Persistent interaction patterns across social media platforms and over time

Growing concern surrounds the impact of social media platforms on public discourse1-4 and their influence on social dynamics5-9, especially in the context of toxicity10-12. Here, to better understand these phenomena, we use a comparative approach to isolate human behavioural patterns across multiple social media platforms. In particular, we analyse conversations in different online communities, focusing on identifying consistent patterns of toxic content. Drawing from an extensive dataset that spans eight platforms over 34 years-from Usenet to contemporary social media-our findings show consistent conversation patterns and user behaviour, irrespective of the platform, topic or time. Notably, although long conversations consistently exhibit higher toxicity, toxic language does not invariably discourage people from participating in a conversation, and toxicity does not necessarily escalate as discussions evolve. Our analysis suggests that debates and contrasting sentiments among users significantly contribute to more intense and hostile discussions. Moreover, the persistence of these patterns across three decades, despite changes in platforms and societal norms, underscores the pivotal role of human behaviour in shaping online discourse.

Cross-platform social dynamics: an analysis of ChatGPT and COVID-19 vaccine conversations

The role of social media in information dissemination and agenda-setting has significantly expanded in recent years. By offering real-time interactions, online platforms have become invaluable tools for studying societal responses to significant events as they unfold. However, online reactions to external developments are influenced by various factors, including the nature of the event and the online environment. This study examines the dynamics of public discourse on digital platforms to shed light on this issue. We analyzed over 12 million posts and news articles related to two significant events: the release of ChatGPT in 2022 and the global discussions about COVID-19 vaccines in 2021. Data was collected from multiple platforms, including Twitter, Facebook, Instagram, Reddit, YouTube, and GDELT. We employed topic modeling techniques to uncover the distinct thematic emphases on each platform, which reflect their specific features and target audiences. Additionally, sentiment analysis revealed various public perceptions regarding the topics studied. Lastly, we compared the evolution of engagement across platforms, unveiling unique patterns for the same topic. Notably, discussions about COVID-19 vaccines spread more rapidly due to the immediacy of the subject, while discussions about ChatGPT, despite its technological importance, propagated more gradually.

The drivers of global news spreading patterns

The web radically changed the dissemination of information and the global spread of news. In this study, we aim to reconstruct the connectivity patterns within nations shaping news propagation globally in 2022. We do this by analyzing a dataset of unprecedented size, containing 140 million news articles from 183 countries and related to 37,802 domains in the GDELT database. Unlike previous research, we focus on the sequential mention of events across various countries, thus incorporating a temporal dimension into the analysis of news dissemination networks. Our results show a significant imbalance in online news spreading. We identify news superspreaders forming a tightly interconnected rich club, exerting significant influence on the global news agenda. To further investigate the mechanisms underlying news dissemination and the shaping of global public opinion, we model countries' interactions using a gravity model, incorporating economic, geographical, and cultural factors. Consistent with previous studies, we find that countries' GDP is one of the main drivers to shape the worldwide news agenda.

Online conspiracy communities are more resilient to deplatforming

Online social media foster the creation of active communities around shared narratives. Such communities may turn into incubators for conspiracy theories-some spreading violent messages that could sharpen the debate and potentially harm society. To face these phenomena, most social media platforms implemented moderation policies, ranging from posting warning labels up to deplatforming, i.e. permanently banning users. Assessing the effectiveness of content moderation is crucial for balancing societal safety while preserving the right to free speech. In this article, we compare the shift in behavior of users affected by the ban of two large communities on Reddit, GreatAwakening and FatPeopleHate, which were dedicated to spreading the QAnon conspiracy and body-shaming individuals, respectively. Following the ban, both communities partially migrated to Voat, an unmoderated Reddit clone. We estimate how many users migrate, finding that users in the conspiracy community are much more likely to leave Reddit altogether and join Voat. Then, we quantify the behavioral shift within Reddit and across Reddit and Voat by matching common users. While in general the activity of users is lower on the new platform, GreatAwakening users who decided to completely leave Reddit maintain a similar level of activity on Voat. Toxicity strongly increases on Voat in both communities. Finally, conspiracy users migrating from Reddit tend to recreate their previous social network on Voat. Our findings suggest that banning conspiracy communities hosting violent content should be carefully designed, as these communities may be more resilient to deplatforming.

Characterizing engagement dynamics across topics on Facebook

Social media platforms heavily changed how users consume and digest information and, thus, how the popularity of topics evolves. In this paper, we explore the interplay between the virality of controversial topics and how they may trigger heated discussions and eventually increase users' polarization. We perform a quantitative analysis on Facebook by collecting ∼57M posts from ∼2M pages and groups between 2018 and 2022, focusing on engaging topics involving scandals, tragedies, and social and political issues. Using logistic functions, we quantitatively assess the evolution of these topics finding similar patterns in their engagement dynamics. Finally, we show that initial burstiness may predict the rise of users' future adverse reactions regardless of the discussed topic.

