Effectiveness of tissue engineered three‐dimensional bioactive graft on bone healing and regeneration: an in vivo study with significant clinical value

Osteoinductive potential of graphene and graphene oxide for bone tissue engineering: a comparative study

BACKGROUND

Bone defects, especially critical-size bone defects, and their repair pose a treatment challenge. Osteoinductive scaffolds have gained importance given their potential in bone tissue engineering applications.

METHODS

Polycaprolactone (PCL) scaffolds are used for their morphological, physical, cell-compatible and osteoinductive properties. The PCL scaffolds were prepared by electrospinning, and the surface was modified by layer-by-layer deposition using either graphene or graphene oxide.

RESULTS

Graphene oxide-coated PCL (PCL-GO) scaffolds showed a trend for enhanced physical properties such as fibre diameter, wettability and mechanical properties, yield strength, and tensile strength, compared to graphene-modified PCL scaffolds (PCL-GP). However, the surface roughness of PCL-GP scaffolds showed a higher trend than PCL-GO scaffolds. In vitro studies showed that both scaffolds were cell-compatible. Graphene oxide on PCL scaffold showed a trend for enhanced osteogenic differentiation of human umbilical cord Wharton's jelly-derived Mesenchymal Stem Cells without any differentiation media than graphene on PCL scaffolds after 21 days.

CONCLUSION

Graphene oxide showed a trend for higher mineralisation, but this trend is not statistically significant. Therefore, graphene and graphene oxide have the potential for bone regeneration and tissue engineering applications. Future in vivo studies and clinical trials are warranted to justify their ultimate clinical use.

Evaluation optimum ratio of synthetic bone graft material and platelet rich fibrin mixture in a metal 3D printed implant to enhance bone regeneration

BACKGROUND

This study aims to evaluate the optimal ratio of synthetic bone graft (SBG) material and platelet rich fibrin (PRF) mixed in a metal 3D-printed implant to enhance bone regeneration.

METHODS

Specialized titanium hollow implants (5 mm in diameter and 6 mm in height for rabbit; 6 mm in diameter and 5 mm in height for pig) were designed and manufactured using 3D printing technology. The implants were divided into three groups and filled with different bone graft combinations, namely (1) SBG alone; (2) PRF to SBG in 1:1 ratio; (3) PRF to SBG in 2:1 ratio. These three groups were replicated tightly into each bone defect in distal femurs of rabbits (nine implants, n = 3) and femoral shafts of pigs (fifteen implants, n = 5). Animal tissue sections were obtained after euthanasia at the 8th postoperative week. The rabbit specimens were stained with analine blue, while the pig specimens were stained with Masson-Goldner's trichrome stain to perform histologically examination. All titanium hollow implants were well anchored, except in fracture specimens (three in the rabbit and one fracture in the pig).

RESULT

Rabbit specimens under analine blue staining showed that collagen tissue increased by about 20% and 40% in the 1:1 ratio group and the 2:1 ratio group, respectively. Masson-Goldner's trichrome stain results showed that new bone growth increased by 32% in the 1:1 ratio PRF to SBG, while - 8% in the 2:1 ratio group.

CONCLUSION

This study demonstrated that placing a 1:1 ratio combination of PRF and SBG in a stabilized titanium 3D printed implant resulted in an optimal increase in bone growth.

Understanding Matrix Stiffness in Vinyl Polymer Hydrogels: Implications in Bone Tissue Engineering

Matrix elasticity helps to direct bone cell differentiation, impact healing processes, and modify extracellular matrix deposition, all of which are required for tissue growth and maintenance. In this work, we evaluated the role of inorganic nanocrystals or mineral inducers such as nanohydroxyapatite, alkaline phosphatase, and nanoclay also known as montmorillonite deposited on vinyl-based hydrogels in generating matrices with different stiffness and their role in cell differentiation. Poly-2-(dimethylamino)ethyl methacrylate (PD) and poly-2-hydroxypropylmethacrylamide (PH) are the two types of vinyl polymers chosen for preparing hydrogels via thermal cross-linking. The hydrogels exhibited porosity, which decreased with an increase in stiffness. Each of the compositions is non-cytotoxic and maintains the viability of pre-osteoblasts (MC3T3-E1) and human bone marrow mesenchymal stem cells (hBMSCs). The PD hydrogels in the presence of ALP showed the highest mineralization ability confirmed through the alizarin assay and a better structural environment for their use as scaffolds for tissue engineering. The study reveals that understanding such interactions can generate hydrogels that can serve as efficient 3D models to study biomineralization.

