Demineralized bone matrix in bone repair: history and use

Strategies for inclusion of growth factors into 3D printed bone grafts

There remains a critical need to develop new technologies and materials that can meet the demands of treating large bone defects. The advancement of 3-dimensional (3D) printing technologies has allowed the creation of personalized and customized bone grafts, with specific control in both macro- and micro-architecture, and desired mechanical properties. Nevertheless, the biomaterials used for the production of these bone grafts often possess poor biological properties. The incorporation of growth factors (GFs), which are the natural orchestrators of the physiological healing process, into 3D printed bone grafts, represents a promising strategy to achieve the bioactivity required to enhance bone regeneration. In this review, the possible strategies used to incorporate GFs to 3D printed constructs are presented with a specific focus on bone regeneration. In particular, the strengths and limitations of different methods, such as physical and chemical cross-linking, which are currently used to incorporate GFs to the engineered constructs are critically reviewed. Different strategies used to present one or more GFs to achieve simultaneous angiogenesis and vasculogenesis for enhanced bone regeneration are also covered in this review. In addition, the possibility of combining several manufacturing approaches to fabricate hybrid constructs, which better mimic the complexity of biological niches, is presented. Finally, the clinical relevance of these approaches and the future steps that should be taken are discussed.

Commercial Bone Grafts Claimed as an Alternative to Autografts: Current Trends for Clinical Applications in Orthopaedics

In the last twenty years, due to an increasing medical and market demand for orthopaedic implants, several grafting options have been developed. However, when alternative bone augmentation materials mimicking autografts are searched on the market, commercially available products may be grouped into three main categories: cellular bone matrices, growth factor enhanced bone grafts, and peptide enhanced xeno-hybrid bone grafts. Firstly, to obtain data for this review, the search engines Google and Bing were employed to acquire information from reports or website portfolios of important competitors in the global bone graft market. Secondly, bibliographic databases such as Medline/PubMed, Web of Science, and Scopus were also employed to analyse data from preclinical/clinical studies performed to evaluate the safety and efficacy of each product released on the market. Here, we discuss several products in terms of osteogenic/osteoinductive/osteoconductive properties, safety, efficacy, and side effects, as well as regulatory issues and costs. Although both positive and negative results were reported in clinical applications for each class of products, to date, peptide enhanced xeno-hybrid bone grafts may represent the best choice in terms of risk/benefit ratio. Nevertheless, more prospective and controlled studies are needed before approval for routine clinical use.

The choice between allograft or demineralized bone matrix is not unambiguous in trauma surgery

In fracture surgery, large bone defects and non-unions often require bone transplantation, and alternatives to autograft bone substitutes in the form of allografts from bone banks and the derivate demineralised bone matrix (DBM) are widely used. With a focus on efficacy, clinical evidence, safety, cost, and patient acceptance, this review evaluated the difference between allogeneic allograft or DBM as a bone substitute in trauma surgery. The efficacy in supporting bone healing from allograft and DBM is highly influenced by donor characteristics and graft processing. Mechanical stability is achieved from a structural graft. Based on the existing literature it is difficult to identify where DBM is useful in trauma surgery, and the level of evidence for the relevant use of allograft bone in trauma is low. The risk of transmitting diseases is negligible, and the lowest risk is from DBM due to the extensive processing procedures. A cost comparison showed that DBM is significantly more expensive. The experiences of dental patients have shown that many patients do not want to receive allografts as a bone substitute. It is not possible to definitively conclude whether it makes a difference if allograft or DBM is used in trauma surgery. It is ultimately the surgeon's individual choice, but this article may be useful in providing considerations before a decision is made.

Osteoformation potential of an allogenic partially demineralized bone matrix in critical-size defects in the rat calvarium

Allogenic demineralized bone matrix has been developed as a reliable alternative to the autologous bone graft. In the present study, we assessed the osteoformation potential of a partially demineralized bone matrix (PDBM) in a paste form obtained without an added carrier. This formulation included the preparation of cancelous bone from femoral heads after decellularision, delipidation, demineralization in HCl and autoclaving at 121 °C. Structural and biochemical characteristics of PDBM were determined using FTIR (Fourier transform infrared spectroscopy), hydroxyproline, DNA content assays, and optical ellipsometry. The osteoformation potential was evaluated in 8-, 6-, and 4-mm-diameter rat-calvarial bone defects by in vivo micro-CT analysis, performed immediately after surgery on days 0, 15, 30, 45, and 60. Moreover, histological and histomorphometric analyses were done on day 60. PDBM was compared to cancelous bone powder (BP) before its partial demineralization. The expression levels of selected inflammation-, angiogenesis-, and bone-related genes were also investigated by RT-PCR, 3, 7, and 14 days after surgery. Compared to the control group, the PDBM group exhibited a significant increase (p < 0.05) in radiopacity in 8-mm- and 6-mm-diameter defects at all time points tested. On day 60, the amount of newly-formed bone was greater (16 and 1.6 folds; p < 0.001; respectively) compared to that in control defects. No bone formation was observed in defects filled with BP regardeless of the size. In 8-mm-diameter defect, PDBM was effective enough to induce the upregulation of genes pertinent to inflammation (i.e., TNFα, IL-6, and IL-8), angiogenesis (i.e., VEGF, VWF), and osteogenesis (ALP, RUNX2, BGLAP, SP7) by day 3 after surgery. This study showed that the tested PDBM deeply influences the early critical events involved in bone regeneration and exhibits efficient osteoformation capacity, making it an attractive graft option for treating defects in periodontal and maxillofacial areas.

Osteogenesis of 3D-Printed PCL/TCP/bdECM Scaffold Using Adipose-Derived Stem Cells Aggregates; An Experimental Study in the Canine Mandible

Three-dimensional (3D) printing is perceived as an innovative tool for change in tissue engineering and regenerative medicine based on research outcomes on the development of artificial organs and tissues. With advances in such technology, research is underway into 3D-printed artificial scaffolds for tissue recovery and regeneration. In this study, we fabricated artificial scaffolds by coating bone demineralized and decellularized extracellular matrix (bdECM) onto existing 3D-printed polycaprolactone/tricalcium phosphate (PCL/TCP) to enhance osteoconductivity and osteoinductivity. After injecting adipose-derived stem cells (ADSCs) in an aggregate form found to be effective in previous studies, we examined the effects of the scaffold on ossification during mandibular reconstruction in beagle dogs. Ten beagles were divided into two groups: group A (PCL/TCP/bdECM + ADSC injection; n = 5) and group B (PCL/TCP/bdECM; n = 5). The results were analyzed four and eight weeks after intervention. Computed tomography (CT) findings showed that group A had more diffuse osteoblast tissue than group B. Evidence of infection or immune rejection was not detected following histological examination. Goldner trichrome (G/T) staining revealed rich ossification in scaffold pores. ColI, Osteocalcin, and Runx2 gene expressions were determined using real-time polymerase chain reaction. Group A showed greater expression of these genes. Through Western blotting, group A showed a greater expression of genes that encode ColI, Osteocalcin, and Runx2 proteins. In conclusion, intervention group A, in which the beagles received the additional ADSC injection together with the 3D-printed PCL/TCP coated with bdECM, showed improved mandibular ossification in and around the pores of the scaffold.

