Demineralized bone matrix and hydroxyapatite/tri-calcium phosphate mixture for bone healing in rats

A Comparative Study of HA/DBM Compounds Derived from Bovine and Porcine for Bone Regeneration

This comparative study investigated the tissue regeneration and inflammatory response induced by xenografts comprised of hydroxyapatite (HA) and demineralized bone matrix (DBM) extracted from porcine (P) and bovine (B) sources. First, extraction of HA and DBM was independently conducted, followed by chemical and morphological characterization. Second, mixtures of HA/DBM were prepared in 50/50 and 60/40 concentrations, and the chemical, morphological, and mechanical properties were evaluated. A rat calvarial defect model was used to evaluate the tissue regeneration and inflammatory responses at 3 and 6 months. The commercial allograft DBM Puros® was used as a clinical reference. Different variables related to tissue regeneration were evaluated, including tissue thickness regeneration (%), amount of regenerated bone area (%), and amount of regenerated collagen area (%). The inflammatory response was evaluated by quantifying the blood vessel area. Overall, tissue regeneration from porcine grafts was superior to bovine. After 3 months of implantation, the tissue thickness regeneration in the 50/50P compound and the commercial DBM was significantly higher (~99%) than in the bovine materials (~23%). The 50/50P and DBM produced higher tissue regeneration than the naturally healed controls. Similar trends were observed for the regenerated bone and collagen areas. The blood vessel area was correlated with tissue regeneration in the first 3 months of evaluation. After 6 months of implantation, HA/DBM compounds showed less regenerated collagen than the DBM-only xenografts. In addition, all animal-derived xenografts improved tissue regeneration compared with the naturally healed defects. No clinical complications associated with any implanted compound were noted.

Engineering Three-Dimensional-Printed Bioactive Polylactic Acid Alginate Composite Scaffolds with Antibacterial and In Vivo Osteoinductive Capacity

Although fused deposition modeling (FDM) has made it possible to create reproducible three-dimensional poly(lactic acid) (PLA) scaffolds, their efficacy for tissue engineering applications is limited by their lack of osteoinductive properties and antibacterial functions. Building on the success of the FDM constructs capable of supporting bone regeneration, we report here on the development of PLA scaffolds infused with sodium alginate cross-linked with both calcium and zinc divalent cations. Zn²⁺ cations were used to confer antibacterial and osteoinductive properties to enhance the performance of nontoxic PLA-alginate. Both the PLA and alginate polymers have been approved by the US Food and Drug Administration. In vivo bone regeneration capacity was demonstrated on a rabbit model by tomography and histological analysis. The scaffolds exhibited antibacterial activity against Gram-positive methicillin-resistant Staphylococcus epidermidis and Gram-negative Pseudomonas aeruginosa, while the control scaffolds could not resist the two microbial species tested. The scaffolds' physical properties were evaluated by field emission scanning electron microscopy with energy-disperse X-ray spectroscopy, Fourier transform infrared spectroscopy, water absorption, porosity measurements, and compression tests in dry and swollen states at body temperature. Their superior compressive properties, water uptake, and osteoinductive and antibacterial activities thus make them promising candidates for bone tissue regeneration.

Evolution of dynamics of physico-chemical and mechanical properties of hydroxyapatite with fluorine addition and degradation stability of new matrices