Conspiracy theories and social media platforms

Conspiracy theories proliferate online. We provide an overview of information consumption patterns related to conspiracy content on four mainstream social media platforms (Facebook, Twitter, YouTube, and Reddit), with a focus on niche ones. Opinion polarisation and echo chambers appear as pivotal elements of communication around conspiracy theories. A relevant role may also be played by the content moderation policies enforced by each social media platform. Banning contents or users from a social media could lead to a level of user segregation that goes beyond echo chambers and reaches the entire social media space, up to the formation of 'echo platforms'. The insurgence of echo platforms is a new online phenomenon that needs to be investigated as it could foster many dangerous phenomena that we observe online, including the spreading of conspiracy theories.

Connections matter: a proxy measure for evaluating network membership with an application to the Seventh Research Framework Programme

Although the topic of networks has received significant attention from the scientific literature, it remains to be seen whether it is possible to quantify the degree to which an organisation benefits from being part of a network. Starting from the concept of network value and that of Metcalfe’s Law, this paper introduces and defines the collective network effect (CNE). CNE is based on the concept that a network member is not only affected by its friends but also by the friends of its friends. By taking into account network connection patterns, CNE provides a proxy for quantifying the benefit of network membership. We computed the CNE for the nodes of a large network built using the whole set of common projects among the participants of the 7th Framework Programme for Research and Technological Development of the European Commission. The obtained results show that nodes with a higher CNE have access to substantially more conspicuous fundings than nodes with a lower CNE. In general, such a measure could supplement other centrality measures and be useful for organisations and companies aiming to evaluate both their current situation and the potential partners they should link with in order to extract the highest benefits from network membership.

Financial interbanking networks resilience under shocks propagation

The concept of resilience-i.e., the ability of a unified structure to absorb shocks-is of high relevance in the context of network modelling and analysis, mainly when referred to finance. This paper starts from this premise, and deals with the resilience of a financial interbanking system. At this aim, we firstly introduce a new measure of the resilience of a network, by taking into full consideration the influence of the topology of the network and the weights of its links in the shocks propagation; then, we build one financial network model related to the quarterly-based interbanking sector, whose weights are calibrated on high quality empirical data; lastly, we compute the resilience measure of the considered networks. A discussion of the results is provided, by considering both finance and network theory perspectives.

Promoting engagement with quality communication in social media

The COVID-19 pandemic made explicit the issues of communicating science in an information ecosystem dominated by social media platforms. One of the fundamental communication challenges of our time is to provide the public with reliable content and contrast misinformation. This paper investigates how social media can become an effective channel to promote engagement and (re)build trust. To measure the social response to quality communication, we conducted an experimental study to test a set of science communication recommendations on Facebook and Twitter. The experiment involved communication practitioners and social media managers from select countries in Europe, applying and testing such recommendations for five months. Here we analyse their feedback in terms of adoption and show that some differences emerge across platforms, topics, and recommendation categories. To evaluate these recommendations' effect on users, we measure their response to quality content, finding that the median engagement is generally higher, especially on Twitter. The results indicate that quality communication strategies may elicit positive feedback on social media. A data-driven and co-designed approach in developing counter-strategies is thus promising in tackling misinformation.

Infodemics: A new challenge for public health

The COVID-19 information epidemic, or "infodemic," demonstrates how unlimited access to information may confuse and influence behaviors during a health emergency. However, the study of infodemics is relatively new, and little is known about their relationship with epidemics management. Here, we discuss unresolved issues and propose research directions to enhance preparedness for future health crises.

Dynamics of online hate and misinformation

Online debates are often characterised by extreme polarisation and heated discussions among users. The presence of hate speech online is becoming increasingly problematic, making necessary the development of appropriate countermeasures. In this work, we perform hate speech detection on a corpus of more than one million comments on YouTube videos through a machine learning model, trained and fine-tuned on a large set of hand-annotated data. Our analysis shows that there is no evidence of the presence of "pure haters", meant as active users posting exclusively hateful comments. Moreover, coherently with the echo chamber hypothesis, we find that users skewed towards one of the two categories of video channels (questionable, reliable) are more prone to use inappropriate, violent, or hateful language within their opponents' community. Interestingly, users loyal to reliable sources use on average a more toxic language than their counterpart. Finally, we find that the overall toxicity of the discussion increases with its length, measured both in terms of the number of comments and time. Our results show that, coherently with Godwin's law, online debates tend to degenerate towards increasingly toxic exchanges of views.

Entropy and complexity unveil the landscape of memes evolution

On the Internet, information circulates fast and widely, and the form of content adapts to comply with users’ cognitive abilities. Memes are an emerging aspect of the internet system of signification, and their visual schemes evolve by adapting to a heterogeneous context. A fundamental question is whether they present culturally and temporally transcendent characteristics in their organizing principles. In this work, we study the evolution of 2 million visual memes published on Reddit over ten years, from 2011 to 2020, in terms of their statistical complexity and entropy. A combination of a deep neural network and a clustering algorithm is used to group memes according to the underlying templates. The grouping of memes is the cornerstone to trace the growth curve of these objects. We observe an exponential growth of the number of new created templates with a doubling time of approximately 6 months, and find that long-lasting templates are associated with strong early adoption. Notably, the creation of new memes is accompanied with an increased visual complexity of memes content, in a continuous effort to represent social trends and attitudes, that parallels a trend observed also in painting art.

