Demineralized bone matrix in bone repair: history and use

Efficacy of sintered Zinc-doped fluorapatite scaffold as an antimicrobial regenerative bone filler for dental applications

OBJECTIVES

The objective of this study was to assess whether zinc-doped fluorapatite (ZnFA) could serve as an effective antimicrobial dental bone filler for bone regeneration compared to autografts.

METHODS

FA and 2 % zinc-doped FA (2ZnFA) were synthesized and characterized in-house. Compressed and sintered FA and 2ZnFA disks were incubated with bacteria to assess antimicrobial properties. Adipose-derived stem cells were cultured on these discs to evaluate the surfaces' ability to support cell growth and promote osteogenic differentiation. Surfaces exhibiting the highest expressions of the bone markers osteopontin and osteocalcin were selected for an in vivo study in a rat mandibular defect model. Twenty rats were divided into 5 groups, equally, and a 5 mm surgical defect of the jaw was left untreated or filled with 2ZnFA, FA, autograft, or demineralized bone matrix (DBM). At 12 weeks, the defects and surrounding tissues were harvested and subjected to microCT and histological evaluations.

RESULTS

Standard techniques such as FTIR, ICP-MS, fluoride probe, and XRD revealed the sintered FA and ZnFA's chemical compositions and structures. Bacterial studies revealed no significant differences in surface bacterial adhesion properties between FA and 2ZnFA, but significantly fewer bacterial loads than control titanium discs (p < 0.05). Cell culture data confirmed that both surfaces could support cell growth and promote the osteogenic differentiation of stem cells. MicroCT analysis confirmed statistical similarities in bone regeneration within FA, 2ZnFA, and autograft groups.

CONCLUSION

The data suggests that both FA and 2ZnFA could serve as alternatives to autograft materials, which are the current gold standard. Moreover, these bone fillers outperformed DBM, an allograft material commonly used as a dental bone void filler.

CLINICAL SIGNIFICANCE

The use of FA or 2ZnFA for treating mandibular defects led to bone regeneration statistically similar to autograft repair and significantly outperformed the widely used dental bone filler, DBM. Additional translational research may confirm FA-based materials as superior substitutes for existing synthetic bone fillers, ultimately enhancing patient outcomes.

Impact of surgical risk factors for non-union on lumbar spinal fusion outcomes using cellular bone allograft at 24-months follow-up

BACKGROUND

The current report investigates fusion rates and patient-reported outcomes following lumbar spinal surgery using cellular bone allograft (CBA) in patients with risk factors for non-union.

METHODS

A prospective, open label study was conducted in subjects undergoing lumbar spinal fusion with CBA (NCT02969616) to assess fusion success rates and patient-reported outcomes in subjects with risk factors for non-union. Subjects were categorized into low-risk (≤ 1 risk factors) and high-risk (> 1 risk factors) groups. Radiographic fusion status was evaluated by an independent review of dynamic radiographs and CT scans. Patient-reported outcome measures included quality of life (EQ-5D), Oswestry Disability Index (ODI) and Visual Analog Scales (VAS) for back and leg pain. Adverse event reporting was conducted throughout 24-months of follow-up.

RESULTS

A total of 274 subjects were enrolled: 140 subjects (51.1%) were categorized into the high-risk group (> 1 risk factor) and 134 subjects (48.9%) into the low-risk group (≤ 1 risk factors). The overall mean age at screening was 58.8 years (SD 12.5) with a higher distribution of females (63.1%) than males (36.9%). No statistical difference in fusion rates were observed between the low-risk (90.0%) and high-risk (93.9%) groups (p > 0.05). A statistically significant improvement in patient-reported outcomes (EQ-5D, ODI and VAS) was observed at all time points (p < 0.05) in both low and high-risk groups. The low-risk group showed enhanced improvement at multiple timepoints in EQ-5D, ODI, VAS-Back pain and VAS-Leg pain scores compared to the high-risk group (p < 0.05). The number of AEs were similar among risk groups.