Recent Trends in the Development of Bone Regenerative Biomaterials

The goal of a biomaterial is to support the bone tissue regeneration process at the defect site and eventually degrade in situ and get replaced with the newly generated bone tissue. Biomaterials that enhance bone regeneration have a wealth of potential clinical applications from the treatment of non-union fractures to spinal fusion. The use of bone regenerative biomaterials from bioceramics and polymeric components to support bone cell and tissue growth is a longstanding area of interest. Recently, various forms of bone repair materials such as hydrogel, nanofiber scaffolds, and 3D printing composite scaffolds are emerging. Current challenges include the engineering of biomaterials that can match both the mechanical and biological context of bone tissue matrix and support the vascularization of large tissue constructs. Biomaterials with new levels of biofunctionality that attempt to recreate nanoscale topographical, biofactor, and gene delivery cues from the extracellular environment are emerging as interesting candidate bone regenerative biomaterials. This review has been sculptured around a case-by-case basis of current research that is being undertaken in the field of bone regeneration engineering. We will highlight the current progress in the development of physicochemical properties and applications of bone defect repair materials and their perspectives in bone regeneration.

A Prospective, Multi-Center, Double-Blind, Randomized Study to Evaluate the Efficacy and Safety of the Synthetic Bone Graft Material DBM Gel with rhBMP-2 versus DBM Gel Used during the TLIF Procedure in Patients with Lumbar Disc Disease

Objective

This study is to evaluate the efficacy and safety of demineralized bone matrix (DBM) gel versus DBM gel with recombinant human bone morphogenetic protein-2 (rhBMP-2) used in transforaminal lumbar interbody fusion (TLIF).

Methods

This study was designed as a prospective, multi-center, double-blind method, randomized study. All randomized subjects underwent TLIF with DBM gel with rhBMP-2 group (40 patients) as an experimental group or DBM gel group (36 patients) as a control group. Post-operative observations were performed at 12, 24, and 48 weeks. The spinal fusion rate on computed tomography scans and X-rays films, Visual analog scale pain scores, Oswestry disability index and SF-36 quality of life (QOL) scores were used for the efficacy evaluation. The incidence rate of adverse device effects (ADEs) and serious adverse device effects (SADEs) were used for safety evaluation.

Results

The spinal fusion rate at 12 weeks for the DBM gel with rhBMP-2 group was higher with 73.68% compared to 58.82% for the DBM gel group. The 24 and 48 weeks were 72.22% and 82.86% for the DBM gel with rhBMP-2 group and 78.79% and 78.13%, respectively, for the DBM gel group. However, there were no significant differences between two groups in the spinal fusion rate at 12, 24, and 48 weeks post-treatment (p=0.1817, p=0.5272, p=0.6247). There was no significant difference between the two groups in the incidence rate of ADEs (p=0.3836). For ADEs in the experimental group, ‘Pyrexia’ (5.00%) was the most common ADE, followed by ‘Hypesthesia’, ‘Paresthesia’, ‘Transient peripheral paralysis’, ‘Spondylitis’ and ‘Insomnia’ (2.50%, respectively). ADEs reported in control group included ‘Pyrexia’, ‘Chest discomfort’, ‘Pain’, ‘Osteoarthritis’, ‘Nephropathy toxic’, ‘Neurogenic bladder’, ‘Liver function analyses’ and ‘Urticaria’ (2.86%, respectively). There was no significant difference between the two groups in the incidence rate of SADEs (p=0.6594). For SADE in the experimental group, ‘‘Pyrexia’ and ‘Spondylitis’ were 2.50%. SADE reported in the control group included 'Chest discomfort’, ‘Osteoarthritis’ and ‘Neurogenic bladder’. All SADEs described above were resolved after medical treatment.

Conclusion

This study demonstrated that the spinal fusion rates of DBM gel group and DBM gel with rhBMP-2 group were not significantly different. But, this study provides knowledge regarding the earlier postoperative effect of rhBMP-2 containing DBM gel and also supports the idea that the longer term follow-up results are essential to confirm the safety and effectiveness.

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

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

Hierarchically Demineralized Cortical Bone Combined With Stem Cell-Derived Extracellular Matrix for Regeneration of the Tendon-Bone Interface

BACKGROUND

Poor healing of the tendon-bone interface after rotator cuff repair is one of the main causes of surgical failure. Previous studies demonstrated that demineralized cortical bone (DCB) could improve healing of the enthesis.

PURPOSE

To evaluate the outcomes of hierarchically demineralized cortical bone (hDCB) coated with stem cell-derived extracellular matrix (hDCB-ECM) in the repair of the rotator cuff in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Tendon-derived stem cells (TDSCs) were isolated, cultured, and identified. Then, hDCB was prepared by the graded demineralization procedure. Finally, hDCB-ECM was fabricated via 2-week cell culture and decellularization, and the morphologic features and biochemical compositions of the hDCB-ECM were evaluated. A total of 24 rabbits (48 samples) were randomly divided into 4 groups: control, DCB, hDCB, and hDCB-ECM. All rabbits underwent bilateral detachment of the infraspinatus tendon, and the tendon-bone interface was repaired with or without scaffolds. After surgery, 8 rabbits were assessed by immunofluorescence staining at 2 weeks, and the others were assessed by micro-computed tomography (CT) examination, immunohistochemical staining, histological staining, and biomechanical testing at 12 weeks.

RESULTS

TDSCs were identified to have universal stem cell characteristics including cell markers, clonogenicity, and multilineage differentiation. The hDCB-ECM contained 3 components (bone, partial DCB, and DCB coated with ECM) with a gradient of calcium and phosphorus elements, and the ECM had stromal cell-derived factor 1, biglycan, and fibromodulin. Macroscopic observations demonstrated the absence of infection and rupture around the enthesis. The results of immunofluorescence staining showed that hDCB-ECM promoted stromal cell recruitment. Results of micro-CT analysis, immunohistochemical staining, and histological staining showed that hDCB-ECM enhanced bone and fibrocartilage formation at the tendon-bone interface. Biomechanical analysis showed that the hDCB-ECM group had higher ultimate tensile stress and Young modulus than the DCB group.

