Surfactant-assisted photo-crosslinked silk fibroin sponges: A versatile platform for the design of bone scaffolds.

Critical size bone defects cannot heal without aid and current clinical approaches exhibit some limitations, underling the need for novel solutions. Silk fibroin, derived from silkworms, is widely utilized in tissue engineering and regenerative medicine due to its remarkable properties, making it a promising candidate for bone tissue regeneration in vitro and in vivo. However, the clinical translation of silk-based materials requires refinements in 3D architecture, stability, and biomechanical properties. In earlier research, improved mechanical resistance and stability of chemically crosslinked methacrylate silk fibroin (Sil-Ma) sponges over physically crosslinked counterparts were highlighted. Furthermore, the influence of photo-initiator and surfactant concentrations on silk properties was investigated. However, the characterization of sponges with Sil-Ma solution concentrations above 10 % (w/V) was hindered by production optimization challenges, with only cell viability assessed. This study focuses on the evaluation of methacrylate sponges' suitability as temporal bone tissue regeneration scaffolds. Sil-Ma sponge fabrication at a fixed concentration of 20 % (w/V) was optimized and the impact of photo-initiator (LAP) concentrations and surfactant (Tween 80) presence/absence was studied. Their effects on pore formation, silk secondary structure, mechanical properties, and osteogenic differentiation of hBM-MSCs were investigated. We demonstrated that, by tuning silk sponges' composition, the optimal combination boosted osteogenic gene expression, offering a strategy to tailor biomechanical properties for effective bone regeneration. Utilizing Design of Experiment (DoE), correlations between sponge composition, porosity, and mechanical properties are established, guiding tailored material outcomes. Additionally, correlation matrices elucidate the microstructure's influence on gene expressions, providing insights for personalized approaches in bone tissue regeneration.

Magnetic resonance imaging based neurosurgical planning on hololens 2: A feasibility study in a paediatric hospital.

Objective: The goal of this work is to show how to implement a mixed reality application (app) for neurosurgery planning based on neuroimaging data, highlighting the strengths and weaknesses of its design. Methods: Our workflow explains how to handle neuroimaging data, including how to load morphological, functional and diffusion tensor imaging data into a mixed reality environment, thus creating a first guide of this kind. Brain magnetic resonance imaging data from a paediatric patient were acquired using a 3 T Siemens Magnetom Skyra scanner. Initially, this raw data underwent specific software pre-processing and were subsequently transformed to ensure seamless integration with the mixed reality app. After that, we created three-dimensional models of brain structures and the mixed reality environment using Unity™ engine together with Microsoft® HoloLens 2™ device. To get an evaluation of the app we submitted a questionnaire to four neurosurgeons. To collect data concerning the performance of a user session we used Unity Performance Profiler. Results: The use of the interactive features, such as rotating, scaling and moving models and browsing through menus, provided by the app had high scores in the questionnaire, and their use can still be improved as suggested by the performance data collected. The questionnaire's average scores were high, so the overall experiences of using our mixed reality app were positive. Conclusion: We have successfully created a valuable and easy-to-use neuroimaging data mixed reality app, laying the foundation for more future clinical uses, as more models and data derived from various biomedical images can be imported.

Facing the Shadow Pandemic: Correlation and Trend Analyses of Violence Reports from Women to the Italian National Anti-Violence Number during 2021.

