Inflammation is an important biological process to be considered in designing successful biomaterial-based therapeutics. Indeed, prolonged inflammation can result in delayed wound healing and, in some cases, may cause the rejection of the biomaterial together with additional tissue damage. Mesenchymal stem cells (MSCs) participate in this critical intercellular communication to modulate bone healing. In this study, MSCs were employed as in vitro model in order to evaluate the biological performances, in terms of immune response, of Bio-Oss®/Avitene™ composite scaffold. Moreover, new bone formation was evaluated in patients undergoing maxillomandibular osteotomy for skeletal malocclusion, facial asymmetry, or aesthetic indications, using a Bio-Oss®/Avitene™ composite scaffold. The early inflammatory response of human bone marrow derived-mesenchymal stem cells (BM-MSCs) was investigated in vitro analysing the gene expression of IL-6 and IL-8 using Droplet Digital PCR and the release of cytokines, chemokines, and growth factors using Bio-Plex approach. Clinical evaluation was performed using Cone Beam Computed Tomography (CBCT). In vitro, Bio-Oss®/Avitene™ decreases the IL-6 expression, quantified with Droplet Digital PCR approach. Bio-Plex reveals that the protein levels of MCP-1 and IL-6 were reduced, while IL-4, IL-8 and VEGF were increased by the scaffold in cells up to day 7. CBCT assessment in patients demonstrated stable outcomes, supporting the potential for long-term aesthetic restoration of the zygomatic region. These findings indicate that Bio-Oss®/Avitene™ possesses immunomodulatory potential and is capable of directing anti-inflammatory, immune-mediated responses associated with bone regrowth for the treatment of dentofacial deformities through orthognathic surgery.

BACKGROUND:The molecular mechanisms of Merkel cell polyomavirus (MCPyV)-negative MCC (VN-MCC) initiation remain poorly understood. Although hsa-miR-34a-5p dysregulation has been reported in MCC, its role in VN-MCC is unknown. OBJECTIVE:We aimed to investigate the functional role of hsa-miR-34a-5p on the malignant phenotype of VN-MCC and elucidate the potential underlying mechanisms. METHODS:Hsa-miR-34a-5p expression was investigated in MCC cell lines (n = 5) and tissues (n = 34), and in fibroblast/epithelial cell lines (n = 2). Functional experiments evaluated the effect of hsa-miR-34a-5p on VN-MCC MCC13 phenotype. Gene expression profiling, enrichment analyses and protein-protein interaction network of hsa-miR-34a-5p target genes (n = 84) were conducted in these cells to identify relevant targets/pathways. The impact of hsa-miR-34a-5p on VN-MCC spheroid volume/growth was investigated. RESULTS:Hsa-miR-34a-5p was significantly downregulated in VN-MCC cells and tissues compared to MCPyV-positive counterparts, as well as to fibroblast/epithelial cells. Mechanistically, ectopic hsa-miR-34a-5p expression in MCC13 cells significantly inhibited proliferation, colony formation, and migration abilities, while promoted apoptosis. Hsa-miR-34a-5p silencing in epithelial HaCaT cells increased colony formation and partially enhanced migration. Ectopic hsa-miR-34a-5p expression in MCC13 cells negatively regulated key target genes and pathways involved in both G1/S transition of the cell cycle (CDK4, CDK6, CCNE2) and epithelial-to-mesenchymal transition (MET, NOTCH1, JAG1, along with Snail protein), leading to anti-proliferative and anti-migratory effects. Ectopic hsa-miR-34a-5p expression strongly inhibited MCC13 spheroid formation, whereas miRNA inhibition yielded the opposite effect in HaCaT spheroids from intermediate through later time points. CONCLUSION:We provide the first functional evidence of the pleiotropic tumor suppressor role of hsa-miR-34a-5p in VN-MCC.

