Atherosclerosis in progeria: insight from new mouse models with systemic and tissue-specific progerin expression

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Medicina, Departamento de Bioquímica. Fecha de lectura: 19-09-2017Esta tesis tiene embargado el acceso al texto completo hasta el 19-03-2019Cardiovascular disease (CVD) is a major cause of morbidity and mortality worldwide due to the progressive aging of our societies. Age-related decline in cardiovascular health is accelerated in a rare genetic disorder called Hutchinson-Gilford progeria syndrome (HGPS). The disease is caused by a de novo point mutation in the LMNA gene, which leads to the expression of “progerin”, a mutant form of the nuclear protein lamin A. Since lamin A possesses important structural and functional properties, progerin expression triggers numerous nuclear abnormalities. Children with HGPS exhibit premature aging symptoms, including alopecia, osteoporosis, lipodystrophy, joint stiffness, and skin wrinkling and mottling. However, the most clinically relevant feature of the disease is accelerated atherosclerosis, which leads to premature death at an average age of 14.6 years, predominantly from myocardial infarction or stroke. The mechanisms through which progerin provokes enhanced atherosclerosis remain poorly understood, in part due to the paucity of suitable models. To address this, we sought to generate new mouse models that allow the study of atherosclerosis in the context of HGPS. When compared with control mice expressing wild-type lamin A/C, mice with ubiquitous progerin expression exhibited a premature aging phenotype, including reduced body weight and shortened survival. In addition, progerin-expressing mice showed increased atherosclerosis burden together with a severe vascular pathology, including the depletion of vascular smooth muscle cells (VSMCs), increased collagen content, medial lipid retention and adventitial fibrosis, resembling most aspects of CVD observed in HGPS. We also found that mice expressing progerin specifically in VSMCs, but not in macrophages, fully recapitulated the vascular pathology observed in the ubiquitous progeria model. Atheromas of both ubiquitous and VSMC-specific models showed evidence of plaque disruption, which might lead to myocardial infarction. Using a transcriptomic approach, we identified endoplasmic reticulum (ER) stress and the unfolded protein response as possible driver mechanisms of progerin-induced VSMC death and accelerated atherosclerosis. Accordingly, treatment with tauroursodeoxycholic acid (TUDCA), a chemical chaperone that increases the capacity of a cell to sustain ER stress, was effective at ameliorating vascular disease (atherosclerosis, VSMC loss and adventitial thickening) in both ubiquitous and VSMC-specific mouse models. TUDCA also prolonged the survival of mice with VSMC-specific progerin expression by 35%. Taken together, these findings indicate that TUDCA may be effective in the treatment of atherosclerosis and associated cardiovascular events in HGPS. Moreover, since progerin accumulates with age in non-HPGS individuals, our data may also shed some light on the mechanisms of normal aging

Vascular Smooth Muscle-Specific Progerin Expression Accelerates Atherosclerosis and Death in a Mouse Model of Hutchinson-Gilford Progeria Syndrome