OBJECTIVES: To help to tackle gender-based violence against women in the aftermath of COVID-19 or other potential crisis situations, as recommended by the European Institute for Gender Equality, the present study aims to investigate the relationship between calls to the National Anti-violence Number (NAN) and the socio-sanitary pandemic factors during 2021, a period in which the scenario changed due to containment measures that gradually allowed women to emerge from the condition of isolation. In addition, the present work aims to identify significant changes in the number of calls to NAN during the progression of the pandemic in 2021. METHODS: Using Italian Civil Protection Department data on the socio-sanitary pandemic factors (defined by daily number of cases, swabs, deaths, hospitalizations, dismissions, intensive care unit hospitalizations, people isolated at home, and quarantine after 15 and 30 days) and NAN data. Correlation analyses, a joinpoint regression analysis, and Granger causality tests were performed. RESULTS: The number of calls correlated with the daily number of cases, swabs, deaths, hospitalizations, dismissions, intensive care unit hospitalizations, and quarantine after 15 and 30 days. The identified joinpoints showed significant changes in the number of daily anti-violence calls during the year. Furthermore, we found evidence of a significant causality between daily hospitalizations, daily home quarantined, daily dismissed patients, and calls to NAN. CONCLUSIONS: The results underline the influence of containment measures on the increased access to NAN, suggesting the need for a greater implementation of social and psychological support services in other potential crisis situations.

Targeting the Inflammatory Hallmarks of Obesity-Associated Osteoarthritis: Towards Nutraceutical-Oriented Preventive and Complementary Therapeutic Strategies Based on n-3 Polyunsaturated Fatty Acids.

Obesity (Ob), which has dramatically increased in the last decade, is one of the main risk factors that contribute to the incidence and progression of osteoarthritis (OA). Targeting the characteristics of obesity-associated osteoarthritis (ObOA) may offer new chances for precision medicine strategies in this patient cohort. First, this review outlines how the medical perspective of ObOA has shifted from a focus on biomechanics to the significant contribution of inflammation, mainly mediated by changes in the adipose tissue metabolism through the release of adipokines and the modification of fatty acid (FA) compositions in joint tissues. Preclinical and clinical studies on n-3 polyunsaturated FAs (PUFAs) are critically reviewed to outline the strengths and weaknesses of n-3 PUFAs' role in alleviating inflammatory, catabolic and painful processes. Emphasis is placed on potential preventive and therapeutic nutritional strategies based on n-3 PUFAs, with a focus on ObOA patients who could specifically benefit from reformulating the dietary composition of FAs towards a protective phenotype. Finally, tissue engineering approaches that involve the delivery of n-3 PUFAs directly into the joint are explored to address the perspectives and current limitations, such as safety and stability issues, for implementing preventive and therapeutic strategies based on dietary compounds in ObOA patients.

On the dynamics of gain and loss: Electrophysiological evidence from associative learning.

Associated relevance affects the sensory encoding of low-level visual features of symbolic stimuli. It is unclear, however, which dimension of low-level visual features benefits from prioritized processing, and how these effects develop throughout the course of relevance acquisition. Moreover, previous evidence is inconclusive regarding the preservation of processing advantage once the association is no longer relevant, as well as its generalization to perceptually similar but novel stimuli. The present study addresses these questions by employing an associative learning paradigm. In two experiments (N = 24 each, between-subject design), different dimensions of low-level visual features of symbolic stimuli were associated with monetary gain, loss, or zero outcome. In a consecutive old/new decision task, associated stimuli were presented together with perceptually similar but novel stimuli. Event-related brain potentials (P1, EPN, LPC) were measured throughout both sessions. Early sensory encoding (P1) was boosted by loss association and appeared to be sensitive to the dimension of the associated low-level visual features. Gain association influenced post-perceptual processing stages (LPC), arising over the course of the learning phase, and are preserved even when the associated outcome was no longer relevant. Gain association also resulted in EPN modulations similar to the effects observed in the case of emotional words. None of the observed effects generalized to perceptually similar stimuli. These results show that acquired relevance can influence the sensory processing of specific dimensions of low-level visual features. Moreover, this study extends previous evidence of a dissociation of early and late neural effects of associated motivational relevance.

Controlled Release of H2S from Biomimetic Silk Fibroin-PLGA Multilayer Electrospun Scaffolds.