CONCLUSIONS

This study demonstrates high fusion rates following lumbar spinal surgery using CBA, regardless of associated risk factors. Patient reported outcomes and fusion rates were not adversely affected by risk factor profiles.

TRIAL REGISTRATION

NCT02969616 (21/11/2016).

Augmented drug resistance of osteosarcoma cells within decalcified bone matrix scaffold: The role of glutamine metabolism

Due to the lack of a precise in vitro model that can mimic the nature microenvironment in osteosarcoma, the understanding of its resistance to chemical drugs remains limited. Here, we report a novel three-dimensional model of osteosarcoma constructed by seeding tumor cells (MG-63 and MNNG/HOS Cl no. 5) within demineralized bone matrix scaffolds. Demineralized bone matrix scaffolds retain the original components of the natural bone matrix (hydroxyapatite and collagen type I), and possess good biocompatibility allowing osteosarcoma cells to proliferate and aggregate into clusters within the pores. Growing within the scaffold conferred elevated resistance to doxorubicin on MG-63 and MNNG/HOS Cl no. 5 cell lines as compared to two-dimensional cultures. Transcriptomic analysis showed an increased enrichment for drug resistance genes along with enhanced glutamine metabolism in osteosarcoma cells in demineralized bone matrix scaffolds. Inhibition of glutamine metabolism resulted in a decrease in drug resistance of osteosarcoma, which could be restored by α-ketoglutarate supplementation. Overall, our study suggests that microenvironmental cues in demineralized bone matrix scaffolds can enhance osteosarcoma drug responses and that targeting glutamine metabolism may be a strategy for treating osteosarcoma drug resistance.

Black Phosphorus-Based Dynamic Self-Healing Hydrogel to Integrate Demineralized Bone Matrix and Noggin-Targeting siRNA for Synergistic Osteogenesis

Although a demineralized bone matrix (DBM) is often used as an alternative to an autologous bone graft, its clinical application is still hampered by easy dispersion of DBM particles and insufficient osteoinductivity in the defect site. Herein, we designed a self-healing hydrogel for DBM that can rapidly restore its structural integrity after damage based on amino-rich black phosphorus (BP) nanosheets and aldehyde-functionalized hyaluronic acid (AHA). Given the increased expression of bone morphogenetic protein (BMP) antagonists by DBM stimulation, the osteogenic potency of DBM in the hydrogel carrier was further enhanced by abrogating the BMP antagonism. The BP/AHA hydrogel provided dynamic polymer-nanosheet networks that combine injectability, modability, and physical stability with high DBM loading, where the BP nanosheets served as osteogenic cross-linkers to promote biomineralization and deliver siRNA to suppress undesirable expression of BMP antagonist noggin by DBM. As a result, the BP/AHA hydrogel integrated with DBM and noggin-targeting siRNA synergistically promoted osteogenic differentiation of mesenchymal stem cells by enhancing BMP/Smad signaling. This work demonstrates a promising strategy to improve the efficacy of bone regeneration using bone graft.

Injectable bioactive poly(propylene fumarate) and polycaprolactone based click chemistry bone cement for spinal fusion in rabbits

Degenerative spinal pathology is a widespread medical issue, and spine fusion surgeries are frequently performed. In this study, we fabricated an injectable bioactive click chemistry polymer cement for use in spinal fusion and bone regrowth. Taking advantages of the bioorthogonal click reaction, this cement can be crosslinked by itself eliminating the addition of a toxic initiator or catalyst, nor any external energy sources like UV light or heat. Furthermore, nano-hydroxyapatite (nHA) and microspheres carrying recombinant human bone morphogenetic protein-2 (rhBMP-2) and recombinant human vascular endothelial growth factor (rhVEGF) were used to make the cement bioactive for vascular induction and osteointegration. After implantation into a rabbit posterolateral spinal fusion (PLF) model, the cement showed excellent induction of new bone formation and bridging bone, achieving results comparable to autograft control. This is largely due to the osteogenic properties of nano-hydroxyapatite (nHA) and the released rhBMP-2 and rhVEGF growth factors. Since the availability of autograft sources is limited in clinical settings, this injectable bioactive click chemistry cement may be a promising alternative for spine fusion applications in addressing various spinal conditions.

