Progeria Research Articles

C10. An ultra-rare case of Hutchinson–Gilford progeria syndrome with severe aortic regurgitation due to bicuspid aortic valve in a 9-year-old girl

Abstract Background Hutchinson-Gilford progeria syndrome (HGPS) is an ultra-rare autosomal dominant that result in progressive premature aging syndrome. Cardiovascular diseases become the main cause of mortality including myocardial infarction, interstitial myocardial fibrosis, hypertension and calcification of the mitral and aortic valves. However, the relationship between HGPS and bicuspid aortic valve (BAV) has not been documented yet. Case Summary A 9-year-old girl with HGPS presented to the outpatient clinic with a complaint of shortness of breath since 5 years ago, especially when she did moderate physical activity. Chest pain and palpitation were denied. Her physical examination revealed short stature, thin, wrinkled skin, craniofacial disproportion with alopecia, shrunken facies and prominent scalp veins. There was failure to thrive and diastolic murmur grade 2/4 is heard on the aortic area. Laboratory test showed leukocytosis. Transthoracic echocardiogram showed severe aortic regurgitation due to calcified bicuspid aortic valve and mild mitral regurgitation. She was managed by conservative therapy because her parents were still considering the aortic valve repair procedure. Discussion The HGPS patient with severe aortic regurgitation due to BAV should be managed to reduce cardiovascular complications. Aortic valve repair is an interesting alternative to replacement managing aortic regurgitation due to BAV in young adults. Recently, advanced science about BAV disease and refinement of surgical techniques improved standardization of BAV repair procedure.

C10. An ultra-rare case of Hutchinson–Gilford progeria syndrome with severe aortic regurgitation due to bicuspid aortic valve in a 9-year-old girl

Abstract Background Hutchinson-Gilford progeria syndrome (HGPS) is an ultra-rare autosomal dominant that result in progressive premature aging syndrome. Cardiovascular diseases become the main cause of mortality including myocardial infarction, interstitial myocardial fibrosis, hypertension and calcification of the mitral and aortic valves. However, the relationship between HGPS and bicuspid aortic valve (BAV) has not been documented yet. Case Summary A 9-year-old girl with HGPS presented to the outpatient clinic with a complaint of shortness of breath since 5 years ago, especially when she did moderate physical activity. Chest pain and palpitation were denied. Her physical examination revealed short stature, thin, wrinkled skin, craniofacial disproportion with alopecia, shrunken facies and prominent scalp veins. There was failure to thrive and diastolic murmur grade 2/4 is heard on the aortic area. Laboratory test showed leukocytosis. Transthoracic echocardiogram showed severe aortic regurgitation due to calcified bicuspid aortic valve and mild mitral regurgitation. She was managed by conservative therapy because her parents were still considering the aortic valve repair procedure. Discussion The HGPS patient with severe aortic regurgitation due to BAV should be managed to reduce cardiovascular complications. Aortic valve repair is an interesting alternative to replacement managing aortic regurgitation due to BAV in young adults. Recently, advanced science about BAV disease and refinement of surgical techniques improved standardization of BAV repair procedure.

Abstract 12533: Progerin Causes a Disproportionate Senescence in Endothelial Cells