The possibility of incorporating H2S slow-release donors inside biomimetic scaffolds can pave the way to new approaches in the field of tissue regeneration and anti-inflammatory treatment. In the present work, GYY4137, an easy-to-handle commercially available Lawesson's reagent derivative, has been successfully incorporated inside biomimetic silk fibroin-based electrospun scaffolds. Due to the instability of GYY4137 in the solvent needed to prepare silk fibroin solutions (formic acid), the electrospinning of the donor together with the silk fibroin turned out to be impossible. Therefore, a multilayer structure was realized, consisting of a PLGA mat containing GYY4137 sandwiched between two silk fibroin nanofibrous layers. Before their use in the multilayer scaffold, the silk fibroin mats were treated in ethanol to induce crystalline phase formation, which conferred water-resistance and biomimetic properties. The morphological, thermal, and chemical properties of the obtained scaffolds were thoroughly characterized by SEM, TGA, DSC, FTIR, and WAXD. Multilayer devices showing two different concentrations of the H2S donor, i.e., 2 and 5% w/w with respect to the weight of PLGA, were analyzed to study their H2S release and biological properties, and the results were compared with those of the sample not containing GYY4137. The H2S release analysis was carried out according to an "ad-hoc" designed procedure based on a validated high-performance liquid chromatography method. The proposed analytical approach demonstrated the slow-release kinetics of H2S from the multilayer scaffolds and its tunability by acting on the donor's concentration inside the PLGA nanofibers. Finally, the devices were tested in biological assays using bone marrow-derived mesenchymal stromal cells showing the capacity to support cell spreading throughout the scaffold and prevent cytotoxicity effects in serum starvation conditions. The resulting devices can be exploited for applications in the tissue engineering field since they combine the advantages of controlled H2S release kinetics and the biomimetic properties of silk fibroin nanofibers.

Overview of Anti-Inflammatory and Anti-Nociceptive Effects of Polyphenols to Halt Osteoarthritis: From Preclinical Studies to New Clinical Insights.

Knee osteoarthritis (OA) is one of the most multifactorial joint disorders in adults. It is characterized by degenerative and inflammatory processes that are responsible for joint destruction, pain and stiffness. Despite therapeutic advances, the search for alternative strategies to target inflammation and pain is still very challenging. In this regard, there is a growing body of evidence for the role of several bioactive dietary molecules (BDMs) in targeting inflammation and pain, with promising clinical results. BDMs may be valuable non-pharmaceutical solutions to treat and prevent the evolution of early OA to more severe phenotypes, overcoming the side effects of anti-inflammatory drugs. Among BDMs, polyphenols (PPs) are widely studied due to their abundance in several plants, together with their benefits in halting inflammation and pain. Despite their biological relevance, there are still many questionable aspects (biosafety, bioavailability, etc.) that hinder their clinical application. This review highlights the mechanisms of action and biological targets modulated by PPs, summarizes the data on their anti-inflammatory and anti-nociceptive effects in different preclinical in vitro and in vivo models of OA and underlines the gaps in the knowledge. Furthermore, this work reports the preliminary promising results of clinical studies on OA patients treated with PPs and discusses new perspectives to accelerate the translation of PPs treatment into the clinics.

Methacrylated Silk Fibroin Additive Manufacturing of Shape Memory Constructs with Possible Application in Bone Regeneration.

Methacrylated silk (Sil-MA) is a chemically modified silk fibroin specifically designed to be crosslinkable under UV light, which makes this material applicable in additive manufacturing techniques and allows the prototyping and development of patient-specific 2D or 3D constructs. In this study, we produced a thin grid structure based on crosslinked Sil-MA that can be withdrawn and ejected and that can recover its shape after rehydration. A complete chemical and physical characterization of Sil-MA was first conducted. Additionally, we tested Sil-MA biocompatibility according to the International Standard Organization protocols (ISO 10993) ensuring the possibility of using it in future trials. Sil-MA was also tested to verify its ability to support osteogenesis. Overall, Sil-MA was shown to be biocompatible and osteoconductive. Finally, two different additive manufacturing technologies, a Digital Light Processing (DLP) UV projector and a pneumatic extrusion technique, were used to develop a Sil-MA grid construct. A proof-of-concept of its shape-memory property was provided. Together, our data support the hypothesis that Sil-MA grid constructs can be injectable and applicable in bone regeneration applications.