Response of human peripheral blood monocyte-derived macrophages (PBMM) to demineralized and decellularized bovine bone graft substitutes

The performance of apparently biocompatible implanted bovine bone grafts may be compromised by unresolved chronic inflammation, and poor graft incorporation leading to implant failure. Monitoring the intensity and duration of the inflammatory response caused by implanted bone grafts is crucial. In this study, the ability of demineralized (DMB) and decellularized (DCC) bovine bone substitutes in initiating inflammatory responses to peripheral blood monocyte-derived macrophages (PBMMs) was investigated. The response of PBMMs to bone substitutes was evaluated by using both direct and indirect cell culture, reactive oxygen species (ROS) generation, apoptosis, immunophenotyping, and cytokine production. Analysis of DMB and DCC substitutes using scanning electron microscope (SEM) showed a roughened surface with a size ranging between 500 and 750 μm. PBMMs treated with DMB demonstrated cell aggregation and clumping mimicking lipopolysaccharide (LPS) treated PBMMs and a higher proliferation ability (166.93%) compared to control (100%) and DCC treatments (115.64%; p<0.001) at 24h. This was associated with a significantly increased production of intracellular ROS in PBMMs exposed to DMB substitutes than control (3158.5 vs 1715.5; p<0.001) and DCC treatment (2117.5). The bone substitute exposure also caused an increase in percentage apoptosis which was significantly (p<0.0001) higher in both DMB (27.85) and DCC (29.2) treatment than control (19.383). A significant increase in proinflammatory cytokine expression (TNF-α: 3.4 folds; p<0.05) was observed in DMB substitute-treated PBMMs compared to control. Notably, IL-1β mRNA was significantly higher in DMB (21.75 folds; p<0.0001) than control and DCC (5.01 folds). In contrast, DCC substitutes exhibited immunoregulatory effects on PBMMs, as indicated by the expression for CD86, CD206, and HLDR surface markers mimicking IL-4 treatments. In conclusion, DMB excites a higher immunological response compared to DCC suggesting decellularization process of tissues dampen down inflammatory reactions when exposed to PBMM.

Static magnetic field enhances the bone remodelling capacity of human demineralized bone matrix in a rat animal model of cranial bone defects

The regeneration of bone defects that exceed 2 cm is a challenge for the human body, necessitating interventional therapies. Demineralized bone matrices (DBM) derived from biological tissues have been employed for bone regeneration and possess notable osteoinductive and osteoconductive characteristics. Nevertheless, their efficiency in regenerating critically sized injuries is limited, and therefore additional signaling cues are required. Thanks to the piezoelectric properties of the bone, external physical stimulation is shown to accelerate tissue healing. We have implanted human DBM in critically sized cranial bone defects in rat animal models and exposed them to an external magnetic field (1 T) to enhance endogenous bone formation. Our in vitro experiments showed the superior cytocompatibility of DBM compared to cell culture plates. Furthermore, alkaline phosphatase activity after 14 days and Alizarin red staining at 28 days demonstrated differentiation of rat bone marrow mesenchymal stem cells into bone lineage on DBM. Computer tomography images together with histological analyses showed that implanting DBM in the injured rats significantly enhanced bone regeneration. Notably, combining DBM transplantation with a 2 h daily exposure to a 1 T magnetic field for 2 weeks (day 7 to 21 post-surgery) significantly improved bone regeneration compared to DBM transplantation alone. This research indicates that utilizing external magnetic stimulation significantly enhances the potential of bone allografts to regenerate critically sized bone defects.