Hutchinson-Gilford progeria syndrome (HGPS) is a premature aging disorder caused by the mutation of LMNA gene leading to irreversibly farnesylated lamin A protein, i.e. progerin. The major causes of death in HGPS are coronary and arterial occlusive disease. In the murine model of HGPS, vascular smooth muscle cells (VSMCs) loss is the primary vascular manifestation, which is quite different from the human arterial occlusive disease. To identify the mechanisms of HGPS vascular disease in humans, we differentiated isogenomic endothelial cells (ECs) and VSMCs from the same lines of HGPS-iPSCs and control-iPSCs. Both HGPS-ECs and HGPS-VSMCs manifested cellular hallmarks of aging, including dysmorphic nuclei, impaired proliferation, increased β-galactosidase staining, shortened telomeres, upregulated secretion of inflammatory cytokines, increased DNA damage, loss of heterochromatin and altered shelterin complex expression. However, at similar passage number, HGPS-ECs are more severely affected compared to VSMCs, as indicated by a higher percentage of β-galactosidase positive cells, significantly shortened telomere length, and greater frequency of DNA damage signals. With increasing passage number, there is progressive senescence in HGPS-ECs that is greater than that observed in HGPS-VSMCs. Using immunoprecipitation and mass spectrometry, we compared the integrity of the Shelterin Protein Complex (SPC), which is composed of six different proteins and whose function is to protect the telomeres, on the ECs and VSMCs of HGPS and control cells. We observed increased γH2A.X binding to RAP1 (member of SPC) and to Lamin A (nuclear envelope) in HGPS cells. The expression of γH2A.X was greater in HGPS ECs than VSMCs, and is associated with loss of SPC integrity, telomere shortening and loss of heterochromatin formation. Whereas progerin expression has deleterious effect in both vascular ECs and VSMCs, the severity of dysfunction is more extensive in HGPS-ECs in comparison to HGPS-VSMCs. These studies indicate that an endothelial-targeted therapy may be useful in HGPS.

Abstract 11821: Telomerase Therapy Reverses Vascular Senescence and Extends Lifespan in Progeria Mice

Background: Hutchinson-Gilford Progeria Syndrome (HGPS) is an accelerated aging syndrome associated with premature vascular disease and death due to heart attack and stroke. In HGPS a mutation in lamin A (progerin), alters nuclear morphology and gene expression. Current therapy increases the lifespan of these children only modestly. Thus, greater understanding of the underlying mechanisms of HGPS is required to improve therapy. Endothelial cells (ECs) differentiated from induced pluripotent stem cells (iPSCs) derived from these patients exhibit hallmarks of senescence including replication arrest, DNA damage, increased expression of inflammatory markers and telomere erosion. We hypothesized that correction of shortened telomeres may reverse these measures of vascular aging. Methods: We generated ECs from iPSCs belong to children with HGPS and their unaffected parents. Telomerase mRNA (hTERT) was used to treat HGPS ECs. Endothelial morphology and functions were assessed, as well as proteomic and transcriptional profiles with attention to inflammatory markers, DNA damage and EC identity genes. In a mouse model of HGPS, we assessed the effects of lentiviral transfection of mTERT on measures of senescence, focusing on the EC phenotype in various organs. Results: hTERT treatment of human HGPS ECs improved replicative capacity; restored endothelial functions such as nitric oxide generation, acLDL uptake and angiogenesis; and reduced the elaboration of inflammatory cytokines. In addition, hTERT treatment improved cellular and nuclear morphology, in association with a normalization of the transcriptional profile, effects which may be mediated in part by a reduction in progerin expression and an increase in SIRT1. Progeria mice treated with mTERT Lentivirus manifested similar improvements, with a reduction in inflammatory and DNA damage markers and increased SIRT1 in their vasculature and other organs. Furthermore, mTERT therapy increased the lifespan of HGPS mice. Conclusion: Vascular rejuvenation using telomerase mRNA is a promising approach for progeria and other age-related diseases.

Abstract 10732: Systemic Administration of Telomerase RNA Reverses Vascular Senescence and Extends Lifespan in Progeria Mice