This multidisciplinary study examined sensitively the change in the dynamics of main mechanical performance, stability of crystal structure, crystallinity quality, strength, corrosion resistance, biocompatibility, resistance to structural degradation/separations and mechanical durability features of hydroxyapatite (HAp) biomedical materials based on the fluorine addition and degradation process to guide future medical and dental treatment studies. In the study, the fluorine ions were used to be the dental coating, filling and supporting material for biologically or synthetically produced bone minerals. The general characteristic properties were investigated by means of standard spectroscopic, structural and mechanical analysis methods including RAMAN, SEM-EDS, TEM, Vickers micro-indentation hardness and density measurements. A time dependent release test was performed to evaluate possible fluorine ion release after the degradation process. It was found that the fundamental characteristic properties of HAp biomedical materials are noted to improve with the increase in the fluoride level up to 2% due much more stabilization of HAp crystal system. The combination of RAMAN spectra and powder XRD analyzes indicates that 2% addition level affects positively the formation velocity of characteristic HAP phase. Besides, fluorine doped HAp materials all exhibited the main characteristic peaks after degradation process. This is attributed to the fact that the fluorine ions enabled the hydroxyapatite to enhance the structural quality and stability towards the corrosion environment. However, in case of excess dopant level of 3% the degradation rates were obtained to increase due to higher contribution rate and especially electrostatic interactions. As for the surface morphology examinations, 2% fluorine added HAp with the highest density of 3.0879 g/cm³ was determined to present the superior crystallinity quality (smallest grain size, best smooth surface, honeycomb pattern, regular shaped particles and densest particle distributions through the specimen surface). Conversely, the excess fluorine triggered to increase seriously degree of micro/macro porosity in the surface morphology and microscopic structural problems in the crystal system. Thus, the HAp doped with 3% was the most affected material from the degradation process. Additionally, the fluorine ion values read after the release process were quite far from the value that could cause toxic effects. Lastly, the optimum fluorine addition provides the positive effects on the highest durability, stiffness and mechanical fracture strength properties as a consequence of differentiation in the surface residual compressive stress regions (lattice strain fields), amplification sites and active operable slip systems in the matrix. Hence, the crack propagations prefer to proceed in the transcrystalline regions rather than the intergranular parts. Similarly, it was found that Vickers micro-indentation hardness tests showed that the microhardness parameters increased after the degradation process. All in all, the fluorine addition level of 2% was noted to be good choice to improve the fundamental characteristic properties of hydroxyapatite biomedical materials for heavy-duty musculoskeletal, orthopedic implant, biological and therapeutic applications in medicine and dentistry application fields.

The effect of biphasic calcium phosphate and demineralized bone matrix on tooth eruption in mongrel dogs

BACKGROUND

Bone grafts can provide an optimal environment for permanent tooth to erupt and enhance the stability of the alveolar maxilla. Although autologous bone is an optimal source for osteogenesis, its inevitable donor site morbidity has led to active research on bone substitutes. This study was designed to evaluate the safety and feasibility of using biphasic calcium phosphate (BCP; Osteon) as a bone substitute in dogs.

METHODS

Bilateral third and fourth premolars of four 15-week-old mongrel dogs were used. All teeth were extracted except the third premolar of the right mandible, which was used as a control. After extraction of the premolars, each dog was administered BCP (Osteon), demineralized bone matrix (DBM; DBX), and no graft in the hollow sockets of the right fourth premolar, left fourth premolar, and left third premolar, respectively. Radiographs were taken at 2-week intervals to check for tooth eruption. After 8 weeks, each dog was sacrificed, and tooth and bone biopsies were performed to check for the presence of tooth and bone substitute particle remnants.

RESULTS

Four weeks after the operation, permanent tooth eruptions had started at all the extraction sites in each dog. Eight weeks after the operation, all teeth had normally erupted, and histological examination revealed BCP particles at the right fourth premolar.

CONCLUSION

In all four dogs, no delay in the eruption of the teeth or shape disfigurement of permanent teeth was observed on gross inspection and radiologic evaluation. On histological examination, most of the BCP and DBM were replaced by new bone. Bone substitutes can be used as graft materials in patients with alveolar clefts.

Metformin-Incorporated Gelatin/Hydroxyapatite Nanofiber Scaffold for Bone Regeneration

Tissue engineering and regenerative medicine has gradually evolved as a promising therapeutic strategy to the modern health care of aging and diseased population. In this study, we developed a novel nanofibrous scaffold and verified its application in the critical bone defect regeneration. The metformin-incorporated nano-gelatin/hydroxyapatite fibers (NGF) was produced by electrospinning, cross-linked, and then characterized by X-ray powder diffractometer and Fourier-transform infrared spectroscopy. Cytotoxicity, cell adhesion, cell differentiation, and quantitative osteogenic gene and protein expression were analyzed by bone marrow stem cells (BMSCs) from rat. Rat forearm critical bone defect model was performed for the in vivo study. The NGF were characterized by their porous structures with proper interconnectivity without significant cytotoxic effects; the adhesion of BMSCs on the NGF could be enhanced. The osteogenic gene and protein expression were upregulated. Postimplantation, the new regenerated bone in bone defect was well demonstrated in the NGF samples. We demonstrated that the metformin-incorporated NGF greatly improved healing potential on the critical-size bone defect. Although metformin-incorporated NGF had advantageous effectiveness during bone regeneration, further validation is required before it can be applied to clinical applications. Impact statement Bone is the structure that supports the rest of the human body. Critical-size bone defect hinders the regeneration of damaged bone tissues and compromises the mechanical strength of the skeletal system. Characterized by their porous structures with proper interconnectivity, the electrospinning nano-gelatin/hydroxyapatite fibrous scaffold developed in this study can greatly improve the healing potential on the critical-size bone defect. Further validation can validate its potential clinical applications.