How German and Italian Laypeople Reason about Distributive Shortages during COVID-19.

(1) Background: The COVID-19 pandemic provided a unique opportunity to investigate how moral reasoning is influenced by individuals' exposure to a crisis and by personal, societal and temporal proximity. We examined how Italians and Germans judged different behaviors that arose because of the pandemic, which affected health and societal matters. (2) Methods: Over the course of four months and three assessment periods, we used an observational online survey to assess participants' judgments regarding seven scenarios that addressed distributive shortages during the pandemic. (3) Results: Overall, there was no clear answering pattern across all scenarios. For a variation of triage and pandemic restrictions, most participants selected a mean value, which can be interpreted as deferring the choice. For the other scenarios, most participants used the extremes of the scale, thereby reflecting a clear opinion of the public regarding the moral issue. In addition, moral reasoning varied across the two countries, assessment periods, fear, and age. (4) Conclusions: By using scenarios that were taken from real-life experiences, the current study addresses criticism that moral research mostly relies on unrealistic scenarios that lack in external validity, plausibility, and proximity to everyday situations. In addition, it shows how lay people regard measures of public health and societal decision-making.

Dietary organosulfur compounds: Emerging players in the regulation of bone homeostasis by plant-derived molecules.

The progressive decline of bone mass and the deterioration of bone microarchitecture are hallmarks of the bone aging. The resulting increase in bone fragility is the leading cause of bone fractures, a major cause of disability. As the frontline pharmacological treatments for osteoporosis suffer from low patients' adherence and occasional side effects, the importance of diet regimens for the prevention of excessive bone fragility has been increasingly recognized. Indeed, certain diet components have been already associated to a reduced fracture risk. Organosulfur compounds are a broad class of molecules containing sulfur. Among them, several molecules of potential therapeutic interest are found in edible plants belonging to the Allium and Brassica botanical genera. Polysulfides derived from Alliaceae and isothiocyanates derived from Brassicaceae hold remarkable nutraceutical potential as anti-inflammatory, antioxidants, vasorelaxant and hypolipemic. Some of these effects are linked to the ability to release the gasotrasmitter hydrogen sulfide (H2S). Recent preclinical studies have investigated the effect of organosulfur compounds in bone wasting and metabolic bone diseases, revealing a strong potential to preserve skeletal health by exerting cytoprotection and stimulating the bone forming activity by osteoblasts and attenuating bone resorption by osteoclasts. This review is intended for revising evidence from preclinical and epidemiological studies on the skeletal effects of organosulfur molecules of dietary origin, with emphasis on the direct regulation of bone cells by plant-derived polysulfides, glucosinolates and isothiocyanates. Moreover, we highlight the potential molecular mechanisms underlying the biological role of these compounds and revise the importance of the so-called 'H2S-system' on the regulation of bone homeostasis.

Optimization of a Monobromobimane (MBB) Derivatization and RP-HPLC-FLD Detection Method for Sulfur Species Measurement in Human Serum after Sulfur Inhalation Treatment.

(1) Background: Hydrogen sulfide (H2S) is a widely recognized gasotransmitter, with key roles in physiological and pathological processes. The accurate quantification of H2S and reactive sulfur species (RSS) may hold important implications for the diagnosis and prognosis of diseases. However, H2S species quantification in biological matrices is still a challenge. Among the sulfide detection methods, monobromobimane (MBB) derivatization coupled with reversed phase high-performance liquid chromatography (RP-HPLC) is one of the most reported. However, it is characterized by a complex preparation and time-consuming process, which may alter the actual H2S level; moreover, a quantitative validation has still not been described. (2) Methods: We developed and validated an improved analytical protocol for the MBB RP-HPLC method. MBB concentration, temperature and sample handling were optimized, and the calibration method was validated using leave-one-out cross-validation and tested in a clinical setting. (3) Results: The method shows high sensitivity and allows the quantification of H2S species, with a limit of detection of 0.5 µM. Finally, it can be successfully applied in measurements of H2S levels in the serum of patients subjected to inhalation with vapors rich in H2S. (4) Conclusions: These data demonstrate that the proposed method is precise and reliable for measuring H2S species in biological matrices and can be used to provide key insights into the etiopathogenesis of several diseases and sulfur-based treatments.

