Presence of Cells in Fresh-Frozen Allogeneic Bone Grafts from Different Tissue Banks

Experimental Study on the Application of Bioactive Xenogeneic Porcine Cancellous Bone for Cervical Intervertebral Fusion in Goats

STUDY DESIGN

An experimental study in a cervical intervertebral fusion goat model.

OBJECTIVE

To investigate the effect of bioactive xenogeneic porcine cancellous bone applied to the intervertebral fusion of goat cervical vertebrae.

SUMMARY OF BACKGROUND DATA

Although autogenous bone achieves satisfied outcome in cervical intervertebral fusion, it is limited and cause several complications. The application of xenogeneic bone has potential to solve these problems.

METHODS

Thirty local goats were randomly divided into 3 groups: group A (12 goats): autogenous tricortical iliac bone group; group B (6 goats): polyetheretherketone (PEEK) cage with autologous bone; and group C (12 goats): PEEK cage with bioactive xenogeneic porcine cancellous bone. C3-C4 discectomy was performed in each group and the above bone graft and bone graft substitutes were implanted. Lateral cervical spine x-rays were taken at preoperative; immediately postoperative; and 4, 8, 12, and 24 weeks postoperatively every goat. Disc space heights (DSHs) were measured on lateral x-rays. CT examination was performed at 12 and 24 weeks after surgery for the fusion score. After 4 and 8 weeks after surgery, 3 goats were euthanized in both groups A and C to evaluate the immune rejection response through histology. At 12 and 24 weeks after surgery, 3 goats were euthanized in each group. The cervical implants fusion outcome was evaluated through specimen histology observation.

RESULT

As time extended, the immune rejection of bioactive xenogeneic porcine cancellous bone gradually subsided. Radiology, specimen observation, and histology manifested that the C3-4 vertebral bodies of goats in each group gradually fused. All the goats in each group achieved bony fusion at 24 weeks after surgery. In terms of preventing intervertebral space collapse, the PEEK cage could achieve better results. There was no significant difference in the remaining experimental data (P>0.05).

CONCLUSIONS

Bioactive xenogeneic porcine cancellous bone can obtain satisfied fusion outcomes in cervical intervertebral fusion and is an ideal intervertebral fusion material in goats.

Biological parameters for quality evaluation of allografts from the Brazilian National Institute of Traumatology and Orthopedics tissue bank

Bone allografts are clinically used in a variety of surgical procedures, and tissue banks are responsible for harvesting, processing, quality testing, storing, and delivering these materials for transplantation. In tissue banks, the bone is processed for the removal of all organic content, remaining only the tissue structure (scaffold). However, several studies have shown that even after using different processing methods, viable cells, functional proteins, and DNA may still persist in the tissue, which constitute the main causes of graft rejection. Therefore, the objective of this study was to establish techniques and biological parameters for quality validation of allografts. To this end, we propose the use of 3 combined methods such as microscopy, histology, and molecular biology techniques to evaluate the quality of allografts harvested and processed by the Brazilian National Institute of Traumatology and Orthopedics (INTO) tissue bank according to the donation criteria of the Brazilian National Health Surveillance Agency and the Brazilian National Transplant System. Bone fragments from different processing stages showed no viable cells on histology, an intact extracellular matrix on scanning electron microscopy, and gradual reduction in DNA amount. Different techniques were used to demonstrate the quality of allografts produced by the INTO tissue bank and to establish biological parameters for ensuring the safety and quality of these products. Future studies need to be undertaken to assess and validate the efficacy of the decellularization process in larger bone grafts with diverse architectural configurations.

Characterization of immunologically detectable T-cell sensitization, Immunohistochemical detection of pro-inflammatory cytokines, and clinical parameters of patients after allogeneic intraoral bone grafting procedures: a prospective randomized controlled clinical trial in humans

BACKGROUND

The null hypotheses were tested that intraoral bone augmentation using two different allogeneic materials has no impact on the patient's blood levels of material-specific lymphocytes and on the immunohistochemical detection of pro-inflammatory cytokines IL-1α, IL1ß and TNF-α and T-cell markers CD4, CD8 in biopsies of the test groups.

