Endothelial senescence in progeria

In modern societies with increasingly older populations, age is becoming a major risk factor for cardiovascular disease (CVD). Aging on the cellular level, particularly in the context of endothelial cells (ECs), which line all blood vessels, is the driver of age-related CVD. However, the molecular mechanisms underlying this phenomenon are still poorly understood. Many aspects of age-related CVD are resembled in the premature aging disorder Hutchinson-Gilford progeria syndrome (HGPS), which is caused by a mutation in the lamin A gene leading to the expression of a mutated form of the protein called progerin. We have established a HGPS mouse model with selective progerin targeting to endothelial tissue (Prog-Tg) to further explore the molecular mechanism of age-related changes in the endothelium and its contribution to age- related CVD. Our recent data show that the Prog-Tg mouse model recapitulates age-related CVD in many aspects such as development of diastolic dysfunction with extensive fibrosis that could be directly linked to an impairment of endothelial function. On the molecular level, using experimental conditions that simulate blood flow, we could show that ECs with progerin were unable to respond to and align in the direction of the flow and to activate signaling pathways that normally maintain a healthy juvenile state of the endothelium. Furthermore, we could show that endothelial cells containing progerin were characterized by a specific aging-signature with increased levels of typical markers of aging and increased secretion of components with deteriorating systemic effects such as molecules with proinflammatory- and gene regulatory function, including some micro RNAs (miRs). Accordingly, we detected an upregulation of a unique set of miRs in plasma of Prog-Tg mice proposed to be high-risk factors for cardiovascular incidents. This, together with our data showing secretory-dependent insults on other cell types indicated that Prog-Tg ECs exert systemic deteriorating effects. Based on these findings, we propose a model of mechano-aging in progerin-ECs that presumably operates similarly in normally aged ECs exposed to pathological mechanical strain. Accordingly, accumulation of progerin or mechanical disturbances cause an impaired mechanoresponse that activates molecular pathways responsible for increased aging and secretion of aging-promoting components such as miRs. In the proposed project, we aim to decipher the molecular pathways that lead to mechano-aging in progeria and to target secreted miRs in vitro but also in vivo in mice using chemical compounds that inhibit their function (antagomiR) with an aim to ameliorate progerin-induced CVD. Altogether we expect this study to provide novel insights into molecular processes that lead to aging of blood vessels paving ground for development of new beneficial therapies for HGPS patients, but possibly for geriatric CVD-patients as well.

In modern societies with increasingly older populations, age is becoming a major risk factor for cardiovascular and bone disease. In regard to the latter, bone changes during aging pose the elderly population at increased risk for bone fractures that in turn increase the risk for developing other comorbidities. Recently, damaged, non-dividing, senescent cells gained on importance as drivers of age-related diseases. However, emerging data point towards high heterogeneity of different senescent cell types and hitherto largely unknown cell type specific effects in vivo, in the organismal context. Furthermore, clear identification and characterization of senescent cells in vivo is largely missing. The major focus of this project was on senescence of endothelial cells lining blood vessels and how these cells in an in vivo system impact different tissues. Using genetically modified approach to introduce premature aging disease, Hutchinson-Gilford progeria syndrome (HGPS) in endothelial cells, we were able by applying several state-of-art methods, to demonstrate existence of senescent endothelial cells in different organs, lungs, heart, liver and bone marrow. Analysis of aged endothelial transcriptomes and secretomes could show upregulation of typical senescence-associated secretory phenotype (SASP) signalling pathways with some endothelial-specific characteristics, such as fibrosis, inflammation and upstream microRNA elements regulating cellular senescence. These findings allowed us to shed more light on the mechanistic level on our previous data showing that endothelial dysfunction contributes to fibrotic changes and diastolic dysfunction in age-related cardiovascular disease. Importantly, we were able to link accumulation of senescent endothelial cells to development of age-related changes in the heart. Moreover, in accordance with high accumulation of senescent endothelial cells in the bone marrow, we were able to show reduced bone formation capacity of bone progenitors in conjunction with cortical thinning demonstrating that aged blood vessels deteriorate bone tissue as well. Finally, using antagomiRs we targeted microRNA agents found upregulated in the circulation as well as endothelial cells, miR34a-5p and miR31-5p, in an attempt to ameliorate endothelial senescence and SASP. We could show that treatment of senescent endothelial cells with antmiR34a-5p led to upregulation of longevity pathways associated with Sirt1 and Wnt de-repression and importantly suppressed the senescence phenotype. On the other hand, antmiR31-5p agents exhibited major benefits in boosting the osteogenic capacity of bone progenitors. Altogether, this project provides novel insights into molecular processes that lead to aging of blood vessels, paving ground for development of new microRNA-based therapies for age-related cardiovascular and bone diseases in elderly and HGPS patients.