An in vitro bone triple culture involving human primary osteoblasts, osteocytes and osteoclasts enables the investigation of bone healing factors, drugs or biomaterials in a model system for native ...bone tissue. The present study analyses the impact of Sr2+ as well as hypoxic cultivation (5% O2 content or chemically induced by Co2+) on bone cells. The three cell types were cultivated together in the presence of 100 µM Sr2+, hypoxic conditions or in the presence of 75 µM Co2+. After cultivation the cell types were separated and analysed on mRNA and protein level individually. In response to Sr2+ osteoblasts showed a downregulation of IBSP expression and a stimulation of ALP activity. Osteocyte gene marker expression of PDPN, MEPE, RANKL, OPG, osteocalcin and likewise the amount of secreted osteocalcin was reduced in the presence of Sr2+. Activity of osteoclast-specific enzymes TRAP and CAII was enhanced compared to the Sr2+ free control. Hypoxic conditions induced by both 5% O2 or a Co2+ treatment led to decreased DNA content of all bone cells and downregulated expression of osteoblast markers ALPL and IBSP as well as osteocyte markers PDPN, RANKL and OPG. In addition, Co2+ induced hypoxia decreased gene and protein expression of osteocalcin in osteocytes. In response to the Co2+ treatment, the TRAP gene expression and activity was increased. This study is the first to analyse the effects of Sr2+ or hypoxia on triple cultures with primary human bone cells. The investigated in vitro bone model might be suitable to reduce animal experiments in early stages of biomaterial and drug development.
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•Triple culture of human primary osteoblasts, osteoclasts and osteocytes.•Impact of Sr2+ on all the three cell species.•Comparison of hypoxia and chemically induced hypoxia (Co2+).•In vitro bone model, suitable for the investigation of various bioactive effectors.
Bioactive glasses have been used for bone regeneration applications thanks to their excellent osteoconductivity, an osteostimulatory effect, and high degradation rate, releasing biologically active ...ions. Besides these properties, mesoporous bioactive glasses (MBG) are specific for their highly ordered mesoporous channel structure and high specific surface area, making them suitable for drug and growth factor delivery. In the present study, calcium (Ca) (15 mol%) in MBG was partially and fully substituted with zinc (Zn), known for its osteogenic and antimicrobial properties. Different MBG were synthesized, containing 0, 5, 10, or 15 mol% of Zn. Up to 7 wt.% of Zn-containing MBG could be mixed into an alginate-methylcellulose blend (algMC) while maintaining rheological properties suitable for 3D printing of scaffolds with sufficient shape fidelity. The suitability of these composites for bioprinting applications has been demonstrated with immortalized human mesenchymal stem cells. Uptake of Ca and phosphorus (P) (phosphate) ions by composite scaffolds was observed, while the released concentration of Zn
corresponded to the initial amount of this ion in prepared glasses, suggesting that it can be controlled at the MBG synthesis step. The study introduces a tailorable bioprintable material system suitable for bone tissue engineering applications.
Geomorphic footprints of past large Himalayan earthquakes are elusive, although they are urgently needed for gauging and predicting recovery times of seismically perturbed mountain landscapes. We ...present evidence of catastrophic valley infill following at least three medieval earthquakes in the Nepal Himalaya. Radiocarbon dates from peat beds, plant macrofossils, and humic silts in fine-grained tributary sediments near Pokhara, Nepal's second-largest city, match the timing of nearby M > 8 earthquakes in ~1100, 1255, and 1344 C.E. The upstream dip of tributary valley fills and x-ray fluorescence spectrometry of their provenance rule out local sources. Instead, geomorphic and sedimentary evidence is consistent with catastrophic fluvial aggradation and debris flows that had plugged several tributaries with tens of meters of calcareous sediment from a Higher Himalayan source >60 kilometers away.