CONCLUSION

The administration of hDCB-ECM promoted healing of the tendon-bone interface.

CLINICAL RELEVANCE

hDCB-ECM could provide useful information for the design of scaffolds to repair the tendon-bone interface, and further studies are needed to determine its effectiveness.

Allografts and Spinal Fusion

BACKGROUND

Back pain is a common chief complaint within the United States and is caused by a multitude of etiologies. There are many different treatment modalities for back pain, with a frequent option being spinal fusion procedures. The success of spinal fusion greatly depends on instrumentation, construct design, and bone grafts used in surgery. Bone allografts are important for both structural integrity and providing a scaffold for bone fusion to occur.

METHOD

Searches were performed using terms "allografts" and "bone" as well as product names in peer reviewed literature Pubmed, Google Scholar, FDA-510k approvals, and clinicaltrials.gov.

RESULTS

This study is a review of allografts and focuses on currently available products and their success in both animal and clinical studies.

CONCLUSION

Bone grafts used in surgery are generally categorized into 3 main types: autogenous (from patient's own body), allograft (from cadaveric or living donor), and synthetic. This paper focuses on allografts and provides an overview on the different subtypes with an emphasis on recent product development and uses in spinal fusion surgery.

Understanding the Future Prospects of Synergizing Minimally Invasive Transforaminal Lumbar Interbody Fusion Surgery with Ceramics and Regenerative Cellular Therapies

Transforaminal lumber interbody fusion (TLIF) is the last resort to address the lumber degenerative disorders such as spondylolisthesis, causing lower back pain. The current surgical intervention for these abnormalities includes open TLIF. However, in recent years, minimally invasive TLIF (MIS-TLIF) has gained a high momentum, as it could minimize the risk of infection, blood loss, and post-operative complications pertaining to fusion surgery. Further advancement in visualizing and guiding techniques along with grafting cage and materials are continuously improving the safety and efficacy of MIS-TLIF. These assistive techniques are also playing a crucial role to increase and improve the learning curve of surgeons. However, achieving an appropriate output through TLIF still remains a challenge, which might be synergized through 3D-printing and tissue engineering-based regenerative therapy. Owing to their differentiation potential, biomaterials such as stem/progenitor cells may contribute to restructuring lost or damaged tissues during MIS-TLIF, and this therapeutic efficacy could be further supplemented by platelet-derived biomaterials, leading to improved clinical outcomes. Thus, based on the above-mentioned strategies, we have comprehensively summarized recent developments in MIS-TLIF and its possible combinatorial regenerative therapies for rapid and long-term relief.

Partially Digested Osteoblast Cell Line-Derived Extracellular Matrix Induces Rapid Mineralization and Osteogenesis

An extracellular matrix (ECM) utilized as a biomaterial can be obtained from organs of living organisms. Therefore, it has some limitations in its supply because of insufficient organs. Furthermore, therapeutic efficacy of ECMs varies depending on factors such as donor's health condition and age. For this reason, ECMs obtained from a cell line could be a good alternative because they can be produced under a controlled environment with uniform quality. Thus, the purpose of this study was to investigate the potential of the MC3T3-E1 cell line-derived ECM as bone graft. The optimized decellularization process was developed to separate the ECM from MC3T3-E1, osteoblast cell line, using Trypsin-EDTA and Triton X-100. The decellularized ECM was partially digested using pepsin. Also, human bone marrow-derived mesenchymal stem cells induced faster osteogenesis on the ECM-coated surface than on the collagen-coated surface. Partially digested ECM fragments were embedded on the polyethylene glycol scaffold without additional chemical modification or crosslinking. Micro-computed tomography and histological analysis results showed that the ECM in the scaffold promoted actual bone regeneration after in vivo implantation to a mouse calvarial defect model. This study suggests that the bone-specific ECM derived from the cell line can replace the ECM from organs for application in tissue engineering and regenerative medicine.

Acid Dentin Lysate Failed to Modulate Bone Formation in Rat Calvaria Defects

Autogenous tooth roots are increasingly applied as a grafting material in alveolar bone augmentation. Since tooth roots undergo creeping substitution similar to bone grafts, it can be hypothesized that osteoclasts release the growth factors stored in the dentin thereby influencing bone formation. To test this hypothesis, collagen membranes were either soaked in acid dentin lysates (ADL) from extracted porcine teeth or serum-free medium followed by lyophilization. Thereafter, these membranes covered standardized 5-mm-diameter critical-size defects in calvarial bone on rats. After four weeks of healing, micro-computed tomography and histological analyses using undecalcified thin ground sections were performed. Micro-computed tomography of the inner 4.5 mm calvaria defects revealed a median bone defect coverage of 91% (CI: 87-95) in the ADL group and 94% (CI: 65-100) in the control group, without significant differences between the groups (intergroup p > 0.05). Furthermore, bone volume (BV) was similar between ADL group (5.7 mm³, CI: 3.4-7.1) and control group (5.7 mm³, CI: 2.9-9.7). Histomorphometry of the defect area confirmed these findings with bone area values amounting to 2.1 mm² (CI: 1.2-2.6) in the ADL group and 2.0 mm² (CI: 1.1-3.0) in the control group. Together, these data suggest that acid dentin lysate lyophilized onto collagen membranes failed to modulate the robust bone formation when placed onto calvarial defects.

TGF-β Activity of a Demineralized Bone Matrix

Allografts consisting of demineralized bone matrix (DBM) are supposed to retain the growth factors of native bone. However, it is not clear if transforming growth factor β1 (TGF-β1) is maintained in the acid-extracted human bone. To this aim, the aqueous solutions of supernatants and acid lysates of OraGRAFT^® Demineralized Cortical Particulate and OraGRAFT^® Prime were prepared. Exposing fibroblasts to the aqueous solution caused a TGF-β receptor type I kinase-inhibitor SB431542-dependent increase in interleukin 11 (IL11), NADPH oxidase 4 (NOX4), and proteoglycan 4 (PRG4) expression. Interleukin 11 expression and the presence of TGF-β1 in the aqueous solutions were confirmed by immunoassay. Immunofluorescence further confirmed the nuclear translocation of Smad2/3 when fibroblasts were exposed to the aqueous solutions of both allografts. Moreover, allografts released matrix metalloprotease-2 activity and blocking proteases diminished the cellular TGF-β response to the supernatant. These results suggest that TGF-β is preserved upon the processing of OraGRAFT^® and released by proteolytic activity into the aqueous solution.