Real-time and automated monitoring of antischistosomal drug activity profiles for screening of compound libraries.

Schistosomiasis is a neglected tropical disease that affects over 200 million people annually. As the antischistosomal drug pipeline is currently empty, repurposing of compound libraries has become a source for accelerating drug development, which demands the implementation of high-throughput and efficient screening strategies. Here, we present a parallelized impedance-based platform for continuous and automated viability evaluation of Schistosoma mansoni schistosomula in 128 microwells during 72 h to identify antischistosomal hits in vitro. By initially screening 57 repurposed compounds against larvae, five drugs are identified, which reduce parasite viability by more than 70%. The activity profiles of the selected drugs are then investigated via real-time dose-response monitoring, and four compounds reveal high potency and rapid action, which renders them suitable candidates for follow-up tests against adult parasites. The study shows that our device is a reliable tool for real-time drug screening analysis of libraries to identify new promising therapeutics against schistosomiasis.

Glucoraphanin Increases Intracellular Hydrogen Sulfide (H2S) Levels and Stimulates Osteogenic Differentiation in Human Mesenchymal Stromal Cell.

Osteopenia and osteoporosis are among the most prevalent consequences of ageing, urging the promotion of healthy nutritional habits as a tool in preventing bone fractures. Glucosinolates (GLSs) are organosulfur compounds considered relatively inert precursors of reactive derivatives isothiocyanates (ITCs). Recent evidence suggests that GLSs may exert biological properties based on their capacity to release hydrogen sulfide (H2S). H2S-donors are known to exert anabolic function on bone cells. Here, we investigated whether a GLS, glucoraphanin (GRA) obtained from Tuscan black kale, promotes osteogenesis in human mesenchymal stromal cells (hMSCs). H2S release in buffer and intracellular H2S levels were detected by amperometric measurements and fluorimetric/cytofluorimetric analyses, respectively. Alizarin red staining assay and real-time PCR were performed to evaluate mineral apposition and mRNA expression of osteogenic genes. Using an in vitro cell culture model, our data demonstrate a sulforaphane (SFN)-independent osteogenic stimulation of GRA in hMSCs, at least partially attributable to H2S release. In particular, GRA upregulated the expression of osteogenic genes and enhanced mineral apposition while increasing intracellular concentrations of H2S. Overall, this study suggests the feasibility of using cruciferous derivatives as natural alternatives to chemical H2S-donors as adjuvant therapies in the treatment of bone-wasting diseases.

The art gallery maze: a novel tool to assess human navigational abilities.

Humans differ widely in their ability to navigate effectively through the environment and in spatial memory skills. Navigation in the environment requires the analysis of many spatial cues, the construction of internal representations, and the use of various strategies. We present a novel tool to assess individual differences in human navigation, consisting of a virtual radial-arm maze presented as an art gallery to explore whether different sets of instructions (intentional or incidental) affect subjects' navigation performance. We furthermore tested the effect of the instructions on exploration strategies during both place learning and recall. We evaluated way-finding ability in 42 subjects, and individual differences in navigation were assessed through the analysis of navigational paths, which permitted the isolation and definition of a few strategies adopted by the incidental and intentional instructions groups. Our results showed that the intentional instruction group performed better than the other group: these subjects correctly paired each central statue and the two paintings in the adjacent arms, and they made less working and reference memory errors. Our analysis of path lengths showed that the intentional instruction group spent more time in the maze (thus being slower), specifically in the central hall, and covered more distance; the time spent in the main hall was, therefore, indicative of the quality of the following performance. Studying how environmental representations and the relative navigational strategies vary among "intentional" and "incidental" groups provides a new window into the acknowledgment of possible strategies to help subjects construct more efficient approaches in human navigation.