METHODS

In this prospective RCT, 60 systemically healthy participants were randomly assigned to two allogeneic test groups (1: Maxgraft®, freeze-dried, multiple donors, and 2: Puros®, solvent-dehydrated, single donor) and an autologous control group (10 patients). Plasma samples were collected pre-(T1) and postoperatively (2 weeks (T2) and 4 months (T3)). The Lymphocyte Transformation Test (LTT) was used for analyzing levels of transformed lymphocytes for type IV immune reactions by 3H-thymidine activity. Bone biopsies were harvested at T3 and immunohistochemically analyzed for IL-1α, IL1ß, TNF-α, CD4, CD8 and correlated with the immunological and clinical findings.

RESULTS

A statistically significant difference between the tested materials was observed for LTT measurements at T3 (p = 0.033). Furthermore, three groups were identified: Group A (LTT negative T1-T3, n = 48), group B (LTT positive T1-T3, n = 7), group C (developing positive LTT at T2, n = 5). A highly significant elevation of IL-1α, IL1ß, TNF-α in patients of group C (p = 0.0001) and a significant elevation of CD4+ cells in patients of group B (p = 0.005) was shown.

CONCLUSION

Our data show that following allogeneic bone grafting, local and systemic immunological reactions can be detected in some patients. These findings were statistically significant for the timepoint T3 between the tested materials as well as for the groups B and C correlated with group A for both tested materials. Therefore, the null hypotheses were rejected. A preoperative compatibility test for allogeneic materials in order to improve patient safety and the predictability of these materials would be desirable.

TRIAL REGISTRATION

Ethical commission of the Ärztekammer Hamburg, Germany (PV5211) as well as by the German Registry of Clinical Studies (DRKS00013010) on 30/07/2018 ( http://apps.who.int/trialsearch/ ).

Improved Biocompatible, Flexible Mesh Composites for Implant Applications via Hydroxyapatite Coating with Potential for 3-Dimensional Extracellular Matrix Network and Bone Regeneration

Hydroxyapatite (HA)-coated metals are biocompatible composites, which have potential for various applications for bone replacement and regeneration in the human body. In this study, we proposed the design of biocompatible, flexible composite implants by using a metal mesh as substrate and HA coating as bone regenerative stimulant derived from a simple sol-gel method. Experiments were performed to understand the effect of coating method (dip-coating and drop casting), substrate material (titanium and stainless steel) and substrate mesh characteristics (mesh size, weave pattern) on implant's performance. HA-coated samples were characterized by X-ray diffractometer, transmission electron microscope, field-emission scanning electron microscope, nanoindenter, polarization and electrochemical impedance spectroscopy, and biocompatibility test. Pure or biphasic nanorod HA coating was obtained on mesh substrates with thicknesses varying from 4.0 to 7.9 μm. Different coating procedures and number of layers did not affect crystal structure, shape, or most intense plane reflections of the HA coating. Moduli of elasticity below 18.5 GPa were reported for HA-coated samples, falling within the range of natural skull bone. Coated samples led to at least 90% cell viability and up to 99.5% extracellular matrix coverage into a 3-dimensional network (16.4% to 76.5% higher than bare substrates). Fluorescent imaging showed no antagonistic effect of the coatings on osteogenic differentiation. Finer mesh size enhanced coating coverage and adhesion, but a low number of HA layers was preferable to maintain open mesh areas promoting extracellular matrix formation. Finally, electrochemical behavior studies revealed that, although corrosion protection for HA-coated samples was generally higher than bare samples, galvanic corrosion occurred on some samples. Overall, the results indicated that while HA-coated titanium grade 1 showed the best performance as a potential implant, HA-coated stainless steel 316 with the finest mesh size constitutes an adequate, lower cost alternative.