Reconstruction of mandibular defects using synthetic octacalcium phosphate combined with bone matrix gelatin in rat model

BACKGROUND

Regeneration of bone defects remains a challenge for maxillofacial surgeons. The objective of this study was to assess the osteogenic potential of octacalcium phosphate (OCP) and bone matrix gelatin (BMG) alone and in combination with together in artificially created mandibular bone defects.

MATERIALS AND METHODS

In this experimental study Forty-eight male Sprague-Dawley rats (6-8 weeks old) were randomly divided into four groups. Defects were created in the mandible of rats and filled with 10 mg of OCP, BMG, or a combination of both (1/4 ratio). Defects were left unfilled in the control group. To assess bone regeneration and determine the amount of the newly formed bone, specimens were harvested at 7, 14, 21, and 56 days postimplantation. The specimens were processed routinely and studied histologically and histomorphometrically using the light microscope and eyepiece graticule. The amount of newly formed bone was quantitatively measured using histomorphometric methods. Histomorphometric data were analyzed using SPSS software. Mean, standard deviation, mode, and medians were calculated. Tukey HSD test was used to compare the means in all groups. P < 0.05 was considered as statistically significant (i.e., 5% significant level).

RESULTS

In the experimental groups, the new bone formation was initiated from the margin of defects during the 7-14 days after implantation. By the end of study, the amount of newly formed bone increased and relatively matured, and almost all of the implanted materials were absorbed. In the control group, slight amount of new bone had been formed at the defect margins (next to the host bone) on day 56. The histomorphometric analysis revealed statistically significant differences in the amount of newly formed bone between the experimental and the control groups (P < 0.001).

CONCLUSION

Combination of OCP/BMG may serve as an optimal biomaterial for the treatment of mandibular bone defects.

Histomorphometric Analysis of Newly-formed Bone Using Octacalcium Phosphate and Bone Matrix Gelatin in Rat Tibial Defects

BACKGROUND

Repair of bone defects is challenging for reconstructive and orthopedic surgeons. In this study, we aimed to histomorphometrically assess new bone formation in tibial bone defects filled with octacalcium phosphate (OCP), bone matrix gelatin (BMG), and a combination of both.

METHODS

A total of 96 male Sprague Dawley rats aged 6-8 weeks weighing 120-150 g were randomly allocated into three experimental (OCP, BMG, and OCP/BMG) and one control group (n=24 in each group). The defects in experimental groups were filled with OCP (6 mg), BMG (6 mg), or a combination of OCP and BMG (6 mg, 2:1 ratio). No material was used to fill the defects in the control group and the defect was only covered with Surgicel. Samples were taken on days 7, 14, 21, and 56 after the surgery. The sections were stained with hematoxylin-eosin (H&E) and assessed using light microscopy.

RESULTS

In our experimental groups, bone formation was started from the margins of the defect towards the center with an increasing rate during the study period. Moreover, the formed bone was more mature. Bone formation in our control group was only limited to the margins of the defect. The newly formed bone mass was significantly higher in the experimental groups (P=0.001).

CONCLUSION

OCP, BMG, and OCP/BMG compound enhanced osteoinduction in long bones.

Computer-Assisted Three-Dimensional Corrective Osteotomy for Malunited Fractures of the Distal Radius Using Prefabricated Bone Graft Substitute

BACKGROUND

Three-dimensional computed tomography (3D-CT) imaging has enabled more accurate preoperative planning. The purpose of this study was to investigate the results of a novel, computer-assisted, 3D corrective osteotomy using prefabricated bone graft substitute to treat malunited fractures of the distal radius.

METHODS

We investigated 19 patients who underwent the computer-assisted 3D corrective osteotomy for a malunited fracture of the distal radius after the operation was stimulated with CT data. A prefabricated bone graft substitute corresponding to the patient's bone defect was implanted and internal fixation was performed using a plate and screws. We compared postoperative radiographic parameters of the patient's operated side with their sound side and analyzed clinical outcomes using Mayo wrist score.