Continuous monitoring of propofol in human serum with fouling compensation by support vector classifier.

We present a new method for electrochemical sensing, which compensates the fouling effect of propofol through machine learning (ML) model. Direct and continuous monitoring of propofol is crucial in the development of automatic systems for control of drug infusion in anaesthesiology. The fouling effect on electrodes discourages the possibility of continuous online monitoring of propofol since polymerization of the surface produces sensor drift. Several approaches have been proposed to limit the phenomenon at the biochemical interface; instead, here, we present a novel ML-based calibration procedure. In this paper, we analyse a dataset of 600 samples acquired through staircase cyclic voltammetry (SCV), resembling the scenario of continuous monitoring of propofol, both in PBS and in undiluted human serum, to demonstrate that ML-based model solves electrode fouling of anaesthetics. The proposed calibration approach is based on Gaussian radial basis function support vector classifier (RBF-SVC) that achieves classification accuracy of 98.9% in PBS, and 100% in undiluted human serum. The results prove the ability of the ML-based model to correctly classify propofol concentration in the therapeutic range between 1µM and 60µM with levels of 10µM, continuously up to ten minutes, with one sample every 30s.

Learning from Monocyte-Macrophage Fusion and Multinucleation: Potential Therapeutic Targets for Osteoporosis and Rheumatoid Arthritis.

Excessive bone resorption by osteoclasts (OCs) covers an essential role in developing bone diseases, such as osteoporosis (OP) and rheumatoid arthritis (RA). Monocytes or macrophages fusion and multinucleation (M-FM) are key processes for generating multinucleated mature cells with essential roles in bone remodelling. Depending on the phenotypic heterogeneity of monocyte/macrophage precursors and the extracellular milieu, two distinct morphological and functional cell types can arise mature OCs and giant cells (GCs). Despite their biological relevance in several physiological and pathological responses, many gaps exist in our understanding of their formation and role in bone, including the molecular determinants of cell fusion and multinucleation. Here, we outline fusogenic molecules during M-FM involved in OCs and GCs formation in healthy conditions and during OP and RA. Moreover, we discuss the impact of the inflammatory milieu on modulating macrophages phenotype and their differentiation towards mature cells. Methodological approach envisaged searches on Scopus, Web of Science Core Collection, and EMBASE databases to select relevant studies on M-FM, osteoclastogenesis, inflammation, OP, and RA. This review intends to give a state-of-the-art description of mechanisms beyond osteoclastogenesis and M-FM, with a focus on OP and RA, and to highlight potential biological therapeutic targets to prevent extreme bone loss.

Sulfurous thermal waters stimulate the osteogenic differentiation of human mesenchymal stromal cells - An in vitro study.

Strategies aimed at delaying the onset of bone tissue degeneration and the resulting skeletal fragility are key to decrease the risk of bone fracture correlated to ageing. The therapeutic properties of sulfurous thermal waters (STWs), rich in hydrogen sulfide (H2S), have been claimed for centuries. However, the direct regulation of bone cells by STWs has not been investigated yet. Here we aimed at analyzing the effect of STWs on cultured human mesenchymal stromal cells (hMSCs) derived from bone tissue. Two concentrations of STWs from 2 health spa centers in Italy (here named STW-1 and STW-2) containing, respectively, high and moderate quantities of H2S, were added to the culture media. Cytotoxicity and osteogenic differentiation were evaluated. We provided first evidence that treatment of hMSCs with STWs results in a sharp increase in intracellular H2S content, coherent with the different concentrations of H2S, thereby reveling that STWs-released H2S is internalized by cells. STWs treatment significantly induced osteogenic differentiation of hMSCs. In particular, mineral apposition was increased with a similar pattern by the two STWs, while mRNA expression of osteogenic markers (BSP, OC, RUNX-2, OPN) was differently affected. Only STW-2 induced a significant, dose-dependent increase in these gene expression. These findings support the rationale for the use of STWs as a complementary treatment of bone wasting diseases.