Methodology and Characterization of a 3D Bone Organoid Model Derived from Murine Cells

Here, we report on the development of a cost-effective, well-characterized three-dimensional (3D) model of bone homeostasis derived from commonly available stocks of immortalized murine cell lines and laboratory reagents. This 3D murine-cell-derived bone organoid model (3D-mcBOM) is adaptable to a range of contexts and can be used in conjunction with surrogates of osteoblast and osteoclast function to study cellular and molecular mechanisms that affect bone homeostasis in vitro or to augment in vivo models of physiology or disease. The 3D-mcBOM was established using a pre-osteoblast murine cell line, which was seeded into a hydrogel extracellular matrix (ECM) and differentiated into functional osteoblasts (OBs). The OBs mineralized the hydrogel ECM, leading to the deposition and consolidation of hydroxyapatite into bone-like organoids. Fourier-transform infrared (FTIR) spectroscopy confirmed that the mineralized matrix formed in the 3D-mcBOM was bone. The histological staining of 3D-mcBOM samples indicated a consistent rate of ECM mineralization. Type I collagen C-telopeptide (CTX1) analysis was used to evaluate the dynamics of OC differentiation and activity. Reliable 3D models of bone formation and homeostasis align with current ethical trends to reduce the use of animal models. This functional model of bone homeostasis provides a cost-effective model system using immortalized cell lines and easily procured supplemental compounds, which can be assessed by measuring surrogates of OB and OC function to study the effects of various stimuli in future experimental evaluations of bone homeostasis.

Self-Assembled Nanocomposite Hydrogels as Carriers for Demineralized Bone Matrix Particles and Enhanced Bone Repair

Demineralized bone matrix (DBM) has been widely used as an allogeneic alternative to autologous bone graft for bone repair. However, more extensive use of DBM is limited due to its particulate nature after demineralization and rapid particle dispersion following irrigation, resulting in unpredictable osteoinductivity. Here, a new design of injectable hydrogel carriers for DBM that combine self-healing ability and osteogenic properties based on the self-assembly of guanidinylated hyaluronic acid and silica-rich nanoclays is reported. The nanoclays serve as reversible linkages to form a dynamic hydrogel network with the guanidine moieties on the polymer chains. Gelation kinetics and mechanical properties can be controlled by altering nanoclay content in the hydrogel. The resulting hydrogel exerts self-healing ability due to its dynamic crosslinks and well retains its overall performance with high DBM loading. The hydrogel exhibits great cytocompatibility and osteogenic effects mediated by the nanoclays. In vivo delivery of DBM using the nanocomposite hydrogel further demonstrates robust bone regeneration in a mouse calvarial defect model in comparison to DBM delivered with aqueous HA. This work suggests a promising hydrogel platform for many applications including therapeutic delivery and tissue engineering.

Demineralized bone matrix for repair and regeneration of maxillofacial defects: A narrative review

OBJECTIVES

Demineralized bone matrix (DBM) is a well-established bone graft material widely accepted by dentists and the public for its favorable osteoconductivity and osteoinductive potential. This article aimed to provide a narrative review of the current therapeutic applications and limitations of DBM in maxillofacial bone defects.

STUDY SELECTION, DATA, AND SOURCES

Randomized controlled trials, prospective or retrospective clinical studies, case series and reports, and systematic reviews. MEDLINE, PubMed, and Google Scholar were searched using keywords.

CONCLUSIONS

Some evidence supported the therapeutic application of DBM in periodontal intrabony defects, maxillary sinus lifts, ridge preservation, ridge augmentation, alveolar cleft repair, orthognathic surgery, and other regional maxillofacial bone defects. However, the limitations of DBM should be considered when using it, including potential low immunogenicity, instability of osteoinductive potential, handling of the graft material, and patient acceptance.

CLINICAL SIGNIFICANCE

With the increasing demand for the treatment of maxillofacial bone defects, DBM is likely to play a greater role as a promising bone graft material. Safe and effective combination treatment strategies and how to maintain a stable osteoinductive potential will be the future challenges of DBM research.