Background: Progerin, an aberrant protein that accumulates with age, causes the rare genetic disease Hutchinson-Gilford progeria syndrome (HGPS). Patients who have HGPS exhibit ubiquitous progerin expression, accelerated aging and atherosclerosis, and die in their early teens, mainly of myocardial infarction or stroke. The mechanisms underlying progerin-induced atherosclerosis remain unexplored, in part, because of the lack of appropriate animal models. Methods: We generated an atherosclerosis-prone model of HGPS by crossing apolipoprotein E-deficient (Apoe(-/-)) mice with Lmna(G609G/G609G) mice ubiquitously expressing progerin. To induce progerin expression specifically in macrophages or vascular smooth muscle cells (VSMCs), we crossed Apoe(-/-)Lmna(LCS/LCS) mice with LysMCre and SM22Cre mice, respectively. Progerin expression was evaluated by polymerase chain reaction and immunofluorescence. Cardiovascular alterations were determined by immunofluorescence and histology in male mice fed normal chow or a high-fat diet. In vivo low-density lipoprotein retention was assessed by intravenous injection of fluorescently labeled human low-density lipoprotein. Cardiac electric defects were evaluated by electrocardiography. Results:Apoe(-/-)Lmna(G609G/G609G) mice with ubiquitous progerin expression exhibited a premature aging phenotype that included failure to thrive and shortened survival. In addition, high-fat diet-fed Apoe(-/-)Lmna(G609G/G609G) mice developed a severe vascular pathology, including medial VSMC loss and lipid retention, adventitial fibrosis, and accelerated atherosclerosis, thus resembling most aspects of cardiovascular disease observed in patients with HGPS. The same vascular alterations were also observed in Apoe(-/-)Lmna(LCS/LCS)SM22Cre mice expressing progerin specifically in VSMCs, but not in Apoe(-/-)Lmna(LCS/LCS)LysMCre mice with macrophage-specific progerin expression. Moreover, Apoe(-/-)Lmna(LCS/LCS)SM22Cre mice had a shortened lifespan despite the lack of any overt aging phenotype. Aortas of ubiquitously and VSMC-specific progerin-expressing mice exhibited increased retention of fluorescently labeled human low-density lipoprotein, and atheromata in both models showed vulnerable plaque features. Immunohistopathological examination indicated that Apoe(-/-)Lmna(LCS/LCS)SM22Cre mice, unlike Apoe(-/-)Lmna(G609G/G609G) mice, die of atherosclerosis-related causes. Conclusions: We have generated the first mouse model of progerin-induced atherosclerosis acceleration, and demonstrate that restricting progerin expression to VSMCs is sufficient to accelerate atherosclerosis, trigger plaque vulnerability, and reduce lifespan. Our results identify progerin-induced VSMC death as a major factor triggering atherosclerosis and premature death in HGPS.Work in Dr Andres' laboratory is supported by grants from the Spanish Ministerio de Economia, Industria y Competitividad (MEIC) (SAF2016-79490-R) and the Instituto de Salud Carlos III (AC16/00091, AC17/00067) with co-funding from the Fondo Europeo de Desarrollo Regional (FEDER, ``Una manera de hacer Europa´´), the Progeria Research Foundation (Established Investigator Award 2014-52), and the Fundacio Marato TV3 (122/C/2015). The MEIC supported Dr Hamczyk (´´Formacion de Personal Investigador´´ predoctoral contract BES-2011-043938) and Dr Villa-Bellosta (´´Juan de la Cierva´´ JCI-2011-09663 postdoctoral contract). The Instituto Universitario de Oncologia is supported by Obra Social Cajastur. The Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC) is supported by the MEIC and the Pro-CNIC Foundation, and is a Severo Ochoa Center of Excellence (award SEV-2015-0505).S

Vascular smooth muscle cell loss underpins the accelerated atherosclerosis in Hutchinson-Gilford progeria syndrome

Lamin A, a product of the LMNA gene, is an essential nuclear envelope component in most differentiated cells. Mutations in LMNA have been linked to premature aging disorders, including Hutchinson-Gilford progeria syndrome (HGPS). HGPS is caused by progerin, an aberrant form of lamin A that leads to premature death, typically from the complications of atherosclerotic disease. A key characteristic of HGPS is a severe loss of vascular smooth muscle cells (VSMCs) in the arteries. Various mouse models of HGPS have been created, but few of them feature VSMC depletion and none develops atherosclerosis, the death-causing symptom of the disease in humans. We recently generated a mouse model that recapitulates most features of HGPS, including VSMC loss and accelerated atherosclerosis. Furthermore, by generating cell-type-specific HGPS mouse models, we have demonstrated a central role of VSMC loss in progerin-induced atherosclerosis and premature death.M.R.H. is supported by a ‘Juan de la Cierva’ postdoctoral fellowship (FJCI-2017-33299) from the Spanish Ministerio de Ciencia, Innovación yUniversidades (MCIU). Work in V.A.’s laboratory is supported by grants from the Spanish Instituto de Salud Carlos III (AC16/00091 and AC17/00067) and MCIU (SAF2016-79490-R), with co-funding from the Fondo Europeo de Desarrollo Regional (FEDER, ‘Una manera de hacer Europa’), the Progeria Research Foundation (Established Investigator Award 2014-52), and the Fundació Marató TV3 (122/C/2015). The CNIC is supported by theMCIU and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505); Instituto de Salud Carlos III [AC16/00091 and AC17/00067]; MCIU [SAF2016-79490-R]; MCIU [FJCI2017-33299]; MCIU [SEV-2015-0505]; Progeria Research Foundation [2014-52].S