Clara Soria-Valles

Nuclear lamina defects cause ATM-dependent NF-κB activation and link accelerated aging to a systemic inflammatory response

Alterations in the architecture and dynamics of the nuclear lamina have a causal role in normal and accelerated aging through both cell-autonomous and systemic mechanisms. However, the precise nature of the molecular cues involved in this process remains incompletely defined. Here we report that the accumulation of prelamin A isoforms at the nuclear lamina triggers an ATM- and NEMO-dependent signaling pathway that leads to NF-κB activation and secretion of high levels of proinflammatory cytokines in two different mouse models of accelerated aging (Zmpste24(-/-) and Lmna(G609G/G609G) mice). Causal involvement of NF-κB in accelerated aging was demonstrated by the fact that both genetic and pharmacological inhibition of NF-κB signaling prevents age-associated features in these animal models, significantly extending their longevity. Our findings provide in vivo proof of principle for the feasibility of pharmacological modulation of the NF-κB pathway to slow down the progression of physiological and pathological aging.

Haematopoietic stem and progenitor cells from human pluripotent stem cells

A variety of tissue lineages can be differentiated from pluripotent stem cells by mimicking embryonic development through stepwise exposure to morphogens, or by conversion of one differentiated cell type into another by enforced expression of master transcription factors. Here, to yield functional human haematopoietic stem cells, we perform morphogen-directed differentiation of human pluripotent stem cells into haemogenic endothelium followed by screening of 26 candidate haematopoietic stem-cell-specifying transcription factors for their capacity to promote multi-lineage haematopoietic engraftment in mouse hosts. We recover seven transcription factors (ERG, HOXA5, HOXA9, HOXA10, LCOR, RUNX1 and SPI1) that are sufficient to convert haemogenic endothelium into haematopoietic stem and progenitor cells that engraft myeloid, B and T cells in primary and secondary mouse recipients. Our combined approach of morphogen-driven differentiation and transcription-factor-mediated cell fate conversion produces haematopoietic stem and progenitor cells from pluripotent stem cells and holds promise for modelling haematopoietic disease in humanized mice and for therapeutic strategies in genetic blood disorders.

Favorable effects of a prolonged treatment with melatonin on the level of oxidative damage and neurodegeneration in senescence-accelerated mice

Abstract:  Senescence‐accelerated mice (SAMP8) and senescence‐accelerated resistant mice (SAMR1) were studied at 5 and 10 months of age, respectively. In the animals, neurodegenerative processes and how they were influenced by melatonin were examined. Melatonin (10 mg/kg) or vehicle (ethanol at 0.066%) treatments were administrated from the age of 1 to 9 months in the drinking water. Differences in the neurodegenerative markers examined were found between the two strains with a more damaged protein, phosphorylated Tau at Ser392, increased neurofibrillary tangles (NT) and higher α‐synuclein expression in SAMP8 versus SAMR1 mice overall, when the mice were 10 months of age. Changes in density of receptors and oxidative stress‐related signaling with age were found in the brains of SAM strains at 10 months as shown by a marked decrease in the level of MT‐1 melatonin receptor and retinoic acid receptor‐related orphan receptor (ROR)‐α1. This diminution was earlier and more pronounced in SAMP8 mice. Likewise, the levels of nuclear factor‐kappa B (NF‐kB) transcriptional factor were higher in SAMP8 mice compared with SAMR1 mice regardless of age confirming the direct role of oxidative stress in the aging process. Treatment with melatonin in SAMP8 and SAMR1 mice reduced the neurodegenerative changes with an increase of ROR‐α1 levels without an apparent influence in the levels of MT‐1 receptor. However, different melatonin effects on NF‐kB signaling were observed suggesting that NF‐kB could trigger inflammatory processes in a different way, being SAM strain‐dependent and associated with age‐related oxidative stress levels. The effectiveness of melatonin in improving age‐related neural impairments is corroborated.