Enhanced Osteoinductivity of Demineralized Bone Matrix with Noggin Suppression in Polymer Matrix

Demineralized bone matrix (DBM), a potential alternative to autologous bone-graft, has been increasingly used for clinical bone repair; however, its application in larger defects isn't successful partly due to the rapid dispersion of DBM particles and relatively lower osteoinductivity. Here, a novel strategy is created to complement the osteoinductivity of DBM by incorporating DBM in biopolymer hydrogel combined with the abrogation of BMP antagonism. Combined treatment of DBM + noggin-suppression displays increased osteogenic potency of human bone marrow mesenchymal stem cells (hBMSCs) in vitro. Injectable chitosan (MeGC)-based hydrogel with heparinization (Hep-MeGC) is further developed to localize and stabilize DBM. Noggin-suppression reveals the significant increase in osteogenesis of hBMSCs in the photopolymerizable Hep-MeGC hydrogels with the encapsulation of DBM. Moreover, the combination of DBM + noggin-suppression in the injectable Hep-MeGC hydrogel displays a robust bone healing in mouse critical-sized calvarial defects in vivo. The mechanistic analysis demonstrates that noggin-suppression increased DBM osteoinductivity by stimulating endogenous BMP/Smad signals. These results have shown promise in DBM's ability as a prominent bone grafting material while being coupled with gene editing mechanism and a localizing three-dimensional scaffold. Together, this approach poses a significant increase in the efficiency of DBM-mediated craniofacial bone repair and dental osteointegration.

Nanohydroxyapatite/polyamide 66 crosslinked with QK and BMP-2-derived peptide prevented femur nonunion in rats

A dual-peptide controlled released system based on nHA/PA66 scaffold for enhancing bone regeneration.

Study on specific proteins involved in articular cartilage regeneration activity induced by decalcified bone transplantation

Background

Through a comprehensive analysis of the joint synovial fluid produced in the process of rabbit articular cartilage regeneration, the role and characteristics of knee synovial fluid in the process of decalcified bone transplantation-induced articular cartilage regeneration were explored.

Methods

Twenty New Zealand white rabbits (approximately 2.5 kg in weight) were selected, and bilateral distal femoral bones from two randomly selected rabbits were extracted. After decalcification, the bones were cut into 2 mm × 4 cm long decalcified bone strips. Meanwhile, the other 18 rabbits were randomly divided into three groups: the test group (8 rabbits), the positive control group (6 rabbits), and the blank group (4 rabbits). In the test group, the decalcified bone joint was transplanted into the rabbits at the articular cartilage defect; in the positive control group, the articular cartilage defect of the rabbits were treated and put aside; in the blank group, no rabbits were treated. On the day of transplantation, and on the 4th, 8th, 12th, and 16th weeks after transplantation, the joint synovial fluid of each group was taken for two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF-MS) analysis, and related database verification and identification, and compared with the positive control group and the blank group.

Results

Using 2D-PAGE to separate various proteins in the synovial fluid of the rabbit knee joints, it was found that there were differential protein spots in the test group compared with the blank group and the positive control group. After conducting a comparative search and query in the UniProt database, through comprehensive analysis, it was finally found that three proteins with molecular weights of 23,429.4, 57,431.4, and 26,071.1 that may be related to the regeneration of articular cartilage appeared in the test group.

Conclusions

In the process of inducing the regeneration of articular cartilage using decalcified bone transplantation, knee joint synovial fluid produced specific proteins, which may play an important role in the regeneration of articular cartilage. These findings may offer novel ideas in laying a foundation for the in-depth study of articular cartilage regeneration.

Trabecular bone organoid model for studying the regulation of localized bone remodeling

Trabecular bone maintains physiological homeostasis and consistent structure and mass through repeated cycles of bone remodeling by means of tightly localized regulation. The molecular and cellular processes that regulate localized bone remodeling are poorly understood because of a lack of relevant experimental models. A tissue-engineered model is described here that reproduces bone tissue complexity and bone remodeling processes with high fidelity and control. An osteoid-inspired biomaterial-demineralized bone paper-directs osteoblasts to deposit structural mineralized bone tissue and subsequently acquire the resting-state bone lining cell phenotype. These cells activate and shift their secretory profile to induce osteoclastogenesis in response to chemical stimulation. Quantitative spatial mapping of cellular activities in resting and activated bone surface coculture showed that the resting-state bone lining cell network actively directs localized bone remodeling by means of paracrine signaling and cell-to-cell contact. This model may facilitate further investigation of trabecular bone niche biology.

PEGylated Coating Affects DBM Osteoinductivity In Vivo by Changing Inflammatory Responses

PEGylation is a widely used modification in device coating or drug delivery by combing materials with poly(ethylene glycol) (PEG). In the present study, a well-established rat ectopic bone formation model was used to elucidate how PEGylated coating affects demineralized bone matrix (DBM) osteoinductivity in vivo by changing the inflammation events at the early phase of implantation. A range of cell-matrix interactions was characterized at the cellular and functional levels, including growth factor activity and kinetics, immune cell migration and activation, and bone formation in vivo. After 28 days, DBM's bone formation potential decreased in groups with increasing PEG concentration in the gelatin carrier. The increasing PEG concentration did not affect DBM's osteoinductive growth factor release or activity. However, increasing PEG cross-linking concentration resulted in decreased DBM-related early phase inflammatory reactions, reduced neutrophil infiltration, decreased coating material degradation, lowered the total number and active mast cells, and decreased CD80+ macrophage expression. Understanding and controlling cell-material responses may improve the design and development of functional medical devices.

Examination of the Role of Cells in Commercially Available Cellular Allografts in Spine Fusion: An in Vivo Animal Study

BACKGROUND

Despite the extensive use of cellular bone matrices (CBMs) in spine surgery, there is little evidence to support the contribution of cells within CBMs to bone formation. The objective of this study was to determine the contribution of cells to spinal fusion by direct comparisons among viable CBMs, devitalized CBMs, and cell-free demineralized bone matrix (DBM).