RESULTS

All patients achieved bone union on X-ray imaging at final follow-up. The mean differences of palmar tilt, radial inclination and ulnar variance between the operation side and the sound side were 4.3°, 2.3° and 1.2 mm, respectively. The Mayo wrist score was fair in 4 patients and poor in 15 patients before surgery. At the final follow-up after surgery, the scores improved to excellent in 3 patients, good in 11 patients and fair in 5 patients. There were two patients with correction loss at the final follow-up, but no patient complained of hand joint pain.

CONCLUSIONS

We believe that computer-assisted 3D corrective osteotomy using prefabricated bone graft substitute achieved good results because it worked as a guide to the accurate angle.

Healing potential of nanohydroxyapatite, gelatin, and fibrin-platelet glue combination as tissue engineered scaffolds in radial bone defects of rats

Different biomaterials have been used in orthopedic surgery. Evaluation of biomaterials for bone healing promotion has been a wide area of research of the orthopedic field. Sixty critical size defects of 5 mm long were bilaterally created in the radial diaphysis of 30 rats. The animals were randomly divided into six equal groups as empty defect, autograft, nanohydroxyapatite (nHA), Gelatin (Gel)-nHA, fibrin-platelet glue (FPG)-nHA, and Gel-FPG-nHA groups (n = 10 in each group). Radiographs of each forelimb were taken postoperatively on the 1st day and then at the 28th and 56th days post injury. After 56 days, the rats were euthanized and their harvested healing bone samples were evaluated by histopathology, scanning electron microscopy, and biomechanical testing. All the treated defects demonstrated significantly superior new bone formation, remodeling, and bone tissue volume. Moreover, the defects treated with FPG-nHA showed significantly higher ultimate load, yield load, and stiffness. The Gel-FPG-nHA moderately improved bone regeneration that was not close to the autograft in some parameters, whereas FPG-nHA significantly improved bone healing closely comparable with the autograft group in most parameters. In conclusion, although all the nHA-containing scaffolds had some beneficial effects on bone regeneration, the FPG-nHA scaffold was more effective in improving the structural and functional properties of the newly formed bone and was more osteoinductive than the Gel and was comparable to the autograft. Therefore, the FPG can be regarded as a promising option to be used in conjunction with mineral scaffolds for bone tissue engineering.

The effects of gelatin, fibrin-platelet glue and their combination on healing of the experimental critical bone defect in a rat model: radiological, histological, scanning ultrastructural and biomechanical evaluation

Fibrin-platelet glue (FPG) is a blood derivative, in which platelets and fibrinogen are concentrated in a small plasma volume, by differential centrifugation and precipitation. It can form a three-dimensional and biocompatible fibrin scaffold with a myriad of growth factors and proteins that are released progressively to the local environment and contribute to the accelerated postoperative bone healing. Gelatin (Gel) is a derivative of collagen and can promote cell adhesion and proliferation due to its unique sequence of amino acids, so it is suitable for bone tissue applications. This study examined the effects of Gel, FPG and their combinations as bone scaffold on the healing of surgically created critical-size defects in rat radius. Fifty critical size defects of 5 mm long were bilaterally created in the radial diaphysis of 25 rats. The animals were randomly divided into five equal groups as empty defect, autograft, Gel, FPG and Gel-FPG groups (n = 10 in each group). Radiographs of each forelimb were taken postoperatively on the 1st day and then at the 28th and 56th days post injury to evaluate bone formation, union and remodeling of the defect. After 56 days, the rats were euthanized and their harvested healing bone samples were evaluated by histopathology, scanning electron microscopy (SEM) and biomechanical testing. The results of present study showed that the Gel alone did not significantly affect bone healing and regeneration; however, the Gel treated defects promoted healing more than those that were left untreated (negative control). Furthermore, the FPG-enhanced grafts provided a good scaffold containing numerous growth factors for proliferation of osteoinduction and was effective in improving the structural and functional properties of the newly formed bone more than that of the untreated and also the Gel treated groups. Incorporation of Gel into the FPG scaffold improved healing potential of the FPG scaffold; however, it was still inferior to the autograft (positive control). Although the Gel-FPG scaffolds had best effectiveness during bone regeneration, it still needs to be further enhanced by incorporation of the ceramic and osteoinductive biomaterials.

