The effect of osteocyte-derived RANKL on bone graft remodeling: An in vivo experimental study.

OBJECTIVES Autologous bone is considered the gold standard for grafting, yet it suffers from a tendency to undergo resorption over time. While the exact mechanisms of this resorption remain elusive, osteocytes have been shown to play an important role in stimulating osteoclastic activity through their expression of receptor activator of NF-κB (RANK) ligand (RANKL). The aim of this study was to assess the function of osteocyte-derived RANKL in bone graft remodeling. MATERIALS AND METHODS In Tnfsf11fl/fl ;Dmp1-Cre mice without osteocyte-specific RANKL as well as in Dmp1-Cre control mice, 2.6 mm calvarial bone disks were harvested and transplanted into mice with matching genetic backgrounds either subcutaneously or subperiosteally, creating 4 groups in total. Histology and micro-computed tomography of the grafts and the donor regions were performed 28 days after grafting. RESULTS Histology revealed marked resorption of subcutaneous control Dmp1-Cre grafts and new bone formation around subperiosteal Dmp1-Cre grafts. In contrast, Tnfsf11fl/fl ;Dmp1-Cre grafts showed effectively neither signs of bone resorption nor formation. Quantitative micro-computed tomography revealed a significant difference in residual graft area between subcutaneous and subperiosteal Dmp1-Cre grafts (p < .01). This difference was not observed between subcutaneous and subperiosteal Tnfsf11fl/fl ;Dmp1-Cre grafts (p = .17). Residual graft volume (p = .08) and thickness (p = .13) did not differ significantly among the groups. Donor area regeneration was comparable between Tnfsf11fl/fl ;Dmp1-Cre and Dmp1-Cre mice and restricted to the defect margins. CONCLUSIONS The results suggest an active function of osteocyte-derived RANKL in bone graft remodeling

Regeneration of alveolar bone defects in the experimental pig model: A systematic review and meta-analysis.

OBJECTIVE Pigs are emerging as a preferred experimental in vivo model for bone regeneration. The study objective was to answer the focused PEO question: in the pig model (P), what is the capacity of experimental alveolar bone defects (E) for spontaneous regeneration in terms of new bone formation (O)? METHODS Following PRISMA guidelines, electronic databases were searched for studies reporting experimental bone defects or extraction socket healing in the maxillae or mandibles of pigs. The main inclusion criteria were the presence of a control group of untreated defects/sockets and the assessment of regeneration via 3D tomography [radiographic defect fill (RDF)] or 2D histomorphometry [new bone formation (NBF)]. Random effects meta-analyses were performed for the outcomes RDF and NBF. RESULTS Overall, 45 studies were included reporting on alveolar bone defects or extraction sockets, most frequently in the mandibles of minipigs. Based on morphology, defects were broadly classified as 'box-defects' (BD) or 'cylinder-defects' (CD) with a wide range of healing times (10 days to 52 weeks). Meta-analyses revealed pooled estimates (with 95% confidence intervals) of 50% RDF (36.87%-63.15%) and 43.74% NBF (30.47%-57%) in BD, and 44% RDF (16.48%-71.61%) and 39.67% NBF (31.53%-47.81%) in CD, which were similar to estimates of socket-healing [48.74% RDF (40.35%-57.13%) and 38.73% NBF (28.57%-48.89%)]. Heterogeneity in the meta-analysis was high (I2  > 90%). CONCLUSION A substantial body of literature revealed a high capacity for spontaneous regeneration in experimental alveolar bone defects of (mini)pigs, which should be considered in future studies of bone regeneration in this animal model

The use of mesenchymal stromal cell secretome to enhance guided bone regeneration in comparison with leukocyte and platelet-rich fibrin.

