Development of a decellularized porcine bone graft by supercritical carbon dioxide extraction technology for bone regeneration

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.

Regenerative Efficacy of Supercritical Carbon Dioxide-Derived Bone Graft Putty in Rabbit Bone Defect Model

Bone defects can arise from numerous reasons, such as aging, tumor, trauma, infection, surgery, and congenital diseases. Bone grafts are commonly used as a substitute to fill the void and regenerate the defect. Due to its clean and green technology, the supercritical carbon dioxide (SCCO2) extraction aided the production of bone grafts is a recent trend. The SCCO2-derived bone graft has osteoconductive and osteoinductive properties along with excellent biocompatible, nontoxic, bioabsorbable, osteoconductive, and good mechanical properties; however, clinical usage during surgery is time-consuming. Therefore, we produced a putty material combining bone graft powder and acellular dermal matrix (ADM) powder and tested its regenerative efficacy in the critical defect in the rabbit model. The putty was found to retain the tubular structure. In addition, the putty depicted excellent stickiness and cohesiveness in both saline and blood medium. The bone regeneration of bone graft and putty was similar; both had excellent bone healing and regeneration of critical defects as evaluated by the X-ray, microtomography, hematoxylin-eosin, Masson trichrome, and alizarin red staining. Putty contains a less washout rate, good mechanical strength, and biocompatibility. In conclusion, the SCCO2-derived moldable putty could be a promising easy-to-use alternative for bone grafts at present which might have real-world usage in orthopedics as a potential bone void filler and dental socket preservation.

Criteria, Challenges, and Opportunities for Acellularized Allogeneic/Xenogeneic Bone Grafts in Bone Repairing

As bone grafts become more commonly needed by patients and as donors become scarcer, acellularized bone grafts (ABGs) are becoming more popular for restorative purposes. While autogeneic grafts are reliable as a gold standard, allogeneic and xenogeneic ABGs have been shown to be of particular interest due to the limited availability of autogeneic resources and reduced patient well-being in long-term surgeries. Because of the complete similarity of their structures with native bone, excellent mechanical properties, high biocompatibility, and similarities of biological behaviors (osteoinductive and osteoconductive) with local bones, successful outcomes of allogeneic and xenogeneic ABGs in both in vitro and in vivo research have raised hopes of repairing patients' bone injuries in clinical applications. However, clinical trials have been delayed due to a lack of standardized protocols pertaining to acellularization, cell seeding, maintenance, and diversity of ABG evaluation criteria. This study sought to uncover these factors by exploring the bone structures, ossification properties of ABGs, sources, benefits, and challenges of acellularization approaches (physical, chemical, and enzymatic), cell loading, and type of cells used and effects of each of the above items on the regenerative technologies. To gain a perspective on the repair and commercialization of products before implementing new research activities, this study describes the differences between ABGs created by various techniques and methods applied to them. With a comprehensive understanding of ABG behavior, future research focused on treating bone defects could provide a better way to combine the treatment approaches needed to treat bone defects.

Supercritical Carbon Dioxide Decellularized Xenograft-3D CAD/CAM Carved Bone Matrix Personalized for Human Bone Defect Repair

About 30-50% of oral cancer patients require mandibulectomy and autologous fibula reconstruction. Autograft is the gold standard choice because of its histocompatibility; however, it requires additional surgery from the patient and with possible complications such as loss of fibula leading to calf weakening in the future. Allograft and xenograft are alternatives but are susceptible to immune response. Currently, no personalized bone xenografts are available in the market for large fascial bone defects. In addition, a large-sized complex shape bone graft cannot be produced directly from the raw material. We propose the use of porcine bones with 3D CAD/CAM carving to reconstruct a personalized, wide range and complex-shaped bone. We anticipate that patients can restore their native facial appearance after reconstruction surgery. Supercritical CO2 (SCCO2) technology was employed to remove the cells, fat and non-collagenous materials while maintaining a native collagen scaffold as a biomedical device for bone defects. We successfully developed 3D CAD/CAM carved bone matrices, followed by SCCO2 decellularization of those large-sized bones. A lock-and-key puzzle design was employed to fulfil a wide range of large and complex-shaped maxillofacial defects. To conclude, the 3D CAD/CAM carved bone matrices with lock and key puzzle Lego design were completely decellularized by SCCO2 extraction technology with intact natural collagen scaffold. In addition, the processed bone matrices were tested to show excellent cytocompatibility and mechanical stiffness. Thus, we can overcome the limitation of large size and complex shapes of xenograft availability. In addition, the 3D CAD/CAM carving process can provide personalized tailor-designed decellularized bone grafts for the native appearance for maxillofacial reconstruction surgery for oral cancer patients and trauma patients.

Supercritical Carbon Dioxide Decellularized Bone Matrix Seeded with Adipose-Derived Mesenchymal Stem Cells Accelerated Bone Regeneration

Large bone fractures with segmental defects are a vital phase to accelerate bone integration. The present study examined the role of supercritical carbon dioxide (scCO2) decellularized bone matrix (scDBM) seeded with allogeneic adipose-derived mesenchymal stem cells (ADSC) as bio-scaffold for bone regeneration. Bio-scaffold produced by seeding ADSC to scDBM was evaluated by scanning electron microscopy (SEM). Rat segmental femoral defect model was used as a non-union model to investigate the callus formation in vivo. Histological analysis and osteotomy gap closure in the defect area were analyzed at 12 and 24 weeks post-surgery. Immunohistochemical expression of Ki-67, BMP-2 and osteocalcin was evaluated to assess the ability of new bone formation scDBM. ADSC was found to attach firmly to scDBM bioscaffold as evidenced from SEM images in a dose-dependent manner. Callus formation was observed using X-ray bone imaging in the group with scDBM seeded with 2 × 106 and 5 × 106 ASCs group at the same time-periods. H&E staining revealed ASCs accelerated bone formation. IHC staining depicted the expression of Ki-67, BMP-2, and osteocalcin was elevated in scDBM seeded with 5 × 106 ASCs group at 12 weeks after surgery, relative to other experimental groups. To conclude, scDBM is an excellent scaffold that enhanced the attachment and recruitment of mesenchymal stem cells. scDBM seeded with ASCs accelerated new bone formation.

Reconstruction of the orbital floor using supercritical CO2 decellularized porcine bone graft

Orbital floor fractures subsequently lead to consequences such as diplopia and enophthalmos. The graft materials used in orbital floor fractures varied from autografts to alloplastic grafts, which possess certain limitations. In the present study, a novel porcine bone matrix decellularized by supercritical CO2 (scCO2), ABCcolla® Collagen Bone Graft, was used for the reconstruction of the orbital framework. The study was approved by the institutional review board (IRB) of Kaohsiung Medical University Chung-Ho Memorial Hospital (KMUH). Ten cases underwent orbital floor reconstruction in KMUH in 2019. The orbital defects were fixed by the implantation of the ABCcolla® Collagen Bone Graft. Nine out of ten cases used 1 piece of customized ABCcolla® Collagen Bone Graft in each defect. The other case used 2 pieces of customized ABCcolla® Collagen Bone Graft in one defect area due to the curved outline of the defect. In the outpatient clinic, all 10 cases showed improvement of enophthalmos on CT (computerized tomography) at week 8 follow-up. No replacement of implants was needed during follow-ups. To conclude, ABCcolla® Collagen Bone Graft proved to be safe and effective in the reconstruction of the orbital floor with high accessibility, high stability, good biocompatibility, low infection rate and low complication rate.