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Responsible innovation has been introduced as an important condition for advancing the field of regenerative medicine. This is reflected in the frequent references to responsible research conduct and responsible innovation in guidelines and recommendations in academic literature. The meaning of responsibility, how responsibility could be fostered and the context in which responsibilities should be enacted, however, remain unclear. The goal of this paper is to clarify the concept of responsibility in stem cell research and to illustrate how this concept could inform strategies to deal effectively with the ethical implications of stem cell research. Responsibility can be dissected into four categories: responsibility-as-accountability, responsibility-as-liability, responsibility-as-an-obligation and responsibility-as-a-virtue. The authors focus on responsible research conduct and responsible innovation in general to move beyond the scope of research integrity and illustrate that different notions of responsibility have different implications for how stem cell research is organized.

Literature and guidelines mention that responsible innovation could help the field of stem cell research to deal with ethical challenges. However, in this literature and guidelines it does not become clear how 'responsibility' should be understood, how responsibilities are recognized, how responsibilities are shared and how someone could take responsibility. In this article, different types of responsibility are discussed: responsibility-as-accountability, responsibility-as-liability, responsibility-as-an-obligation and responsibility-as-a-virtue. The types are discussed according to how they are different from one another and how they can be used to organize stem cell research. It is shown that these different types of responsibility help not only with research integrity issues but also with societal and other types of ethical challenges.

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OBJECTIVE: Drug delivery platforms that allow for gradual drug release after intra-articular administration have become of much interest as a treatment strategy for osteoarthritis (OA). The aim of this study was to investigate the safety and efficacy of an intra-articular sustained release formulation containing celecoxib (CXB), a cyclooxygenase-2 (COX-2) selective inhibitor. METHODS: Amino acid-based polyesteramide microspheres (PEAMs), a biodegradable and non-toxic platform, were loaded with CXB and employed in two in vivo models of arthritis: an acute inflammatory arthritis model in rats (n = 12), and a randomized controlled study in chronic OA dog patients (n = 30). In parallel, the bioactivity of sustained release of CXB was evaluated in monolayer cultures of primary dog chondrocytes under inflammatory conditions. RESULTS: Sustained release of CXB did not alleviate acute arthritis signs in the rat arthritis model, based on pain measurements and synovitis severity. However, in OA dog patients, sustained release of CXB improved limb function as objective parameter of pain and quality of life based on gait analysis and owner questionnaires. It also decreased pain medication dependency over a 2-month period and caused no adverse effects. Prostaglandin E2 levels, a marker for inflammation, were lower in the synovial fluid of CXB-treated dog OA patients and in CXB-treated cultured dog chondrocytes. CONCLUSION: These results show that local sustained release of CXB is less suitable to treat acute inflammation in arthritic joints, while safe and effective in treating pain in chronic OA in dogs.

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Dental pulp stem cells (DPSCs) are particularly promising for tissue engineering (TE) due to the ease of their isolation procedure, great expansion potential and capability to differentiate towards several cell types of the mesodermal, ectodermal and endodermal lineages. Although several studies hint that DPSCs exhibit potential for cartilage tissue formation, the chondrogenic potential of DPSCs has only been marginally explored. Thus, the aim of the present study was to closely investigate the chondrogenic differentiation capacity of DPSCs for TE applications. More specifically, the potential of DPSCs for engineering hyaline and fibrous cartilage was determined. DPSCs obtained from 7 human molars were expanded and chondrogenically differentiated in a 3D pellet culture model. After 21 d of differentiation with chondrogenic stimuli, DPSCs displayed glycosaminoglycan, aggrecan and limited collagen type II deposition. Cells presented an elongated morphology and produced a collagen-rich extracellular matrix, with a predominance of collagen type I in most of the samples, a characteristic of fibrous cartilage tissue. Variations in the administration periods of several chondro-inductive growth factors, including transforming growth factor beta 3, bone morphogenetic protein-2, -6, -7 and insulin-like growth factor-1, did not increase glycosaminoglycan or collagen type II deposition, typical markers of hyaline cartilage tissue. Furthermore, DPSCs could not be stimulated to go into hypertrophic chondrogenesis. These results indicated that under a large variety of chondro-inductive culture conditions, DPSCs could form fibrocartilaginous tissues but not hyaline cartilage. Thus, DPSCs represent a valuable cell source for the regeneration of fibrocartilage in joints.