OBJECTIVES Secretomes of mesenchymal stromal cells (MSC) represent a novel strategy for growth-factor delivery for tissue regeneration. The objective of this study was to compare the efficacy of adjunctive use of conditioned media of bone-marrow MSC (MSC-CM) with collagen barrier membranes vs. adjunctive use of conditioned media of leukocyte- and platelet-rich fibrin (PRF-CM), a current growth-factor therapy, for guided bone regeneration (GBR). METHODS MSC-CM and PRF-CM prepared from healthy human donors were subjected to proteomic analysis using mass spectrometry and multiplex immunoassay. Collagen membranes functionalized with MSC-CM or PRF-CM were applied on critical-size rat calvaria defects and new bone formation was assessed via three-dimensional (3D) micro-CT analysis of total defect volume (2 and 4 weeks) and 2D histomorphometric analysis of central defect regions (4 weeks). RESULTS While both MSC-CM and PRF-CM revealed several bone-related proteins, differentially expressed proteins, especially extracellular matrix components, were increased in MSC-CM. In rat calvaria defects, micro-CT revealed greater total bone coverage in the MSC-CM group after 2 and 4 weeks. Histologically, both groups showed a combination of regular new bone and 'hybrid' new bone, which was formed within the membrane compartment and characterized by incorporation of mineralized collagen fibers. Histomorphometry in central defect sections revealed greater hybrid bone area in the MSC-CM group, while the total new bone area was similar between groups. CONCLUSION Based on the in vitro and in vivo investigations herein, functionalization of membranes with MSC-CM represents a promising strategy to enhance GBR

Impact of a Static Magnetic Field on Early Osseointegration: A Pilot Study in Canines.

A static magnetic field generated by neodymium-iron-boron (NdFeB) magnets placed in the inner cavity of dental implants can enhance bone regeneration in rabbits. It is, however, unknown whether static magnetic fields support osseointegration in a canine model. We therefore determined the potential osteogenic effect of implants carrying NdFeB magnets inserted in the tibia of six adult canines in the early stages of osseointegration. Here, we report that after 15 days of healing, magnetic and regular implants showed a high variation with a median new bone-to-implant contact (nBIC) in the cortical (41.3% and 7.3%) and the medullary (28.6% and 44.8%) region, respectively. Consistently, the median new bone volume/tissue volume (nBV/TV) in the cortical (14.9% and 5.4%) and the medullary (22.2% and 22.4%) region were not significantly different. One week of healing only resulted in negligible bone formation. These findings suggest that considering the large variation and the pilot nature of this study, magnetic implants failed to support peri-implant bone formation in a canine model

Regeneration of segmental defects in metatarsus of sheep with vascularized and customized 3D-printed calcium phosphate scaffolds

Although autografts are considered to be the gold standard treatment for reconstruction of large bone defects resulting from trauma or diseases, donor site morbidity and limited availability restrict their use. Successful bone repair also depends on sufficient vascularization and to address this challenge, novel strategies focus on the development of vascularized biomaterial scaffolds. This pilot study aimed to investigate the feasibility of regenerating large bone defects in sheep using 3D-printed customized calcium phosphate scaffolds with or without surgical vascularization. Pre-operative computed tomography scans were performed to visualize the metatarsus and vasculature and to fabricate customized scaffolds and surgical guides by 3D printing. Critical-sized segmental defects created in the mid-diaphyseal region of the metatarsus were either left empty or treated with the 3D scaffold alone or in combination with an axial vascular pedicle. Bone regeneration was evaluated 1, 2 and 3 months post-implantation. After 3 months, the untreated defect remained non-bridged while the 3D scaffold guided bone regeneration. The presence of the vascular pedicle further enhanced bone formation. Histology confirmed bone growth inside the porous 3D scaffolds with or without vascular pedicle inclusion. Taken together, this pilot study demonstrated the feasibility of precised pre-surgical planning and reconstruction of large bone defects with 3D-printed personalized scaffolds.Peer ReviewedPostprint (published version

Bone regeneration in rat calvarial defects using dissociated or spheroid mesenchymal stromal cells in scaffold-hydrogel constructs