Dual-functional thermosensitive hydrogel for reducing infection and enhancing bone regeneration in infected bone defects

The contamination of bone defects is a serious therapeutic problem. The treatment of infected bone defects involves rigorous infection control followed by bone reconstruction. Considering these two processes, the development of biomaterials possessing antibacterial and osteogenic properties offers a promising approach for the treatment of infected bone defects. In this study, a dual-functional, thermosensitive, and injectable hydrogel composed of chitosan (CS), quaternized CS (QCS), and nano-hydroxyapatite (nHA) was designed, and the ratio of CS to QCS in the hydrogel was optimized to enhance the antibacterial efficacy of CS while reducing the cytotoxicity of QCS. In vitro studies demonstrated that the hydrogel with an 85 %:15 % ratio of CS to QCS exhibited excellent biocompatibility and antibacterial properties while also possessing suitable mechanical characteristics and degradability. The incorporation of nHA into the hydrogel enhanced MC3T3-E1 proliferation and osteogenic differentiation. Moreover, this hydrogel demonstrated superior in vivo therapeutic effectiveness in a rabbit model of infected bone defect. In summary, this study provides a promising material design and a comprehensive one-step treatment strategy for infected bone defects.

Effects of cerium-doped bioactive glass incorporation on an alginate/gelatin scaffold for bone tissue engineering: In vitro characterizations

Bioactive glasses (BGs) have been extensively employed in treating bone defects due to their capacity to bond and integrate with hard and soft tissues. To promote their characteristics, BGs are doped with therapeutic inorganic ions; Among these, Cerium (Ce) is of special attention because of its material and biological properties. This study aimed to investigate the effects of the addition of Ce to BG on the physicochemical and biological properties of the alginate/gelatin (Alg-Gel) scaffold compared with a similar scaffold that only contains BG45S5. The scaffolds were characterized for their biocompatibility using human bone marrow-derived mesenchymal stem cells (hBM-MSCs) by MTT analysis. The osteogenic differentiation of hBM-MSCs cultured on the scaffolds was assessed by evaluating the alkaline phosphatase (ALP) activity and the expression of osteogenic-related genes. Scanning electron microscopy of the prepared scaffolds showed an interconnected porous structure with an average diameter of 212-272 μm. The Young's modulus of the scaffolds significantly increased from 13 ± 0.82 MPa for Alg-Gel to 91 ± 1.76 MPa for Alg-Gel-BG/Ce. Ce doping improved the osteogenic differentiation of hBM-MSCs and ALP secretion compared to the other samples, even without adding an osteogenic differentiation medium. The obtained results demonstrated the biocompatibility and osteo-inductive potentials of the Alg-Gel-BG/Ce scaffold for bone tissue engineering.

Viability of Collagen Matrix Grafts Associated with Nanohydroxyapatite and Elastin in Bone Repair in the Experimental Condition of Ovariectomy

Bone lesions have the capacity for regeneration under normal conditions of the bone metabolism process. However, due to the increasing incidence of major traumas and diseases that cause bone-mineral deficiency, such as osteoporosis, scaffolds are needed that can assist in the bone regeneration process. Currently, natural polymeric scaffolds and bioactive nanoparticles stand out. Therefore, the objective of the study was to evaluate the osteoregenerative potential in tibiae of healthy and ovariectomized rats using mineralized collagen and nanohydroxyapatite (nHA) scaffolds associated with elastin. The in-vivo experimental study was performed with 60 20-week-old Wistar rats, distributed into non-ovariectomized (NO) and ovariectomized (O) groups, as follows: Controls (G1-NO-C and G4-O-C); Collagen with nHA scaffold (G2-NO-MSH and G5-O-MSH); and Collagen with nHA and elastin scaffold (G3-NO-MSHC and G6-O-MSHC). The animals were euthanized 6 weeks after surgery and the samples were analyzed by macroscopy, radiology, and histomorphometry. ANOVA and Tukey tests were performed with a 95% CI and a significance index of p < 0.05. In the histological analyses, it was possible to observe new bone formed with an organized and compact morphology that was rich in osteocytes and with maturity characteristics. This is compatible with osteoconductivity in both matrices (MSH and MSHC) in rats with normal conditions of bone metabolism and with gonadal deficiency. Furthermore, they demonstrated superior osteogenic potential when compared to control groups. There was no significant difference in the rate of new bone formation between the scaffolds. Ovariectomy did not exacerbate the immune response but negatively influenced the bone-defect repair process.