METHODS

Three commercially available grafts were tested: a CBM containing particulate DBM (CBM-particulate), a CBM containing DBM fibers (CBM-fiber), and a cell-free product with DBM fibers only (DBM-fiber). CBMs were used in viable states (CBM-particulatev and CBM-fiberv) and devitalized (lyophilized) states (CBM-particulated and CBM-fiberd), resulting in 5 groups. Viable cell counts and bone morphogenetic protein-2 (BMP-2) content on enzyme-linked immunosorbent assay (ELISA) within each graft material were measured. A single-level posterolateral lumbar fusion was performed on 45 athymic rats with 3 lots of each product implanted into 9 animals per group. After 6 weeks, fusion was assessed using manual palpation, micro-computed tomography (μ-CT), and histological analysis.

RESULTS

The 2 groups with viable cells were comparable with respect to cell counts, and pairwise comparisons showed no significant differences in BMP-2 content across the 5 groups. Manual palpation demonstrated fusion rates of 9 of 9 in the DBM-fiber specimens, 9 of 9 in the CBM-fiberd specimens, 8 of 9 in the CBM-fiberv specimens, and 0 of 9 in both CBM-particulate groups. The μ-CT maturity grade was significantly higher in the DBM-fiber group (2.78 ± 0.55) compared with the other groups (p < 0.0001), while none of the CBM-particulate samples demonstrated intertransverse fusion in qualitative assessments. The viable and devitalized samples in each CBM group were comparable with regard to fusion rates, bone volume fraction, μ-CT maturity grade, and histological features.

CONCLUSIONS

The cellular component of 2 commercially available CBMs yielded no additional benefits in terms of spinal fusion. Meanwhile, the groups with a fiber-based DBM demonstrated significantly higher fusion outcomes compared with the CBM groups with particulate DBM, indicating that the DBM component is probably the key determinant of fusion.

CLINICAL RELEVANCE

Data from the current study demonstrate that cells yielded no additional benefit in spinal fusion and emphasize the need for well-designed clinical studies on cellular graft materials.

Biocompatibility and Physico-Chemical Properties of Highly Porous PLA/HA Scaffolds for Bone Reconstruction

The major problem in bone tissue engineering is the development of scaffolds which can simultaneously meet the requirements of porous structure, as well as have the ability to guide the regeneration of damaged tissue by biological fixation. Composites containing biodegradable matrix and bioactive filler are the new hope in this research field. Herein we employed a simple and facile solvent casting particulate-leaching method for producing polylactide acid/hydroxyapatite (PLA/HA) composites at room temperature. FT-IR analysis confirmed the existence of necessary functional groups associated with the PLA/HA composite, whereas energy-dispersive X-ray (EDX) spectra indicated the uniform distribution of hydroxyapatite particles in the polymer matrix. The beehive-like surface morphology of the composites revealed the presence of macropores, ranged from 300 to 400 μm, whereas the thickness of the pores was noticed to be 1-2 μm. The total porosity of the scaffolds, calculated by hydrostatic weighing, was found to be 79%. The water contact angle of pure PLA was decreased from 83.6 ± 1.91° to 62.4 ± 4.17° due to the addition of hydroxyapatite in the polymer matrix. Thus, the wettability of the polymeric biomaterial could be increased by preparing their composites with hydroxyapatite. The adhesion of multipotent mesenchymal stromal cells over the surface of PLA/HA scaffolds was 3.2 times (p = 0.03) higher than the pure PLA sample. Subcutaneous implantation in mice demonstrated a good tolerance of all tested porous scaffolds and widespread ingrowth of tissue into the implant pores. HA-containing scaffolds showed a less pronounced inflammatory response after two weeks of implantation compared to pure PLA. These observations suggest that PLA/HA composites have enormous potential for hard tissue engineering and restoring maxillofacial defects.

Innovative Molecular and Cellular Therapeutics in Cleft Palate Tissue Engineering

Clefts of the lip and/or palate are the most prevalent orofacial birth defects occurring in about 1:700 live human births worldwide. Early postnatal surgical interventions are extensive and staged to bring about optimal growth and fusion of palatal shelves. Severe cleft defects pose a challenge to correct with surgery alone, resulting in complications and sequelae requiring life-long, multidisciplinary care. Advances made in materials science innovation, including scaffold-based delivery systems for precision tissue engineering, now offer new avenues for stimulating bone formation at the site of surgical correction for palatal clefts. In this study, we review the present scientific literature on key developmental events that can go awry in palate development and the common surgical practices and challenges faced in correcting cleft defects. How key osteoinductive pathways implicated in palatogenesis inform the design and optimization of constructs for cleft palate correction is discussed within the context of translation to humans. Finally, we highlight new osteogenic agents and innovative delivery systems with the potential to be adopted in engineering-based therapeutic approaches for the correction of palatal defects. Impact statement Tissue-engineered scaffolds supplemented with osteogenic growth factors have attractive, largely unexplored possibilities to modulate molecular signaling networks relevant to driving palatogenesis in the context of congenital anomalies (e.g., cleft palate). Constructs that address this need may obviate current use of autologous bone grafts, thereby avoiding donor-site morbidity and other regenerative challenges in patients afflicted with palatal clefts. Combinations of biomaterials and drug delivery of diverse regenerative cues and biologics are currently transforming strategies exploited by engineers, scientists, and clinicians for palatal cleft repair.

Caprine demineralized bone matrix (DBMc) in the repair of non-critical bone defects in rabbit tibias. A new bone xenograft

Purpose

To evaluate the use of demineralized bone matrix of caprine origin in experimental bone defects of the tibia in New Zealand rabbits.

Methods

Fragments of the tibia diaphysis were collected aseptically from clinically healthy goats. The bones were sectioned into 1 cm fragments and stored at -20°C for subsequent hydrochloric acid (HCL) demineralization. A 70 mg portion of DBMc was used to fill the experimental bone defects. Twenty-four female adult New Zealand rabbits were divided into 2 groups: the MG (matrix group, left tibia) and CG (control group, right tibia). Additionally, they were separated into 4 groups with 6 animals, according to the period of analysis (15, 30, 60 and 90 days postoperatively). Using microCT, volumetric parameters were evaluated: bone volume, relationship between bone volume and total volume, bone surface area, relationship between bone surface area and total volume, number of trabeculae, trabecular thickness and trabecular separation.

Results

There was a statistically significant difference (P<0.05) between groups considering bone volume (BV) and bone:total volume (BV/TV), on 15, 30 and 90 days postoperatively. Control group showed a statistically significant superiority (P < 0.05) considering the mean of the variables bone surface (BS), number of trabeculae (Tb.N) and between bone surface and total volume (BS/TV) at 15 and 90 days.