Background Three-dimensional (3D) spheroid culture can promote the osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSC). 3D printing offers the possibility to produce customized scaffolds for complex bone defects. The aim of this study was to compare the potential of human BMSC cultured as 2D monolayers or 3D spheroids encapsulated in constructs of 3D-printed poly-L-lactide-co-trimethylene carbonate scaffolds and modified human platelet lysate hydrogels (PLATMC-HPLG) for bone regeneration. Methods PLATMC-HPLG constructs with 2D or 3D BMSC were assessed for osteogenic differentiation based on gene expression and in vitro mineralization. Subsequently, PLATMC-HPLG constructs with 2D or 3D BMSC were implanted in rat calvarial defects for 12 weeks; cell-free constructs served as controls. Bone regeneration was assessed via in vivo computed tomography (CT), ex vivo micro-CT and histology. Results Osteogenic gene expression was significantly enhanced in 3D versus 2D BMSC prior to, but not after, encapsulation in PLATMC-HPLG constructs. A trend for greater in vitro mineralization was observed in constructs with 3D versus 2D BMSC (p > 0.05). In vivo CT revealed comparable bone formation after 4, 8 and 12 weeks in all groups. After 12 weeks, micro-CT revealed substantial regeneration in 2D BMSC (62.47 ± 19.46%), 3D BMSC (51.01 ± 24.43%) and cell-free PLATMC-HPLG constructs (43.20 ± 30.09%) (p > 0.05). A similar trend was observed in the histological analysis. Conclusion Despite a trend for superior in vitro mineralization, constructs with 3D and 2D BMSC performed similarly in vivo. Regardless of monolayer or spheroid cell culture, PLATMC-HPLG constructs represent promising scaffolds for bone tissue engineering applications.publishedVersio

Functionalizing Collagen Membranes with MSC-Conditioned Media Promotes Guided Bone Regeneration in Rat Calvarial Defects.

Functionalizing biomaterials with conditioned media (CM) from mesenchymal stromal cells (MSC) is a promising strategy for enhancing the outcomes of guided bone regeneration (GBR). This study aimed to evaluate the bone regenerative potential of collagen membranes (MEM) functionalized with CM from human bone marrow MSC (MEM-CM) in critical size rat calvarial defects. MEM-CM prepared via soaking (CM-SOAK) or soaking followed by lyophilization (CM-LYO) were applied to critical size rat calvarial defects. Control treatments included native MEM, MEM with rat MSC (CEL) and no treatment. New bone formation was analyzed via micro-CT (2 and 4 weeks) and histology (4 weeks). Greater radiographic new bone formation occurred at 2 weeks in the CM-LYO group vs. all other groups. After 4 weeks, only the CM-LYO group was superior to the untreated control group, whereas the CM-SOAK, CEL and native MEM groups were similar. Histologically, the regenerated tissues showed a combination of regular new bone and hybrid new bone, which formed within the membrane compartment and was characterized by the incorporation of mineralized MEM fibers. Areas of new bone formation and MEM mineralization were greatest in the CM-LYO group. Proteomic analysis of lyophilized CM revealed the enrichment of several proteins and biological processes related to bone formation. In summary, lyophilized MEM-CM enhanced new bone formation in rat calvarial defects, thus representing a novel 'off-the-shelf' strategy for GBR

Preclinical biological and physicochemical evaluation of two-photon engineered 3D biomimetic copolymer scaffolds for bone healing

A major challenge in orthopedics is the repair of large non-union bone fractures. A promising therapy for this indication is the use of biodegradable bioinspired biomaterials that stabilize the fracture site, relieve pain and initiate bone formation and healing. This study uses a multidisciplinary evaluation strategy to assess immunogenicity, allergenicity, bone responses and physicochemical properties of a novel biomaterial scaffold. Two-photon stereolithography generated personalized custom-built scaffolds with a repeating 3D structure of Schwarz Primitive minimal surface unit cell with a specific pore size of ∼400 μm from three different methacrylated poly(D,L-lactide-co-ε-caprolactone) copolymers with lactide to caprolactone monomer ratios of 16 : 4, 18 : 2 and 9 : 1. Using in vitro and in vivo assays for bone responses, immunological reactions and degradation dynamics, we found that copolymer composition influenced the scaffold physicochemical and biological properties. The scaffolds with the fastest degradation rate correlated with adverse cellular effects and mechanical stiffness correlated with in vitro osteoblast mineralization. The physicochemical properties also correlated with in vivo bone healing and immune responses. Overall these observations provide compelling support for these scaffolds for bone repair and illustrate the effectiveness of a promising multidisciplinary strategy with great potential for the preclinical evaluation of biomaterials