Modeling of the PHEMA-gelatin scaffold enriched with graphene oxide utilizing finite element method for bone tissue engineering

The development of computer-aided facilities has contributed to the optimization of tissue engineering techniques due to the reduction in necessary practical assessments and the removal of animal or human-related ethical issues. Herein, a bone scaffold based on poly (2-hydroxyethyl methacrylate) (PHEMA), gelatin and graphene oxide (GO), was simulated by SOLIDWORKS and ABAQUS under a normal compression force using finite element method (FEM). Concerning the mechanotransduction impact, GO could support the stability of the structure and reduce the possibility of the failure resulting in the integrity and durability of the scaffold efficiency which would be beneficial for osteogenic differentiation.

Nano-Hydroxyapatite Composite Scaffolds Loaded with Bioactive Factors and Drugs for Bone Tissue Engineering

Nano-hydroxyapatite (n-HAp) is similar to human bone mineral in structure and biochemistry and is, therefore, widely used as bone biomaterial and a drug carrier. Further, n-HAp composite scaffolds have a great potential role in bone regeneration. Loading bioactive factors and drugs onto n-HAp composites has emerged as a promising strategy for bone defect repair in bone tissue engineering. With local delivery of bioactive agents and drugs, biological materials may be provided with the biological activity they lack to improve bone regeneration. This review summarizes classification of n-HAp composites, application of n-HAp composite scaffolds loaded with bioactive factors and drugs in bone tissue engineering and the drug loading methods of n-HAp composite scaffolds, and the research direction of n-HAp composite scaffolds in the future is prospected.

Biomaterial-assisted tumor therapy: A brief review of hydroxyapatite nanoparticles and its composites used in bone tumors therapy

Malignant bone tumors can inflict significant damage to affected bones, leaving patients to contend with issues like residual tumor cells, bone defects, and bacterial infections post-surgery. However, hydroxyapatite nanoparticles (nHAp), the principal inorganic constituent of natural bone, possess numerous advantages such as high biocompatibility, bone conduction ability, and a large surface area. Moreover, nHAp's nanoscale particle size enables it to impede the growth of various tumor cells via diverse pathways. This article presents a comprehensive review of relevant literature spanning the past 2 decades concerning nHAp and bone tumors. The primary goal is to explore the mechanisms responsible for nHAp's ability to hinder tumor initiation and progression, as well as to investigate the potential of integrating other drugs and components for bone tumor diagnosis and treatment. Lastly, the article discusses future prospects for the development of hydroxyapatite materials as a promising modality for tumor therapy.

Osteoregenerative efficacy of a novel synthetic, resorbable Ca/P/S-based bone graft substitute in intra- and peri-articular fractures: a brief medical image-based report

Background

When a fracture goes into or around a joint, it usually damages the cartilage at the ends of bones and other joint tissue. As a result, the affected joints are prone to traumatic arthritis, leading to stiffness. Repairing bone damage, maintaining joint integrity, and avoiding subchondral and metaphyseal defects caused by comminuted fractures is often a great challenge for orthopedic surgeons. Tissue engineering of synthetic bone substitutes has proven beneficial to the attachment and proliferation of bone cells, promoting the formation of mature tissues with sufficient mechanical strength and has become a promising alternative to autograft methods. The purpose of this study is to retrospectively evaluate the clinical outcome and efficacy of a novel synthetic, highly biocompatible, and fully resorbable Ca/P/S-based bone substitute based on medical image findings.

