Metabolic control of stemness and differentiation

Prove crescenti evidenziano un ruolo fondamentale per il metabolismo nella fisiologia delle cellule staminali e nella specifica del lignaggio [1, 2]. Il metabolismo, infatti, non è più considerato solo una fonte di energia né un endpoint della regolazione genica. Invece, i metaboliti e l'ambiente nutritivo sono attori attivi nel determinare la segnalazione intracellulare e le attività enzimatiche e di conseguenza modulatori del destino delle cellule staminali. Inoltre, gli intermedi metabolici del metabolismo cellulare regolano i meccanismi epigenetici, comprese le modificazioni degli istoni, la metilazione del DNA e gli RNA non codificanti, modulando in tal modo il paesaggio e lo staminali dell'epigenoma globale [3]. Questo numero speciale riunisce 9 documenti per evidenziare i recenti sviluppi nel campo.Increasing evidence highlights a pivotal role for metabolism in stem cell physiology and lineage specification [1, 2]. Metabolism, indeed, is no longer considered merely an energy source nor an endpoint of gene regulation. Instead, metabolites and the nutrient environment are active players in determining intracellular signaling and enzymatic activities and consequently modulators of stem cell fate. Moreover, metabolic intermediates of cellular metabolism regulate epigenetic mechanisms, including histone modifications, DNA methylation, and noncoding RNAs, thereby modulating the global epigenome landscape and stemness [3]. This special issue brings together 9 papers to highlight recent developments in the field

The RESEARCH project. Soil-related hazards and archaeological heritage in the challenge of climate change

Archaeological Heritage, naturally endangered by environmental processes and anthropogenic pressures, is today increasingly at risk, because of intense human activities and climate change, and their impact on atmosphere and soil. European research is increasingly dedicated to the development of good practices for monitoring archaeological sites and their preservation. One of the running projects about these topics is RESEARCH (Remote Sensing techniques for Archaeology; H2020-MSCA-RISE, grant agreement: 823987), started in 2018 and ending in 2022. RESEARCH aims at testing risk assessment methodology using an integrated system of documentation and research in the fields of archaeology and environmental studies. It will introduce a strategy and select the most efficient tools for the harmonization of different data, criteria, and indicators in order to produce an effective risk assessment. These will be used to assess and monitor the impact of soil erosion, land movement, and land-use change on tangible archaeological heritage assets. As a final product, the Project addresses the development of a multi-task thematic platform, combining advanced remote sensing technologies with GIS application. The demonstration and validation of the Platform will be conducted on six case studies located in Italy, Greece, Cyprus, and Poland, and variously affected by the threats considered by the Project. In the frame of RISE (Research and Innovation Staff Exchange), RESEARCH will coordinate the existing expertise and research efforts of seven beneficiaries into a synergetic plan of collaborations and exchanges of personnel (Ph.D. students and research staff), to offer a comprehensive transfer of knowledge and training environment for the researchers in the specific area. This paper aims at illustrating the results of the activities conducted during the first year of the Project, which consisted in developing an effective risk assessment methodology for soil-related threats affecting archaeological heritage, and defining the scientific requirements and the user requirements of the Platform. The activities have been conducted in synergy with all the Partners and were supported by the possibility of staff exchange allowed by the funding frame MSCA-RISE

HDAC4 is necessary for satellite cell differentiation and muscle regeneration

In response to injury, skeletal muscle exhibits high capacity to regenerate and epigenetics controls multiple steps of this process (Giordani et al., 2013). It has been demonstrated in vitro that completion of muscle differentiation requires shuttling of histone deacetylase 4 (HDAC4), a member of class IIa HDACs, from the nucleus to the cytoplasm and consequent activation of MEF2-dependent differentiation genes (McKinsey et al., 2000). In vivo, HDAC4 expression is up-regulated in skeletal muscle upon injury, suggesting a role for this protein in muscle regeneratio

The mechanical stimulation of myotubes counteracts the effects of tumor-derived factors through IL-4 secretion and the modulation of the activin/follistatin ratio