Background: The effects of dexamethasone during in vitro human osteogenesis present a complex picture. On one side, dexamethasone promotes the osteogenic differentiation of human bone marrow mesenchymal stromal cells (BMSCs) by downregulating SOX9. On the other side, it simultaneously promotes adipogenesis through the upregulation of PPARG. The regulation of SOX9 and PPARG levels appears to be mediated by the transactivation function of the glucocorticoid receptor (GR), suggesting an indirect effect of dexamethasone on SOX9 downregulation. This study aims to determine whether PPAR-γ affects the expression levels of SOX9, as suggested by several studies. Methods: Human BMSCs were isolated from bone marrow and cultured in different osteogenic induction media containing 10 or 100 nM dexamethasone. Undifferentiated cells were used as control. Cells were treated either with a pharmacological PPAR-γ inhibitor (T0070907) or with a PPARG-targeting siRNA. Differentiation markers or PPAR-γ target genes were analysed by RT-qPCR. Mineral deposition was assessed by Alizarin Red staining. Two-way ANOVA followed by a Sidak multiple comparison test was used to compare the effects of treatments. Results: Pharmacological inhibition of PPAR-γ had a mild effect on the expression of PPAR-γ target genes but hindered adipocyte formation. Neither RUNX2 nor SOX9 expression were affected by T0070907. siRNA treatment successfully downregulated PPARG expression, as well as that of PPAR-γ target genes LPL, LPAR1, and ADIPOQ. Contrary to expectations, RUNX2 was significantly downregulated by the PPARG-siRNA treatment during osteogenic differentiation both in the absence and presence of dexamethasone, while SOX9 levels were downregulated in undifferentiated cells. Overall, Alizarin Red staining analysis showed no change in mineralization levels when PPARG expression or activity was inhibited. Conclusions: Understanding how dexamethasone regulates human BMSC differentiation is crucial to refine current in vitro models. These results suggest that PPAR-γ is not involved in SOX9 or RUNX2 repression during in vitro osteogenic differentiation of human cells. ### Competing Interest Statement The authors have declared no competing interest. AO Foundation, https://ror.org/04v7vb598 Italian Ministry of Education, Universities and Research, PRIN 2017 Orthopaedic Research Society, 2024 Orthopaedic Research Society International Section of Fracture Repair (ORS-ISFR) Interdisciplinary Academic Exchange Grant

Human Pleural Mesothelioma (HPM) is an aggressive asbestos-related tumor with limited treatment options and a poor prognosis. MicroRNAs (miRNAs), known to play key roles in the pathogenesis of HPM, have emerged as promising candidates for both diagnostic and therapeutic applications. Among them, miR-197-3p has been previously identified as dysregulated in sera from HPM patients and workers ex-exposed to asbestos fibers. To investigate the functional role of miR-197-3p, loss- and gain-of-function studies were performed in HPM cell lines and human mesothelial cells (HMC) using miR-197-3p-specific antagomiR and mimic. The effects of miR-197-3p modulation on cell proliferation, viability, migration, and apoptosis were evaluated. In addition, bioinformatics analyses were performed to identify potential miR-197-3p target genes, which were subsequently evaluated at both mRNA and protein levels. MiR-197-3p tested significantly upregulated in HPM cells. Its inhibition led to a marked reduction of the HPM cell proliferation, whereas its overexpression in HMC promoted a proliferative phenotype, supporting a potential role in cell growth regulation. Among the predicted targets, TGF-β1 and p120 showed modulation at the mRNA level, although protein-level changes were limited or only partially consistent. These findings suggest that miR-197-3p may contribute to HPM pathogenesis by promoting cell proliferation and influencing critical molecular pathways. However, the underlying molecular mechanisms remain to be fully elucidated, and the interaction with candidate targets, such as TGF-β1 and p120, should be considered putative. Further investigations, including functional and mechanistic validation in more representative experimental models, will be required to clarify the role of miR-197-3p in HPM pathobiology.