Materials and methods

A synthetic, inorganic and highly porous Ca/P/S-based bone-substituting material (Ezechbone® Granule, CBS-400) has been developed by National Cheng-Kung University. We collected fourteen cases of complex intra- and peri-articular fractures with Ezechbone® Granule bone grafting between 2019/11 and 2021/11. We studied the evidence of bone healing by reviewing, interpreting and analyzing the medical image recordings.

Results

In the present study, CBS-400 was observed to quickly integrate into surrounding bone within three weeks after grafting during the initial callus formation of the early stage of repair. All of these cases healed entirely within three months. In addition, the patient may return to daily life function after 3.5 months of follow-up and rehabilitation treatment.

Conclusions

Ezechbone® Granule CBS-400 was proved capable of promoting bone healing and early rehabilitation to prevent soft tissue adhesions and joint contractures. Moreover, it has a high potential for avoiding ectopic bone formation or abnormal synostosis.

Trial registration

The Institutional Review Board at National Cheng Kung University Hospital (NCKUH) approved the study protocol (A-ER-109-031, 3-13-2020).

Selected mechanical properties of human cancellous bone subjected to different treatments: short-term immersion in physiological saline and acetone treatment with subsequent immersion in physiological saline

Background

Physiological saline (0.9% NaCl) and acetone are extensively used for storage (as well as hydration) and removal of bone marrow, respectively, of cancellous bone during preparation and mechanical testing. Our study aimed to investigate the mechanical properties of cancellous bone subjected to short-term immersion in saline and acetone treatment with subsequent immersion in saline.

Methods

Cylindrical samples (Ø6 × 12 mm) were harvested from three positions (left, middle, and right) of 1 thoracic vertebral body, 19 lumbar vertebral bodies, and 5 sacral bones, as well as from 9 femoral heads. All samples were divided into two groups according to the different treatments, (i) samples from the left and middle sides were immersed in saline at 4℃ for 43 h (saline-immersed group, n = 48); (ii) samples from the respective right side were treated with a combination of acetone and ultrasonic bath (4 h), air-dried at room temperature (21℃, 15 h), and then immersed in saline at room temperature (21℃, 24 h) (acetone and saline-treated group, n = 38). All samples were subjected, both before and after treatment, to a non-destructive compression test with a strain of 0.45%, and finally destructive tests with a strain of 50%. Actual density (ρ_act), initial modulus (E₀), maximum stress (σ_max), energy absorption (W), and plateau stress (σ_p) were calculated as evaluation indicators.

Results

Based on visual observation, a combination of acetone and ultrasonic bath for 4 h failed to completely remove bone marrow from cancellous bone samples. The mean values of ρ_act, σ_max, W, and σ_p were significantly higher in the femoral head than in the spine. There was no significant difference in E₀ between non-treated and saline-immersed samples (non-treated 63.98 ± 20.23 vs. saline-immersed 66.29 ± 20.61, p = 0.132). The average E₀ of acetone and saline-treated samples was significantly higher than that of non-treated ones (non-treated 62.17 ± 21.08 vs. acetone and saline-treated 74.97 ± 23.98, p = 0.043).

Conclusion

Short-term storage in physiological saline is an appropriate choice and has no effect on the E₀ of cancellous bone. Treatment of cancellous bone with acetone resulted in changes in mechanical properties that could not be reversed by subsequent immersion in physiological saline.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03265-4.

The healing of bone defects by cell-free and stem cell-seeded 3D-printed PLA tissue-engineered scaffolds

In this paper, the in-vivo healing of critical-sized bony defects by cell-free and stem cell-seeded 3D-printed PLA scaffolds was studied in rat calvaria bone. The scaffolds were implanted in the provided defect sites and histological analysis was conducted after 8 and 12 weeks. The results showed that both cell-free and stem cell-seeded scaffolds exhibited superb healing compared with the empty defect controls, and new bone and connective tissues were formed in the healing site after 8 and 12 weeks, postoperatively. The higher filled area, bone formation and bone maturation were observed after 12 weeks, particularly for PLA + Cell scaffolds.

