Platelet-rich fibrin combined with new bone graft material for mandibular defect repair: A in vivo study on rabbits

Insufficient bone mass is still a difficult point to be solved in oral implantation, so new bone graft materials are continuously researched and discussed in clinical practice in order to obtain better bone augmentation. In order to explore whether platelet-rich fibrin (PRF) can promote the formation of new bone in mineralized collagen (MC), MC/PRF and pure MC were implanted into the bilateral mandibular defect model in rabbits, respectively. Micro-CT scan and histological evaluation of the target area at 4, 8, and 12 weeks after operation. The results of Micro-CT three-dimensional reconstruction analysis showed that the ratio of bone volume to total volume (BV/TV), trabecular bone number (Tb.N), trabecular bone thickness (Tb.Th) and trabecular bone separation (Tb.Sp) and residual material volume fraction (RMVF) in the MC/PRF group were better than those in the MC group (p<0.05). The results of HE and Masson staining showed that the new bone formation and material degradation rate of the MC/PRF group were better than those of the MC group. The results suggest that PRF can accelerate the formation of new bone in MC, and provide new ideas for the clinical application of new bone graft materials.

Application of medical imaging methods and artificial intelligence in tissue engineering and organ-on-a-chip

Organ-on-a-chip (OOC) is a new type of biochip technology. Various types of OOC systems have been developed rapidly in the past decade and found important applications in drug screening and precision medicine. However, due to the complexity in the structure of both the chip-body itself and the engineered-tissue inside, the imaging and analysis of OOC have still been a big challenge for biomedical researchers. Considering that medical imaging is moving towards higher spatial and temporal resolution and has more applications in tissue engineering, this paper aims to review medical imaging methods, including CT, micro-CT, MRI, small animal MRI, and OCT, and introduces the application of 3D printing in tissue engineering and OOC in which medical imaging plays an important role. The achievements of medical imaging assisted tissue engineering are reviewed, and the potential applications of medical imaging in organoids and OOC are discussed. Moreover, artificial intelligence - especially deep learning - has demonstrated its excellence in the analysis of medical imaging; we will also present the application of artificial intelligence in the image analysis of 3D tissues, especially for organoids developed in novel OOC systems.

Computed Tomography as a Characterization Tool for Engineered Scaffolds with Biomedical Applications

The ever-growing field of materials with applications in the biomedical field holds great promise regarding the design and fabrication of devices with specific characteristics, especially scaffolds with personalized geometry and architecture. The continuous technological development pushes the limits of innovation in obtaining adequate scaffolds and establishing their characteristics and performance. To this end, computed tomography (CT) proved to be a reliable, nondestructive, high-performance machine, enabling visualization and structure analysis at submicronic resolutions. CT allows both qualitative and quantitative data of the 3D model, offering an overall image of its specific architectural features and reliable numerical data for rigorous analyses. The precise engineering of scaffolds consists in the fabrication of objects with well-defined morphometric parameters (e.g., shape, porosity, wall thickness) and in their performance validation through thorough control over their behavior (in situ visualization, degradation, new tissue formation, wear, etc.). This review is focused on the use of CT in biomaterial science with the aim of qualitatively and quantitatively assessing the scaffolds’ features and monitoring their behavior following in vivo or in vitro experiments. Furthermore, the paper presents the benefits and limitations regarding the employment of this technique when engineering materials with applications in the biomedical field.

Micro-Computed Tomography Analysis on Administration of Mesenchymal Stem Cells - Bovine Teeth Scaffold Composites for Alveolar Bone Tissue Engineering