Comparison of Clinical and Radiological Outcomes of Lumbar Interbody Fusion Using a Combination of Hydroxyapatite and Demineralized Bone Matrix and Autografts for Lumbar Degenerative Spondylolisthesis

Study Design

Prospective, cohort, non-inferiority study.

Purpose

This study evaluated the clinical and radiological outcomes of interbody fusion using a combination of demineralized bone matrix (DBM) and hydroxyapatite (HA).

Overview of Literature

The use of autografts remains a gold standard in lumbar interbody fusion, but the limited availability and donor site morbidity encourages the use of bone substitutes. In addition to autografts, a combination of HA and DBM is being increasingly use for lumbar interbody fusion. However, there are no data on the clinical and radiological outcomes of this procedure.

Methods

We examined 35 patients with lumbar degenerative spondylolisthesis who underwent transforaminal interbody fusion. Autografts were used in 18 patients, and 17 patients received a combination of HA and DBM. Clinical outcomes were evaluated using the visual analog scale (VAS) for back and leg pain, Oswestry disability index (ODI), and Japanese Orthopaedic Association (JOA) scores at 3, 6, and 12 months postoperatively. Fusion was evaluated using computed tomography images obtained at 12 months postoperatively.

Results

The mean ODI, JOA, and back and leg pain VAS scores increased significantly in both groups. However, the VAS, JOA, and ODI scores did not differ significantly between the two groups (p=0.599, p=0.543, and p=0.780, respectively). The fusion rates at 1 year postoperatively were 77.8% and 76.5% in the autograft and HA+DBM groups, respectively (p=0.99).

Conclusions

The clinical and radiological outcomes of using a combination of HA and DBM in lumbar interbody fusion were not inferior to those of using autografts. A combination of HA and DBM can be considered as an alternative in patients with lumbar degenerative spondylolisthesis requiring surgery.

Effects of Rat Bone Marrow-Derived Mesenchymal Stem Cells and Demineralized Bone Matrix on Cranial Bone Healing

BACKGROUND

Studies in tissue engineering about mesenchymal stem cells (MSCs) provide promising results for bone regeneration. The aim of this study was to evaluate the effects of rat bone marrow-derived MSCs (rMSCs) alone and when combined with demineralized bone matrix (DBM) on critical-sized cranial defects of rats.

METHODS

Ten rats were used to obtain allogeneic rMSCs. Forty rats were separated equally into 4 groups. A full-thickness circular bone defect was created in the frontal bone of the rats. Group 1 was an operative control group. In group 2 DBM, in group 3 rMSCs, and in group 4 DBM combined with rMSCs were applied into the defects. Bone regeneration was evaluated by computed tomographic analysis and immunohistochemistry.

RESULTS

In radiological evaluation, the percentage of area healed in group 3 at the 12th week was statistically significantly greater than in group 1. In group 3 and group 4, distributed healing patterns were observed more than in group 2 and in group 1. Immunohistochemical evaluation revealed that group 4 had the best osteoinductive potential. Osteoinductive potential of group 3 was similar to group 2 and was better than group 1.

CONCLUSIONS

Allogeneic rMSC applications have created a statistically significant radiologic reduction of the bone defect areas at the end of the 12 weeks. The MSC applications have also increased the bone density and changed the healing patterns. Combined use of the DBM and rMSCs has created more osteoinductive responses. This combination can provide better results in craniofacial bone reconstruction.

Assessment of polycaprolacton (PCL) nanocomposite scaffold compared with hydroxyapatite (HA) on healing of segmental femur bone defect in rabbits

Segmental bone loss due to trauma, infection, and tumor resection and even non-union results in the vast demand for replacement and restoration of the function of the lost bone. The objective of this study is to utilize novel inorganic-organic nanocomposites for biomedical applications. Biodegradable implants have shown great promise for the repair of bone defects and have been commonly used as bone substitutes, which traditionally would be treated using metallic implants. In this study, 45 mature male New Zealand white rabbits 6-8 months and weighting 3-3.5 kg were examined. Rabbits were divided into three groups. Surgical procedures were done after an intramuscular injection of Ketamine 10% (ketamine hydrochloride, 50 mg/kg), Rompun 5% (xylazine, 5 mg/kg). Then an approximately 6 mm diameter - 5 mm cylinder bone defect was created in the femur of one of the hind limbs. After inducing the surgical wound, all rabbits were colored and randomly divided into three experimental groups of nine animals each: Group 1 received medical pure nanocomposite polycaprolactone (PCL) granules, Group 2 received hydroxyapatite and Group 3 was a control group with no treatment. Histopathological evaluation was performed on days 15, 30 and 45 after surgery. On day 45 after surgery, the quantity of newly formed lamellar bone in the healing site in PCL group was better than onward compared with HA and control groups. Finally, nanocomposite PCL granules exhibited a reproducible bone-healing potential.