Conclusions

Caprine demineralized bone matrix was safe and tolerable. No signs of material rejection were seen macroscopically. It is an alternative for the treatment of bone defects when autologous graft is not available or in insufficient quantities.

Recent Progress in Carbon Nanotube Polymer Composites in Tissue Engineering and Regeneration

Scaffolds are important to tissue regeneration and engineering because they can sustain the continuous release of various cell types and provide a location where new bone-forming cells can attach and propagate. Scaffolds produced from diverse processes have been studied and analyzed in recent decades. They are structurally efficient for improving cell affinity and synthetic and mechanical strength. Carbon nanotubes are spongy nanoparticles with high strength and thermal inertness, and they have been used as filler particles in the manufacturing industry to increase the performance of scaffold particles. The regeneration of tissue and organs requires a significant level of spatial and temporal control over physiological processes, as well as experiments in actual environments. This has led to an upsurge in the use of nanoparticle-based tissue scaffolds with numerous cell types for contrast imaging and managing scaffold characteristics. In this review, we emphasize the usage of carbon nanotubes (CNTs) and CNT–polymer composites in tissue engineering and regenerative medicine and also summarize challenges and prospects for their potential applications in different areas.

Tissue-Specific Decellularization Methods: Rationale and Strategies to Achieve Regenerative Compounds

The extracellular matrix (ECM) is a complex network with multiple functions, including specific functions during tissue regeneration. Precisely, the properties of the ECM have been thoroughly used in tissue engineering and regenerative medicine research, aiming to restore the function of damaged or dysfunctional tissues. Tissue decellularization is gaining momentum as a technique to obtain potentially implantable decellularized extracellular matrix (dECM) with well-preserved key components. Interestingly, the tissue-specific dECM is becoming a feasible option to carry out regenerative medicine research, with multiple advantages compared to other approaches. This review provides an overview of the most common methods used to obtain the dECM and summarizes the strategies adopted to decellularize specific tissues, aiming to provide a helpful guide for future research development.

Natural hydrogels R&D process: technical and regulatory aspects for industrial implementation

Since hydrogel therapies have been introduced into clinic treatment procedures, the biomedical industry has to face the technology transfer and the scale-up of the processes. This will be key in the roadmap of the new technology implementation. Transfer technology and scale-up are already known for some applications but other applications, such as 3D printing, are still challenging. Decellularized tissues offer a lot of advantages when compared to other natural gels, for example they display enhanced biological properties, due to their ability to preserve natural molecules. For this reason, even though their use as a source for bioinks represents a challenge for the scale-up process, it is very important to consider the advantages that originate with overcoming this challenge. Therefore, many aspects that influence the scaling of the industrial process should be considered, like the addition of drugs or cells to the hydrogel, also, the gelling process is important to determine the chemical and physical parameters that must be controlled in order to guarantee a successful process. Legal aspects are also crucial when carrying out the scale-up of the process since they determine the industrial implementation success from the regulatory point of view. In this context, the new law Regulation (EU) 2017/745 on biomedical devices will be considered. This review summarizes the different aspects, including the legal ones, that should be considered when scaling up hydrogels of natural origin, in order to balance these different aspects and to optimize the costs in terms of raw materials and engine.

First Human Leucocyte Antigen (HLA) Response and Safety Evaluation of Fibrous Demineralized Bone Matrix in a Critical Size Femoral Defect Model of the Sprague-Dawley Rat

Treatment of large bone defects is one of the great challenges in contemporary orthopedic and traumatic surgery. Grafts are necessary to support bone healing. A well-established allograft is demineralized bone matrix (DBM) prepared from donated human bone tissue. In this study, a fibrous demineralized bone matrix (f-DBM) with a high surface-to-volume ratio has been analyzed for toxicity and immunogenicity. f-DBM was transplanted to a 5-mm, plate-stabilized, femoral critical-size-bone-defect in Sprague-Dawley (SD)-rats. Healthy animals were used as controls. After two months histology, hematological analyses, immunogenicity as well as serum biochemistry were performed. Evaluation of free radical release and hematological and biochemical analyses showed no significant differences between the control group and recipients of f-DBM. Histologically, there was no evidence of damage to liver and kidney and good bone healing was observed in the f-DBM group. Reactivity against human HLA class I and class II antigens was detected with mostly low fluorescence values both in the serum of untreated and treated animals, reflecting rather a background reaction. Taken together, these results provide evidence for no systemic toxicity and the first proof of no basic immunogenic reaction to bone allograft and no sensitization of the recipient.

Bioactive Factors-imprinted Scaffold Vehicles for Promoting Bone Healing: The Potential Strategies and the Confronted Challenges for Clinical Production

Abstract Wound repair of bone is a complicated multistep process orchestrated by inflammation, angiogenesis, callus formation, and bone remodeling. Many bioactive factors (BFs) including cytokine and growth factors (GFs) have previously been reported to be involved in regulating wound healing of bone and some exogenous BFs such as bone morphogenetic proteins (BMPs) were proven to be helpful for improving bone healing. In this regard, the BFs reported for boosting bone repair were initially categorized according to their regulatory mechanisms. Thereafter, the challenges including short half-life, poor stability, and rapid enzyme degradation and deactivation for these exogenous BFs in bone healing are carefully outlined in this review. For these issues, BFs-imprinted scaffold vehicles have recently been reported to promote the stability of BFs and enhance their half-life in vivo. This review is focused on the incorporation of BFs into the modulated biomaterials with various forms of bone tissue engineering applications: firstly, rigid bone graft substitutes (BGSs) were used to imprint BFs for large scale bone defect repair; secondly, the soft sponge-like scaffold carrying BFs is discussed as filling materials for the cavity of bone defects; thirdly, various injectable vehicles including hydrogel, nanoparticles, and microspheres for the delivery of BFs were also introduced for irregular bone fracture repair. Meanwhile, the challenges for BFs-imprinted scaffold vehicles are also analyzed in this review.