Asbestos Exposure of Chrysotile Miners and Millers in Balangero, Italy.

The largest chrysotile mine in Western Europe was active in Balangero (Italy) from 1917 to 1990. We quantitatively assessed exposure to asbestos in the framework of a cohort study on mortality of Balangero miners and millers. Using documents filed at the Italian State Archive we reconstructed the job-histories of cohort members. The concentration of asbestos fibres by work-area was derived from industrial hygiene surveys since 1968 and monitoring programs since 1975. Earlier exposures had been estimated based on the experimental reconstruction of past working conditions. In the mine concentrations of about 20 fibres per millilitre (f/ml) were initially present, decreasing to 5 in the mid-1950s and to <1 in late 1970s. In milling areas higher levels were present and did not fall below 1 f/ml until the mid-1980s. Cumulative exposure of cohort members, as the sum over their job-history of their year- and area-specific exposures, were <10 fibre/millilitre years (f/ml-y) in 18% of workers, 10-100 in 32%, 100-1000 in 37%, and >1000 in 13%. Compared with recently published estimates for the Russian chrysotile mine in Asbest, fibre concentrations in Balangero were higher during the 1950s and 1960s. Such difference may be partly accounted for by difficulties in converting dust measurements to fibre concentrations in the Russian study and the need to rely on the experimental reconstruction of exposures before 1968 in our study.

Hydrogen Sulfide in Bone Tissue Regeneration and Repair: State of the Art and New Perspectives.

The importance of hydrogen sulfide (H2S) in the regulation of multiple physiological functions has been clearly recognized in the over 20 years since it was first identified as a novel gasotransmitter. In bone tissue H2S exerts a cytoprotective effect and promotes bone formation. Just recently, the scientific community has begun to appreciate its role as a therapeutic agent in bone pathologies. Pharmacological administration of H2S achieved encouraging results in preclinical studies in the treatment of systemic bone diseases, such as osteoporosis; however, a local delivery of H2S at sites of bone damage may provide additional opportunities of treatment. Here, we highlight how H2S stimulates multiple signaling pathways involved in various stages of the processes of bone repair. Moreover, we discuss how material science and chemistry have recently developed biomaterials and H2S-donors with improved features, laying the ground for the development of H2S-releasing devices for bone regenerative medicine. This review is intended to give a state-of-the-art description of the pro-regenerative properties of H2S, with a focus on bone tissue, and to discuss the potential of H2S-releasing scaffolds as a support for bone repair.

Hydrogen sulfide-releasing silk fibroin scaffold for bone tissue engineering.

Hydrogen sulfide (H2S)-based therapy is a promising therapeutic strategy for several biomedical applications. Following the observation that endogenous and exogenous H2S plays a prominent role as a bone anabolic agent, we recently developed a silk fibroin (SF) porous scaffold loaded with GYY4137 (GYY), an H2S donor, for applications in bone tissue engineering. Here, we assayed whether the combination of SF with H2S potentiates the osteoconductive properties of SF. Biocompatibility and osteoanabolic activity were assayed in vitro using human bone marrow mesenchymal stromal cells. Cell cultures were performed on a perfusion bioreactor to obtain results closer to the in vivo microenvironment. Cytotoxicity was excluded by lactate dehydrogenase and live/dead assays. Cell colonization and mineral apposition were evaluated by Haematoxylin & Eosin and Von Kossa/Alizarin Red-S stainings respectively. PCR array for human osteogenesis and immunohistochemical analyses were performed to identify pathways and targets involved. Our findings show that H2S-releasing SF scaffolds supported cell adhesion, proliferation and viability. Moreover, H2S activated genes and proteins involved in ossification, osteoblast differentiation, bone mineral metabolism and angiogenesis allowing a high and early mineralization. Based on these properties, we suggest the use of H2S-releasing SF scaffolds for bone healing and regeneration applications.