Merkel cells are specialized oval-shaped epithelial cells located in the basal epidermis and hair follicles, connected with afferent nerve endings responsible for sensory perception of light touch. Recent advances in developmental biology have shed light on the complex regulatory networks governing Merkel cell maturation. The most recent evidence indicates a crosstalk among epigenetic pathways, notably Polycomb multi-subunit complexes, Merkel cell-lineage transcription factors such as atonal BHLH transcription factor 1 (ATOH1), SRY-box transcription factor 2 (SOX2), ISL LIM homeobox 1 (ISL1) and additional players in the regulation of Merkel cell developmental programs. At the same time, the implications of dysregulated Merkel cell-lineage transcription factors during Merkel cell carcinoma (MCC) onset is under investigation. This review offers a comprehensive overview of the current understanding of the genetic and epigenetic pathways crucial for Merkel cell differentiation. It covers the implication of Merkel cell-specific developmental programs, the role of epigenetic regulatory Polycomb complexes, and how genetic and epigenetic mechanisms converge to orchestrate Merkel cell differentiation.

Autoimmune rheumatic diseases (AIRDs) encompass a spectrum of disorders with a partially understood pathogenesis. A role for polyomaviruses in AIRDs occurrence has been reported. However, the involvement of Merkel cell polyomavirus (MCPyV), the main causative factor of Merkel cell carcinoma (MCC), an aggressive skin neoplasm related to immunosuppression, in AIRDs is unknown. The prevalence/serological profiles of immunoglobulin G (IgG) antibodies to MCPyV large and small T (LT/sT) oncoproteins and viral capsid proteins 1 and 2 (VP1/2) were investigated herein in 540 immunosuppressive treatment-naive AIRD patients, encompassing 447 rheumatoid arthritis (RA) and 93 ankylosing spondylitis (AS) patients by seven MCPyV-specific immunoassays. Control sera from 500 healthy subjects (HS) and 128 MCC patients were included. MCPyV DNA and LT/VP1 mRNAs were evaluated in peripheral blood mononuclear cells (PBMCs) from 75 randomly selected AIRD patients. AIRD patients exhibited higher prevalence and levels (optical densities) of serum anti-oncoprotein IgGs (12%–13%, 0.2–0.6) compared to HS (2%–7%, 0.1–0.4), but lower than MCC patients (70%–83%, 0.2–0.7) (P < .05), with the increase being more pronounced in AS (24%–29%, 0.3–0.8) than in RA (9%–11%, 0.2–0.8) (P < .05). Conversely, similar rates and levels of serum anti-capsid proteins IgGs were determined in most cases between study and control groups (60%–73%, 0.1–0.3) (P > .05). Moreover, receiver operating characteristic (ROC) curves indicated that the MCPyV serology can discriminate AIRD patients from HS (P < .0001). A fraction (11%) of AIRD PBMCs tested MCPyV DNA (7.4 ± 2.6 [copy/104 cells]) and mRNA-positive (0.5–0.1 [1/ΔCt]), while matched sera showed high rates and levels of anti-oncoproteins IgGs (38%–75%, 0.2–2). Our study provides the first evidence that AIRD patients are immunologically responsive to MCPyV oncoproteins, with a fraction of these patients presenting an increased presentation of MCPyV LT and sT antigens, possibly due to viral LT/sT oncogene expression in their PBMCs. These data suggest an association between MCPyV infection and AIRDs pathogenesis.

The increasing incidence of bone diseases has driven research towards Bone Tissue Engineering (BTE), an innovative discipline that uses biomaterials to develop three-dimensional (3D) scaffolds capable of mimicking the natural environment of bone tissue. Traditional approaches relying on two-dimensional (2D) models have exhibited significant limitations in simulating cellular interactions and the complexity of the bone microenvironment. In response to these challenges, 3D models such as organoids and cellular spheroids have emerged as effective tools for studying bone regeneration. Adult mesenchymal stem cells have proven crucial in this context, as they can differentiate into osteoblasts and contribute to bone tissue repair. Furthermore, the integration of composite biomaterials has shown substantial potential in enhancing bone healing. Advanced technologies like microfluidics offer additional opportunities to create controlled environments for cell culture, facilitating more detailed studies on bone regeneration. These advancements represent a fundamental step forward in the treatment of bone pathologies and the promotion of skeletal health. In this review, we report on the evolution of in vitro culture models applied to the study of bone healing/regrowth, starting from 2 to 3D cultures and microfluids. The different methodologies of in vitro model generation, cells and biomaterials are presented and discussed.