A Mechanistic and Preclinical Assessment of BioRestore Bioactive Glass as a Synthetic Bone Graft Extender and Substitute for Osteoinduction and Spine Fusion

STUDY DESIGN

Preclinical animal study.

OBJECTIVE

Evaluate the osteoinductivity and bone regenerative capacity of BioRestore bioactive glass.

SUMMARY OF BACKGROUND DATA

BioRestore is a Food and Drug Administration (FDA)-approved bone void filler that has not yet been evaluated as a bone graft extender or substitute for spine fusion.

METHODS

In vitro and in vivo methods were used to compare BioRestore with other biomaterials for the capacity to promote osteodifferentiation and spinal fusion. The materials evaluated (1) absorbable collagen sponge (ACS), (2) allograft, (3) BioRestore, (4) Human Demineralized Bone Matrix (DBM), and (5) MasterGraft. For in vitro studies, rat bone marrow-derived stem cells (BMSC) were cultured on the materials in either standard or osteogenic media (SM, OM), followed by quantification of osteogenic marker genes (Runx2, Osx, Alpl, Bglap, Spp1) and alkaline phosphatase (ALP) activity. Sixty female Fischer rats underwent L4-5 posterolateral fusion (PLF) with placement of 1 of 5 implants: (1) ICBG from syngeneic rats; (2) ICBG+BioRestore; (3) BioRestore alone; (4) ICBG+Allograft; or (5) ICBG+MasterGraft. Spines were harvested 8 weeks postoperatively and evaluated for bone formation and fusion via radiography, blinded manual palpation, microCT, and histology.

RESULTS

After culture for 1 week, BioRestore promoted similar expression levels of Runx2 and Osx to cells grown on DBM. At the 2-week timepoint, the relative ALP activity for BioRestore-OM was significantly higher (P<0.001) than that of ACS-OM and DBM-OM (P<0.01) and statistically equivalent to cells grown on allograft-OM. In vivo, radiographic and microCT evaluation showed some degree of bridging bone formation in all groups tested, with the exception of BioRestore alone, which did not produce successful fusions.

CONCLUSIONS

This study demonstrates the capacity of BioRestore to promote osteoinductivity in vitro. In vivo, BioRestore performed similarly to commercially available bone graft extender materials but was incapable of producing fusion as a bone graft substitute.

LEVEL OF EVIDENCE

Level V.

Biofabrication of nanocomposite-based scaffolds containing human bone extracellular matrix for the differentiation of skeletal stem and progenitor cells

Autograft or metal implants are routinely used in skeletal repair. However, they fail to provide long-term clinical resolution, necessitating a functional biomimetic tissue engineering alternative. The use of native human bone tissue for synthesizing a biomimetic material ink for three-dimensional (3D) bioprinting of skeletal tissue is an attractive strategy for tissue regeneration. Thus, human bone extracellular matrix (bone-ECM) offers an exciting potential for the development of an appropriate microenvironment for human bone marrow stromal cells (HBMSCs) to proliferate and differentiate along the osteogenic lineage. In this study, we engineered a novel material ink (LAB) by blending human bone-ECM (B) with nanoclay (L, Laponite®) and alginate (A) polymers using extrusion-based deposition. The inclusion of the nanofiller and polymeric material increased the rheology, printability, and drug retention properties and, critically, the preservation of HBMSCs viability upon printing. The composite of human bone-ECM-based 3D constructs containing vascular endothelial growth factor (VEGF) enhanced vascularization after implantation in an ex vivo chick chorioallantoic membrane (CAM) model. The inclusion of bone morphogenetic protein-2 (BMP-2) with the HBMSCs further enhanced vascularization and mineralization after only seven days. This study demonstrates the synergistic combination of nanoclay with biomimetic materials (alginate and bone-ECM) to support the formation of osteogenic tissue both in vitro and ex vivo and offers a promising novel 3D bioprinting approach to personalized skeletal tissue repair.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s42242-023-00265-z.