A bone matrix-simulating scaffold to alleviate replicative senescence of mesenchymal stem cells during long-term expansion

Replicative senescence during in vitro augmentation, which is mostly induced by the loss of physiological microenvironment, hinders the application of mesenchymal stem cells (MSCs) in the clinic. Here, we investigated whether MSCs senescence could be prevented by bio-scaffold mimicking the natural tissue matrix. Human umbilical cord mesenchymal stem cells (hUCMSCs) exhibited a senescent phenotype during a long-term passage in the conventional culture dish. To fabricate the bone matrix, a naturally based matrix composed of nano-hydroxyapatite/chitosan/poly lactide-co-glycolide (nHA/CS/PLGA) was produced. Long-term passage resulted in an obvious increase in the expression of senescence markers and a reduction in the expression of master genes involved in tissue regeneration. Functional assay confirmed that nHA/CS/PLGA scaffold preserved the proliferation and differentiation of hUCMSCs even after being passaged 27 times. Moreover, in vivo ectopic bone formation assay revealed that the bone formation of hUCMSCs cultured on the nano-scaffolds for the long term was as robust as the cells in the early passage. In summary, our results demonstrate that nHA/CS/PLGA scaffold effectively preserves the stemness and youth of hUCMSCs in the long-term passage. Taken advantage of its compatibility and bioactivity, nHA/CS/PLGA scaffold is of great potential in large-scale expansion of MSCs for stem cell therapy and tissue engineering.

Demineralized bone matrix paste formulated with biomimetic PLGA microcarriers for the vancomycin hydrochloride controlled delivery: Release profile, citotoxicity and efficacy against S. aureus

Infection and resulting bone defects caused by Staphylococcus aureus is one of the major issues in orthopaedic surgeries. Vancomycin hydrochloride (VaH) is largely used to manage these events. Here, a human derived bone paste supplemented with biopolymer microcarriers for VaH sustained delivery to merge osteoinductive and antimicrobial actions is described. In detail, different emulsion formulations were tested to fabricate micro-carriers of poly-lactic-co-glycolic acid (PLGA) and hydroxyapatite (HA) by a proprietary technology (named Supercritical Emulsion Extraction). These carriers (mean size 827 ± 68 μm; loading 47 mg_VaH/g_PLGA) were assembled with human demineralized bone matrix (DBM) to obtain an antimicrobial bone paste system (250 mg/0.5 cm³ w/v, carrier/DBM). Release profiles in PBS indicated a daily drug average release of about 4 µg/mL over two weeks. This concentration was close to the minimum inhibitory concentration and able to effectively inhibit the S. aureus growth in our experimental sets. Carriers cytotoxicity tests showed absence of adverse effects on cell viability at the concentrations used for paste assembly. This approach points toward the potential of the DBM-carrier-antibiotic system in hampering the bacterial growth with accurately controlled antibiotic release and opens perspectives on functional bone paste with PLGA carriers for the controlled release of bioactive molecules.

Review on calcium- and magnesium-based silicates for bone tissue engineering applications

Bone is a self-engineered structural component of the human body with multifaceted mechanical strength, which provides indomitable support to the effective functioning of the human body. It is indispensable to find a suitable biomaterial for substituting the bone as the bone substitute material requirement is very high due to the rate of bone fracture and infection lead to osteoporosis in human beings increases rapidly. It is not an easy task to design a material with good apatite deposition ability, a faster rate of dissolution, superior resorbability, high mechanical strength, and significant bactericidal activity. Since the synthetic hydroxyapatite was not able to achieve the dahlite phase of hydroxyapatite (natural bone mineral phase), silicates emerged as an alternate biomaterial to meet the need for bone graft substitutes. All silicates do not exhibit the properties required for bone graft substitutes, as their composition and methodology adopted for the synthesis are different. Calcium, magnesium, and silicon play a major role in the formation of bone mineral and their metabolism during bone formation. In this review, the relationship between composition and activity of calcium, magnesium-based silicates have been discussed along with the future scope of these materials for hard tissue engineering 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.

Repair of segmental rabbit radial defects with Cu/Zn co-doped calcium phosphate scaffolds incorporating GDF-5 carrier

Repair of segmental bone defects is a challenge in orthopaedics. A bone substitute is a potential solution for this challenge, and angiogenesis and osteogenesis are critical to the performance of scaffold materials. For enhancing angiogenesis and osteogenesis activities of implanted scaffolds, Cu/Zn co-doped calcium phosphate scaffolds carrying GDF-5-release microspheres were prepared and implanted into surgically created critical-sized rabbit radial defects. Radiological examination, histological analysis and biomechanical tests were used to evaluate the bone healing-union. Results showed that, with increasing Cu/Zn concentrations, new bone area, new blood vessel density, and bending failure load all increased significantly. Furthermore, Cu/Zn co-doped scaffolds incorporating GDF-5-release microspheres exhibited further increased angiogenesis and osteogenesis (vs. Cu/Zn co-doped alone), as well as a superior bending failure load. These show that, simultaneous incorporation of trace essential ions and GDF-5 combines pro-angiogenic and pro-osteogenic actions of these bioactive substances, potentially offering an effective approach to assist the healing of critical-sized bone defects.

Mesenchymal stem cell-derived microvesicles mediate BMP2 gene delivery and enhance bone regeneration

Microvesicles–polyethyleneimine/pDNA formed via layer-by-layer self-assembly increase the delivery of hBMP2 plasmids and enhance bone repair.

Applications of decellularized materials in tissue engineering: advantages, drawbacks and current improvements, and future perspectives

Decellularized materials (DMs) are attracting more and more attention in tissue engineering because of their many unique advantages, and they could be further improved in some aspects through various means.

Clinical outcomes of treatment with cage-shaped demineralized bone plus local bone grafts vs. autogenous iliac crest bone grafts in instrumented single-level lumbar fusion: A retrospective cohort study

The aim of the present study was to compare the clinical outcomes of cage-shaped demineralized bone plus local bone grafts (CDBLG) with those of autogenous iliac crest bone grafts (ICBG) implanted for the treatment of single-level lumbar intervertebral disc degenerative diseases. A total of 69 cases of degenerative spinal disorder treated between January 2011 and December 2013 were retrospectively analyzed. Of these, 44 were treated with CDBLG and 25 with autogenous ICBG. All fusions were instrumented single level. Fusion was assessed after 6, 12 and 24 months by X-ray and CT scans post-operatively. Clinical outcomes were determined during follow-up and assessments included the Oswestry Disability Index, Visual Analogue Scale for back and leg pain and the Short Form-36 general health survey physical component summary. The results indicated that the overall fusion rate at 24 months post-operatively was higher in the ICBG group compared with that in the CDBLG group, although not significantly (P>0.05). All other outcome measures were significantly improved in the two groups after the surgery (P<0.05), but no significant differences were observed between the two groups (P>0.05). Blood loss and mean duration of surgery in the CDBLG group were significantly lower compared with those in the ICBG group (P<0.05). In conclusion, CDBLG achieved a similar fusion rate and clinical outcome as ICBG but was associated with significantly reduced blood loss and mean duration of surgery. In conclusion, the present study provided CDBLG bone graft as an alternative option for single-level fusion.