The skin is the most extensive organ in the human body. Photo exposure to ultraviolet (UV) rays causes several damages to skin cells, including premature skin aging, the onset of possible DNA mutations, and the risk of developing cancers, including melanoma. Protecting skin from the damaging effects of sun exposure through the application of creams and filters is important to prevent irreversible damages. Several natural extracts and biomolecules with antioxidant activity are widely used in the production of dietary supplements or topical products, for the prevention and treatment of skin affections. Within this context, we pre-treated human skin fibroblasts (HFF1), skin-isolated stem cells (SSCs) and keratinocytes (HaCaT) with two creams containing a specific solar protection factor (SPF) for 72 h and then exposed the cells to UV light. Gene expression analysis was performed for the key cell cycle regulators (p16, p19, p21, p53 and TERT). Cell senescence was assessed by colorimetric assays of beta-galactosidase and antioxidant potential, revealing the ability of treated cells to counteract free radical production as a result of oxidative stress. Finally, possible mutations in DNA induced by photo exposure were studied. The results obtained demonstrated that the tested products elicit positive effects on all skin cell populations, preserving them from photo exposure damages and premature senescence, being also able to increase the DNA repairing mechanisms and inducing a youngest phenotype.

Bone diseases represent a growing healthcare challenge due to population aging and lifestyle changes. Although bone has a natural regenerative capacity, approximately 10% of fractures fail to heal properly, requiring advanced therapeutic approaches. Bone tissue engineering (BTE) has advanced the use of osteoinductive and osteoconductive biomaterials to support bone regeneration. Among them, Bio-Oss® Collagen, a composite of bovine hydroxyapatite and collagen, has shown excellent biocompatibility and bioactivity properties. This study analyzes the effect of Bio-Oss® Collagen on human bone marrow-derived mesenchymal stem cells (hBMSCs), assessing its osteoinductive and immunomodulatory potential. After 7 days of culture, the biomaterial modulated the expression of key genes involved in osteogenesis and chondrogenesis, which are known for their role in bone formation and maturation. At the same time, a downregulation of genes associated with bone resorption was observed. Secretome analysis revealed a controlled release of pro-regenerative cytokines, suggesting a role of the biomaterial in modulating inflammation to promote bone regeneration. Furthermore, immunofluorescence confirmed the high expression of osteocalcin and osteopontin, which are key markers of bone mineralization. These findings indicate that Bio-Oss® Collagen supports osteogenesis and modulates the immune response, creating a microenvironment favorable for bone regeneration.

Background: Pleural mesothelioma (PM) is a rare and highly aggressive tumor, primarily caused by asbestos exposure. Its long latency period and late-stage diagnosis severely limit therapeutic options. Aim: Recent evidence suggests that non-coding RNAs (ncRNAs)—including microRNAs (miRNAs), long ncRNAs (lncRNAs), and circular RNAs (circRNAs)—play key roles in PM biology. This review aims to synthesize current knowledge on ncRNA dysregulation in PM and explore their diagnostic, prognostic, and therapeutic potential. Scope: We summarize studies addressing the expression and function of ncRNAs in tumors and in circulating biofluids of PM patients. Particular attention is given to how ncRNAs regulate proliferation, apoptosis, and migration, and how competing endogenous RNA (ceRNA) networks shape gene regulation in PM. Novelty and Conclusion: Unlike previous reviews, this work integrates findings across different classes of ncRNAs and their interactions, highlighting the emerging concept of ceRNA networks in PM. By bridging molecular mechanisms with potential clinical applications, we provide an updated and comprehensive framework that may inform future strategies for diagnosis, prognosis, and targeted therapy in PM.