Incorporation of nanostructured hydroxyapatite and poly(N-isopropylacrylamide) in demineralized bone matrix enhances osteoblast and human mesenchymal stem cell activity

Demineralized bone matrix (DBM) is currently used in many clinical applications for bone augmentation and repair. DBM is normally characterized by the presence of bone morphogenetic proteins. In this study, the authors have optimized methods to obtain DBM under good manufacturing practice, resulting in enhanced bioactivity. The processed DBM can be used alone, together with nanostructured hydroxyapatite (nanoHA), or dispersed in a physiological carrier or hydrogel. In this study, osteoblasts (MG-63) and human bone marrow derived mesenchymal stem cells (hMSCs) were cultured on DBM pastes made in phosphate buffered saline solution or poly(N-isopropylacrylamide) (PNIPAAM) hydrogels with or without nanoHA. The authors observed that the presence of PNIPAAM reduced osteoblast adhesion, while the addition of nanoHA increased osteoblast adhesion, proliferation, interleukin-6 (IL-6) production, and reduced lactate dehydrogenase (LDH) production. Increasing concentrations of PNIPAAM in combination with nanoHA further increased osteoblast proliferation, and decreased IL-6 and LDH production. Incorporation of PNIPAAM in DBM enhanced hMSCs proliferation and collagen type-I production. Furthermore, a combination of PNIPAAM and nanoHA further increased alkaline phosphatase and osteocalcin production in hMSCs, independently from the concentration of PNIPAAM. This study shows that combinations of DBM with nanoHA and PNIPAAM seem to offer a promising route to enhance cell activity and induce osteogenic differentiation.

Histologic Evaluation of Critical Size Defect Healing With Natural and Synthetic Bone Grafts in the Pigeon ( Columba livia ) Ulna

Fracture and bone segment loss are major clinical problems in birds. Achieving bone formation and clinical union in a fracture case is important for the survival of the bird. To evaluate the efficacy of bone grafts for defect healing in birds, 2 different bone grafts were investigated in the healing of a bone defect in 24 healthy pigeons ( Columba livia ). In each bird, a 1-cm critical size defect (CSD) was created in the left ulna, and the fracture was stabilized with external skeletal fixation (ESF). A graft of hydroxyapatite (HA) alone (n = 12 birds) or demineralized bone matrix (DBM) combined with HA (n = 12 birds) was implanted in the CSD. The CSD healing was evaluated at 3 endpoints: 3, 6, and 12 weeks after surgery. Four birds were euthanatized at each endpoint from each treatment group, and bone graft healing in the ulna CSD was evaluated by histologic examination. The CSD and graft implants were evaluated for quality of union, cortex development, and bone graft incorporation. Results showed no graft rejection in any bird, and all birds had connective tissue formation in the defect because of the bone graft application. These results suggest that bone defect healing can be achieved by a combination of osteoinductive and osteoconductive bone graft materials for clinical union and new bone regeneration in birds. The combination of DBM and HA resulted in a better quality bone graft (P < .05) than did HA alone, but there was no significant differences in cortex development or bone graft incorporation at 3, 6, or 12 weeks. From the results of this study, we conclude that HA bone grafts, alone or in combination with DBM, with external skeletal fixation is suitable and safe for bone defect and fracture treatment in pigeons.

Transplantation of mesenchymal stem cells, recombinant human BMP-2,and their combination in accelerating the union after osteotomy and increasing, the mechanical strength of extracorporeally irradiated femoral autograft in rat models

BACKGROUND

Delayed union, nonunion, and mechanical failure is still problems encountered in limb salvage surgery (LSS) using extracorporeal irradiation (ECI). This study aimed to determine whether bone marrow mesenchymal stem cells (MSC) and recombinant human bone morphogenetic protein-2 (rhBMP-2) improve hostgraft union after osteotomy and also increase its mechanical strength.