Introduction: Hutchinson-Gilford Progeria Syndrome (HGPS) is an accelerated aging syndrome associated with premature vascular disease and death due to heart attack and stroke. In HGPS, a mutation in lamin A (progerin) alters nuclear morphology and gene expression. iPSCs derived endothelium from progeria patients show impairment in their morphology and function including replication arrest, DNA damage, increased expression of inflammatory markers, and telomere erosion, compared to iPSCs derived endothelial cells from their unaffected parents. We have shown that hTERT mRNA therapy rescues their senescent phenotypes and restores normal function and gene expression in-vitro. To validate our finding in-vivo, we have used lentivirus harboring mouse telomerase to treat mice model of progeria and investigated the beneficial effects on mice vasculature in different organs. Hypothesis: Gene therapy with mRNA encoding mice telomerase improves survival and reversing cell senescence in a mice model of HGPS. Methods: HGPS mice were injected twice with a lentivirus construct encoding mice telomerase via tail vein. Mice were monitored for survival; endothelial cells were isolated at the time of euthanasia and concentrations of cytokines, chemokines, and growth factors were analyzed using Elisa, PCR and immunofluorescence staining. For clinical translation we developed a lipid nanoparticle formulation to deliver mRNA encoding mTERT to mice, validating its function using mRNA encoding Luciferase to demonstrate biodistribution and safety profile. Results: Two treatments with lentiviral mTERT increased the lifespan of HGPS mice by 20% and reduced mediators of inflammation and thrombosis in HGPS such as thrombomodulin. HGPS mice treated with mTERT had lower DNA damage markers and increased SIRT1 in their vasculature and other organs. A Lipid nanoparticle encapsulating mTERT RNA and shows a favorable safety profile and the capacity to systemically and safely deliver luciferase mRNA, generating active luciferase, documenting a predominantly hepatic biodistribution. Conclusions: Vascular rejuvenation using telomerase mRNA is a promising approach for progeria and other age-related diseases. Further development in systemic delivery is thus underway

Abstract 11757: Telomerase Treatment Restores Transcriptional Profile and Epigenetic Landscape in Progeria Vascular Cells

Hutchinson-Gilford progeria syndrome (HGPS) is a model of accelerated vascular aging caused by a de novo mutation of a single nucleotide in the Lamin A gene. The accumulation of abnormal lamin A (progerin) in the nuclear envelope induces a nuclear dysmorphology associated with global gene dysregulation, increased expression of inflammatory cytokines, impaired vascular function, and accelerated telomere erosion. These individuals succumb to myocardial infarction or stroke in their mid-teens. We hypothesized that restoration of telomere length might reverse some of the observed derangements in cell function, transcriptional profile and epigenetic alterations. Accordingly, we generated iPSC-derived endothelial cells (ECs) from HGPS children and their unaffected parents. By comparison to the parental controls, HGPS ECs have severely impaired replicative capacity, cellular functions (e.g. NO synthesis, acLDL uptake, network formation, cytokine secretion) and severe telomere shortening. We observed that transient transfection with mRNA encoding human telomerase (hTERT) increases telomere length, restores cellular replicative capacity and improves HGPS-EC functions. Notably, RNAseq studies revealed that that approximately 1200 genes were dysregulated in Progeria, most of which were improved by hTERT treatment, among which approximately 250+ genes were fully normalized. Intriguingly, hTERT treatment reduces DNA damage signals (γH2Ax) and reverses the aberrant chromatin accessibility observed in HGPS-ECs, as assessed by a reduction in the activating histone mark H3K4me3; an increase in the suppressive mark H3K4me3; and normalizes the level of heterochromatin markers HP1, Histone H1 and H3. Preliminary results from ChIPseq studies targeting histone marks characteristic of activators, repressors and enhancers as well as chromatin remodeling proteins; together with Hi-C analyses indicate that there are global changes in topologically associated domains (TADs) and other features of the chromatin landscape in HGPS ECs, which are partially restored by hTERT treatment. We conclude that hTERT treatment has surprisingly global effects on transcriptional profile and epigenetic landscape in addition to telomere extension.

