| Name | Tiziana |
| Surname | Squillaro |
| Institution | Università degli Studi della Campania Luigi Vanvitelli |
| tiziana.squillaro@unicampania.it | |
| Address | Department of Medical, Surgical, Neurological, Metabolic Sciences, and Aging, 2nd Division of Neurology, Center for Rare Diseases, University of Campania "Luigi Vanvitelli", Napoli, Italy |
Chromatin modifiers play a crucial role in maintaining cell identity through modulation of gene expression patterns. Their deregulation can have profound effects on cell fate and functions. Among epigenetic regulators, the MECP2 protein is particularly attractive. Mutations in the gene are responsible for more than 90% of cases of Rett syndrome (RTT), a progressive neurodevelopmental disorder. As a chromatin modulator, MECP2 can have a key role in the government of stem cell biology. Previously, we showed that deregulated MECP2 expression triggers senescence in mesenchymal stromal cells (MSCs) from (RTT) patients. Over the last few decades, it has emerged that senescent cells show alterations in the metabolic state. Metabolic changes related to stem cell senescence are particularly detrimental, since they contribute to the exhaustion of stem cell compartments, which in turn determine the falling in tissue renewal and functionality. Herein, we dissect the role of impaired MECP2 function in triggering senescence along with other senescence-related aspects, such as metabolism, in MSCs from a mouse model of RTT. We found that MECP2 deficiencies lead to senescence and impaired mitochondrial energy production. Our results support the idea that an alteration in mitochondria metabolic functions could play an important role in the pathogenesis of RTT.
Base excision repair (BER) is a frontline repair mechanism that operates through the G phase of the cell cycle, which ensures the genome integrity by repairing thousands of DNA lesions due to endogenous and exogenous agents. Its correct functioning is fundamental for cell viability and the health of the organism. Uracil is one of the most prevalent lesions that appears in DNA arising by spontaneous or enzymatic deamination of cytosine or misincorporation of the deoxyuridine 5'-triphosphate nucleotide (dUTP) in place of deoxythymidine 5'-triphosphate (dTTP) during DNA replication. In the first pathway, the uracil will preferentially pair with adenine, leading to C:G → T:A transition. When uracil in DNA arises from misincorporation of dUTP instead of dTTP, this process will result in A:U pairs. Organisms counteract the mutagenic effects of uracil in DNA using the BER repair system, which is mediated by a member of the uracil-DNA glycosylase (UDG) superfamily. Several assays evaluating the in vitro BER enzyme activity have been described so far. Some of these measure the BER activity by an oligonucleotide incision assay using radiolabeled duplex oligo. Others use circular double-stranded DNA substrates containing a defined lesion. The novelty of our method resides in its rapidity and safety (radioactive free detection) as well as in the possibility of having a reliable quantitative determination of UDG activity in both cell and tissue extracts. We also demonstrated the effectiveness of our method in assessing UDG activity in cell lines with a reduced DNA repair capacity and in different kinds of tissues. KEY MESSAGES: • Base excision repair is a fundamental repair mechanism ensuring the genome integrity. • Uracil is one of the most prevalent lesions that appears in DNA. • The mutagenic effects of uracil in DNA are mitigated by the uracil-DNA glycosylase. • Several assays evaluating the in vitro BER activity have been described so far. • A safe and quantitative assay evaluating the in vitro UDG activity is required.
Research on physiopathology of obesity may receive new hints from studies on skinny people (SP). These are individuals who show a poor or null gaining of body weight, in spite of high-calorie intake, by far exceeding the body requirements.
Metabolic syndrome (MetS) is defined as the co-occurrence of metabolic risk factors that includes insulin resistance, hyperinsulinemia, impaired glucose tolerance, type 2 diabetes mellitus, dyslipidemia, and visceral obesity. The clinical significance of MetS consists of identifying a subgroup of patients sharing a common physiopathological state predisposing to chronic diseases. Clinical and scientific studies pinpoint lifestyle modification as an effective strategy aiming to reduce several features accountable for the risk of MetS onset. Among the healthy dietary patterns, the Mediterranean diet (MedDiet) emerges in terms of beneficial properties associated with longevity. Current evidence highlights the protective effect exerted by MedDiet on the different components of MetS. Interestingly, the effect exerted by polyphenols contained within the representative MedDiet components (i.e., olive oil, red wine, and nuts) seems to be accountable for the beneficial properties associated to this dietary pattern. In this review, we aim to summarize the principal evidence regarding the effectiveness of MedDiet-polyphenols in preventing or delaying the physiopathological components accountable for MetS onset. These findings may provide useful insights concerning the health properties of MedDiet-polyphenols as well as the novel targets destined to a tailored approach to MetS.
Mesenchymal stem cells, a subpopulation of mesenchymal stromal cells (MSCs), are present in the stroma of several tissues. MSC cultivation for clinical treatments may greatly affect MSC properties. A primary handicap is replicative senescence that impairs MSC functions. Hyaluronan (HA) is present in the extracellular matrix that composes the stem cell niche environment and is under investigation as a key factor for stem cell growth. We evaluated the effect on MSC cultivation of HA hybrid cooperative complexes (HCC) that are obtained from high (H) and low (L) weight molecules (NAHYCO™). We compared this HCC with H-HA and L-HA. We investigated the effects of these HAs on proliferation, cell cycle, apoptosis, senescence, and differentiation following the addition of the polymer solutions in the culture media at concentrations that did not drastically modify the medium viscosity. Interestingly, 0,16% HCC significantly delayed the senescence compared with the controls. This occurred without alteration of the cell cycle, cytotoxicity, or apoptosis. HCCs also promoted adipogenic and chondrogenic differentiation. Our finding could suggest a potential functional role of HCC above the updated scientific reports of its effects and pave the way to optimization of MSC cultivation for therapeutic application.