Pleural mesothelioma (PM) poses a significant challenge in oncology due to its intricate molecular and metabolic landscape, chronic inflammation, and heightened oxidative stress, which contribute to its notorious resilience and clinical complexities. Despite advancements, the precise mechanisms driving PM carcinogenesis remain elusive, impeding therapeutic progress. Here, we explore the interplay between tumor growth dynamics, lipid metabolism, and NF-κB dysregulation in malignant pleural mesothelioma, shedding light on novel molecular mechanisms underlying its pathogenesis. Our study reveals distinctive growth dynamics in PM cells, characterized by heightened proliferation, altered cell cycle progression, and resistance to apoptosis. Intriguingly, PM cells exhibit increased intracellular accumulation of myristic, palmitic, and stearic acids, suggestive of augmented lipid uptake and altered biosynthesis. Notably, we identify FABP5 as a key player in driving metabolic alterations and inflammation through NF-κB dysregulation in mesothelioma cells, distinguishing them from normal mesothelial cells. Silencing of FABP5 leads to significant alterations in cell dynamics, metabolism, and NF-κB activity, highlighting its potential as a therapeutic target. Our findings unveil a reciprocal relationship between lipid metabolism and inflammation in PM, providing a foundation for targeted therapeutic strategies. Overall, this comprehensive investigation offers insights into the intricate molecular mechanisms driving PM pathogenesis and identifies potential avenues for therapeutic intervention.

Background:Pleural mesothelioma (PM) is an aggressive tumor of the serous cavities primarily caused by the inhalation of asbestos, a carcinogenic and immunomodulatory mineral. Other factors, such as oncogenic viruses, might be involved in PM onset. Merkel cell polyomavirus (MCPyV) is a ubiquitous oncogenic DNA virus whose increased activity has been documented in conditions of immunosuppression. In this study, we aimed to investigate the immunological response to MCPyV in PM patients and workers ex-exposed to asbestos (WEA). Methods:MCPyV serology was investigated herein in sera from 108 PM patients, 102 WEA, and 110 healthy subjects (HS). Total serum immunoglobulin G (IgG) levels were evaluated. The presence of MCPyV DNA and viral protein (VP)1 and large T (LT) messenger RNAs (mRNAs) was evaluated by droplet-digital polymerase chain reaction (ddPCR)/quantitative polymerase chain reaction (qPCR) in 50 tumor specimens from PM patients unrelated to PM serum donors. Results:Reduced serum anti-MCPyV IgG rates and optical densities (ODs) were detected in PM (26.9% and 0.08-0.09) and WEA (27.5% and 0.08-0.09) compared to HS (60.9% and 0.16-0.33) (P<0.001), while the mean total IgG concentrations were similar among groups (4.3-5.7 mg/mL) (P>0.05). Biphasic PM histotype exhibited the lowest MCPyV IgG levels. WEAs with the highest asbestos exposure had the lowest rate and ODs of serum anti-MCPyV IgGs (5.6% and 0.074-0.083) in contrast to WEA (44.4% and 0.083-0.096) with lower exposure. Spearman analyses revealed an inverse correlation between ODs and both cumulative asbestos exposure and years of asbestos exposure (P<0.05), while a direct correlation was detected between years since last exposure and ODs (P=0.02). MCPyV DNA was detected in 32% of PM specimens with a mean viral DNA load of 0.39±0.2 copy/cell. VP1 mRNA was detected in all MCPyV DNA-positive PMs, while 69% of these specimens tested LT mRNA-positive. Conclusions:Our study provides the first evidence that PM and WEA may experience a specific impairment of their immune response to MCPyV. This might possibly depend on the immunomodulatory effect of asbestos, a well-known immunosuppressive mineral.

Pleural Mesothelioma (PM) is an aggressive tumor with a poor prognosis and limited therapeutic options. Despite the notion that resveratrol (RSV) significantly inhibits the growth of PM cancer cells, it is necessary to evaluate the effects of this stilbene as a tumor suppressor agent. In this work, the effects of the natural polyphenol were investigated on PM cell lines (MSTO-211H and IST-MES 2) to evaluate its action as a potential adjuvant agent, together with chemotherapy. Our results showed that RSV treatment was effective in PM cell lines, in particular in MSTO-211H. RES treatment decreases the viability evaluated with the MTT assay and Live/Dead staining. RSV stimulates the apoptotic process with positive staining for Annexin V-PI and Caspase-3/7 and inhibits the migration ability of both PM cell lines. In IST-MES 2, RSV causes a reduction in mitochondrial and cytoplasmic calcium levels. Moreover, RSV affects cellular morphology, E-cadherin protein expression, and decreased nuclear localization of β-catenin, attenuating Wnt/β-catenin signaling, which regulates tumor cell proliferation. At the molecular level, RSV modulated the expression of key genes that play an important role in cellular adhesion, proliferation, and metabolic activity, as well as AMPK signaling. RSV seems to be a promising therapeutic adjuvant agent for PM treatment.