Abstract 10730: Vascular Smooth Muscle Cell Phenotypic Switch and Replication Stress as a Key Contributors in CVD in HGPS

Hutchinson Gilford Progeria Syndrome is a premature aging disease caused by LMNA gene mutation and production of a truncated lamin A protein “progerin” that elicits cellular and organismal toxicity. Patients show severe aging phenotypes, including alopecia, reduced fat and bone density, and cardiovascular disease (CVD), which ultimately causes their death as teenagers. HGPS has no cure and clinical trials obtained only minor benefits. It is urgent to identify mechanisms of progerin toxicity to target therapeutically. Progerin accumulates preferentially in the vasculature, being especially toxic for vascular smooth muscle cells (VSMC). Patients' autopsies show that vessel stiffening and aortic atherosclerosis are accompanied by VSMCs depletion in the media, increased extracellular matrix (ECM), and adventitia thickening. Mechanisms whereby progerin causes massive VSMC loss and ECM accumulation are unknown. We previously demonstrated that progerin expression in fibroblasts hinders DNA replication, causes genomic instability, and triggers a phenotypic switch towards activated fibroblasts/myofibroblasts. These cells are known to promote tissue fibrosis by ECM deposition and release of inflammatory cytokines. VSMCs can also undergo phenotypic modulation or de-differentiation, a process whereby contractile cells revert to a synthetic/proliferative phenotype, leading to pathological accumulation of ECM and CVD. Here we show that progerin expression in VSMCs causes a switch towards the synthetic/proliferative phenotype. Similarly to fibroblasts, progerin represents a challenge for DNA replication in VSMC, triggering replication stress, genomic instability and ultimately VSMC death. Importantly, we found that calcitriol -hormonal active form of vitamin D- prevents VSMC switch and replication stress. Our data suggest that replication stress might be an underlying cause of VSMC loss in progeria and that preventing the phenotypic switch-induced replication stress with compounds such as calcitriol might prevent the massive loss of VSMC and the vascular stiffness in HGPS patients.

Ocular manifestations in a case of progeroid syndrome

Progeria syndromes are very rare genetic diseases characterized by premature aging changes. There are several phenotypes and variables noted in literature in some cases difficult to specifically classify a specific syndrome. It occurs due to mutation in DNA repair genes. The most common ocular findings are loss of eyebrow and eyelashes, brow ptosis, lid margin changes, entropion, Meibomian gland dysfunction, severe dry eye, corneal opacity, cataract, poor mydriasis, and rod-cone dystrophy. We report this case with all the above ocular manifestations in 19year old teenager with additional finding being retinal detachment.

Toward CRISPR Therapies for Cardiomyopathies.

Toward CRISPR Therapies for Cardiomyopathies.

The Impact of Rare Human Variants on Barrier-To-Auto-Integration Factor 1 (Banf1) Structure and Function.

Barrier-to-Autointegration Factor 1 (Banf1/BAF) is a critical component of the nuclear envelope and is involved in the maintenance of chromatin structure and genome stability. Banf1 is a small DNA binding protein that is conserved amongst multicellular eukaryotes. Banf1 functions as a dimer, and binds non-specifically to the phosphate backbone of DNA, compacting the DNA in a looping process. The loss of Banf1 results in loss of nuclear envelope integrity and aberrant chromatin organisation. Significantly, mutations in Banf1 are associated with the severe premature ageing syndrome, Néstor–Guillermo Progeria Syndrome. Previously, rare human variants of Banf1 have been identified, however the impact of these variants on Banf1 function has not been explored. Here, using in silico modelling, biophysical and cell-based approaches, we investigate the effect of rare human variants on Banf1 structure and function. We show that these variants do not significantly alter the secondary structure of Banf1, but several single amino acid variants in the N- and C-terminus of Banf1 impact upon the DNA binding ability of Banf1, without altering Banf1 localisation or nuclear integrity. The functional characterisation of these variants provides further insight into Banf1 structure and function and may aid future studies examining the potential impact of Banf1 function on nuclear structure and human health.