The tissue engineering approach for periodontal tissue regeneration using a combination of stem cells and scaffold has been vastly developed. Mesenchymal Stem Cells (MSCs) seeded with Bovine Teeth Scaffold (BTSc) can repair alveolar bone damage in periodontitis cases. The alveolar bone regeneration process was analyzed by micro-computed tomography (µ-CT) to observe the structure of bone growth and to visualize the scaffold in 3-Dimensional (3D). The purpose of this study is to analyze alveolar bone regeneration by µ-CT following the combination of MSCs and bovine teeth scaffold (MSCs-BTSc) implantation in the Wistar rat periodontitis model. Methods. MSCs were cultured from adipose-derived mesenchymal stem cells of rats. BTSc was taken from bovine teeth and freeze-dried with a particle size of 150-355 µm. MSCs were seeded on BTSc for 24 hours and transplanted in a rat model of periodontitis. Thirty-five Wistar rats were made as periodontitis models with LPS induction from P. gingivalis injected to the buccal section of interproximal gingiva between the first and the second mandibular right-molar teeth for six weeks. There were seven groups (control group, BTSc group on day 7, BTSc group on day 14, BTSc group on day 28, MSCs-BTSc group on day 7, MSCs-BTSc group on day 14, MSCs-BTSc group on day 28). The mandibular alveolar bone was analyzed and visualized in 3D with µ-CT to observe any new bone growth. Statistical Analysis. Group data were subjected to the Kruskal Wallis test followed by the Mann-Whitney (p <0.05). The µ-CT qualitative analysis shows a fibrous structure, which indicates the existence of new bone regeneration. Quantitative analysis of the periodontitis model showed a significant difference between the control model and the model with the alveolar bone resorption (p <0.05). The bone volume and density measurements revealed that the MSCs-BTSc group on day 28 formed new bone compared to other groups (p <0.05). Administration of MSCs-BTSc combination has the potential to form new alveolar bone.

Bone Regeneration Using PEVAV/β-Tricalcium Phosphate Composite Scaffolds in Standardized Calvarial Defects: Micro-Computed Tomographic Experiment in Rats

Bone regeneration using beta-tricalcium phosphate (β-TCP) can be practiced using a biocomposite scaffold. Poly(ethylene-co-vinylalcohol)/poly(δ-valerolactone)/β-tricalcium phosphate (PEVAV/β-TCP) composite scaffolds showed promising in vitro results. This study evaluated the bone regenerative potential of PEVAV/β-TCP biocomposite scaffolds in standardized calvarial defects in a rat model over 4 and 10 weeks. Bilateral calvarial defects (5 mm in diameter and about 1.5 mm thick, equivalent to the thickness of the calvaria) were created in 40 male Wistar albino rats. The defects were grafted with either commercially available β-TCP (positive control), PEVAV/β-TCP 70, or PEVAV/β-TCP 50, or left empty (negative control), depending on the group to which the animal was randomly assigned, to be covered before flap closure with resorbable collagen membrane (RCM). At 4 and 10 weeks post-surgery, the collected rat calvaria were evaluated using micro computed tomography (micro-CT) analysis, to assess the newly formed bone volume (NFBV), newly formed bone mineral density (NFBMD), and remaining graft volume (RGV). The results showed that calvarial defects grafted with the PEVAV/β-TCP biocomposite exhibited higher NFBV than did control defects, both at 4 and 10 weeks post-surgery. Furthermore, calvarial defects grafted with PEVAV/β-TCP 70 showed the highest NFBV among all grafting conditions, with a statistically significant difference recorded at 10 weeks post-surgery. The PEVAV/β-TCP composite scaffold showed potentiality for the regeneration of critical-sized calvarial bone defects in a rat model.

Electrospun vascular grafts fabricated from poly(L-lactide-co-ε-caprolactone) used as a bypass for the rabbit carotid artery

The study involved the electrospinning of the copolymer poly(L-lactide-co-ε-caprolactone) (PLCL) into tubular grafts. The subsequent material characterization, including micro-computed tomography analysis, revealed a level of porosity of around 70%, with pore sizes of 9.34 ± 0.19 μm and fiber diameters of 5.58 ± 0.10 μm. Unlike fibrous polycaprolactone, the electrospun PLCL copolymer promoted fibroblast and endothelial cell adhesion and proliferation in vitro. Moreover, the regeneration of the vessel wall was detected following implantation and, after six months, the endothelialization of the lumen and the infiltration of arranged smooth muscle cells producing collagen was observed. However, the degradation rate was found to be accelerated in the rabbit animal model. The study was conducted under conditions that reflected the clinical requirements-the prostheses were sutured in the end-to-side fashion and the long-term end point of prosthesis healing was assessed. The regeneration of the vessel wall in terms of endothelialization, smooth cell infiltration and the presence of collagen fibers was observed after six months in vivo. A part of the grafts failed due to the rapid degradation rate of the PLCL copolymer.

Note on the use of different approaches to determine the pore sizes of tissue engineering scaffolds: what do we measure?

Background

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).

Methods

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).

Results

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.

Conclusion

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.

Electronic supplementary material

The online version of this article (10.1186/s12938-018-0543-z) contains supplementary material, which is available to authorized users.