Nano apatite growth on demineralized bone matrix capped with curcumin and silver nanoparticles: Dental implant mechanical stability and optimal cell growth analysis

OBJECTIVES

The prevention of implant-associated infections is becoming increasingly clinically important in the field of dentistry. Extensive investigations into the development of innovative antibacterial materials that interact effectively to reinforce their functionality are currently being conducted in the biomedical sector. In the present study, a novel dental nano putty (D-nP) has been developed using demineralized bone matrix (DBM), calcium sulfate hemihydrate (CSH), curcumin nanoparticles (CU-NPs), and silver nanoparticles (AgNPs).

METHODS

The produced D-nP was evaluated using physicochemical, mechanical, and in vitro analyses. Surface characterization, particularly the analysis of calcium and phosphorus content, was performed before and after immersion in the simulated body fluid (SBF). In addition, the impact of surface treatment on biological activity was studied.

RESULTS

The results showed that the mechanical properties of the D-nP were outstanding and its performance is promising. D-nP exhibited excellent antibacterial activity against Actinomyces naeslundii (5.22 ± 0.07 mm) and Streptococcus oralis (5.41 ± 0.1 mm). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was conducted using MG-63 osteoblast cells, which exhibited 95 % viability in D-nP.

CONCLUSIONS

Based on these characterization results, the D-nP developed in this study exhibited excellent performance for tooth tissue in bone repair.

Decellularized extracellular matrix biomaterials for regenerative therapies: Advances, challenges and clinical prospects

Tissue engineering and regenerative medicine have shown potential in the repair and regeneration of tissues and organs via the use of engineered biomaterials and scaffolds. However, current constructs face limitations in replicating the intricate native microenvironment and achieving optimal regenerative capacity and functional recovery. To address these challenges, the utilization of decellularized tissues and cell-derived extracellular matrix (ECM) has emerged as a promising approach. These biocompatible and bioactive biomaterials can be engineered into porous scaffolds and grafts that mimic the structural and compositional aspects of the native tissue or organ microenvironment, both in vitro and in vivo. Bioactive dECM materials provide a unique tissue-specific microenvironment that can regulate and guide cellular processes, thereby enhancing regenerative therapies. In this review, we explore the emerging frontiers of decellularized tissue-derived and cell-derived biomaterials and bio-inks in the field of tissue engineering and regenerative medicine. We discuss the need for further improvements in decellularization methods and techniques to retain structural, biological, and physicochemical characteristics of the dECM products in a way to mimic native tissues and organs. This article underscores the potential of dECM biomaterials to stimulate in situ tissue repair through chemotactic effects for the development of growth factor and cell-free tissue engineering strategies. The article also identifies the challenges and opportunities in developing sterilization and preservation methods applicable for decellularized biomaterials and grafts and their translation into clinical products.

Bone Organoids: Recent Advances and Future Challenges

Bone defects stemming from tumorous growths, traumatic events, and diverse conditions present a profound conundrum in clinical practice and research. While bone has the inherent ability to regenerate, substantial bone anomalies require bone regeneration techniques. Bone organoids represent a new concept in this field, involving the 3D self-assembly of bone-associated stem cells guided in vitro with or without extracellular matrix material, resulting in a tissue that mimics the structural, functional, and genetic properties of native bone tissue. Within the scientific panorama, bone organoids ascend to an esteemed status, securing significant experimental endorsement. Through a synthesis of current literature and pioneering studies, this review offers a comprehensive survey of the bone organoid paradigm, delves into the quintessential architecture and ontogeny of bone, and highlights the latest progress in bone organoid fabrication. Further, existing challenges and prospective directions for future research are identified, advocating for interdisciplinary collaboration to fully harness the potential of this burgeoning domain. Conclusively, as bone organoid technology continues to mature, its implications for both clinical and research landscapes are poised to be profound.