Wound closure, angiogenesis and antibacterial behaviors of tetracalcium phosphate/hydroxyethyl cellulose/hyaluronic acid/gelatin composite dermal scaffolds

Polymeric and tetracalcium phosphate (TTCP)-containing polymeric scaffolds were fabricated using a freeze-drying technique, with a homogenous solution of hydroxyethyl cellulose (HEC)/hyaluronic acid (HA)/gelatin (G) or suspension of 15 or 20% TTCP) particles in HEC/HA/G solution. The morphology, phase composition, chemical bands, and swelling behavior of the scaffold were determined. In vitro fibroblast cell viability and migration potential of the scaffolds were determined by MTT, live/dead staining, and scratch assay for wound healing. The in vivo chick embryo angiogenesis test was also carried out. Finally, the initial antibacterial activity of the scaffolds was determined using Staphylococcus aureus. The scaffolds exhibited an enormous porous structure in which the size of pores increased by the presence of TTCP particles. While the polymeric scaffold was amorphous, the formation of low crystalline hydroxyapatite phase and the initial TTCP particles was determined in the composition of TTCP-added scaffolds. TTCP increased swelling behavior of the polymeric scaffold in PBS. The results demonstrated that the amount of TTCP was a crucial factor in cell life. A high concentration of TTCP could restrict cell viability, although all the scaffolds were nontoxic. The scratch assessments determined better cell migration and wound closure in treating with TTCP-containing scaffolds so that after 24 h, a wound closure of 100% was observed. Furthermore, TTCP-incorporated scaffolds significantly improved the angiogenesis, in the chick embryo test. The presence of TTCP had a significant effect on reducing the bacterial activity and 20% TTCP-containing scaffold exhibited better antibacterial activity than the others.

3D Bioprinting of Polycaprolactone-Based Scaffolds for Pulp-Dentin Regeneration: Investigation of Physicochemical and Biological Behavior

In this study, two structurally different scaffolds, a polycaprolactone (PCL)/45S5 Bioglass (BG) composite and PCL/hyaluronic acid (HyA) were fabricated by 3D printing technology and were evaluated for the regeneration of dentin and pulp tissues, respectively. Their physicochemical characterization was performed by field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), contact angle, and compressive strength tests. The results indicated that the presence of BG in the PCL/BG scaffolds promoted the mechanical properties, surface roughness, and bioactivity. Besides, a surface treatment of the PCL scaffold with HyA considerably increased the hydrophilicity of the scaffolds which led to an enhancement in cell adhesion. Furthermore, the gene expression results showed a significant increase in expression of odontogenic markers, e.g., dentin sialophosphoprotein (DSPP), osteocalcin (OCN), and dentin matrix protein 1 (DMP-1) in the presence of both PCL/BG and PCL/HyA scaffolds. Moreover, to examine the feasibility of the idea for pulp-dentin complex regeneration, a bilayer PCL/BG-PCL/HyA scaffold was successfully fabricated and characterized by FESEM. Based on these results, it can be concluded that PCL/BG and PCL/HyA scaffolds have great potential for promoting hDPSC adhesion and odontogenic differentiation.

Biomimetic reduced graphene oxide coated collagen scaffold for in situ bone regeneration

A variety of bone-related diseases and injures and limitations of traditional regeneration methods require new tissue substitutes. Tissue engineering and regeneration combined with nanomedicine can provide different natural or synthetic and combined scaffolds with bone mimicking properties for implantation in the injured area. In this study, we synthesized collagen (Col) and reduced graphene oxide coated collagen (Col-rGO) scaffolds, and we evaluated their in vitro and in vivo effects on bone tissue repair. Col and Col-rGO scaffolds were synthesized by chemical crosslinking and freeze-drying methods. The surface topography, and the mechanical and chemical properties of scaffolds were characterized, showing three-dimensional (3D) porous scaffolds and successful coating of rGO on Col. The rGO coating enhanced the mechanical strength of Col-rGO scaffolds to a greater extent than Col scaffolds by 2.8 times. Furthermore, Col-rGO scaffolds confirmed that graphene addition induced no cytotoxic effects and enhanced the viability and proliferation of human bone marrow-derived mesenchymal stem cells (hBMSCs) with 3D adherence and expansion. Finally, scaffold implantation into rabbit cranial bone defects for 12 weeks showed increased bone formation, confirmed by Hematoxylin–Eosin (H&E) and alizarin red staining. Overall, the study showed that rGO coating improves Col scaffold properties and could be a promising implant for bone injuries.