Human mobility in response to COVID-19 in France, Italy and UK

The COVID-19 pandemic is one of the defining events of our time. National Governments responded to the global crisis by implementing mobility restrictions to slow down the spread of the virus. To assess the impact of those policies on human mobility, we perform a massive comparative analysis on geolocalized data from 13 M Facebook users in France, Italy, and the UK. We find that lockdown generally affects national mobility efficiency and smallworldness-i.e., a substantial reduction of long-range connections in favor of local paths. The impact, however, differs among nations according to their mobility infrastructure. We find that mobility is more concentrated in France and UK and more distributed in Italy. In this paper we provide a framework to quantify the substantial impact of the mobility restrictions. We introduce a percolation model mimicking mobility network disruption and find that node persistence in the percolation process is significantly correlated with the economic and demographic characteristics of countries: areas showing higher resilience to mobility disruptions are those where Value Added per Capita and Population Density are high. Our methods and findings provide important insights to enhance preparedness for global critical events and to incorporate resilience as a relevant dimension to estimate the socio-economic consequences of mobility restriction policies.

Municipal waste management: A complex network approach with an application to Italy

The paper contributes to the debate concerning the management of municipal solid waste by providing an analysis of two key aspects of waste management - namely, waste separation and dispatch to treatment plants. Our analysis aims at detecting the extent to which actual behavior in (close-by) municipalities is similar with respect to those two aspects. To pursue our scope, a complex network approach is followed. In particular, we conceptualize, explore and compare two networks, whose nodes are the municipalities, while weights synthesize in one network the percentage of sorted waste that is collected at a municipal level, and in the other one the distance from the waste processing plants used by each municipality. The theoretical network models are implemented through an empirical study based on a high quality dataset referred to Italian municipalities. In this regard, the detection of communities of municipalities and their geospatial contextualization are introduced as devices for a complete description of current practices of municipal waste separation and transfers in Italy.

The echo chamber effect on social media

Social media may limit the exposure to diverse perspectives and favor the formation of groups of like-minded users framing and reinforcing a shared narrative, that is, echo chambers. However, the interaction paradigms among users and feed algorithms greatly vary across social media platforms. This paper explores the key differences between the main social media platforms and how they are likely to influence information spreading and echo chambers' formation. We perform a comparative analysis of more than 100 million pieces of content concerning several controversial topics (e.g., gun control, vaccination, abortion) from Gab, Facebook, Reddit, and Twitter. We quantify echo chambers over social media by two main ingredients: 1) homophily in the interaction networks and 2) bias in the information diffusion toward like-minded peers. Our results show that the aggregation of users in homophilic clusters dominate online interactions on Facebook and Twitter. We conclude the paper by directly comparing news consumption on Facebook and Reddit, finding higher segregation on Facebook.

Network constraints on the mixing patterns of binary node metadata

We consider the network constraints on the bounds of the assortativity coefficient, which aims to quantify the tendency of nodes with the same attribute values to be connected. The assortativity coefficient can be considered as the Pearson's correlation coefficient of node metadata values across network edges and lies in the interval [-1,1]. However, properties of the network, such as degree distribution and the distribution of node metadata values, place constraints upon the attainable values of the assortativity coefficient. This is important as a particular value of assortativity may say as much about the network topology as about how the metadata are distributed over the network-a fact often overlooked in literature where the interpretation tends to focus simply on the propensity of similar nodes to link to each other, without any regard on the constraints posed by the topology. In this paper we quantify the effect that the topology has on the assortativity coefficient in the case of binary node metadata. Specifically, we look at the effect that the degree distribution, or the full topology, and the proportion of each metadata value has on the extremal values of the assortativity coefficient. We provide the means for obtaining bounds on the extremal values of assortativity for different settings and demonstrate that under certain conditions the maximum and minimum values of assortativity are severely limited, which may present issues in interpretation when these bounds are not considered.

The COVID-19 social media infodemic

We address the diffusion of information about the COVID-19 with a massive data analysis on Twitter, Instagram, YouTube, Reddit and Gab. We analyze engagement and interest in the COVID-19 topic and provide a differential assessment on the evolution of the discourse on a global scale for each platform and their users. We fit information spreading with epidemic models characterizing the basic reproduction number [Formula: see text] for each social media platform. Moreover, we identify information spreading from questionable sources, finding different volumes of misinformation in each platform. However, information from both reliable and questionable sources do not present different spreading patterns. Finally, we provide platform-dependent numerical estimates of rumors' amplification.

Time, space and social interactions: exit mechanisms for the Covid-19 epidemics

We develop a minimalist compartmental model to study the impact of mobility restrictions in Italy during the Covid-19 outbreak. We show that, while an early lockdown shifts the contagion in time, beyond a critical value of lockdown strength the epidemic tends to restart after lifting the restrictions. We characterize the relative importance of different lockdown lifting schemes by accounting for two fundamental sources of heterogeneity, i.e. geography and demography. First, we consider Italian Regions as separate administrative entities, in which social interactions between age classes occur. We show that, due to the sparsity of the inter-Regional mobility matrix, once started, the epidemic spreading tends to develop independently across areas, justifying the adoption of mobility restrictions targeted to individual Regions or clusters of Regions. Second, we show that social contacts between members of different age classes play a fundamental role and that interventions which target local behaviours and take into account the age structure of the population can provide a significant contribution to mitigate the epidemic spreading. Our model aims to provide a general framework, and it highlights the relevance of some key parameters on non-pharmaceutical interventions to contain the contagion.