Age-Acquired Downregulation of Lmna Leads to Epigenetic Deregulation and Altered HSPC Function

Hematopoietic stem cells (HSCs) exhibit epigenetic reprogramming and decline in function with aging, and these changes may be predisposing mechanisms for development of clonal hematopoiesis and myeloid malignancies. Our recent study characterizing the epigenetic and transcriptional landscape of young (18-30 years) and aged (65-75 years) human CD34 +CD38 - bone marrow (BM) cells identified Lamin-A/C (LMNA) as one of the most downregulated genes with aging (7.9-fold, p=1.9x10 -13). LMNA encodes the nuclear lamina protein Lamin-A/C and is mutated in the premature aging disorder Hutchinson-Gilford Progeria Syndrome.To determine whether downregulation of LMNA contributes to the phenotype of human HSC aging, we knocked down LMNA (LMNA KD) using shRNA in young, mobilized peripheral blood CD34 + cells. With an average knockdown of 60%, we observed ~33% increase in myeloid colony forming potential (p<0.05). LMNA KD also impaired differentiation in liquid culture as determined by persistence of CD34 expression in twice as many cells as controls (p<0.0001) while induction of myeloid CD11b expression was reduced by ~29% (p<0.05), as well as a trend to reduced erythroid (CD71 +GYPA +) differentiation. To investigate the effects of Lmna loss-of-function in vivo, we conditionally deleted Lmna in mice using Vav-Cre. Loss of Lmna (Lmna KO) had no effect on steady state hematopoiesis in young (10 weeks) or middle-aged (14 months) knockout mice. However, Lmna KO BM cells from middle-aged mice generated 2-fold more total colonies than wild-type, floxed controls (WT=126 vs KO=292, p<0.01).Given that nuclear architecture provides a layer of epigenetic regulation through chromatin-lamina interactions, we investigated how the epigenome changes in the context of LMNA deficiency. By super-resolution microscopy, we observed loss of LMNA localization from the nuclear periphery in LMNA KD human CD34 +cells (p<0.05). Since lamina-associated domains generally contain regions of repressed chromatin, we stained for histone H3K9me2 and observed that LMNA KD cells displayed increased scattering throughout the nucleus without a change in its density. Next, we performed ATAC-seq and identified 603 open chromatin sites showing changes in accessibility (FDR<0.1). Over 73% of these sites show reduced accessibility and were associated with genes showing reduced expression by RNA-seq. Gene ontology analysis of these sites identified genes associated with heme biosynthetic and cell differentiation processes (FDR<0.005). Moreover, gene set enrichment analysis of the RNA-seq confirmed that downregulated genes were enriched for genes downregulated in our previously reported CD34 + aging signature (NES=-1.46, FDR=0.001). To determine whether LMNA KD alters the epigenome, we performed ChIP-seq for active (H3K4me3, H3K27ac) and repressive (H3K9me2) histone marks. LMNA KD resulted in significant reduction of 36% of H3K27ac peaks, which mimics our previous observation of marked age-related losses of H3K27ac. Most differential peaks localized to gene promoters (50%) and introns (34%) and include genes involved in nuclear pore organization and gene silencing (FDR<0.001). Notably, for peaks located at intergenic regions, >35% overlapped with active enhancers we reported as lost with aging and were associated with genes involved in regulation of p38 MAPK cascade (enrichment=2.34E -5), an important signaling pathway regulating proliferation and differentiation of HSCs and leukemic cells.Taken together, LMNA deficiency recapitulates features of aging at the functional and epigenetic level. LMNA KD in young, human CD34 + cells impaired their differentiation while increasing their colony forming potential. Similarly in middle-aged mice, LMNA KO BM cells showed increased colony forming potential. Genomic changes induced by LMNA deficiency include reduced accessibility and gene transcription, accompanied by changes in localization and occupancy of histone H3K9me2 and H3K27ac, respectively. These epigenetic changes affect genes regulating differentiation and signaling pathways. Thus, we have demonstrated that in addition to its structural role, LMNA also contributes to chromatin regulation of hematopoietic pathways important for normal CD34 + function. DisclosuresNo relevant conflicts of interest to declare.