Neurodegenerative diseases (NDs) and brain tumors are severe, disabling, and incurable disorders that represent a critical problem regarding human suffering and the economic burden on the healthcare system. Because of the lack of effective therapies to treat NDs and brain tumors, the challenge for physicians is to discover new drugs to improve their patients' quality of life. In addition to risk factors such as genetics and environmental influences, increased cellular oxidative stress has been reported as one of the potential common etiologies in both disorders. Given their antioxidant and anti-inflammatory potential, dietary polyphenols are considered to be one of the most bioactive natural agents in chronic disease prevention and treatment. Despite the protective activity of polyphenols, their inefficient delivery systems and poor bioavailability strongly limit their use in medicine and functional food. A potential solution lies in polymeric nanoparticle-based polyphenol delivery systems that are able to enhance their absorption across the gastrointestinal tract, improve their bioavailability, and transport them to target organs. In the present manuscript, we provide an overview of the primary polyphenols used for ND and brain tumor prevention and treatment by focusing on recent findings, the principal factors limiting their application in clinical practice, and a promising delivery strategy to improve their bioavailability.
Exposure to high levels of ionizing radiation (IR) (>0.5Gy), negatively affect health. but, less is known about the effects of low dose IR (LDIR) but recent, evidence suggests that it may have profound effects on cellular functions. We are commonly exposed to LDIR over natural background levels from numerous sources: people may be exposed to low dose IR for medical diagnosis and therapy, air travel, illegal IR waste dumpsites or by occupational exposures in the nuclear and medical sectors. Stem cells reside for long periods of time in our bodies, and this increases the possibility that they may be accumulate genotoxic damage derived from extrinsic LDIR or intrinsic sources (such as DNA replication). In this review we provide an overview of LDIR effects on biology of stem cell compartments. The principal findings and issues reported in the scientific literature are discussed in order to present the current understanding of the LDIR exposure risk, and assess whether it may impact human health. We first consider the general biological consequences of LDIR exposure. Following this, we discuss the effects of LDIR on stem cells as discovered through in vitro and in vivo studies. This article is protected by copyright. All rights reserved.
Mesenchymal stromal cells (MSCs) are not a homogenous population but comprehend several cell types, such as stem cells, progenitor cells, fibroblasts, and other types of cells. Among these is a population of pluripotent stem cells, which represent around 1-3% of MSCs. These cells, named multilineage-differentiating stress enduring (Muse) cells, are stress-tolerant cells. Stem cells may undergo several rounds of intrinsic and extrinsic stresses due to their long life and must have a robust and effective DNA damage checkpoint and DNA repair mechanism, which, following a genotoxic episode, promote the complete recovery of cells rather than triggering senescence and/or apoptosis. We evaluated how Muse cells can cope with DNA damaging stress in comparison with MSCs. We found that Muse cells were resistant to chemical and physical genotoxic stresses better than non-Muse cells. Indeed, the level of senescence and apoptosis was lower in Muse cells. Our results proved that the DNA damage repair system (DDR) was properly activated following injury in Muse cells. While in non-Muse cells some anomalies may have occurred because, in some cases, the activation of the DDR persisted by 48 hr post damage, in others no activation took place. In Muse cells, the non-homologous end joining (NHEJ) enzymatic activity increases compared to other cells, while single-strand repair activity (NER, BER) does not. In conclusion, the high ability of Muse cells to cope with genotoxic stress is related to their quick and efficient sensing of DNA damage and activation of DNA repair systems.
Several aspects of stem cell life are governed by epigenetic variations, such as DNA methylation, histone modifications, and chromatin remodeling. Epigenetic events are also connected with the impairment of stem cell functions. For example, during senescence, there are significant changes in chromatin organization that alter transcription. The MECP2 protein can bind methylated cytosines and contribute to regulating gene expression at one of the highest hierarchical levels. Researchers are particularly interested in this protein, as up to 90% of Rett syndrome patients have an MECP2 gene mutation. Nevertheless, the role of MECP2 in this disease remains poorly understood. We used a mouse model of Rett syndrome to evaluate whether residual MECP2 activity in neural stem cells (NSCs) induced the senescence phenomena that could affect stem cell function. Our study clearly demonstrated that the reduced expression of MECP2 is connected with an increase in senescence, an impairment in proliferation capacity, and an accumulation of unrepaired DNA foci. Mecp2 NSCs did not cope with genotoxic stress in the same way as the control cells did. Indeed, after treatment with different DNA-damaging agents, the NSCs from mice with mutated Mecp2 accumulated more DNA damage foci (γ-H2AX+) and were more prone to cell death than the controls. Senescence in Mecp2 NSCs decreased the number of stem cells and progenitors and gave rise to a high percentage of cells that expressed neither stem/progenitor nor differentiation markers. These cells could be senescent and dysfunctional.