Study of Cell Viability and Etiology of Contamination in Decalcified Bone Allograft: A Pilot Study

BACKGROUND

Bone allografts can elicit immune responses which is correlated with the presence of Human Leukocyte Antigen (HLA) and cellular DNA. It also has risk of causing occult infection arising out of contamination during its processing and storage. The presence of immunogenic materials like cells, cellular remnants and DNA in a decalcified bone allograft during different phases of processing has never been studied. Present study was conducted to explore- the cell viability using routine Hematoxylin and Eosin, presence of DNA using Feulgen staining and etiology of contamination in decalcified bone allograft during procurement, demineralization and ethanol preservation.

METHODS

The harvested bones from patients undergoing hemireplacement/THR/TKR were processed to prepare decalcified bone allografts. The samples during procurement (A), HCL treatment (B) and ethanol preservation (C) were sent for histopathological analysis (number of osteocytes in the maximum density field under 40x and the cells demonstrating presence of DNA on feulgen stain) and microbiological assessment (aerobic/anaerobic/fungal cultures).

RESULTS

Histopathological study demonstrated the presence of osteocytes and other cells like bone marrow, adipocytes, endothelial cells in the decal bone allograft. The average number of osteocytes gradually decreased from 55.47, 9.6, 0.86 in sample A, B, C, respectively. Feulgen staining confirmed the presence of DNA in osteocytes and other cells which decreased both qualitatively and quantitatively in subsequent stages of processing. Rate of contamination demonstrated at the procurement was 6.67% (Staphylococcus aureus). After treatment with HCl (demineralisation), 7.14% of non-contaminated allografts were found contaminated (Staphylococcus epidermidis). None of the remaining 13 non-contaminated allografts showed contamination after storage in ethanol. Overall 13% of the patients had positive cultures on microbiological assessment.

CONCLUSION

The population of osteocytes in the harvested bone reduced significantly after processing with HCl and ethanol preservation. Presence of DNA, demonstrated by using Feulgen staining, was observed in bone marrow cells, adipocytes along with osteocytes which showed quantitative reduction on processing. Hence, antigenicity, conferred by cells and their DNA, reduced significantly after processing of decal bone. Contamination rate of banked decalcified allograft was 13%. Thus, culture and sensitivity tests should be carried out at each step of processing of decal bone allograft.

Fresh-frozen homologous bone in sinus lifting: histological and radiological analysis

BACKGROUND

The aim of this study was to evaluate radiological and histological characteristics of fresh-frozen homologous bone as grafting material for maxillary sinus floor augmentation. Radiological, histological and clinical evaluations were made.

METHODS

Twenty-three patients with a 2 mm to 6 mm alveolar ridge height in the posterior maxilla have been enrolled. Unilateral or bilateral sinus floor augmentations were performed with fresh frozen morcelized homologous bone. Together with implant placement, 7 months after surgery, a bone core was harvested for histological analysis. Radiological measurements were obtained by superimposition of CT scans carried out at the surgery time and six months later. A total of 93 implants were positioned.

RESULTS

A mean (±SD) increase in mineralized tissue height of 10.74±2.82 mm was noticed by comparing the CT scans. Histological analysis revealed the presence of newly formed bone in the grafted sites. The follow up period after the prosthetic load ranged from 8 to 31 months. One implant failure occurred.

CONCLUSIONS

Fresh frozen homologous bone seems to have a good healing pattern and to be a successful and steady grafting material for the treatment of maxillary ridge atrophy. It might be considered a valid alternative to autologous bone in sinus floor augmentation procedures.