Exercise counteracts cachexia, but it is unclear to which extent the exercise-dependent mechanical stimulation of muscle per se plays a role in exercise beneficial effects. To study the mechanisms underlying mechanical stimulation, we cultured C2C12 myotubes in the absence or in the presence of a cyclic mechanical stretching stimulus (MS) and in the absence or presence of C26 tumour-derived factors (C26-CM), so as to mimic the mechanical stimulation of exercise and cancer cachexia, respectively. We found that C26-CM contains activin and induces activin release by myotubes, further exacerbating its negative effects, consisting in myotube atrophy and in hampering myoblast recruitment and fusion into myotubes. A high level of circulating activin is an adverse prognostic factor in cancer patients, and our in vitro results demonstrate that activin may be a direct player and not just a marker of cachexia. We also found that MS is sufficient to counteract the adverse tumour-mediated effects on muscle cells, in association with an increased follistatin/activin ratio in the cell culture medium, indicating that myotubes actively release follistatin upon stretching. In addition, MS induces IL- 4 secretion by muscle cells. Recombinant follistatin counteracts C26 tumour effects on myotubes exclusively by rescuing fusion index, while recombinant IL-4 ameliorates fusion index, as well as the myotube size, both in terms of myotube diameter and number of nuclei per myotube. Our results indicate that tumour cells negatively affect muscle cells by releasing soluble factors and that MS is sufficient to counteract these effects, by affecting the muscle secretome with autocrine/paracrine pathways. Activin and Act-R ligands are becoming increasingly important as triggers of muscle wasting and as pharmacological targets to treat cachexia; however, since follistatin alone is incapable to entirely block the C26-CM effects, the development of novel activintargeted approaches should consider the existence of further significant tumour-secreted factors mediating cachexia

Interplay between Metabolites and the Epigenome in Regulating Embryonic and Adult Stem Cell Potency and Maintenance

The environment surrounding stem cells has the ability to elicit profound, heritable epigenetic changes orchestrated by multiple epigenetic mechanisms, which can be modulated by the level of specific metabolites. In this review, we highlight the significance of metabolism in regulating stem cell homeostasis, cell state, and differentiation capacity, using metabolic regulation of embryonic and adult muscle stem cells as examples, and cast light on the interaction between cellular metabolism and epigenetics. These new regulatory networks, based on the dynamic interplay between metabolism and epigenetics in stem cell biology, are important, not only for understanding tissue homeostasis, but to determine in vitro culture conditions which accurately support normal cell physiology

HDAC4 regulates satellite cell proliferation and differentiation by targeting P21 and Sharp1 genes

Skeletal muscle exhibits a high regenerative capacity, mainly due to the ability of satellite cells to replicate and differentiate in response to appropriate stimuli. Epigenetic control is effective at different stages of this process. It has been shown that the chromatin-remodeling factor HDAC4 is able to regulate satellite cell proliferation and commitment. However, its molecular targets are still uncovered. To explain the signaling pathways regulated by HDAC4 in satellite cells, we generated tamoxifen-inducible mice with conditional inactivation of HDAC4 in Pax7+ cells (HDAC4 KO mice). We found that the proliferation and differentiation of HDAC4 KO satellite cells were compromised, although similar amounts of satellite cells were found in mice. Moreover, we found that the inhibition of HDAC4 in satellite cells was sufficient to block the differentiation process. By RNA-sequencing analysis we identified P21 and Sharp1 as HDAC4 target genes. Reducing the expression of these target genes in HDAC4 KO satellite cells, we also defined the molecular pathways regulated by HDAC4 in the epigenetic control of satellite cell expansion and fusion

Histone deacetylase 4 protects from denervation and skeletal muscle atrophy in a murine model of amyotrophic lateral sclerosis