New pharmaceuticals approved by FDA in 2020: Small-molecule drugs derived from amino acids and related compounds.

Amino acids (AAs) play an important role in the modern health industry as key synthetic precursors for pharmaceuticals, biomaterials, biosensors, and drug delivery systems. Currently, over 30% of small-molecule drugs contain residues of tailor-made AAs or derived from them amino-alcohols and di-amines. In this review article, we profile 12 AA-derived new pharmaceuticals approved by the FDA in 2020. These newly introduced drugs include Tazverik (epithelioid sarcoma), Gemtesa (overactive bladder), Zeposia (multiple sclerosis), Byfavo (induction and maintenance of procedural sedation), Cu 64 dotatate, and Gallium 68 PSMA-11 (both PET imaging), Rimegepant (acute migraine), Zepzelca (lung cancer), Remdesivir (COVID-19), Amisulpride (nausea and vomiting), Setmelanotide (obesity), and Lonafarnib (progeria syndrome). For each compound, we describe the spectrum of biological activity, medicinal chemistry discovery, and synthetic preparation.

Cardiovascular Progerin Suppression and Lamin A Restoration Rescue Hutchinson-Gilford Progeria Syndrome.

Hutchinson-Gilford progeria syndrome (HGPS) is a rare disorder characterized by premature aging and death mainly because of myocardial infarction, stroke, or heart failure. The disease is provoked by progerin, a variant of lamin A expressed in most differentiated cells. Patients look healthy at birth, and symptoms typically emerge in the first or second year of life. Assessing the reversibility of progerin-induced damage and the relative contribution of specific cell types is critical to determining the potential benefits of late treatment and to developing new therapies. We used CRISPR-Cas9 technology to generate LmnaHGPSrev/HGPSrev (HGPSrev) mice engineered to ubiquitously express progerin while lacking lamin A and allowing progerin suppression and lamin A restoration in a time- and cell type-specific manner on Cre recombinase activation. We characterized the phenotype of HGPSrev mice and crossed them with Cre transgenic lines to assess the effects of suppressing progerin and restoring lamin A ubiquitously at different disease stages as well as specifically in vascular smooth muscle cells and cardiomyocytes. Like patients with HGPS, HGPSrev mice appear healthy at birth and progressively develop HGPS symptoms, including failure to thrive, lipodystrophy, vascular smooth muscle cell loss, vascular fibrosis, electrocardiographic anomalies, and precocious death (median lifespan of 15 months versus 26 months in wild-type controls, P<0.0001). Ubiquitous progerin suppression and lamin A restoration significantly extended lifespan when induced in 6-month-old mildly symptomatic mice and even in severely ill animals aged 13 months, although the benefit was much more pronounced on early intervention (84.5% lifespan extension in mildly symptomatic mice, P<0.0001, and 6.7% in severely ill mice, P<0.01). It is remarkable that major vascular alterations were prevented and lifespan normalized in HGPSrev mice when progerin suppression and lamin A restoration were restricted to vascular smooth muscle cells and cardiomyocytes. HGPSrev mice constitute a new experimental model for advancing knowledge of HGPS. Our findings suggest that it is never too late to treat HGPS, although benefit is much more pronounced when progerin is targeted in mice with mild symptoms. Despite the broad expression pattern of progerin and its deleterious effects in many organs, restricting its suppression to vascular smooth muscle cells and cardiomyocytes is sufficient to prevent vascular disease and normalize lifespan.