The potential impact of polyethylenimine on biological behavior of 3D-printed alginate scaffolds

Three-dimensional (3D) printing using biocompatible materials is a novel technology having a great potential for fabricating precise 3D scaffolds for tissue engineering. Alginate hydrogel undergoes unstable swelling and degradation properties as well as suffers from poor cell adhesion due to the lack of cell binding domains. These limit its applications in tissue engineering. In this study, 3D-printed alginate scaffolds were coated by branch polyethylenimine (PEI) to overcome the limitation of alginate because the branch PEI is a cationic polymer with a large number of active N-H groups. The results indicated that surface modification of 3D-printed alginate scaffolds using an appropriate concentration of PEI potentially promoted the fibroblast cells functions in 3D-printed alginate scaffolds, increased cell adhesion, cell proliferation and cell spreading through providing a large amount of N-H groups and increasing hydrophilicity of the surface. The degradation rate of alginate was degraded by interaction between N-H groups in PEI and -COO- groups in alginate structure and followed by the formation strong barrier layer in the interface of alginate and PEI. Therefore, ALG-PEI scaffolds can be a good candidate for tissue engineering and wound dressing applications.

Role of bone 1stem cell-seeded 3D polylactic acid/polycaprolactone/hydroxyapatite scaffold on a critical-sized radial bone defect in rat

Osteoconductive biomaterials were used to find the most reliable materials in bone healing. Our focus was on the bone healing capacity of the stem cell-loaded and unloaded PLA/PCL/HA scaffolds. The 3D scaffold of PLA/PCL/HA was characterized by scanning electron microscopy (SEM), rheology, X-ray diffraction (XRD), and Fourier transform-infrared (FT-IR) spectroscopy. Bone marrow stem cells (BMSCs) have multipotential differentiation into osteoblasts. Forty Wistar male rats were used to organize four experimental groups: control, autograft, scaffold, and BMSCs-loaded scaffold groups. qRT-PCR showed that the BMSCs-loaded scaffold had a higher expression level of CD31 and osteogenic markers compared with the control group (P < 0.05). Radiology and computed tomography (CT) scan evaluations showed significant improvement in the BMSCs-loaded scaffold compared with the control group (P < 0.001). Biomechanical estimation demonstrated significantly higher stress (P < 0.01), stiffness (P < 0.001), and ultimate load (P < 0.01) in the autograft and BMSCs-loaded scaffold groups compared with the untreated group and higher strain was seen in the control group than the other groups (P < 0.01). Histomorphometric and immunohistochemical (IHC) investigations showed significantly improved regeneration scores in the autograft and BMSCs-loaded scaffold groups compared with the control group (P < 0.05). Also, there was a significant difference between the scaffold and control groups in all tests (P < 0.05). The results depicted that our novel approach will allow to develop PLA/PCL/HA 3D scaffold in bone healing via BMSC loading.

Can the Combination of Simvastatin and Melatonin Create a Synergistic Effect on Bone Regeneration?

PURPOSE

The present study evaluated the potential bone regeneration capacity of combining melatonin and simvastatin, with a goal of producing more osteogenic bone substitutes.

MATERIALS AND METHODS

A total of 48 male Wistar rats were randomly divided into 4 groups. The following were administered into critical-sized calvarial defects of the rats: Group I-human allograft; Group II-human allograft + 10 mg melatonin; Group III-human allograft + 0.1 mg simvastatin; and Group IV-human allograft + 10 mg melatonin + 0.1 mg simvastatin. Histopathologic, histomorphometric, and microcomputed tomographic evaluations were performed postprocedurally at 4 and 8 weeks. A P value < .05 was considered significant for all evaluations.

RESULTS

Groups II and III had significantly superior regeneration compared to Group I at weeks 4 and 8. Group III had significantly superior regeneration compared to Group II, particularly in week 4. Group IV had significantly superior regeneration compared to all groups at week 8.

CONCLUSIONS

The local administration of melatonin and simvastatin resulted in increased new bone mass and quality of bone microstructure than was seen in the control group. Simvastatin shortened the defect regeneration time more effectively than melatonin did. The combined use of melatonin and simvastatin provided a synergic effect on bone regeneration, particularly in the late phase of healing.