Selective exposure shapes the Facebook news diet

The social brain hypothesis approximates the total number of social relationships we are able to maintain at 150. Similar cognitive constraints emerge in several aspects of our daily life, from our mobility to the way we communicate, and might even affect the way we consume information online. Indeed, despite the unprecedented amount of information we can access online, our attention span still remains limited. Furthermore, recent studies have shown that online users are more likely to ignore dissenting information, choosing instead to interact with information adhering to their own point of view. In this paper, we quantitatively analyse users' attention economy in news consumption on social media by analysing 14 million users interacting with 583 news outlets (pages) on Facebook over a time span of six years. In particular, we explore how users distribute their activity across news pages and topics. On the one hand, we find that, independently of their activity, users show a tendency to follow a very limited number of pages. On the other hand, users tend to interact with almost all the topics presented by their favoured pages. Finally, we introduce a taxonomy accounting for users' behaviour to distinguish between patterns of selective exposure and interest. Our findings suggest that segregation of users in echo chambers might be an emerging effect of users' activity on social media and that selective exposure-i.e. the tendency of users to consume information adhering to their preferred narratives-could be a major driver in their consumption patterns.

Evaluating relevance and redundancy to quantify how binary node metadata interplay with the network structure

Networks are real systems modelled through mathematical objects made up of nodes and links arranged into peculiar and deliberate (or partially deliberate) topologies. Studying these real-world topologies allows for several properties of interest to be revealed. In real networks, nodes are also identified by a certain number of non-structural features or metadata. Given the current possibility of collecting massive quantity of such metadata, it becomes crucial to identify automatically which are the most relevant for the observed structure. We propose a new method that, independently from the network size, is able to not only report the relevance of binary node metadata, but also rank them. Such a method can be applied to networks from any domain, and we apply it in two heterogeneous cases: a temporal network of technology transfer and a protein-protein interaction network. Together with the relevance of node metadata, we investigate the redundancy of these metadata displaying by the results on a Redundancy-Relevance diagram, which is able to highlight the differences among vectors of metadata from both a structural and a non-structural point of view. The obtained results provide insights of a practical nature into the importance of the observed node metadata for the actual network structure.

Role of P53 Mutations in the Radiosensitivity Status of Tumor Cells

Wild-type p53 is involved in cellular response to DNA damage including cell cycle control, DNA repair and activation of apoptosis. Accumulation of p53 protein following DNA damage may initiate the apoptotic process, resulting in cell death. DNA damage induced by radiation is an example of apoptotic stimulus involving p53. Regulation of apoptosis by p53 can occur through transcriptional regulation of pro-apoptotic (e.g. bax) and anti-apoptotic (e.g. bel-2) factors. Although wild-type p53 usually sensitizes cells to radiation therapy, p53 mutations have a variable effect on radiation response. For example p53 mutations in bone or breast tumors have been found to be associated with resistance to chemotherapeutic drugs or ionizing radiation. Mutated p53 has has been reported to increase sensitivity to radiation and drugs in colorectal and bladder tumors. The present brief commentary tries to find an explanation at molecular level of these conflicting results.

Autologous stem cell transplantation improves microcirculation in systemic sclerosis

Background:

In systemic sclerosis (SSc) reduced capillary density decreases blood flow and leads to tissue ischaemia and fingertip ulcers. Nail fold videocapillaroscopy (NVC) is a diagnostic and follow-up parameter useful to evaluate the severity, activity and the stage of SSc microvascular damage. Autologous haemopoietic stem cell transplantation (HSCT) is a new treatment for patients with severe diffuse cutaneous systemic sclerosis (dcSSc) refractory to conventional therapies. We aimed to evaluate the improvement of microvasculature after HSCT using NVC.

Methods:

A total of 16 patients with severe dcSSc with a “late” videocapillaroscopy pattern underwent an immunesuppressive treatment: 6 were treated with HSCT and 10 with monthly pulse cyclophosphamide (CYC) 1 g for 6 months and then orally with 50 mg/day for further 6 months.

NVC was performed before and after 3 months from the beginning of each treatment and then repeated every 3 months.

Results:

In all patients, before HSCT NVC showed large avascular areas and ramified capillaries and vascular architectural disorganisation (“late” pattern). At 3 months after HSCT, the NVC pattern changed from “late” into “active”, showing frequent giant capillaries (>6/mm) and haemorrhages, absence of avascular areas and angiogenesis phenomena; 1 year after HSCT, microvascular abnormalities were still in the “active” pattern. In patients treated with CYC, no NVC modifications were observed during 24 months of follow-up and the pattern always remained “late”.

Conclusions:

These results indicate that HSCT with a high dose CYC regimen may foster vascular remodelling, while CYC at lower doses and with a chronic regimen does not influence the microvasculature.