Background: Histone deacetylase 4 (HDAC4) has been proposed as a target for Amyotrophic Lateral Sclerosis (ALS) because it mediates nerve-skeletal muscle interaction and since its expression in skeletal muscle correlates with the severity of the disease. However, our recent studies on the skeletal muscle response upon long-term denervation highlighted the importance of HDAC4 in maintaining muscle integrity. Methods: To fully identify the yet uncharacterized HDAC4 functions in ALS, we genetically deleted HDAC4 in skeletal muscles of a mouse model of ALS. Body weight, skeletal muscle, innervation and spinal cord were analyzed over time by morphological and molecular analyses. Transcriptome analysis was also performed to delineate the signaling modulated by HDAC4 in skeletal muscle of a mouse model of ALS. Findings: HDAC4 deletion in skeletal muscle caused earlier ALS onset, characterized by body weight loss, muscle denervation and atrophy, and compromised muscle performance, although the main catabolic pathways were not activated. Transcriptome analysis identified the gene networks modulated by HDAC4 in ALS, revealing UCP1 as a top regulator that may be implicated in worsening ALS features. Interpretation: HDAC4 plays an important role in preserving innervations and skeletal muscle in ALS, likely by modulating the UCP1 gene network. Our study highlights a possible risk in considering HDAC inhibitors for the treatment of ALS. Fund: This work was supported by FIRB grant (RBFR12BUMH) from Ministry of Education, Universities and Research, by Fondazione Veronesi, by Sapienza research project 2017 (RM11715C78539BD8) and Polish National Science Center grant (UMO-2016/21/B/NZ3/03638)

Aerobic Exercise and Pharmacological Treatments Counteract Cachexia by Modulating Autophagy in Colon Cancer

Recent studies have correlated physical activity with a better prognosis in cachectic patients, although the underlying mechanisms are not yet understood. In order to identify the pathways involved in the physical activity-mediated rescue of skeletal muscle mass and function, we investigated the effects of voluntary exercise on cachexia in colon carcinoma (C26)-bearing mice. Voluntary exercise prevented loss of muscle mass and function, ultimately increasing survival of C26-bearing mice. We found that the autophagic flux is overloaded in skeletal muscle of both colon carcinoma murine models and patients, but not in running C26-bearing mice, thus suggesting that exercise may release the autophagic flux and ultimately rescue muscle homeostasis. Treatment of C26-bearing mice with either AICAR or rapamycin, two drugs that trigger the autophagic flux, also rescued muscle mass and prevented atrogene induction. Similar effects were reproduced on myotubes in vitro, which displayed atrophy following exposure to C26-conditioned medium, a phenomenon that was rescued by AICAR or rapamycin treatment and relies on autophagosome-lysosome fusion (inhibited by chloroquine). Since AICAR, rapamycin and exercise equally affect the autophagic system and counteract cachexia, we believe autophagy-triggering drugs may be exploited to treat cachexia in conditions in which exercise cannot be prescribed

Modelling gravitational instabilities: slab break-off and Rayleigh-Taylor diapirism

A non-standard new code to solve multiphase viscous thermo–mechanical problems applied to geophysics is presented. Two numerical methodologies employed in the code are described: A level set technique to track the position of the materials and an enrichment of the solution to allow the strain rate to be discontinuous across the interface. These techniques have low computational cost and can be used in standard desktop PCs. Examples of phase tracking with level set are presented in two and three dimensions to study slab detachment in subduction processes and Rayleigh–Taylor instabilities, respectively. The modelling of slab detachment processes includes realistic rheology with viscosity depending on temperature, pressure and strain rate; shear and adiabatic heating mechanisms; density including mineral phase changes and varying thermal conductivity. Detachment models show a first prolonged period of thermal diffusion until a fast necking of the subducting slab results in the break–off. The influence of several numerical and physical parameters on the detachment process is analyzed: The shear heating exerts a major influence accelerating the detachment process, reducing the onset time to one half and lubricating the sinking of the detached slab. The adiabatic heating term acts as a thermal stabilizer. If the mantle temperature follows an adiabatic gradient, neglecting this heating term must be included, otherwise all temperature contrasts are overestimated. As expected, the phase change at 410 km depth (olivine–spinel transition) facilitates the detachment process due to the increase in negative buoyancy. Finally, simple plume simulations are used to show how the presented numerical methodologies can be extended to three dimensions.Peer ReviewedPostprint (author’s final draft