Effectiveness of a biodegradable 3D polylactic acid/poly(ɛ-caprolactone)/hydroxyapatite scaffold loaded by differentiated osteogenic cells in a critical-sized radius bone defect in rat

The effects of a scaffold made of polylactic acid, poly (ɛ-caprolactone) and hydroxyapatite by indirect 3D printing method with and without differentiated bone cells was tested on the regeneration of a critical radial bone defect in rat. The scaffold characterization and mechanical performance were determined by the rheology, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectrometry. The defects were created in forty Wistar rats which were randomly divided into the untreated, autograft, scaffold cell-free, and differentiated bone cell-seeded scaffold groups (n = 10 in each group). The expression level of angiogenic and osteogenic markers, analyzed by quantitative real time-polymerase chain reaction (in vitro), significantly improved (p < 0.05) in the scaffold group compared to the untreated one. Radiology and computed tomography scan demonstrated a significant improvement in the cell-seeded scaffold group compared to the untreated one (p < 0.001). Biomechanical, histopathological, histomorphometric, and immunohistochemical investigations showed significantly better regeneration scores in the cell-seeded scaffold and autograft groups compared to the untreated group (p < 0.05). The cell-seeded scaffold and autograft groups did show comparable results on the 80^th day post-treatment (p > 0.05), however, most results in the scaffold group were significantly higher than the untreated group (p < 0.05). Differentiated bone cells can enhance bone regeneration potential of the scaffold.

Local effect of simvastatin combined with different osteoconductive biomaterials and collagen sponge on new bone formation in critical defects in rat calvaria

Purpose

To evaluate the local effect of simvastatin (SVT) combined with deproteinized bovine bone (DBB) with hydroxyapatite/β-tricalcium phosphate biphasic ceramics (HA/TCP) and with collagen sponge (CS) on bone repair in critical size defects (CSDs) in rat calvaria.

Methods

Forty-two 5-mm diameter CSDs were made bilaterally in the calvaria of 18 rats. The animals were allocated according to the type of biomaterial and associations used to fill the CSD. After 8 weeks, the animals were euthanized, and their calvaria were evaluated for repaired tissue composition using histologic and histometric analyses.

Results

In the histometric analysis, the use of SVT showed to increase bone formation in the CSDs when combined with all the bone substitutes tested in this study (p<0.05). Greater bone formation was observed in the groups with SVT compared to the groups without SVT.

Conclusions

The use of SVT without the need for a vehicle and combined with a commercially available biomaterial may be a cheaper way to potentiate the formation of bone tissue without the need to produce new biomaterials. Therefore, SVT combined with DBB induced significantly greater new bone formation than did the other treatments.

Bone union formation in the rat mandibular symphysis using hydroxyapatite with or without simvastatin: effects on healthy, diabetic, and osteoporotic rats

OBJECTIVE

The objective is to compare new bone formation in critical defects in healthy, diabetic, and osteoporotic rats filled with hydroxyapatite (HA) alone and HA combined with simvastatin (SV).

MATERIALS AND METHODS

A total of 48 adult female Sprague-Dawley rats were randomized into three groups (n = 16 per group): Group, 1 healthy; Group 2, diabetics; and Group 3, osteoporotics. Streptozotocin was used to induce type 1 diabetes in Group 2, while bilateral ovariectomy was used to induce osteoporosis in Group 3. The central portion of the rat mandibular symphysis was used as a physiological critical bone defect. In each group, eight defects were filled with HA alone and eight with HA combined with SV. The animals were sacrificed at 4 and 8 weeks, and the mandibles were processed for micro-computed tomography to analyze radiological union and bone mineral density (BMD); histological analysis of the bone union; and immunohistochemical analysis, which included immunoreactivity of vascular endothelial growth factor (VEGF) and bone morphogenetic protein 2 (BMP-2).

RESULTS

In all groups (healthy, diabetics, and osteoporotics), the defects filled with HA + SV presented greater radiological bone union, BMD, histological bone union, and more VEGF and BMP-2 positivity, in comparison with bone defects treated with HA alone.

CONCLUSIONS

Combined application of HA and SV improves bone regeneration in mandibular critical bone defects compared with application of HA alone in healthy, diabetic, and osteoporotic rats.