Bosentan regulates the expression of adhesion molecules on circulating T cells and serum soluble adhesion molecules in systemic sclerosis-associated pulmonary arterial hypertension

Objectives:

To study the expression of adhesion molecules in patients with systemic sclerosis (SSc) with and without pulmonary arterial hypertension (PAH) and the effects of therapy with the endothelin-1 (ET-1) receptor antagonist, bosentan.

Methods:

In all, 35 patients with SSc and 25 healthy donors (HD) were selected for this study. Of 35 patients, 10 had isolated PAH assessed by Doppler echocardiography and treated with bosentan. Peripheral blood (PB) lymphocytes were isolated by density gradient centrifugation, and the expression of lymphocyte function-associated antigen-1 (LFA-1), very late antigen-4 (VLA-4) and L-selectin on CD3 T cells was assessed by double immunofluorescence and flow-cytometry. As endothelial activation markers, serum soluble P-selectin, platelet/endothelial cell adhesion molecule (PECAM)-1, vascular cell adhesion molecule (VCAM)-1, intercellular adhesion molecule (ICAM)-1 and von Willebrand factor (vWF) antigen were assessed by ELISA. In patients with SSc-PAH, T cell subsets and soluble endothelial markers were assessed at baseline and after 6 and 12 months of bosentan therapy.

Results:

In patients with SSc-PAH, serum soluble ICAM-1, VCAM-1, P-selectin and PECAM-1 levels were higher than in HD at baseline and fell to normal values after 12 months of bosentan therapy. CD3–LFA1 T cells were significantly higher in PAH-SSc at baseline than in HD or SSc and significantly decreased after therapy. CD3–L-selectin T cells were significantly lower in SSc-PAH at baseline than in HD or SSc and rose to normal levels after bosentan therapy.

Conclusions:

This study confirms that endothelial activation occurs in SSc, and suggests that changes in the T cell/endothelium interplay take place in SSc-associated PAH. Bosentan seems to be able to hamper these changes and restore T cell functions in these patients.

Systemic sclerosis fibroblasts inhibit in vitro angiogenesis by MMP-12-dependent cleavage of the endothelial cell urokinase receptor

Failure of endothelial cells to develop new vessels in response to hypoxia is a distinctive feature of systemic sclerosis (SSc) in the avascular phase. We have previously shown that SSc endothelial cells over-express matrix metalloproteinase-12 (MMP-12), which blocks angiogenesis by cleavage of the endothelial urokinase-type plasminogen activator receptor (uPAR). In the present study, we have investigated whether over-expression of MMP-12 and of angiostatic factors, or hypo-expression of angiogenic factors by SSc fibroblasts, contributes to impaired angiogenesis in SSc. Dermal fibroblasts were isolated from healthy subjects (N-Fb) and patients with diffuse SSc (SSc-Fb). Angiogenesis of target normal human microvascular endothelial cells (H-MVECs) was assayed by Matrigel invasion, cell proliferation, and capillary morphogenesis. uPAR cleavage and MMP-12 activity were evaluated by western blotting. We show that the over-expression of MMP-12 by SSc-Fb determines uPAR cleavage in H-MVECs. Conditioned medium from SSc-Fb impaired H-MVEC proliferation, invasion, and capillary morphogenesis. Anti-MMP-12 antibodies restored such impairment. Altered expression of angiostatic/angiogenic factors, including transforming growth factor beta1, did not account for SSc-Fb-dependent impairment of angiogenesis. The over-expression of MMP-12 by both SSc-Fb and SSc endothelial cells indicates that MMP-12 over-production may have a critical pathogenic role in SSc-associated vascular alterations.

Impairment of endothelial cell differentiation from bone marrow-derived mesenchymal stem cells: new insight into the pathogenesis of systemic sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is a disorder characterized by vascular damage and fibrosis of the skin and internal organs. Despite marked tissue hypoxia, there is no evidence of compensatory angiogenesis. The ability of mesenchymal stem cells (MSCs) to differentiate into endothelial cells was recently demonstrated. The aim of this study was to determine whether impaired differentiation of MSCs into endothelial cells in SSc might contribute to disease pathogenesis by decreasing endothelial repair.

METHODS

MSCs obtained from 7 SSc patients and 15 healthy controls were characterized. The number of colony-forming unit-fibroblastoid colonies was determined. After culture in endothelial-specific medium, the endothelial-like MSC (EL-MSC) phenotype was assessed according to the surface expression of vascular endothelial growth factor receptors (VEGFRs). Senescence, chemoinvasion, and capillary morphogenesis studies were also performed.

RESULTS

MSCs from SSc patients displayed the same phenotype and clonogenic activity as those from controls. In SSc MSCs, a decreased percentage of VEGFR-2+, CXCR4+, VEGFR-2+/CXCR4+ cells and early senescence was detected. After culturing, SSc EL-MSCs showed increased expression of VEGFR-1, VEGFR-2, and CXCR4, did not express CD31 or annexin V, and showed significantly decreased migration after specific stimuli. Moreover, the addition of VEGF and stromal cell-derived factor 1 to cultured SSc EL-MSCs increased their angiogenic potential less than that in controls.

CONCLUSION

Our data strongly suggest that endothelial repair may be affected in SSc. The possibility that endothelial progenitor cells could be used to increase vessel growth in chronic ischemic tissues may open up new avenues in the treatment of vascular damage caused by SSc.