NF-κB activation impairs somatic cell reprogramming in ageing.

Ageing constitutes a critical impediment to somatic cell reprogramming. We have explored the regulatory mechanisms that constitute age-associated barriers, through derivation of induced pluripotent stem cells (iPSCs) from individuals with premature or physiological ageing. We demonstrate that NF-κB activation blocks the generation of iPSCs in ageing. We also show that NF-κB repression occurs during cell reprogramming towards a pluripotent state. Conversely, ageing-associated NF-κB hyperactivation impairs the generation of iPSCs by eliciting the reprogramming repressor DOT1L, which reinforces senescence signals and downregulates pluripotency genes. Genetic and pharmacological NF-κB inhibitory strategies significantly increase the reprogramming efficiency of fibroblasts from Néstor–Guillermo progeria syndrome and Hutchinson–Gilford progeria syndrome patients, as well as from normal aged donors. Finally, we demonstrate that DOT1L inhibition in vivo extends lifespan and ameliorates the accelerated ageing phenotype of progeroid mice, supporting the interest of studying age-associated molecular impairments to identify targets of rejuvenation strategies.

Melatonin alters cell death processes in response to age‐related oxidative stress in the brain of senescence‐accelerated mice

Abstract:  We studied the effect of age and melatonin on cell death processes in brain aging. Senescence‐accelerated prone mice 8 (SAMP8) and senescence‐accelerated resistant mice (SAMR1) at 5 and 10 months of age were used as models of the study. Melatonin (10 mg/kg) or its vehicle (ethanol at 0.066%) was administered in the drinking water from 1 to 9 months of age. Neurodegeneration, previously shown in the aged brain of SAMP8 and SAMR1 at 10 months of age, may be due to a drop in age‐related proteolytic activities (cathepsin D, calpains, and caspase‐3). Likewise, lack of apoptotic and macroautophagic processes were found, without apparent modification by melatonin. However, the caspase‐independent cell death, owing to high p53 and apoptosis‐inducing factor (AIF) levels, might be an alternative pathway of cell death in the aged brain. The main effects of melatonin treatment were observed in the aged SAMR1 mice; in this strain we observed a marked increase in antioxidant activity (catalase and superoxide dismutase). Likewise, a key antioxidant role of apoptosis‐related proteins, Bcl‐2 and AIF, was suggested in the aged brain of SAM mice, which was clearly influenced by melatonin. Moreover, the age‐related increase of lysosomal activity of cathepsin B and a lysosomal membrane‐associated protein 2 supports the possibility of the maintenance of lysosomal viability in addition to age‐related impairments of the proteolytic or macroautophagic activities. The effectiveness of melatonin against the oxidative stress‐related impairments and apoptosis during the aging process is, once more, corroborated in this article.

The anti-metastatic activity of collagenase-2 in breast cancer cells is mediated by a signaling pathway involving decorin and miR-21

Matrix metalloproteinases (MMPs) have been traditionally implicated in cancer progression because of their ability to degrade the extracellular matrix. However, some members of the MMP family have recently been identified as proteases with antitumor properties. Thus, it has been described that collagenase-2 (MMP-8) has a protective role in tumor and metastasis progression, but the molecular mechanisms underlying these effects are unknown. We show herein that Mmp8 expression causes a decrease in miR-21 levels that in turn leads to a reduction in tumor growth and lung metastasis formation by MDA-MB-231 (4175) breast cancer cells. By using both in vitro and in vivo models, we demonstrate that the mechanism responsible for these MMP-8 beneficial effects involves cleavage of decorin by MMP-8 and a subsequent reduction of transforming growth factor β (TGF-β) signaling that controls miR-21 levels. In addition, miR-21 downregulation induced by MMP-8 increases the levels of tumor suppressors such as programmed cell death 4, which may also contribute to the decrease in tumor formation and metastasis of breast cancer cells overexpressing this metalloproteinase. These findings reveal a new signaling pathway for cancer regulation controlled by MMP-8, and contribute to clarify the molecular mechanisms by which tumor-defying proteases may exert their protective function in cancer and metastasis.

