The primary objective of Tissue engineering is a regeneration or replacement of tissues or organs damaged by disease, injury, or congenital anomalies. At present, Tissue engineering repairs damaged tissues and organs with artificial supporting structures called scaffolds. These are used for attachment and subsequent growth of appropriate cells. During the cell growth gradual biodegradation of the scaffold occurs and the final product is a new tissue with the desired shape and properties. In recent years, research workplaces are focused on developing scaffold by bio-fabrication techniques to achieve fast, precise and cheap automatic manufacturing of these structures. Most promising techniques seem to be Rapid prototyping due to its high level of precision and controlling. However, this technique is still to solve various issues before it is easily used for scaffold fabrication. In this article we tested printing of clinically applicable scaffolds with use of commercially available devices and materials. Research presented in this article is in general focused on “scaffolding” on a field of bone tissue replacement. Commercially available 3D printer and Polylactic acid were used to create originally designed and possibly suitable scaffold structures for bone tissue engineering. We tested printing of scaffolds with different geometrical structures. Based on the osteosarcoma cells proliferation experiment and mechanical testing of designed scaffold samples, it will be stated that it is likely not necessary to keep the recommended porosity of the scaffold for bone tissue replacement at about 90%, and it will also be clarified why this fact eliminates mechanical properties issue. Moreover, it is demonstrated that the size of an individual pore could be double the size of the recommended range between 0.2–0.35 mm without affecting the cell proliferation. Rapid prototyping technique based on Fused deposition modelling was used for the fabrication of designed scaffold structures. All the experiments were performed in order to show how to possibly solve certain limitations and issues that are currently reported by research workplaces on the field of scaffold bio-fabrication. These results should provide new valuable knowledge for further research.

Collagen-based scaffolds provide a promising option for the treatment of bone defects. One of the key parameters of such scaffolds consists of porosity, including pore size. However, to date, no agreement has been found with respect to the methodology for pore size evaluation. Since the determination of the exact pore size value is not possible, the comparison of the various methods applied is complicated. Hence, this study focuses on the comparison of two widely-used methods for the characterization of porosity—scanning electron microscopy (SEM) and micro-computed tomography (micro-CT). 7 types of collagen-based composite scaffold models were prepared by means of lyophilization and collagen cross-linking. Micro-CT analysis was performed in 3D and in 2D (pore size parameters were: major diameter, mean thickness, biggest inner circle diameter and area-equivalent circle diameter). Afterwards, pore sizes were analyzed in the same specimens by an image analysis of SEM microphotographs. The results were statistically evaluated. The comparison of the various approaches to the evaluation of pore size was based on coefficients of variance and the semi-quantitative assessment of selected qualities (e.g. the potential for direct 3D analysis, whole specimen analysis, non-destructivity). The pore size values differed significantly with respect to the parameters applied. Median values of pore size values were ranging from 20 to 490 µm. The SEM values were approximately 3 times higher than micro-CT 3D values for each specimen. The Mean thickness was the most advantageous micro-CT 2D approach. Coefficient of variance revealed no differences among pore size parameters (except major diameter). The semi-quantitative comparison approach presented pore size parameters in descending order with regard to the advantages thereof as follows: (1) micro-CT 3D, (2) mean thickness and SEM, (3) biggest inner circle diameter, major diameter and area equivalent circle diameter. The results indicated that micro-CT 3D evaluation provides the most beneficial overall approach. Micro-CT 2D analysis (mean thickness) is advantageous in terms of its time efficacy. SEM is still considered as gold standard for its widespread use and high resolution. However, exact comparison of pore size analysis in scaffold materials remains a challenge.

Significance: The sympathetic nervous system plays a critical role in stimulating heart rate and contractility to increase cardiac output and thereby insure adequate tissue O ₂ delivery. Altered sympathetic output contributes to cardiac pathologies, such as sudden cardiac death and heart failure. Our data provide insight into the role of the transcription factor hypoxia-inducible factor 1α (HIF-1α) in the development of sympathetic ganglion neurons and cardiac sympathetic innervation. We found that genetic deletion of HIF-1α resulted in increased cell death and decreased proliferation of neuronal progenitors of the sympathetic system. These findings suggest that dysregulated HIF-1α expression may contribute to cardiac dysfunction and disease associated with defects in the cardiac sympathetic system by affecting the function and survival of sympathetic neurons.

Introduction: A standard osteosynthetic material for maxillofacial skeleton is titanium and its alloys. The convenience of degradable material is avoiding of second surgery in cases, where removal of the material is necessary. Magnesium biodegradable alloys have similar mechanic properties as cortical bone – reasonable corrosion and sufficient biologic properties. They might be used in facial skeleton fixation. Materials and methods: The study included a total of 16 rabbits, and they were randomly divided into two groups. Each group received two screws (WE4 and titanium as a standard material) in artificially drilled defect into right tibia. Animals were euthanized at four-week intervals. Bone samples with implants underwent microfocus CT scans and were histologically examined. Results: WE43 alloys showed fragmentation of the material on the 16th week – statistically significant volume loss was found between weeks 12 and 16. Bone healing around the WE43 screws was of similar quality as around titanium screws, and no adverse effect was noticed. Conclusion: The study showed good quality of bone healing around WE43 implants. From this point of view, the WE43 alloy meets the requirements of osteosynthetic material for maxillofacial skeleton.