Piascledine modulates the production of VEGF and TIMP-1 and reduces the invasiveness of rheumatoid arthritis synoviocytes

BACKGROUND

In rheumatoid arthritis (RA), hypertrophy of the synovial membrane generates a tumour-like pannus that invades the joint cavity and erodes cartilage and bone. Invasion of the extracellular matrix (ECM) is accompanied by angiogenesis, in which vascular endothelial growth factor (VEGF) and tissue inhibitors of metalloproteinases (TIMPs), produced by synoviocytes lining the pannus, have a primary role. Piascledine (PSD) is used in the treatment of osteoarthritis and has anti-inflammatory effects in vitro.

OBJECTIVE

To study the effects of PSD on levels of VEGF and TIMP-1 and chemoinvasion in RA synoviocytes and healthy controls.

METHODS

The effects of PSD 5, 10, and 20 microg/mL were evaluated, with/without interleukin-1beta (IL-1beta) and tumour necrosis factor-alpha (TNFalpha) 20 ng/mL, on synoviocytes. The levels of VEGF and TIMP-1 were assayed in the culture medium by enzyme-linked immunosorbent assay (ELISA). Chemoinvasion was measured by the Boyden chamber invasion assay.

RESULTS

RA synoviocytes treated with PSD showed, compared to basal, lower levels of VEGF (41080+/-830 vs. 79210+/-920 pg/106 cells, p<0.001) and increased levels of TIMP-1 (23540+/-93.2 vs. 12860+/-42.9 ng/106 cells, p<0.001). PSD decreased dose-dependently IL-1beta and TNFalpha induced migration.

CONCLUSIONS

In RA synoviocytes, and also to a lesser extent in control cells, PSD modulates VEGF and TIMP-1 and decreases chemoinvasion. PSD might have a role in the treatment of RA synovitis controlling invasiveness.

Etrurians vs Greeks: May ACE I/D polymorphism still be considered as a marker of susceptibility to SSc?

OBJECTIVE

SSc is characterized by immune dysfunction and microvascular involvement. A different genetic background may determine a different polymorphic allele frequency between different populations, and data from literature reported conflicting results about the role of genetic components in predisposing to the disease. We carried out this study in order to compare the ACE I/D polymorphism genotype distribution and alleles frequency in two different populations from the Mediterranean area.

METHODS

Forty-eight Italian and 41 Greek SSc patients compared with 112 Italian and 93 Greek controls, have been studied. The ACE I/D polymorphism has been analysed.

RESULTS

The genotype distribution and allele frequency were in Hardy-Weinberg equilibrium for Italian and Greek SSc patients and controls. Among the Italian patients a significantly higher ACE D allele frequency than in the controls was found, whereas among the Greeks a higher prevalence was observed in the healthy subjects. A significant difference in ACE D allele frequency between Italian and Greek controls was observed (p = 0.04). ACE D allele was associated to the predisposition to SSc in Italians, but not in Greeks.

CONCLUSION

We confirm that Italian SSc patients have a higher ACE D allele frequency that is not present in the Greek patients. Thus, the two populations living in different Mediterranean areas and resulting from the Mediterranean civilization, do not show the same ACE-gene related allele frequencies. Other populations of the Mediterranean area must be investigated by using unlinked genetic markers to verify the homogeneity of the genetic background, and to test for a "true" difference in their ethnic origin.

Raloxifene reduces urokinase-type plasminogen activator-dependent proliferation of synoviocytes from patients with rheumatoid arthritis

Extracellular fibrinolysis, controlled by the membrane-bound fibrinolytic system, is involved in cartilage damage and rheumatoid arthritis (RA) synovitis. Estrogen status and metabolism seem to be impaired in RA, and synoviocytes show receptors for estrogens. Our aims in this study were to evaluate in healthy and RA synoviocytes the effects of Raloxifene (RAL), a selective estrogen receptor modulator (SERM), on: proliferation; the components of the fibrinolytic system; and chemoinvasion. The effects of RAL were studied in vitro on synoviocytes from four RA patients and four controls. Proliferation was evaluated as cell number increase, and synoviocytes were treated with 0.5 microM and 1 microM RAL with and without urokinase-plasminogen activator (u-PA) and anti-u-PA/anti-u-PA receptor (u-PAR) antibodies. Fibrinolytic system components (u-PA, u-PAR and plasminogen activator inhibitor (PAI)-1) were assayed by ELISA with cells treated with 0.5 microM and 1 microM RAL for 48 h. u-PA activity was evaluated by zymography and a direct fibrinolytic assay. U-PAR/cell and its saturation were studied by radioiodination of u-PA and a u-PA binding assay. Chemoinvasion was measured using the Boyden chamber invasion assay. u-PA induced proliferation of RA synoviocytes was blocked by RAL (p < 0.05) and antagonized by antibodies alone. The inhibitory effect of RAL was not additive with u-PA/u-PAR antagonism. RA synoviocytes treated with RAL showed, compared to basal, higher levels of PAI-1 (10.75 +/- 0.26 versus 5.5 +/- 0.1 microg/10(6) cells, respectively; p < 0.01), lower levels of u-PA (1.04 +/- 0.05 versus 3.1 +/- 0.4 ng/10(6) cells, respectively; p < 0.001), and lower levels of u-PAR (11.28 +/- 0.22 versus 23.6 +/- 0.1 ng/10(6) cells, respectively; p < 0.001). RAL also significantly inhibited u-PA-induced migration. Similar effects were also shown, at least partially, in controls. RAL exerts anti-proliferative and anti-invasive effects on synoviocytes, mainly modulating u-PAR and, to a lesser extent, u-PA and PAI-1 levels, and inhibiting cell migration and proliferation.