Development of electrospun nanofibers with suitable properties to promote wound healing is an advantage in developing non-invasive skin treatments. We showed the potential application of Polyvinyl acetate (PVA) and Polyvinylpyrrolidone (PVP) combined with Helichrysum italicum oil (HO) in wound healing. During this process, Tight junctions (TJs) play a crucial role in maintaining skin integrity. TJs are intercellular junctions composed of a variety of transmembrane proteins, including Occludin (OCLN), observed also in migrating epithelial cells. Changes in OCLN expression affect epidermal permeability, indicating an active role in the healing process. Within this context, we studied the OCLN expression during healing after scratch assay on Keratinocytes (HaCaT), by a confocal microscopic analysis. In addition, we evaluated the effect of treatment after scratch on cell elasticity by Atomic Force Microscopy (AFM) analysis. All results show a positive trend in cell proliferation and viability on HaCaT treated with functionalized nanofibers. These results were confirmed by the expression of genes involved in the early stages of the regenerative process. Understanding the cell mechanisms involved in skin changes during repair process would allow future application of nanomaterials combined with HO in vivo.

Merkel cell polyomavirus (MCPyV) is the foremost causative factor of Merkel cell carcinoma (MCC), a rare yet highly aggressive skin cancer. Although the evaluation of circulating IgG antibodies against Merkel cell polyomavirus (MCPyV) LT/sT oncoproteins is clinically useful for MCC diagnosis/prognosis, a limited number of assays for identifying such antibodies have been developed. Herein, a novel indirect immunoassay with synthetic epitopes/mimotopes of MCPyV oncoproteins was computationally designed and experimentally validated on control sera and sera from healthy individuals and MCC patients. Upon computational design of five synthetic peptides, the performance of the immunoassay in detecting anti-oncoprotein IgGs in MCPyV-positive and -negative control sera was evaluated. The immunoassay was afterwards extended on sera from healthy individuals, and, for longitudinal analysis, MCC patients. Performance properties such as sensitivity and specificity and positive/negative predictive values were adequate. Receiver-operating characteristic (ROC) curves indicated that the areas under the curves (AUCs) were within the low/moderately accurate ranges. Immunoassay was repeatable, reproducible and accurate. As expected, the serum anti-oncoprotein IgG prevalence in healthy individuals was low (2%-5%). Anti-oncoprotein IgGs slightly increased when MCC patients experienced partial tumour remission and/or stable disease, compared to baseline. Our data indicate that the newly developed immunoassay is reliable for detecting circulating anti-oncoprotein IgGs both in healthy individuals and MCC patients.

Human osteogenic differentiation is a complex and well-orchestrated process which involves a plethora of molecular players and cellular processes.A growing number of studies have underlined that circular RNAs (circRNAs) play an important regulatory role during human osteogenic differentiation.CircRNAs are single-stranded, covalently closed non-coding RNA molecules that are acquiring increased attention as epigenetic regulators of gene expression.Given their intrinsic high conformational stability, abundance, and specificity, circRNAs can undertake various biological activities in order to regulate multiple cellular processes, including osteogenic differentiation.The most recent evidence indicates that circRNAs control human osteogenesis by preventing the inhibitory activity of miRNAs on their downstream target genes, using a competitive endogenous RNA mechanism.The aim of this review is to draw attention to the currently known regulatory mechanisms of circRNAs during human osteogenic differentiation.Specifically, we provide an understanding of recent advances in research conducted on various human mesenchymal stem cell types that underlined the importance of circRNAs in regulating osteogenesis.A comprehensive understanding of the underlying regulatory mechanisms of circRNA in osteogenesis will improve knowledge on the molecular processes of bone growth, resulting in the potential development of novel preclinical and clinical studies and the discovery of novel diagnostic and therapeutic tools for bone disorders.