Sediment archives in the terrestrial and marine realm are regularly analyzed to infer changes in climate, tectonic, or anthropogenic boundary conditions of the past. However, contradictory ...observations have been made regarding whether short period events are faithfully preserved in stratigraphic archives; for instance, in marine sediments offshore large river systems. On the one hand, short period events are hypothesized to be non-detectable in the signature of terrestrially derived sediments due to buffering during sediment transport along large river systems. On the other hand, several studies have detected signals of short period events in marine records offshore large river systems. We propose that this apparent discrepancy is related to the lack of a differentiation between different types of signals and the lack of distinction between river response times and signal propagation times. In this review, we (1) expand the definition of the term ‘signal’ and group signals in sub-categories related to hydraulic grain size characteristics, (2) clarify the different types of ‘times’ and suggest a precise and consistent terminology for future use, and (3) compile and discuss factors influencing the times of signal transfer along sediment routing systems and how those times vary with hydraulic grain size characteristics. Unraveling different types of signals and distinctive time periods related to signal propagation addresses the discrepancies mentioned above and allows a more comprehensive exploration of event preservation in stratigraphy – a prerequisite for reliable environmental reconstructions from terrestrially derived sedimentary records.
The efficiency of sediment routing from land to the ocean depends on the position of submarine canyon heads with regard to terrestrial sediment sources. We aim to identify the main controls on ...whether a submarine canyon head remains connected to terrestrial sediment input during Holocene sea‐level rise. Globally, we identified 798 canyon heads that are currently located at the 120m‐depth contour (the Last Glacial Maximum shoreline) and 183 canyon heads that are connected to the shore (within a distance of 6 km) during the present‐day highstand. Regional hotspots of shore‐connected canyons are the Mediterranean active margin and the Pacific coast of Central and South America. We used 34 terrestrial and marine predictor variables to predict shore‐connected canyon occurrence using Bayesian regression. Our analysis shows that steep and narrow shelves facilitate canyon‐head connectivity to the shore. Moreover, shore‐connected canyons occur preferentially along active margins characterized by resistant bedrock and high river‐water discharge.
Plain Language Summary
Since the last glaciation about 20,000 years ago, sea level has risen by about 120 m. As a consequence, most coastlines have migrated landward, inundating large shelf areas. Some of these areas are now dissected by submarine canyons. However, with only 4% of the world’s submarine canyons reaching today's coastline, these canyons remain the exception. Here, we aim to identify the environmental factors and processes that control whether rates of headward canyon incision can keep pace with landward migration of the coastline during the Holocene. We determine 34 variables that potentially predict whether a canyon remains connected to the coastline. We find that shore‐connected canyons preferentially occur along continental margins with narrow and steep shelves, such as the Mediterranean active margin and the Pacific coast of Central and South America. Moreover, our analysis supports the occurrence of such canyons offshore river basins, that are characterized by resistant bedrock and high water discharge. Such rivers deliver coarse‐grained sediment to submarine canyons, which can erode the canyon head and floor. To this end, our analysis offers new insights into the formation and maintenance of submarine canyons that are required to efficiently transport sediments, pollutants, and organic carbon from rivers to the ocean floor.
Key Points
Presently, 183 submarine canyons are connected to the shoreline (within 6 km) along the world’s major continents
Narrow shelves and high shelf gradients precondition the maintenance of canyon‐head connectivity to the shore
Canyon heads preferentially remain connected to the shore offshore river catchments with resistant bedrock and high water discharge
Two novel scaffold models made of chitosan fibers were designed, fabricated, and investigated. Raw chitosan fibers were either tightened between plastic rings or were processed into stand-alone ...scaffolds. Chitosan fiber scaffolds were further modified by coating with a thin layer of fibrillar collagen type I to biologize the surface. Cell culture experiments were carried out using murine osteoblast-like cells (7F2). Confocal laser scanning microscopy (cLSM) as well as scanning electron microscopy (SEM) revealed fast attachment and morphological adaptation of the cells on both the raw chitosan fibers and the collagen-coated scaffolds. Cells were cultivated for up to 4 weeks on the materials and proliferation as well as osteogenic differentiation was quantitatively analyzed in terms of lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) activity. We found a 14−16-fold increase of cell number and the typical pattern of ALP activity, whereas the collagen coating does not remarkably influence these parameters. The maintenance of osteogenic phenotype on the novel materials was furthermore confirmed by immunostaining of osteocalcin and study of matrix mineralization. The feature of the collagen-coated but also the raw chitosan fiber scaffolds to support the attachment, proliferation, and differentiation of osteoblast-like cells suggest a potential application of chitosan fibers and textile chitosan scaffolds for the tissue engineering of bone.