METHODS

Thirty Sprague Dawley rats were randomly divided into five groups. Group I (control) underwent LSS using ECI method with 150 Gy single doses. Similar procedures were applied to other groups. Group II received hydroxyapatite (HA) scaffold. Group III received HA scaffold and MSC. Group IV received HA scaffold and rhBMP-2. Group V received HA scaffolds, MSC, and rhBMP-2. Radiograph were taken at week-2, 4, 6, and 8; serum alkaline phosphatase and osteocalcin were measured at week-2 and 4. Histopathological evaluation and biomechanical study was done at week-8.

RESULTS

The highest radiological score was found in group IV and V Similar result was obtained in histological score and ultimate bending force. These results were found to be statistically significant. There was no significant difference among groups in serum alkaline phosphatase and osteocalcin level.

CONCLUSION

Combination of MSC and rhBMP-2 was proven to accelerate union and improve mechanical strength of ECI autograft.

Effect of extracorporeal irradiation on segmental bone autograft incorporation in Sprague-Dawley rats

Background: Bone graft has been widely used in bone tumor reconstructive surgery. Extracorporeal irradiation (ECI) is commonly used to eliminate malignant cells before bone autograft. However, it may have negative effects on autograft incorporation. This study aimed to evaluate the ability of bone autograft incorporation after extra corporeal irradiation.Methods: 24 Sprague-Dawley rats underwent 7-mm en bloc resection of tibial diaphysis, and were divided into 4 groups. The first group did not receive irradiation; the 2nd, 3rd, and 4th groups received 50, 150 and 300 Gy bone irradiation respectively, and then reimplanted. Radiologic score were evaluated at week-6 and -8, while histopathology, osteoblast count and BMP-2 expression were examined at week-8. Data were analyzed with ANOVA or Kruskal-Wallis tests.Results: At week-6, radiologic scores in group 150 and 300 Gy were significantly lower compared to control group (4 vs 6 dan 4 vs 6; p = 0.011; p = 0.01). The same results were also obtained at week-8 (5.40 vs 7.14; p = 0.009 in the group 150 Gy and 5.60 vs 7.14; p = 0.018 in the group 300 Gy. Histopathological scores of the groups receiving 50, 150 and 300 Gy were significantly lower compared to the control group (6 vs 7, p = 0.017; 4 vs 7, p = 0.005; 6 vs 7, p = 0.013). Osteoblast count and BMP-2 expression were not significantly different among all groups.Conclusion: ECI with the dose of 50 to 300 Gy is associated with delayed bone autograft incorporation. However, the osteoinductive and osteogenesis capacity for autograft incorporation were maintained.

Reconstruction of radial bone defect using gelatin sponge and a BMP-2 combination graft

Many bioactive molecules like recombinant human bone morphogenetic protein 2 (rhBMP-2) have been developed for mineralized bone grafts, for which proper scaffolds are necessary to successfully apply the bioactive molecules. In this study, we tested the osteogenic efficacy of rhBMP-2 produced in-house in combination with gelatin sponge as the scaffold carrier in a rabbit radial defect model. The efficacy of the rhBMP-2 was determined by alkaline phosphatase activity assay of C2C12 cells. Two groups of ten rabbits each were treated with rhBMP-2/gelatin sponge, or gelatin sponge only. At 4 weeks, rhBMP-2/gelatin sponge grafts showed more bone regeneration than gelatin sponge grafts, as determined by X-ray radiography, micro-computed tomography, and histological analyses. At 8 weeks, rhBMP-2/gelatin sponge grafts exerted much stronger osteogenic effects. The study demonstrates the improved osteogenic efficacy of the rhBMP-2/gelatin sponge grafts in a rabbit radial bone defect model acting as a bone-inductive material. [BMB Reports 2013; 46(6): 328-333]

Combined effects of porous hydroxyapatite and demineralized bone matrix on bone induction: in vitro and in vivo study using a nude rat model