The fibrinolytic system components are increased in systemic sclerosis and modulated by Alprostadil (alpha1 ciclodestryn)

OBJECTIVES

To evaluate urokinase plasminogen activator (u-PA), urokinase plasminogen activator soluble receptor (su-PAR), plasminogen activator inhibitor 1 (PAI-1) and tissue plasminogen activator (t-PA) plasma levels in SSc patients (pts) versus healthy controls and their modulation by intravenous alphacyclodestrine (Alprostadil).

METHODS

Plasma levels of u-PA, su-PAR, PAI-1 and t-PA were measured in 40 SSc (34 lSSc and 6 dSSc) pts and in 30 healthy controls. In SSc, blood was drawn before and after 3 consecutive daily of Alprostadil infusion (60 mg in 250 cc NaCl 0.9%).

RESULTS

In SSc su-PAR basal levels were higher than controls (7.48 +/- 2.5 vs 4.69 +/- 0.4 ng/ml; p = 0.001) and were significantly reduced by Alprostadil (5.93 +/- 1.7; p = 0.002), but remain higher than controls (p = 0.03). u-PA basal levels were higher than controls (3.78 +/- 1.5 vs 1.29 +/- 0.3 ng/ml; p < 0.001) and were reduced by Alprostadil (2.39 +/- 1.7; p < 0.001) to control levels. SSc PAI-1 basal levels were lower than controls (31.60 +/- 7.7 vs 48.30 +/- 6.8 ng/ml; p < 0.001) and increased by Alprostadil (34.66 +/- 5.4; p = 0.04), but lower than controls (p < 0.001). SSc t-PA basal levels were higher in respect to controls (1645.81 +/- 792.7 vs 571.95 +/- 75.5 pg/ml; p < 0.0001) and reduced by Alprostadil (1318.06 +/- 603.5; p = 0.04), but still higher than controls (p = 0.001).

CONCLUSION

Fibrinolysis were increased in SSc. Infusions of Alprostadil modulate u-PA, su-PAR, PAI-1 and t-PA, restoring near normal levels. In SSc, fibrinolysis system may become a potential target for new therapies.

Deflazacort modulates the fibrinolytic pattern and reduces uPA-dependent chemioinvasion and proliferation in rheumatoid arthritis synoviocytes

OBJECTIVE

Extracellular fibrinolysis, controlled by the cell-associated fibrinolytic system (urokinase plasminogen activator, uPA; uPA receptor, uPAR; plasminogen activator inhibitor type-1, PAI-1), is involved in cartilage damage generation and in rheumatoid arthritis (RA) synovitis. Since steroids reduce the rate of radiological progression of RA, we planned to evaluate in healthy and RA synoviocytes the effects of the steroid deflazacort on uPA, uPAR and PAI-1 expression, and subsequent phenotypic modifications in terms of uPA/uPAR-dependent invasion and proliferation.

METHODS

uPA, uPAR and PAI-1 levels were studied by ELISA, RT-PCR (uPAR) and zymography (uPA) in synoviocytes from four RA patients and four healthy controls. Chemoinvasion was assessed by the Boyden chamber invasion assay, using Matrigel as the invasion substrate. Proliferation was evaluated by cell counting. Both invasion and proliferation were measured upon treatment with deflazacort 5 muM with or without parallel stimulation with uPA 500 ng/ml or in the presence of monoclonal anti-uPA and anti-uPAR antibodies.

RESULTS

Invasion and proliferation of RA synoviocytes require a proper functional balance of the fibrinolytic system. Both deflazacort and monoclonal antibodies against uPA and uPAR reduced expression and activity of the system, thus inhibiting invasion and proliferation. In RA synoviocytes, deflazacort induced higher PAI-1 and lower uPA and uPAR levels, as well as a decrease in uPA enzymatic activity. The levels of uPAR mRNA were concomitantly reduced, as was uPA-induced chemoinvasion. All these effects were also shown in controls, though to a lesser extent.

CONCLUSIONS

Deflazacort might control RA synovial proliferation and invasion by differential modulation of single members of the fibrinolytic system.

Rheumatoid synovial fibroblasts constitutively express the fibrinolytic pattern of invasive tumor-like cells

OBJECTIVE

In rheumatoid arthritis (RA) the synovial membrane proliferates and invades the underlying tissues. The cell-associated fibrinolytic system (urokinase-type plasminogen activator, uPA; uPA receptor, uPAR; plasminogen activator inhibitor-type 1, PAI-1) is pivotal in cell invasion and proliferation. For this reason, the expression and the role of such enzymatic system was investigated in synovial fibroblasts (SF) of normal and RA patients.