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Macrophages play a key role in the foreign body response. In this study it was investigated whether obesity affects the acute response of macrophages to biomaterials in vitro and whether this response is associated with biomarkers in blood. CD14 + monocytes were isolated from blood from obese and age and gender matched lean persons. Monocyte subsets were determined based on CD14 and CD16 on their surface. C-reactive protein (CRP) was measured in peripheral blood. The response of monocyte-derived macrophages to polypropylene (PP), polylactic acid (PLA), polyethylene terephthalate (PET) monofilament, and PET-multifilament (mPET) in culture was based on cytokine production. More IL-6 (for PET), less CCL18 (all materials) and IL-1ra (for PLA) was produced by macrophages from obese patients than lean subjects. Body mass index, serum CRP and to a lesser extend percentages of monocyte subtypes correlated with IL-6, TNFα, CCL18, and IL-1ra production. Taken together, monocyte-derived macrophages of obese patients respond more pro-inflammatory and less anti-inflammatory to biomaterials than macrophages from lean subjects, depending on the material. These results are a step towards personalized medicine for the development of a model or even a blood test to decide which biomaterial might be suitable for each patient.

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OBJECTIVE: Macrophages play a crucial role in the progression of osteoarthritis (OA). Their phenotype may range from pro-inflammatory to anti-inflammatory. The aim of this study was to evaluate the direct effects of macrophage subtypes on cartilage by culturing macrophage conditioned medium (MCM) on human articular cartilage. DESIGN: Human OA cartilage explants were cultured with MCM of pro-inflammatory M(IFNγ+TNFα), or anti-inflammatory M(IL-4) or M(IL-10) human monocyte-derived macrophages. To assess effects of anti-inflammatory macrophages, the cartilage was cultured with a combination of MCM phenotypes as well as pre-stimulated with IFNγ+TNFα cartilage before culture with MCM. The reactions of the explants were assessed by gene expression, nitric oxide (NO) production and release of glycosaminoglycans (GAGs). RESULTS: M(IFNγ+TNFα) MCM affected OA cartilage by upregulation of IL1B (Interleukin 1ß), IL6, MMP13 (Matrix Metalloproteinase-13) and ADAMTS5 (A Disintegrin And Metalloproteinase with Thrombospondin Motifs-5), while inhibiting ACAN (aggrecan) and COL2A1 (collagen type II). M(IL-10) upregulated IL1B and Suppressor of cytokine signaling 1 (SOCS1). NO production and GAG release by the cartilage was increased when cultured with M(IFNγ+TNFα) MCM. M(IL-4) and M(IL-10) did not inhibit the effects of M(IFNγ+TNFα) MCM of neither phenotype affected IFNγ+TNFα pre-stimulated cartilage, in which an inflammatory gene response was deliberately induced. CONCLUSION: M(IFNγ+TNFα) macrophages have a prominent direct effect on OA cartilage, while M(IL-4) and M(IL-10) do not inhibit the effects of M(IFNγ+TNFα), or IFNγ+TNFα induced inflammation of the cartilage. Therapies aiming at inhibiting cartilage degeneration may take this into account by directing suppression of pro-inflammatory macrophages or stimulation of anti-inflammatory macrophages.

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OBJECTIVE: The aims of this study were to modulate inflammation in synovial explants with the compounds: dexamethasone, rapamycin, bone morphogenetic protein 7 (BMP-7) and pravastatin, and to investigate the modulatory capacity of the compounds on specific macrophage phenotypes. DESIGN: Synovial explants from osteoarthritis (OA) patients were treated with 10(-6) M dexamethasone, 100 ng/mL rapamycin, 500 ng/mL BMP-7 or 50 µM pravastatin. Half of the explants were pre-stimulated with IFNγ + TNFα to simulate acute inflammation. Inflammatory state of the synovium was assessed with gene expression analysis. Primary human monocytes were isolated and stimulated towards macrophage phenotypes M(IFNγ + TNFα), M(IL-4) and M(IL-10) with the respective cytokines, followed by treatment with the compounds. RESULTS: Dexamethasone had an anti-inflammatory effect on IFNγ + TNFα stimulated and osteoarthritic synovium, likely due to suppression of pro-inflammatory M(IFNγ + TNFα) macrophages while enhancing anti-inflammatory M(IL4) and M(IL10) macrophages. Rapamycin and BMP-7 further enhanced inflammation in stimulated synovium, but rapamycin did not have a clear effect on non-stimulated synovium. Rapamycin suppressed M(IL-4) and M(IL-10) macrophages without affecting M(IFNγ + TNFα). BMP-7 suppressed M(IFNγ + TNFα) and enhanced M(IL-10) in the macrophage cultures. Pravastatin did not affect synovium, but enhanced M(IL-10). CONCLUSIONS: These data indicate that macrophage phenotype modulation can be used to guide joint inflammation and thereby contribute to the development of new therapies to delay the progression of OA. The varying effects of the compounds on synovium of different degrees of inflammation, indicate that the modulatory capacity of the compounds depends on OA stage and underlines the importance of identifying this stadium for adequate treatment.

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