of mice at the end of the 4-week period (30% versus 50% in Col3a1(+/-) and Col3a1(+/+) mice; P=0.30). Finally, norepinephrine infusion (3.9 µg/kg per minute) did not induced significant mortality in both groups, whereas it significantly increased systolic BP, comparably with the high and with the low dose of AngII in Col3a1(+/-) mice (P=0.53 and P=1.00, respectively). Our findings demonstrated the extreme sensitivity of Col3a1 insufficient mice to prematurely develop thoracic aortic ruptures in response to AngII and its associated high levels in BP.

A new methodology for quantification of alternatively spliced exons reveals a highly tissue-specific expression pattern of WNK1 isoforms.

Mutations in the WNK1 gene, encoding a serine-threonine kinase of the WNK (With No lysine (K)) family, have been implicated in two rare human diseases, Familial Hyperkalemic Hypertension (FHHt) and Hereditary Sensory and Autonomic Neuropathy type 2 (HSAN2). Alternative promoters give rise to a ubiquitous isoform, L-WNK1, and a kidney-specific isoform, KS-WNK1. Several other isoforms are generated through alternative splicing of exons 9, 11 and 12 but their precise tissue distribution is not known. Two additional exons, 8b and HSN2, involved in HSAN2, are thought to be specifically expressed in the nervous system. The purpose of this study was to establish an exhaustive description of all WNK1 isoforms and to quantify their relative level of expression in a panel of human and mouse tissues and in mouse nephron segments. For the latter purpose, we developed a new methodology allowing the determination of the proportions of the different isoforms generated by alternative splicing. Our results evidenced a striking tissue-specific distribution of the different isoforms and the unexpected presence of exon HSN2 in many tissues other than the nervous system. We also found exon 26 to be alternatively spliced in human and identified two new exons, 26a and 26b, within intron 26, specifically expressed in nervous tissues both in humans and mice. WNK1 should therefore no longer be designated as a 28- but as a 32-exon gene, with 8 of them - 8b, HSN2, 9, 11, 12, 26, 26a and 26b - alternatively spliced in a tissue-specific manner. These tissue-specific isoforms must be considered when studying the different roles of this ubiquitous kinase.