Electromagnetized gold nanoparticles improve neurogenesis and cognition in the aged brain

Adult neurogenesis is the lifelong process by which new neurons are generated in the dentate gyrus. However, adult neurogenesis capacity decreases with age, and this decrease is closely linked to cognitive and memory decline. Our study demonstrated that electromagnetized gold nanoparticles (AuNPs) promote adult hippocampal neurogenesis, thereby improving cognitive function and memory consolidation in aged mice. According to single-cell RNA sequencing data, the numbers of neural stem cells (NSCs) and neural progenitors were significantly increased by electromagnetized AuNPs. Additionally, electromagnetic stimulation resulted in specific activation of the histone acetyltransferase Kat2a, which led to histone H3K9 acetylation in adult NSCs. Moreover, in vivo electromagnetized AuNP stimulation efficiently increased hippocampal neurogenesis in aged and Hutchinson-Gilford progeria mouse brains, thereby alleviating the symptoms of aging. Therefore, our study provides a proof-of-concept for the in vivo stimulation of hippocampal neurogenesis using electromagnetized AuNPs as a promising therapeutic strategy for the treatment of age-related brain diseases.

Atherosclerosis and Cardiovascular Diseases in Progeroid Syndromes.

Hutchinson–Gilford progeria syndrome (HGPS) and Werner syndrome (WS) are two of the representative genetic progeroid syndromes and have been widely studied in the field of aging research. HGPS is a pediatric disease in which premature aging symptoms appear in early childhood, and death occurs at an average age of 14.5 years, mainly due to cardiovascular disease (CVD). Conversely, WS patients exhibit accelerated aging phenotypes after puberty and die in their 50s due to CVD and malignant tumors. Both diseases are models of human aging, leading to a better understanding of the aging-associated development of CVD. In this review, we discuss the pathogenesis and treatment of atherosclerotic diseases presented by both progeroid syndromes with the latest findings.

Genomic instability in the naturally and prematurely aged myocardium

Genomic instability, the unresolved accumulation of DNA variants, is hypothesized as one of the contributors to the natural aging process. We assessed the frequency of unresolved DNA damage reaching the transcriptome of the murine myocardium during the course of natural aging and in hearts from four distinct mouse models of premature aging with established aging-related cardiac dysfunctions. RNA sequencing and variant calling based on total RNA sequencing was compared between hearts from naturally aging mice, mice with cardiomyocyte-specific deficiency of Ercc1, a component of the DNA repair machinery, mice with reduced mitochondrial antioxidant capacity, Tert-deficient mice with reduced telomere length, and a mouse model of human Hutchinson-Gilford progeria syndrome (HGPS). Our results demonstrate that no enrichment in variants is evident in the naturally aging murine hearts until 2 y of age from the HGPS mouse model or mice with reduced telomere lengths. In contrast, a dramatic accumulation of variants was evident in Ercc1 cardiomyocyte-specific knockout mice with deficient DNA repair machinery, in mice with reduced mitochondrial antioxidant capacity, and in the intestine, liver, and lung of naturally aging mice. Our data demonstrate that genomic instability does not evidently contribute to naturally aging of the mouse heart in contrast to other organs and support the contention that the endogenous DNA repair machinery is remarkably active to maintain genomic integrity in cardiac cells throughout life.

Genetic reduction of mTOR extends lifespan in a mouse model of Hutchinson-Gilford Progeria syndrome.

Hutchinson‐Gilford progeria syndrome (HGPS) is a rare accelerated aging disorder most notably characterized by cardiovascular disease and premature death from myocardial infarction or stroke. The majority of cases are caused by a de novo single nucleotide mutation in the LMNA gene that activates a cryptic splice donor site, resulting in production of a toxic form of lamin A with a 50 amino acid internal deletion, termed progerin. We previously reported the generation of a transgenic murine model of progeria carrying a human BAC harboring the common mutation, G608G, which in the single‐copy state develops features of HGPS that are limited to the vascular system. Here, we report the phenotype of mice bred to carry two copies of the BAC, which more completely recapitulate the phenotypic features of HGPS in skin, adipose, skeletal, and vascular tissues. We further show that genetic reduction of the mechanistic target of rapamycin (mTOR) significantly extends lifespan in these mice, providing a rationale for pharmacologic inhibition of the mTOR pathway in the treatment of HGPS.