METHODS

In SF obtained from RA patients and control subjects, uPA, uPAR and PAI-1 were measured by ELISA of cell lysates and culture medium and by RT-PCR of mRNAs. uPA was also studied by zymography. Proliferation was measured by cell counting and cell invasion with the Boyden chamber.

RESULTS

RA-SF over-express uPAR and PAI-1 and are more prone than the normal counterpart to spontaneous and uPA-challenged invasion and proliferation, which are counteracted by antagonists of the fibrinolytic system.

CONCLUSIONS

RA-SF display the fibrinolytic pattern and behaviour of invasive tumor-like cells. Antagonists of the fibrinolytic system are able to revert growth and invasion of both normal and RA-SF.

Prospective comparison of arm veins and greater saphenous veins as infrageniculate bypass grafts

OBJECTIVES

to compare arm and saphenous veins for infrageniculate bypass grafting.

DESIGN

prospective non-randomised study.

MATERIALS

two hundred patients, of which 197 had ischaemic tissue loss or rest pain.

METHODS

two hundred and eleven infrageniculate vein bypass procedures using 176 greater saphenous veins and 35 arm veins.

RESULTS

the cumulative primary graft patency rate at 1-month and 2 years was 80% and 61% for saphenous vein and 89% and 42% for arm vein. The corresponding rates for secondary patency were 84.5% and 68%, and 91% and 57%, respectively. These results corresponded to a relative risk of secondary failure of 1.53 (95% CI 0.71, 3.31) for arm vein grafts. In subgroup analyses, this estimate was 0.93 and 2.1 for primary vs secondary bypasses and 0.38 and 2.06 for single-vein vs spliced-vein bypasses. Among arm veins, cephalic vein grafts performed better than basilic vein grafts. Early mortality was 14% for arm vein and 10% for saphenous vein.

CONCLUSION

in the setting of infrageniculate bypass grafting, arm vein grafts are not equivalent to greater saphenous vein grafts, but contribute importantly to a policy of using autologous veins. The possibility of equivalence remains for the arm vein graft that uses a cephalic vein or is a primary procedure.

Apoptosis : molecular regulation of cell death and hematologic malignancies

Apoptosis, or programmed cell death, represents in cell biology a functional program as important as cell growth or differentiation. Programmed cell death is of basic importance for the development of multicellular organisms and its basic mechanisms are conserved during the evolution of metazoa. Mammalian cells exhibit several different apoptotic pathways that converge to a common endpoint. Each pathway is triggered by a different stimulus: growth factor default, irradiation, induction of the p53 oncosuppressor protein, glucocorticoid hormones (in lymphocytes), ligand binding to Fas/APO (CD95), or tumor necrosis factor receptor (TNF-R), perforin secreted by cytotoxic T cells (reviewed by Hale et al. [1]). As opposed to necrosis, apoptosis is a "clean" process: as the cell shrinks, the cell membrane turns into the "apoptotic shell," the nucleus is condensed and reduced in volume, and eventually the cell disappears from the tissue, due to phagocytosis by neighboring cells or professional phagocytes, such as macrophages.

Bypass to the genicular arteries for revascularisation of the lower limb

OBJECTIVE

To describe an initial experience with infrainguinal bypass grafts inserted distally in a genicular artery.

DESIGN

Retrospective case series study.

SUBJECTS AND METHODS

Eleven patients with Grade III chronic limb ischaemia in whom arteriography showed femoropopliteal occlusive disease and at least one genicular branch suitable for receiving a bypass. Bypass grafts were done to the descending genicular artery (n=4) or the medial sural artery (n=6) using segments of autologous veins; one bypass was not completed.

RESULTS

Primary graft patency and foot salvage rates were 73% at 1 month and 24 months of follow-up. Patient survival rate was 100% and 90%, respectively. Major amputation was required in two of three patients following early graft failure. Of the eight patients who had a patent graft, the Doppler ankle-brachial systolic pressure index showed no change in one patient, an increase of 0.13-0.66 in six patients, and was not measured in one patient. The former patient underwent a below-knee amputation whereas the other seven patients showed complete healing of their skin ulcers and sites of minor amputation.

CONCLUSION

The genicular bypass is a useful alternative that may extend the limits of infrainguinal arterial reconstruction with autologous tissue and the potential for long-term patient benefit.

Chronic treatment of human fibroblasts cultures with diacylglycerol induces down-regulation of p53 functional activity

We found that many spontaneous human tumors exhibit increased levels of endocellular diacylglycerol (DAG) which is synthesized de novo as a byproduct of glycolysis. It has been shown that DAG mimics phorbol esters as a full tumor promoter in mouse skin carcinogenesis. A short term DAG treatment activates protein kinase C (PKC), while a long term "chronic" treatment down-regulates PKC. We show here that chronic treatment of human fibroblast with DAG induces p53 down-regulation and inhibition of p53 functional activity, and protection from UV-induced apoptosis. As PKC phosphorylation is necessary for p53 functional activity, we propose that chronic DAG treatment mimics the same event occurring in vivo for the effect of glycolysis in tumor progression.