Epigallocatechin Gallate-Modified Gelatin Sponges Treated by Vacuum Heating as a Novel Scaffold for Bone Tissue Engineering

Chemical modification of gelatin using epigallocatechin gallate (EGCG) promotes bone formation in vivo. However, further improvements are required to increase the mechanical strength and bone-forming ability of fabricated EGCG-modified gelatin sponges (EGCG-GS) for practical applications in regenerative therapy. In the present study, we investigated whether vacuum heating-induced dehydrothermal cross-linking of EGCG-GS enhances bone formation in critical-sized rat calvarial defects. The bone-forming ability of vacuum-heated EGCG-GS (vhEGCG-GS) and other sponges was evaluated by micro-computed tomography and histological staining. The degradation of sponges was assessed using protein assays, and cell morphology and proliferation were verified by scanning electron microscopy and immunostaining using osteoblastic UMR106 cells in vitro. Four weeks after the implantation of sponges, greater bone formation was detected for vhEGCG-GS than for EGCG-GS or vacuum-heated gelatin sponges (dehydrothermal cross-linked sponges without EGCG). In vitro experiments revealed that the relatively low degradability of vhEGCG-GS supports cell attachment, proliferation, and cell-cell communication on the matrix. These findings suggest that vacuum heating enhanced the bone forming ability of EGCG-GS, possibly via the dehydrothermal cross-linking of EGCG-GS, which provides a scaffold for cells, and by maintaining the pharmacological effect of EGCG.

Topical simvastatin improves the pro-angiogenic and pro-osteogenic properties of bioglass putty in the rat calvaria critical-size model

Objective was to describe the effect of bioactive glass putty with and without topical simvastatin on new bone formation in critical-sized defects of rat calvaria. A calvarial bone defect was created in 20 male Wistar rats and filled with bioactive glass alone (n = 10) or combined with simvastatin (n = 10). After 4 weeks, the defects were histomorphometrically evaluated for volume fraction (Vv) of woven bone, vessel density, bioglass quantity, and inflammation. Compared to the bioglass-only group, rats treated with simvastatin had greater Vv of blood vessels (3.3% ± 0.7 vs 1.6% ± 0.1, P = .0002) and new bone (2.3% ± 0.2 vs 1.8% ± 2.5, P = .003). The Vv of the bioglass remnants in the bioglass-only group was higher than in the group treated with simvastatin (2.4% ± 0.08 vs 1.7% ± 0.3, P < .0004). Chronic inflammation was noted in 1 rat from each group. Topical simvastatin seems to improve the pro-angiogenic and pro-osteogenic properties of bioglass putty in rat calvaria critical-size defects without significant inflammation.

Screening of candidate biomaterials for alveolar augmentation using a critical-size rat calvaria defect model

OBJECTIVE

To screen candidate biomaterials intended for alveolar augmentation relative to their potential to enhance local bone formation using a routine critical-size (ø8-mm) rat calvaria defect model.

METHODS

One hundred and forty male Sprague Dawley outbred rats, age 11-12 weeks, weight 325-375 g, obtained from USDA approved breeder, randomised into 14 groups of 10 animals, each received one of the following treatments: sham-surgery (empty control), Bio-Oss (bovine HA/reference control), or candidate biomaterials including bovine HA, synthetic HA/ß-TCP and calcium phosphate constructs, mineralised/demineralised human bone preparations, a ß-TCP/calcium sulphate and an HA/calcium sulphate putty. A 4-week healing interval was chosen to discern local bone formation using incandescent and polarised light microscopy. Statistical analysis used one-way ANOVA followed by Bonferroni for pairwise comparisons.

RESULTS

Candidate biomaterials all displayed biocompatibility. They exhibited limited, if any, appreciable bioerosion or biodegradation. No statistically significant differences in mean linear defect closure were observed among experimental groups, sham-surgery displaying the highest score (48.1 ± 24.3%). Sham-surgery also showed a significantly greater bone area fraction than all other groups (19.8 ± 13.9%, p < .001). The HA/calcium sulphate putty showed a significantly greater residual biomaterial area fraction than all other groups (61.1 ± 8.5%, p < .01).

CONCLUSION

Within the limitations of this animal model, although biocompatible, none of the tested biomaterials enhanced local bone formation beyond the innate regenerative potential of this craniotomy defect.

Spongostan™ Leads to Increased Regeneration of a Rat Calvarial Critical Size Defect Compared to NanoBone® and Actifuse