Histological Evaluation of a New Beta-Tricalcium Phosphate/Hydroxyapatite/Poly (1-Lactide-Co-Caprolactone) Composite Biomaterial in the Inflammatory Process and Repair of Critical Bone Defects

Background: The use of biomaterials is commonplace in dentistry for bone regeneration. The aim of this study was to evaluate the performance of a new alloplastic material for bone repair in critical defects and to evaluate the extent of the inflammatory process. Methods: Forty-five New Zealand rabbits were divided into five groups according to evaluation time (7, 14, 30, 60, 120 days), totaling 180 sites with six-millimeter diameter defects in their tibiae. The defects were filled with alloplastic material consisting of poly (lactide-co-caprolactone), beta-tricalcium phosphate, hydroxyapatite and nano-hydroxyapatite (BTPHP) in three different presentations: paste, block, and membrane. Comparisons were established with reference materials, such as Bio-ossTM, Bio-oss CollagenTM, and Bio-gideTM, respectively. The samples were HE-stained and evaluated for inflammatory infiltrate (scored for intensity from 0 to 3) and the presence of newly formed bone at the periphery of the defects. Results: Greater bone formation was observed for the alloplastic material and equivalent inflammatory intensity for both materials, regardless of evaluation time. At 30 days, part of the synthetic biomaterial, regardless of the presentation, was resorbed. Conclusions: We concluded that this novel alloplastic material showed osteoconductive potential, biocompatibility, low inflammatory response, and gradual resorption, thus an alternative strategy for guided bone regeneration.

Detection of major histocompatibility complex molecules in processed allogeneic bone blocks for use in alveolar ridge reconstruction

OBJECTIVES

Because processed allogenic bone blocks contain remnants of cells and other organic material, the present study examined the putative presence of major histocompatibility complex (MHC) molecules in protein extracts derived from processed allogeneic bone blocks.

STUDY DESIGN

Protein content and the immunogenic potential of 3 different processed allografts (Osteograft, DIZG, Berlin, Germany; Caput femoris, DIZG, Berlin, Germany; Human Spongiosa, Charité Tissue Bank, Berlin, Germany) were assessed by protein extraction and analysis of the presence of MHC class 1 and 2 molecules prior to grafting. MHC concentration was measured by using enzyme-linked immunosorbent assay.

RESULTS

Protein content in the allograft materials varied between 0.87 and 1.61 µg protein/mg. In the allograft Human Spongiosa, no MHC was detected, whereas in the allogeneic bone blocks Osteograft and Caput femoris MHC 1 (0.04-0.037 ng/mg graft material) and in Osteograft MHC class 2 molecules were detectable.

CONCLUSIONS

The results of the present study suggest that despite thorough processing, a potential antigenicity of allografts is not eliminated. MHC molecules in allografts may sensitize the immune system.

Evaluation of the Safety and Clinical Efficacy of Allogeneic Bone Grafts in the Reconstruction of the Maxilla and Mandible

INTRODUCTION

Loss of teeth caused by inflammatory processes or trauma is one of the causes of bone atrophy of the maxilla alveolar process and the alveolar part of the mandible. Often, restoring these deficiencies with dental implants requires additional reconstructive procedures. Methods using autogenous, allogeneic, xenogeneic, or synthetic bone grafts are commonly used.

MATERIALS AND METHODS

Patients who had bone atrophy of the maxilla or mandible were qualified for deep-frozen transplantation, radiation-sterilized allogeneic bone from the Bank of Tissues in the form of cortico-spongy bone blocks and spongy bone granules. Bone blocks were stabilized with titanium screws, and the free spaces were additionally supplemented with chips from autogenous bone and covered with allogeneic pericardial transplants and platelet-rich fibrin (PRF). Four months after the bone reconstruction, titanium implants were placed, and then after the osseointegration period prosthetic restoration was performed. Clinical safety and efficacy were determined by analyzing the quantity and quality of the reconstructed bone tissue and the degree of resorption was assessed.

RESULTS

The surgical procedures performed confirmed the safety and efficacy of biological material in the reconstruction of the jaw. In two cases, the treatment was not effective and the transplant was removed. In the remaining cases, titanium implants were successfully placed and loaded with prosthetic works.

DISCUSSION

Implanting deeply frozen, radiation-sterilized bone is a safe and effective surgical procedure. As an appropriate technique for fixing the allogeneic bone block, additional use of autogenous bone chips and PRF allows one to obtain a good, long-lasting clinical result.