Euthanasie v praxi

In the interplay of critical and self-conscious patients and an ever-aging society the question arises how far patient autonomy sensibly should go and which parameters are deemed to be relevant for end-of-life-decisions. The progress in medicine over the last decades has led on one hand to the possibility of saving lives and maintaining them in situations where before it seemed to be impossible. Nowadays Therefore more and more people are afraid that this boom can be to their detriment when it prolongs instead of shortens their suffering. The fear of unbearable pain and of loss of control fuels the discussion about whether or not euthanasia is morally permissible and should be legalized. This thesis deals with the questions: What speaks in favor of and against the legalization of euthanasia? What forms of treatment are subsumed under the term "euthanasia"? What is the current legal situation in Austria? How far should patient autonomy go? In order to answer these questions a literature research was done which revealed that active euthanasia is not allowed in Austria but in the Netherlands, Belgium, Luxemburg and partly allowed in Switzerland. Interviews conducted among medical staff showed that medical personnel in Austria mostly are in favor of active euthanasia because they are not satisfied with the end of life care that is provided at the moment. They also embrace the trend of patient autonomy and think that patients can have the autonomous wish to end their lives but that it is difficult to determine a patient's autonomy. The reason for this is that autonomy is a gradual value that comprises patients' capacity as well as patients' long-standing goals, values, and preferences that were developed during their life. Therefore it can be concluded that increasing the availability of appropriate end-of-life care could be a solution that prevents medical staff from taking uncomfortable decisions and still enables patients to die in a dignified way

Haftung des Veranstalters bei Sportveranstaltungen in der Natur

Es ist schmutzig und scheint gefährlich. Hunderte Frauen und Männer schreien die verschiedensten Schlachtrufe, sie strecken die Arme nach oben. Entschlossenheit liest man in ihren Gesichtern, einige stecken in Kostümen, andere in ihren besten Sportgewändern oder aber auch nur mit einem Schottenrock bekleidet. Ein lauter Knall der Startschuss - und schon geht es los. Die Menge begibt sich auf den Weg, um Holzwände hochzuklettern, Schlammgräben zu durchwaten, unter Hindernissen durchzukriechen, Wasserfälle zu bezwingen, Seen zu durchschwimmen und viele weitere verschiedene sogenannte Obstacles (Hindernisse) zu meistern. Die Rennen finden sowohl im Winter als auch im Sommer statt, bei jeder Witterung, jedem Wetter. Und Klatsch! Abermals ist eine AthletIn beim Versuch, ein Hindernis zu überwinden, in das Wasser gefallen. Zum Glück nicht verletzt weiter geht es. Je nach Länge des Rennens kommen die TeilnehmerInnen Stunden später meist erschöpft, aber mit einem Lächeln im Gesicht, ins Ziel. Die Anzahl der Obstacle Races steigt jährlich an. Alleine der Veranstalter Tough Mudder organisiert mindestens 70 Rennen im Jahr und bringt rund eine Million Menschen jährlich dazu, sich freiwillig diesen Quälereien auszusetzen und dies weltweit. Auch in Österreich bemühen sich zahlreiche Anbieter dieser Rennen, sich den Markt zu erkämpfen. Das sind die Spartan Race, der Celtic Warrior, der Wienerwaldkraxler, die XCross Challenge, der Hochkönig Cross Warrior, das Predator Race, der Gladiators Run und der Fishermans‘ Friend Strongman Run, um nur ein paar zu erwähnen. Es finden sich zahlreiche Seiten im Internet, welche solche Veranstaltungen sammeln und diverse Informationen dazu vereinen. Ein Beispiel dafür ist die dirtrun.company. ^Nur was passiert, wenn der Sturz von einer über zwei Meter hohen Wand dann doch nicht so glimpflich ausgeht oder gar das Durchschwimmen eines Sees im Krankenhaus endet? Vielleicht wurde beim Anlegen eines Wassergrabens ein großer Stein im Wasser übersehen und führte dadurch zu schlimmen Verletzungen? Wer haftet für etwaige Verletzungen? Ist der/die SportlerIn für sich alleine verantwortlich oder hat auch der/die VeranstalterIn Pflichten? Kann sich der/die VeranstalterIn vertraglich von der Haftung befreien? All diese Fragen und noch weitere sollen im Laufe dieser Arbeit beantwortet werden und sowohl den AthletInnen als auch den SportveranstalterInnen Klarheit verschaffen, wo die Verantwortungen liegen.eingereicht von Ing. Johannes Kampleitner BScUniversität Linz, Masterarbeit, 2019(VLID)436559