CLINICAL RELEVANCE

This study might help to patients with osteoporosis or uncontrolled diabetes type 1, but future studies should be done.

Importance of crosslinking strategies in designing smart biomaterials for bone tissue engineering: A systematic review

Biomaterials are of significant importance in biomedical applications as these biological macromolecules have moderately replaced classical tissue grafting techniques owing to its beneficial properties. Despite of its favourable advantages, poor mechanical and degradative properties of biomaterials are of great concern. To this regard, crosslinkers have emerged as a smart and promising tool to augment the biological functionality of biopolymers. Different crosslinkers have been extensively used in past decades to develop bone substitutes, but the implications of toxic response and adverse reactions are truly precarious after implantation. Traditional crosslinker like glutaraldehyde has been widely used in numerous bio-implants but the potential toxicity is largely being debated with many disproving views. As alternative, green chemicals, enzymatic and non-enzymatic chemicals, bi-functional epoxies, zero-length crosslinkers and physical crosslinkers have been introduced to achieve the desired properties of a bone substitute. In this review, systematic literature search was performed on PubMed database to identify the most commonly used crosslinkers for developing promising bone like materials. The relevant articles were identified, analysed and reviewed in this paper giving due importance to different crosslinking methodologies and comparing their effectiveness and efficacy in regard to material composition, scaffold production, crosslinker dosage, toxicity and immunogenicity. This review summarizes the recent developments in crosslinking mechanism with an emphasis placed on their ability to link proteins through bonding reactions. Finally, this study also covers the convergent and divergent methodologies of crosslinking strategies also giving special importance in retrieving the current limitations and future opportunities of crosslinking modalities in bone tissue engineering.

Improved connective integration of a degradable 3D-nano-apatite/agarose scaffold subcutaneously implanted in a rat model

In this work, we evaluate the tissue response and tolerance to a designed 3D porous scaffold composed of nanocrystalline carbonate-hydroxyapatite and agarose as a preliminary step in bone repair and regeneration. These scaffolds were subcutaneously implanted into rats, which were sacrificed at different times. CD4+, CD8+ and ED1+ cells were evaluated as measurements of inflammatory reaction and tolerance. We observed some inflammatory response early after subcutaneous implantation. The 3D interconnected porosity increased scaffold integration via the formation of granulation tissue and the generation of a fibrous capsule around the scaffold. The capsule is initially formed by collagen which progressively invades the scaffold, creating a network that supports the settlement of connective tissue and generating a compact structure. The timing of the appearance of CD4+ and CD8+ cell populations is in agreement with the resolved inflammatory response. The appearance of macrophage activity evidences a slow and gradual degradation activity. Degradation started with the agarose component of the scaffold, but the nano-apatite was kept intact for up to 30 days. Therefore, this apatite/agarose scaffold showed a high capacity for integration by a connective network that stabilizes the scaffold and results in slow nano-apatite degradation. The fundamental properties of the scaffold would provide mechanical support and facilitate bone mobilization, which is of great importance in the masticatory system or large bones.

Scaffolds for the repair of bone defects in clinical studies: a systematic review

Background

This systematic review aims to summarize the clinical studies on the use of scaffolds in the repair of bony defects.

Methods

The relevant articles were searched through PubMed database. The following keywords and search terms were used: “scaffolds,” “patient,” “clinic,” “bone repair,” “bone regeneration,” “repairing bone defect,” “repair of bone,” “osteanagenesis,” “osteanaphysis,” and “osteoanagenesis.” The articles were screened according to inclusion and exclusion criteria, performed by two reviewers.

Results

A total of 373 articles were obtained using PubMed database. After screening, 20 articles were identified as relevant for the purpose of this systematic review. We collected the data of biological scaffolds and synthetic scaffolds. There are eight clinical studies of biological scaffolds included collagen, gelatin, and cellular scaffolds for bone healing. In addition, 12 clinical studies of synthetic scaffolds on HAp, TCP, bonelike, and their complex scaffolds for repairing bone defects were involved in this systematic review.

Conclusions

There are a lot of clinical evidences showed that application of scaffolds had a good ability to facilitate bone repair and osteogenesis. However, the ideal and reliable guidelines are insufficiently applied and the number and quality of studies in this field remain to be improved.