Embedding of mammalian cells into hydrogel scaffolds of predesigned architecture by rapid prototyping technologies has been intensively investigated with focus on tissue engineering and organ ...printing. The study demonstrates that such methods can be extended to cells originating from the plant kingdom. By using 3D plotting, microalgae of the species Chlamydomonas reinhardtii were embedded in 3D alginate‐based scaffolds. The algae survived the plotting process and were able to grow within the hydrogel matrix. Under illumination, the cell number increased as indicated by microscopic analyses and determination of the chlorophyll content which increased 16‐fold within 12 days of cultivation. Photosynthetic activity was evidenced by measurement of oxygen release: within the first 24 h, an oxygen production rate of 0.05 mg L−1 h−1 was detected which rapidly increased during further cultivation (0.25 mg L−1 h−1 between 24 and 48 h). Furthermore, multichannel plotting was applied to combine human cells and microalgae within one scaffold in a spatially organized manner and hence, to establish a patterned coculture system in which the algae are cultivated in close vicinity to human cells. This might encourage the development of new therapeutic concepts based on the delivery of oxygen or secondary metabolites as therapeutic agents by microalgae.
Recent studies showed that the non-neuronal cholinergic system (NNCS) is taking part in bone metabolism. Most studies investigated its role in osteoblasts, but up to now, the involvement of the NNCS ...in human osteoclastogenesis remains relatively unclear. Thus, aim of the present study was to determine whether the application of acetylcholine (ACh, 10−4M), nicotine (10−6M), mineralized collagen membranes or brain derived neurotrophic factor (BDNF, 40ng/mL) influences the mRNA regulation of molecular components of the NNCS and the neurotrophin family during osteoclastogenesis.
Peripheral blood mononuclear cells (PBMCs) were isolated from the blood of young healthy donors (n=8) and incubated with bone fragments and osteoclast differentiation media for 21days. All the results are based on the measurement of RNA.
Real-time RT-PCR analysis demonstrated a down-regulation of nicotinic acetylcholine receptor (nAChR) subunit α2 and muscarinic acetylcholine receptor (mAChR) M3 by osteoclastogenesis while BDNF mRNA expression was not regulated. Application of ACh, nicotine, BDNF or collagen membranes did not affect osteoclastic differentiation. No regulation was detected for nAChR subunit α7, tropomyosin-related kinase receptor B (TrkB), and choline acetyltransferase (ChAT).
Taken together, we assume that the transcriptional level of osteoclastogenesis of healthy young humans is not regulated by BDNF, ACh, and nicotine. Thus, these drugs do not seem to worsen bone degradation and might therefore be suitable as modulators of bone substitution materials if having a positive effect on bone formation.
•Application of ACh, nicotine, and BDNF did not alter osteoclastogenesis.•Osteoclast differentiation was not affected by addition of collagen scaffolds.•nAChR subunit α2 and mAChR M3 mRNA was decreased during osteoclastogenesis.•BDNF mRNA expression was not regulated.
Additive manufacturing enables the fabrication of scaffolds with defined architecture. Versatile printing technologies such as extrusion-based 3D plotting allow in addition the incorporation of ...biological components increasing the capability to restore functional tissues. We have recently described the fabrication of calcium phosphate cement (CPC) scaffolds by 3D plotting of an oil-based CPC paste under mild conditions. In the present study, we have developed a strategy for growth factor loading based on multichannel plotting: a biphasic scaffold design was realised combining CPC with VEGF-laden, highly concentrated hydrogel strands. As hydrogel component, alginate and an alginate–gellan gum blend were evaluated; the blend exhibited a more favourable VEGF release profile and was chosen for biphasic scaffold fabrication. After plotting, two-step post-processing was performed for both, hydrogel crosslinking and CPC setting, which was shown to be compatible with both materials. Finally, a scaffold was designed and fabricated which can be applied for testing in a rat critical size femur defect. Optimization of CPC plotting enabled the fabrication of highly resolved structures with strand diameters of only 200
µ
m. Micro-computed tomography revealed a precise strand arrangement and an interconnected pore space within the biphasic scaffold even in swollen state of the hydrogel strands.
Tissue engineering, the application of stem and progenitor cells in combination with an engineered extracellular matrix, is a promising strategy for bone regeneration. However, its success is limited ...by the lack of vascularization after implantation. The concept of in situ tissue engineering envisages the recruitment of cells necessary for tissue regeneration from the host environment foregoing ex vivo cell seeding of the scaffold. In this study, we developed a novel scaffold system for enhanced cell attraction, which is based on biomimetic mineralized collagen scaffolds equipped with a central biopolymer depot loaded with chemotactic agents. In humid milieu, as after implantation, the signaling factors are expected to slowly diffuse out of the central depot forming a gradient that stimulates directed cell migration toward the scaffold center. Heparin, hyaluronic acid, and alginate have been shown to be capable of depot formation. By using vascular endothelial growth factor (VEGF) as model factor, it was demonstrated that the release kinetics can be adjusted by varying the depot composition. While alginate and hyaluronic acid are able to reduce the initial burst and prolong the release of VEGF, the addition of heparin led to a much stronger retention that resulted in an almost linear release over 28 days. The biological activity of released VEGF was proven for all variants using an endothelial cell proliferation assay. Furthermore, migration experiments with endothelial cells revealed a relationship between the degree of VEGF retention and migration distance: cells invaded deepest in scaffolds containing a heparin-based depot indicating that the formation of a steep gradient is crucial for cell attraction. In conclusion, this novel in situ tissue engineering approach, specifically designed to recruit and accommodate endogenous cells upon implantation, appeared highly promising to stimulate cell invasion, which in turn would promote vascularization and finally new bone formation.
Through enabling an efficient supply of cells and tissues in the health sector on demand, cryopreservation is increasingly becoming one of the mainstream technologies in rapid translation and ...commercialization of regenerative medicine research. Cryopreservation of tissue-engineered constructs (TECs) is an emerging trend that requires the development of practically competitive biobanking technologies. In our previous studies, we demonstrated that conventional slow-freezing using dimethyl sulfoxide (Me2SO) does not provide sufficient protection of mesenchymal stromal cells (MSCs) frozen in 3D collagen-hydroxyapatite scaffolds. After simple modifications to a cryopreservation protocol, we report on significantly improved cryopreservation of TECs.
Porous 3D scaffolds were fabricated using freeze-drying of a mineralized collagen suspension and following chemical crosslinking. Amnion-derived MSCs from common marmoset monkey Callithrix jacchus were seeded onto scaffolds in static conditions. Cell-seeded scaffolds were subjected to 24 h pre-treatment with 100 mM sucrose and slow freezing in 10% Me2SO/20% FBS alone or supplemented with 300 mM sucrose. Scaffolds were frozen ‘in air’ and thawed using a two-step procedure. Diverse analytical methods were used for the interpretation of cryopreservation outcome for both cell-seeded and cell-free scaffolds. In both groups, cells exhibited their typical shape and well-preserved cell-cell and cell-matrix contacts after thawing. Moreover, viability test 24 h post-thaw demonstrated that application of sucrose in the cryoprotective solution preserves a significantly greater portion of sucrose-pretreated cells (more than 80%) in comparison to Me2SO alone (60%).
No differences in overall protein structure and porosity of frozen scaffolds were revealed whereas their compressive stress was lower than in the control group. In conclusion, this approach holds promise for the cryopreservation of ‘ready-to-use’ TECs.
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