Nuclear membrane ruptures underlie the vascular pathology in a mouse model of Hutchinson-Gilford progeria syndrome

The mutant nuclear lamin protein (progerin) produced in Hutchinson-Gilford progeria syndrome (HGPS) results in loss of arterial smooth muscle cells (SMCs), but the mechanism has been unclear. We found that progerin induces repetitive nuclear membrane (NM) ruptures, DNA damage, and cell death in cultured SMCs. Reducing lamin B1 expression and exposing cells to mechanical stress — to mirror conditions in the aorta — triggered more frequent NM ruptures. Increasing lamin B1 protein levels had the opposite effect, reducing NM ruptures and improving cell survival. Remarkably, raising lamin B1 levels increased nuclear compliance in cells and was able to offset the increased nuclear stiffness caused by progerin. In mice, lamin B1 expression in aortic SMCs is normally very low, and in mice with a targeted HGPS mutation (LmnaG609G), levels of lamin B1 decrease further with age while progerin levels increase. Those observations suggest that NM ruptures might occur in aortic SMCs in vivo. Indeed, studies in LmnaG609G mice identified NM ruptures in aortic SMCs, along with ultrastructural abnormalities in the cell nucleus that preceded SMC loss. Our studies identify NM ruptures in SMCs as likely causes of vascular pathology in HGPS.

Telomerase therapy reverses vascular senescence and extends lifespan in progeria mice.

Hutchinson-Gilford progeria syndrome (HGPS) is an accelerated ageing syndrome associated with premature vascular disease and death due to heart attack and stroke. In HGPS a mutation in lamin A (progerin) alters nuclear morphology and gene expression. Current therapy increases the lifespan of these children only modestly. Thus, greater understanding of the underlying mechanisms of HGPS is required to improve therapy. Endothelial cells (ECs) differentiated from induced pluripotent stem cells (iPSCs) derived from these patients exhibit hallmarks of senescence including replication arrest, increased expression of inflammatory markers, DNA damage, and telomere erosion. We hypothesized that correction of shortened telomeres may reverse these measures of vascular ageing. We generated ECs from iPSCs belonging to children with HGPS and their unaffected parents. Telomerase mRNA (hTERT) was used to treat HGPS ECs. Endothelial morphology and functions were assessed, as well as proteomic and transcriptional profiles with attention to inflammatory markers, DNA damage, and EC identity genes. In a mouse model of HGPS, we assessed the effects of lentiviral transfection of mTERT on measures of senescence, focusing on the EC phenotype in various organs. hTERT treatment of human HGPS ECs improved replicative capacity; restored endothelial functions such as nitric oxide generation, acetylated low-density lipoprotein uptake and angiogenesis; and reduced the elaboration of inflammatory cytokines. In addition, hTERT treatment improved cellular and nuclear morphology, in association with a normalization of the transcriptional profile, effects that may be mediated in part by a reduction in progerin expression and an increase in sirtuin 1 (SIRT1). Progeria mice treated with mTERT lentivirus manifested similar improvements, with a reduction in inflammatory and DNA damage markers and increased SIRT1 in their vasculature and other organs. Furthermore, mTERT therapy increased the lifespan of HGPS mice. Vascular rejuvenation using telomerase mRNA is a promising approach for progeria and other age-related diseases.

Hutchinson-Gilford progeria syndrome

ハッチンソン・ギルフォード早老症候群は遺伝性早老症の中でも超希少（全世界で350～400人）かつ特に重篤（平均寿命は14.6歳）な疾患である．LMNA遺伝子のエクソン11内の点突然変異c.1824C＞T（p.Gly608Gly）が主因である．この変異により変異LaminAタンパク（Progerin）が合成されることが病態の本質である．本疾患の臨床症状，分子病理，診断基準や新しい治療法について概説する．