Bone substitute materials are becoming increasingly important in oral and maxillofacial surgery. Reconstruction of critical size bone defects is still challenging for surgeons. Here, we compared the clinically applied organic bone substitute materials NanoBone^® (nanocrystalline hydroxyapatite and nanostructured silica gel; n = 5) and Actifuse (calcium phosphate with silicate substitution; n = 5) with natural collagen-based Spongostan™ (hardened pork gelatin containing formalin and lauryl alcohol; n = 5) in bilateral rat critical-size defects (5 mm diameter). On topological level, NanoBone is known to harbour nanopores of about 20 nm diameter, while Actifuse comprises micropores of 200–500 µm. Spongostan™, which is clinically applied as a haemostatic agent, combines in its wet form both nano- and microporous topological features by comprising 60.66 ± 24.48 μm micropores accompanied by nanopores of 32.97 ± 1.41 nm diameter. Micro-computed tomography (µCT) used for evaluation 30 days after surgery revealed a significant increase in bone volume by all three bone substitute materials in comparison to the untreated controls. Clearly visual was the closure of trepanation in all treated groups, but granular appearance of NanoBone^® and Actifuse with less closure at the margins of the burr holes. In contrast, transplantion of Spongostan™ lead to complete filling of the burr hole with the highest bone volume of 7.98 ccm and the highest bone mineral density compared to all other groups. In summary, transplantation of Spongostan™ resulted in increased regeneration of a rat calvarial critical size defect compared to NanoBone and Actifuse, suggesting the distinct nano- and microtopography of wet Spongostan™ to account for this superior regenerative capacity. Since Spongostan™ is a clinically approved product used primarily for haemostasis, it may represent an interesting alternative in the reconstruction of defects in the maxillary region.

Bone regeneration using Wollastonite/β-TCP scaffolds implants in critical bone defect in rat calvaria

In order to provide favorable conditions for bone regeneration, a lot of biomaterials have been developed and evaluated, worldwide. Composite biomaterials have gained notoriety, as they combine desirable properties of each isolated material. Thus, in this research, bone repair capacity of three developed formulations of ceramic scaffolds were evaluated histomorphometrically, after implantation. Scaffolds were based on wollastonite (W) andβ-tricalcium phosphate (β-TCP) composites in three different ratios (wt.%). ThirtyWistarrats were randomly assigned to three experimental groups: W-20 (20 W/80β-TCP wt.%), W-60 (60 W/40β-TCP wt.%), and W-80 (80 W/20β-TCP wt.%), evaluated by optical microscopy at biological tests after 15 and 45 days of implantation. Throughout the study, the histological results evidenced that the scaffolds remained at the implantation site, were biocompatible and presented osteogenic potential. The percentage of neoformed mineralized tissue was more evident in the W-20 group (51%), at 45 days. The composite of the W-80 group showed more evident biodegradation than the biomaterials of the W-20 and W-60 groups. Thus, it is concluded that the scaffold containing 20 W/80β-TCP (wt.%) promoted more evident bone formation, but all composites evaluated in this study showed notorious bioactivity and promising characteristics for clinical application.

An Extrudable Partially Demineralized Allogeneic Bone Paste Exhibits a Similar Bone Healing Capacity as the "Gold Standard" Bone Graft

Autologous bone grafts (BGs) remain the reference grafting technique in various clinical contexts of bone grafting procedures despite their numerous peri- and post-operative limitations. The use of allogeneic bone is a viable option for overcoming these limitations, as it is reliable and it has been widely utilized in various forms for decades. However, the lack of versatility of conventional allogeneic BGs (e.g., blocks, powders) limits their potential for use with irregular or hard-to-reach bone defects. In this context, a ready- and easy-to-use partially demineralized allogeneic BG in a paste form has been developed, with the aim of facilitating such bone grafting procedures. The regenerative properties of this bone paste (BP) was assessed and compared to that of a syngeneic BG in a pre-clinical model of intramembranous bone healing in critical size defects in rat calvaria. The microcomputed tridimensional quantifications and the histological observations at 7 weeks after the implantation revealed that the in vivo bone regeneration of critical-size defects (CSDs) filled with the BP was similar to syngeneic bone grafts (BGs). Thus, this ready-to-use, injectable, and moldable partially demineralized allogeneic BP, displaying equivalent bone healing capacity than the “gold standard,” may be of particular clinical relevance in the context of oral and maxillofacial bone reconstructions.

Bone Regeneration in Defects Created on Rat Calvaria Grafted with Porcine Xenograft and Synthetic Hydroxyapatite Reinforced with Titanium Particles-A Microscopic and Histological Study

(1) Background: Alveolar bone regeneration in dentistry has become important with the evolution of implantology. Biomaterials used for bone grafting are increasingly used to provide resistant bone support that is favorable for the insertion of dental implants. The aim of the study was to analyze the degree of biocompatibility and bone neoformation of two biomaterials compared to natural healing. (2) Methods: Bone defects of 3 mm diameter were created in the calvaria of 15 adult male Wistar rats. Three groups were created: group A, in which natural healing was achieved; group B, in which porcine xenograft was added; and group C, in which experimental synthetic bone based on hydroxyapatite reinforced with titanium particles was added. Samples were collected at 2 and 4 months postoperatively and analyzed microscopically and histologically. (3) Results: Data were obtained on the healing pattern of the created cavities, as well as the degree of their filling with newly formed bone tissue. Following the results obtained from the stereomicroscope analysis and histological analysis, statistically significant differences were observed between the two biomaterials regarding the time required for the transformation process of the graft particles into bone. Thus, the porcine xenograft was incorporated more quickly into the native bone, while the synthetic bone required a longer period of time. (4) Conclusions: The bone graft materials used acted as scaffolds for the newly formed bone, but each biomaterial required a different amount of time for the particles to be incorporated into the native bone.