While stem cell/biomaterial studies provide solid evidences that biomaterial intrinsic cues deeply affect cell fate, current strategies tend to neglect their effects on mesenchymal stem cells (MSCs) secretory activities and resulting cell-crosstalks. The present study aims to investigate the impact of bone-mimetic material (B-MM), with intrinsic osteoinductive property, on MSCs mediator secretions; and to explore underlying effects on cells involved in bone regeneration. Human MSCs were cultured, on B-MM, made from inorganic calcium phosphate supplemented with chitosan and hyaluronic acid biopolymers. Collected MSCs culture media were assessed for mediators release quantification and used further to stimulate endothelial cells (ECs) and alveolar bone derived osteoblasts (OBs). Without osteogenic supplements, MSCs committed into bone lineage forming thus 3D bone-like nodules after 21 days. Despite a weak percentage of cell commitment, our data elucidate new aspects of osteoinductive material effect on MSCs functions through the regulation of the secretion of mediators involved in bone regeneration and subsequently the MSCs/ECs indirect crosstalk with osteogenesis-boosting effect. Using MSCs culture media, we demonstrate a large potential of osteoinductive materials and MSCs in bone regenerative medicine. Such strategies could help to address some insights in cell-free therapies using MSCs derived media.

In inflammatory diseases, polymorphonuclear neutrophils (PMNs) are known to produce elevated levels of pro-inflammatory cytokines and proteases. To limit ensuing exacerbated cell responses and tissue damage, novel therapeutic agents are sought. 4aa and 4ba, two pyridazinone-scaffold-based phosphodiesterase-IV inhibitors are compared in vitro to zardaverine for their ability to: (1) modulate production of pro-inflammatory mediators, reactive oxygen species (ROS), and phagocytosis; (2) modulate degranulation by PMNs after transepithelial lung migration. Compound 4ba and zardaverine were tested in vivo for their ability to limit tissue recruitment of PMNs in a murine air pouch model. In vitro treatment of lipopolysaccharide-stimulated PMNs with compounds 4aa and 4ba inhibited the release of interleukin-8, tumor necrosis factor-α, and matrix metalloproteinase-9. PMNs phagocytic ability, but not ROS production, was reduced following treatment. Using a lung inflammation model, we proved that PMNs transmigration led to reduced expression of the CD16 phagocytic receptor, which was significantly blunted after treatment with compound 4ba or zardaverine. Using the murine air pouch model, LPS-induced PMNs recruitment was significantly decreased upon addition of compound 4ba or zardaverine. Our data suggest that new pyridazinone derivatives have therapeutic potential in inflammatory diseases by limiting tissue recruitment and activation of PMNs.

Infection and inflammation are two key features to consider to avoid septic or aseptic loosening of bone-implanted biomaterials. In this context, various approaches to fine-tune the biomaterial's properties have been studied in order to modulate the crosstalk between immune and skeletal cells. Cation-doping strategies for tuning of calcium phosphates properties has been evidenced as a promising way to control the biomaterial-induced inflammatory process, and thus improving their osteoimmunomodulatory properties. Copper(II) ions are recognized for their antibacterial potential, but the literature on their impact on particulate material-induced acute inflammation is scarce. We synthesized copper(II) ions-doped biphasic calcium phosphate (BCP), intended to exhibit osteoimmunomodulatory properties. We addressed in vitro, for the first time, the inflammatory response of human primary polymorphonuclear neutrophils (PMNs) to copper(II) ions-doped or undoped (BCP) powders, synthesized by an original and robust wet method, in the presence or absence of LPS as a costimulant to mimic an infectious environment. ELISA and zymography allowed us to evidence, in vitro, a specific increase in IL-8 and GRO-α secretion but not MIP-1β, TNF-α, or MMP-9, by PMNs. To assess in vivo relevance of these findings, we used a mouse air pouch model. Thanks to flow cytometry analysis, we highlighted an increased PMN recruitment with the copper(II) ions-doped samples compared to undoped samples. The immunomodulatory effect of copper(II) ions-doped BCP powders and the consequent induced moderate level of inflammation may promote bacterial clearance by PMNs in addition to the antimicrobial potential of the material. Copper(II) doping provides new insights into calcium phosphate (CaP)-based biomaterials for prosthesis coating or bone reconstruction by effectively modulating the inflammatory environment.

Osteosarcoma is a rare primary bone cancer that mostly affects children and young adults. Current therapeutic approaches consist of combining surgery and chemotherapy but remain unfortunately insufficient to avoid relapse and metastases. Progress in terms of patient survival has remained the same for 30 years. In this study, novel pyridazinone derivatives have been evaluated as potential anti-osteosarcoma therapeutics because of their anti-type 4 phosphodiesterase activity, which modulates the survival of several other cancer cells. By using five—four human and one murine osteosarcoma—cell lines, we demonstrated differential cytotoxic effects of four pyridazinone scaffold-based compounds (mitochondrial activity and DNA quantification). Proapoptotic (annexin V positive cells and caspase-3 activity), anti-proliferative (EdU integration) and anti-migratory effects (scratch test assay) were also observed. Owing to their cytotoxic activity in in vitro conditions and their ability to limit tumor growth in a murine orthotopic osteosarcoma model, our data suggest that these pyridazinone derivatives might be hit-candidates to develop new therapeutic strategies against osteosarcoma.

L’ostéosarcome est un cancer primitif rare de l’os dont les approches thérapeutiques actuelles sont encore malheureusement insuffisantes pour espérer une totale guérison, et pour lequel la recherche de nouvelles molécules efficaces est constante. De plus, après exérèse de la tumeur, le défaut généré peut nécessiter de recourir à des matériaux aidant la reconstruction osseuse. Or le potentiel inflammatoire de ces matériaux est bien documenté. Les inhibiteurs de phosphodiestérase de type 4, parmi lesquels des molécules à motif pyridazinone, ont d’ores et déjà fait leurs preuves en tant qu’agents anti-cancéreux et anti-inflammatoires dans un certain nombre de modèles cellulaires. L’objectif de ce travail a été d’évaluer les effets anti-cancéreux et anti-inflammatoires de nouvelles molécules à motif pyridazinone dérivant de précurseurs agrosourcées. Les effets anti-inflammatoires ont été validés sur la production cytokinique, le potentiel migratoire et le maintien des capacités phagocytaires des neutrophiles primaires humains in vitro et dans un modèle murin d’inflammation in vivo. Ces molécules ont également montré leur potentiel thérapeutique dans des modèles d’ostéosarcomes in vitro où elles sont en capacité de bloquer la prolifération et la migration cellulaire tout en induisant l’apoptose des cellules cancéreuses. In vivo ces molécules sont capables de ralentir la progression tumorale et de maintenir la qualité minérale osseuse. Les résultats obtenus indiquent que ces nouvelles molécules à motif pyridazinone pourraient s’intégrer dans des polythérapies pour leurs potentiels thérapeutiques à la fois anti-cancéreux et anti-inflammatoire.