The present study analyzes the capacity of collagen (coll)/sulfated glycosaminoglycan (sGAG)-based surface coatings containing bioactive glass nanoparticles (BGN) in promoting the osteogenic ...differentiation of human mesenchymal stroma cells (hMSC). Physicochemical characteristics of these coatings and their effects on proliferation and osteogenic differentiation of hMSC were investigated. BGN were stably incorporated into the artificial extracellular matrices (aECM). Oscillatory rheology showed predominantly elastic, gel-like properties of the coatings. The complex viscosity increased depending on the GAG component and was further elevated by adding BGN. BGN-containing aECM showed a release of silicon ions as well as an uptake of calcium ions. hMSC were able to proliferate on coll and coll/sGAG coatings, while cellular growth was delayed on aECM containing BGN. However, a stimulating effect of BGN on ALP activity and calcium deposition was shown. Furthermore, a synergistic effect of sGAG and BGN was found for some donors. Our findings demonstrated the promising potential of aECM and BGN combinations in promoting bone regeneration. Still, future work is required to further optimize the BGN/aECM combination for increasing its combined osteogenic effect.
Bone remodelling, important for homeostasis and regeneration involves the controlled action of osteoblasts, osteocytes and osteoclasts. The present study established a three-dimensional human in ...vitro bone model as triple culture with simultaneously differentiating osteocytes and osteoclasts, in the presence of osteoblasts. Since high sulfated hyaluronan (sHA3) was reported as a biomaterial to enhance osteogenesis as well as to dampen osteoclastogenesis, the triple culture was exposed to sHA3 to investigate cellular responses compared to the respective bone cell monocultures. Osteoclast formation and marker expression was stimulated by sHA3 only in triple culture. Osteoprotegerin (OPG) gene expression and protein secretion, but not receptor activator of NF-κB ligand (RANKL) or sclerostin (SOST), were strongly enhanced, suggesting an important role of sHA3 itself in osteoclastogenesis with other targets than indirect modulation of the RANKL/OPG ratio. Furthermore, sHA3 upregulated osteocalcin (BGLAP) in osteocytes and osteoblasts in triple culture, while alkaline phosphatase (ALP) was downregulated.
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•Expression of OCy-markers (MEPE, SOST, DMP1) is upregulated by BMP-2.•OCy and OC can be differentiated simultaneously in triple culture with OBs.•sHA3 stimulates OC-formation in triple culture but not in monoculture.•TRAP activity of OC is enhanced by sHA3, whereas resorption is inhibited.•BGLAP is upregulated in response to sHA3, whereas ALP is downregulated.
Can the individuality of self‐build and the orderliness of planned urbanism come together, while ensuring future adaptability? Cologne‐based practice BeL Sozietät für Architektur have been ...investigating through NEUBAU – affordable development initiatives for urban peripheries. From an initial hybrid of multistorey housing and self‐build erected for a major exhibition, to broader proposals for the outskirts of Hamburg, Leipzig, Düsseldorf and Munich, NEUBAU involves a co‐productive process between architects, planners and users that can reduce costs and help build communities – as BeL cofounders
Anne‐Julchen Bernhardt and Jörg Leeser
explain.
Due to affordability, and the ability to parametrically control the vital processing parameters, material extrusion is a widely accepted technology in tissue engineering. Material extrusion offers ...sufficient control over pore size, geometry, and spatial distribution, and can also yield different levels of in-process crystallinity in the resulting matrix. In this study, an empirical model based on four process parameters-extruder temperature, extrusion speed, layer thickness, and build plate temperature-was used to control the level of in-process crystallinity of polylactic acid (PLA) scaffolds. Two sets of scaffolds were fabricated, with low- and high-crystallinity content, and subsequently seeded with human mesenchymal stromal cells (hMSC). The biochemical activity of hMSC cells was tested by examining the DNA content, lactate dehydrogenase (LDH) activity, and alkaline phosphatase (ALP) tests. The results of this 21-day in vitro experiment showed that high level crystallinity scaffolds performed significantly better in terms of cell response. Follow-up tests revealed that the two types of scaffolds were equivalent in terms of hydrophobicity, and module of elasticity. However, detailed examination of their micro- and nanosurface topographic features revealed that the higher crystallinity scaffolds featured pronounced nonuniformity and a larger number of summits per sampling area, which was the main contributor to a significantly better cell response.
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