Hydroxyapatite (HA) is an osteoconductive material used as a bone graft extender and demineralized bone matrix (DBM) has been used as a source of osteoinductive factors. A combination of DBM and HA is expected to create a composite with both osteoconductive and osteoinductive properties. This study examined the effect of a combination of DBM and HA on osteogenesis both in vitro and in vivo using an athymic nude rat abdominal muscle pouch model, and evaluated the possibility of HA as a carrier of DBM. Alkaline phosphatase (ALP) staining, ALP assay and measurements of the mRNA expression of ALP and Runx2 by RT-PCR were performed by transplanting human mesenchymal stem cells onto a plate. Five athymic nude rats each were assigned to one of two experimental groups (DBM/HA putty and only HA, i.e. 15 pouches per group). The muscle pouches were filled with DBM/HA putty or only HA. Radiographs were obtained at weeks 4 and 8, postoperatively. The animals were sacrificed at week 8 postoperatively and high resolution microCT was used to confirm the newly formed mineralized tissue. Each pouch was fixed, embedded, sectioned and processed for hematoxylin and eosin staining. The ALP value of the DBM/HA putty was higher than those of HA and control (p < 0.05, each). The expression of ALP mRNA appeared higher on the DBM/HA putty than on HA and control. MicroCT and histology examinations of the DBM/HA putty demonstrated the presence of newly generated mineralized tissues but there was no mineralized tissue in the HA cases. In conclusion, the DBM/HA putty indicated osteoblastic differentiation in vitro and showed ectopic mineralized tissue formation in the rat abdominal pouch model. These findings indicate that the DBM/HA putty can retain its oteoinductivity and HA can be used as a carrier of DBM.

Influence of polymer content in Ca-deficient hydroxyapatite-polycaprolactone nanocomposites on the formation of microvessel-like structures

Calcium phosphate (CaP) ceramics are widely used in bone tissue engineering due to their good osteoconductivity. The mechanical properties of CaP can be modified by the addition of small volume fractions of biodegradable polymers such as polycaprolactone (PCL). Nevertheless, it is also important to evaluate how the polymer content influences cell-material or cell-cell interactions because of potential consequences for bone regeneration and vascularization. In this study we assessed the general biocompatibilty of Ca-deficient hydroxyapatite (CDHA)-PCL disks containing nominally 11 and 24% polycaprolactone using human umbilical vein endothelial cells and human primary osteoblasts. Confocal microscopy showed that both CDHA-PCL variants supported the growth of both cell types. In terms of the endothelial cells grown on CDHA-PCL nanocomposites with 24% PCL, an increased expression of the endothelial marker vWF compared to CDHA-PCL with 11% PCL was observed in real-time polymerase chain reaction analysis. In addition to monocultures, co-cultures of outgrowth endothelial cells, derived from peripheral blood, and primary osteoblasts were assessed as an example of a more complex test system for bone regeneration and vascularization. Constructs based on CDHA with different PCL contents were investigated with regard to the formation of microvessel-like structures induced by the co-culture process using confocal microscopy and quantitative image analysis. Furthermore, the osteogenic differentiation of the co-culture was assessed. As a result, more pre-vascular structures were observed after 1 week on the CDHA-PCL disks with 24% PCL, whereas after 4 weeks of culture the extent of microvessel-like structure formation was slightly higher on the CDHA with 11% PCL. In contrast to this, variation of PCL content had no effect on the osteogenic differentiation in the co-culture.

COMPARATIVE STUDY OF BONE NEOFORMATION USING AUTOLOGOUS GRAFTING AND THREE REPLACEMENTS: BONE DEFECTS IN RATS

Objective: Compare the percentage of bone neoformation promoted by autologous bone grafting and three kinds of replacement materials with different characteristics in rats' femoral holes. Methods: Two holes measuring 5.4×2.7mm, were produced on each femur (right and left) of 14 isogenic Wistar rats. Each of the four defects produced was filled by autologous bone or by one of three tested materials-hydroxyapatite (HA), Genphos^® (HA+ β-TCP) and GenMix^® (a combined bovine bone graft). In the end of the 6-week (n = 6) and 12-week (n = 8) periods, the animals were sacrificed. The sections (stained with Picro-Sirius) were assessed by optical microscopy and specific software. Results: The groups with autologous bone were shown to be significantly superior to the others at both assessed times, showing a mean bone formation rate ± SD of 90.6 ± 10.8% in six weeks, and 98 ± 9.2% in 12 weeks (p > 0.0001 for both assessed times). In six weeks, the results for the other groups were the following: Genphos^®, 46 ± 7.1%; HA, 43.1 ± 8.4%; and GenMix^®, 57.3 ± 4.5%. In 12 weeks: Genphos^®, 47.8 ± 11.1%; HA, 39.9 ± 5.4%; GenMix^®, 59.7 ± 4.8%, significant (p = 0.007). Conclusions: In both assessed times, the three bone replacement materials tested in the study showed to be inferior to autologous bone graft for bone neoformation percentage.