The use of demineralised bone fibres (DBF) in conjunction with supercritical carbon dioxide (SCCO2) treated allograft in anterior lumbar interbody fusion (ALIF)

Spinal fusion is a common procedure for the treatment of various spinal pathologies. Since the early days, spinal fusion has been carried out with the use of bone grafts as interbody spacers. With the development of synthetic interbody implants, bone grafts were used to facilitate fusion. Although autograft provides the best outcomes for fusion, allografts have been sought after due to donor site morbidity and other shortcomings. Currently, a vast variety of demineralised bone matrix (DBM) products are available with their methods of processing and preparation impacting their properties and clinical outcomes. Demineralised bone fibres (DBF), a form a DBM can be easily packed into implants when mixed with other substances such as allograft bone and patient's blood providing a scaffold for the mixture. We report two cases of anterior lumbar interbody fusion (ALIF) utilising a titanium-polyetheretherketone (PEEK) interbody cage filled with DBF, allograft and patient's blood with a maximum of 12 months follow-up outcome.

The roles of circRFWD2 and circINO80 during NELL-1-induced osteogenesis

Bone defects caused heavy social and economic burdens worldwide. Nel‐like molecule, type 1 (NELL‐1) could enhance the osteogenesis and the repairment of bone defects, while the specific mechanism remains to be elucidated. Circular RNAs (circRNAs) have been found to play critical roles in the tissue development and serve as biomarkers for various diseases. However, it remains unclear that the expression patterns of circRNAs and the roles of them played in recombinant NELL‐1‐induced osteogenesis of human adipose‐derived stem cells (hASCs). In this study, we performed RNA‐sequencing to investigate the expression profiles of circRNAs in recombinant NELL‐1‐induced osteogenic differentiation and identified two key circRNAs, namely circRFWD2 and circINO80. These two circRNAs were confirmed to be up‐regulated during recombinant NELL‐1‐induced osteogenesis, and knockdown of them affected the positive effect of NELL‐1 on osteogenesis. CircRFWD2 and circINO80 could interact with hsa‐miR‐6817‐5p, which could inhibit the osteogenesis. Silencing hsa‐miR‐6817‐5p could partially reverse the negative effect of si‐circRFWD2 and si‐circINO80 on the osteogenesis. Therefore, circRFWD2 and circINO80 could regulate the expression of hsa‐miR‐6817‐5p and influence the recombinant NELL‐1‐induced osteogenic differentiation of hASCs. It opens a new window to better understanding the effects of NELL‐1 on the osteogenic differentiation of hASCs and provides potential molecular targets and novel methods for bone regeneration efficiently and safely.

Inflammatory response and macrophage polarization using different physicochemical biomaterials for oral and maxillofacial reconstruction

Knowledge about the action of immune system in the recognition of biomaterials has been extremely helpful when it comes about understanding host response and biomaterials' fate in human body. This study aimed to investigate inflammatory response and macrophage polarization during bone healing process of rat's calvaria critical defects using different bone materials in order to evaluate their influence on bone repair and on the quality of the newly formed bone tissue. Eighty male albinus Wistar rats underwent surgical procedure for the confectioning of a 5-mm diameter bone defect in their right parietal bone, and divided in four groups (n = 20 each), according the biomaterial: AG - Control, particulate intramembranous autogenous bone graft, HA/TCP - particulate biphasic calcium phosphate with HA/TCP (60/40), DBB - particulate deproteinized bovine bone, VC - particulate bioactive vitroceramic. After 3, 7, 21, and 45 days, the specimens were removed and prepared for microcomputed tomography (microCT), light and polarized microscopy, immunohistochemical analysis, and histomorphometry. No significant differences were detected considering percentage of leukocytes among the groups and periods, as well as in relation to immunolabeling for inflammatory (M1) and reparative (M2) macrophages. However, immunolabeling for bone marker indicated a delayed osteoblast differentiation in VC group, resulting in a decrease in mineralized bone matrix parameters in this group, revealed by microCT. In addition, AG and HA/TCP presented a satisfactory bone collagenous content. Despite the distinct origins and physicochemical properties of the tested biomaterials, they presented similar immune-inflammatory responses in the present experimental model, influencing bone-related proteins and bone quality, which must be considered according to their use.

Regenerative Materials for Surgical Reconstruction: Current Spectrum of Materials and a Proposed Method for Classification

Chronic wound management is an enormous economic strain and quality-of-life issue for patients. Current treatments are ineffective or expensive and invasive. Materials (native and artificial) can act as the basis to enhance wound repair but often fall short of complete healing. The therapeutic index of materials have often been enhanced by combining them with drug or biologic elution technologies. Combination of materials with living drugs (cells) presents a new paradigm for enhancing therapy. Cell material interaction and therapeutic output will depend on variables ascribed to the living drug as well as variables ascribed to the underlying matrix. In this article, we review medical matrices currently approved by the US Food and Drug Administration (FDA) that would likely be the first generation of materials to be used in this manner. Currently there are hundreds of different materials on the market. Identification of the right combinations would benefit from a classification scheme to group materials with similar composition or derivation. We provide a classification scheme and FDA documentation references that should provide researchers and clinicians a starting point for testing these materials in the laboratory and rapidly transitioning cell therapies to the bedside.

Graft Materials and Biologics for Spinal Interbody Fusion

Spinal fusion is the most widely performed procedure in spine surgery. It is the preferred treatment for a wide variety of pathologies including degenerative disc disease, spondylolisthesis, segmental instability, and deformity. Surgeons have the choice of fusing vertebrae by utilizing cages containing autografts, allografts, demineralized bone matrices (DBMs), or graft substitutes such as ceramic scaffolds. Autografts from the iliac spine are the most commonly used as they offer osteogenic, osteoinductive, and osteoconductive capabilities, all while avoiding immune system rejection. Allografts obtained from cadavers and living donors can also be advantageous as they lack the need for graft extraction from the patient. DBMs are acid-extracted organic allografts with osteoinductive properties. Ceramic grafts containing hydroxyapatite can be readily manufactured and are able to provide osteoinductive support while having a long shelf life. Further, bone-morphogenetic proteins (BMPs), mesenchymal stem cells (MSCs), synthetic peptides, and autologous growth factors are currently being optimized to assist in improving vertebral fusion. Genetic therapies utilizing viral transduction are also currently being devised. This review provides an overview of the advantages, disadvantages, and future directions of currently available graft materials. The current literature on growth factors, stem cells, and genetic therapy is also discussed.