Loss of MT1-MMP causes cell senescence and nuclear defects which can be reversed by retinoic acid

MT1‐MMP (MMP14) is a collagenolytic enzyme located at the cell surface and implicated in extracellular matrix (ECM) remodeling. Mmp14−/− mice present dwarfism, bone abnormalities, and premature death. We demonstrate herein that the loss of MT1‐MMP also causes cardiac defects and severe metabolic changes, and alters the cytoskeleton and the nuclear lamina structure. Moreover, the absence of MT1‐MMP induces a senescent phenotype characterized by up‐regulation of p16INK4a and p21CIP1/WAF1, increased activity of senescence‐associated β‐galactosidase, generation of a senescence‐associated secretory phenotype, and somatotroph axis alterations. Consistent with the role of retinoic acid signaling in nuclear lamina stabilization, treatment of Mmp14−/− mice with all‐trans retinoic acid reversed the nuclear lamina alterations, partially rescued the cell senescence phenotypes, ameliorated the pathological defects in bone, skin, and heart, and extended their life span. These results demonstrate that nuclear architecture and cell senescence can be modulated by a membrane protease, in a process involving the ECM as a key regulator of nuclear stiffness under cell stress conditions.

Analysis of the disintegrin‐metalloproteinases family reveals ADAM29 and ADAM7 are often mutated in melanoma

We performed a mutational analysis of the 19 disintegrin‐metalloproteinases (ADAMs) genes in human cutaneous metastatic melanoma and identified eight to be somatically mutated in 79 samples, affecting 34% of the melanoma tumors analyzed. Functional analysis of the two frequently mutated ADAM genes, ADAM29 and ADAM7 demonstrated that the mutations affect adhesion of melanoma cells to specific extracellular matrix proteins and in some cases increase their migration ability. This suggests that mutated ADAM genes could play a role in melanoma progression.

iPSCs: On the Road to Reprogramming Aging

Aging is characterized by irreversible loss of physiological integrity, often accompanied by an organisms loss of function and increased vulnerability to death. Defects in the mechanisms preserving cellular homeostasis over time may give rise to accelerated aging. Somatic cell reprogramming of aged cells can be associated with rejuvenation, erasing certain age-associated features, and illustrating the reversibility potential of aging. Here, we focus on recent advances in the generation of human induced pluripotent stem cells from progeroid syndromes and late-onset diseases such as Alzheimers or Parkinsons. These cellular models have contributed to a better understanding of such pathologies, as well as to the development of novel therapeutic approaches. We also discuss different strategies to identify and target age-associated reprogramming barriers to facilitate the treatment of age-related disorders.

Hallmarks of progeroid syndromes: lessons from mice and reprogrammed cells

ABSTRACT Ageing is a process that inevitably affects most living organisms and involves the accumulation of macromolecular damage, genomic instability and loss of heterochromatin. Together, these alterations lead to a decline in stem cell function and to a reduced capability to regenerate tissue. In recent years, several genetic pathways and biochemical mechanisms that contribute to physiological ageing have been described, but further research is needed to better characterize this complex biological process. Because premature ageing (progeroid) syndromes, including progeria, mimic many of the characteristics of human ageing, research into these conditions has proven to be very useful not only to identify the underlying causal mechanisms and identify treatments for these pathologies, but also for the study of physiological ageing. In this Review, we summarize the main cellular and animal models used in progeria research, with an emphasis on patient-derived induced pluripotent stem cell models, and define a series of molecular and cellular hallmarks that characterize progeroid syndromes and parallel physiological ageing. Finally, we describe the therapeutic strategies being investigated for the treatment of progeroid syndromes, and their main limitations. Summary: This Review defines the molecular and cellular hallmarks of progeroid syndromes according to the main cellular and animal models, and discusses the therapeutic strategies developed to date.