IntroductionHuman polyomaviruses (HPyVs) cause persistent/latent infections in a large fraction of the population. HPyV infections may cause severe diseases in immunocompromised patients. Malawi polyomavirus (MWPyV) is the 10th discovered human polyomavirus (HPyV 10). MWPyV was found in stool samples of healthy children. So far, the few investigations carried out on HPyV 10 did not find an association with human disease.MethodsIn this study, to verify the putative association between MWPyV and human diseases, MWPyV seroprevalence was investigated in patients affected by i) lymphoproliferative disorders (LPDs) and ii) immune system disorders, i.e., autoimmune diseases (ADs), and in iii) healthy subjects. An indirect ELISA, employing virus-like particles (VLPs) to detect serum IgG antibodies against MWPyV/HPyV 10, was carried out. The study also revealed the prevalence of another polyomavirus, Merkel cell polyomavirus (MCPyV).ResultsSera from patients with distinct autoimmune diseases (n = 44; mean age 20 years) had a prevalence of MWPyV antibodies of 68%, while in patients with lymphoproliferative disorders (n = 15; mean age 14 years), subjected to bone marrow transplantation, the prevalence was 47%. In healthy subjects (n = 66; mean age 13 years), the prevalence of MWPyV antibodies was 67%. Our immunological investigation indicates that MWPyV/HPyV 10 seroconversion occurs early in life and MWPyV/HPyV 10 appears to be another polyomavirus ubiquitous in the human population. A significantly lower MWPyV antibody reactivity together with a lower immunological profile was detected in the sera of LPD patients compared with HS2 (*p < 0.05) (Fisher’s exact test). LPD and AD patients have a similar MCPyV seroprevalence compared with healthy subjects.DiscussionMWPyV seroprevalence indicates that this HPyV is not associated with lymphoproliferative and autoimmune diseases. However, the ability to produce high levels of antibodies against MWPyV appears to be impaired in patients with lymphoproliferative disorders. Immunological investigations indicate that MWPyV seroconversion occurs early in life. MCPyV appears to be a ubiquitous polyomavirus, like other HPyVs, in the human population.

The effects of dexamethasone (dex), during in vitro human osteogenesis, are contrasting. Indeed, dex downregulates SOX9 during osteogenic differentiation of human bone marrow mesenchymal stromal cells (HBMSCs). However, dex also promotes PPARG expression, resulting in the formation of adipocyte-like cells within the osteogenic monolayers. The regulation of both SOX9 and PPARG seems to be downstream the transactivation activity of the glucocorticoid receptor (GR), thus the effect of dex on SOX9 downregulation is indirect. This study aims at determining whether PPAR-γ regulates SOX9 expression levels, as suggested by several studies.HBMSCs were isolated from bone marrow of patients with written informed consent. HBMSCs were cultured in different osteogenic induction media containing 10 or 100 nM dex. Undifferentiated cells were used as controls. Cells were treated either with a pharmacological PPAR-γ inhibitor T0070907 (donors n=4) or with a PPARG-targeting siRNA (donors n=2). Differentiation markers or PPAR-γ target genes were analysed by RT-qPCR. Mineral deposition was assessed by ARS staining. Two-way ANOVA followed by a Tukey's multiple comparison test compared the effects of treatments.At day 7, T0070907 downregulated ADIPOQ and upregulated CXCL8, respectively targets of PPAR-γ-mediated transactivation and transrepression. RUNX2 and SOX9 were also significantly downregulated in absence of dex. PPARG was successfully downregulated by siRNA. ADIPOQ expression was also inhibited, while CXCL8 did not show any significant difference between siRNA treatment groups. RUNX2 was downregulated by the PPARG-siRNA treatment in presence of 100 nM dexamethasone, while SOX9 levels were not affected. ARS showed no change in the mineralization levels when PPARG expression or activity was inhibited.Understanding how dex regulates HBMSC differentiation is of pivotal importance to refine current in vitro models. These results suggest that PPARG does not mediate SOX9 downregulation. Unexpectedly, RUNX2 expression was also unaltered or even downregulated after PPAR-γ inhibition.Acknowledgements: AO Foundation, AO Research Institute (CH) and PRIN 2017 MUR (IT) for financial support.