Notochordal cells: A potential therapeutic option for intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a prevalent musculoskeletal degenerative disorder worldwide, and ~40% of chronic low back pain cases are associated with IDD. Although the pathogenesis of IDD remains unclear, the reduction in nucleus pulposus cells (NPCs) and degradation of the extracellular matrix (ECM) are critical factors contributing to IDD. Notochordal cells (NCs), derived from the notochord, which rapidly degrades after birth and is eventually replaced by NPCs, play a crucial role in maintaining ECM homeostasis and preventing NPCs apoptosis. Current treatments for IDD only provide symptomatic relief, while lacking the ability to inhibit or reverse its progression. However, NCs and their secretions possess anti-inflammatory properties and promote NPCs proliferation, leading to ECM formation. Therefore, in recent years, NCs therapy targeting the underlying cause of IDD has emerged as a novel treatment strategy. This article provides a comprehensive review of the latest research progress on NCs for IDD, covering their biological characteristics, specific markers, possible mechanisms involved in IDD and therapeutic effects. It also highlights significant future directions in this field to facilitate further exploration of the pathogenesis of IDD and the development of new therapies based on NCs strategies.

Spinal fusion of biodegradable poly(propylene fumarate) and poly(propylene fumarate-co-caprolactone) copolymers in rabbits

Background

Autologous bone grafts are currently the standard in orthopedic surgery despite limited donor sources and the prevalence of donor site morbidity. Other alternatives such as allografts are more readily available than autografts but have lower rates of graft incorporation.

Methods

Here, we propose a novel graft alternative consisting of an injectable poly(propylene fumarate) (PPF) and poly(propylene fumarate-co-caprolactone) P(PF-co-CL) copolymer with a recombinant human bone morphogenetic protein-2 (rhBMP-2)/vascular epithelial growth factor (VEGF) release system accompanied by hydroxyapatite (HA). The efficacy of scaffold formulations was studied using a standard, bilateral, L-level (L5-L6) posterolateral transverse spinal fusion using New Zealand white rabbits. Rabbits were divided into 4 experimental groups: group I, negative control; group II, autograft (positive control); group III, injectable PPF scaffold with rhBMP-2/VEGF release system and HA; group IV, injectable P(PF-co-CL)scaffold with rhBMP-2/VEGF release system and HA. Spines were harvested at 6 weeks and 12 weeks after surgery, and spinal fusions were assessed using manual palpation, radiographic analysis, micro-computed tomography (μCT) assessment, and histologic analysis.

Results

Of the 4 experimental groups, the injectable P(PF-co-CL) scaffold displayed superior initial strength and faster degradation than scaffolds constructed from PPF alone and facilitated the fusion of lateral processes in the rabbit standard posterolateral spinal fusion model. The results obtained from manual palpation, radiology, and μCT showed no difference between the P(PF-co-CL) group and the PPF group. However, histologic sections showed more osteogenesis with the new injectable P(PF-co-CL) scaffold.

Conclusion

Injectable P(PF-co-CL) polymers showed promising spine fusion abilities in rabbits after 12 weeks of posterolateral implantation.

Bone regeneration in critical-size defects of the mandible using biomechanically adapted CAD/CAM hybrid scaffolds: An in vivo study in miniature pigs

The study aimed to analyze bone regeneration in critical-size defects using hybrid scaffolds biomechanically adapted to the specific defect and adding the growth factor rhBMP-2. For this animal study, ten minipigs underwent bilateral defects in the corpus mandibulae and were subsequently treated with novel cylindrical hybrid scaffolds. These scaffolds were designed digitally to suit the biomechanical requirements of the mandibular defect, utilizing finite element analysis. The scaffolds comprised zirconium dioxide-tricalcium phosphate (ZrO2-TCP) support struts and TCP foam ceramics. One scaffold in each animal was loaded with rhBMP-2 (100 μg/cm³), while the other served as an unloaded negative control. Fluorescent dyes were administered every 2 weeks, and computed tomography (CT) scans were conducted every 4 weeks. Euthanasia was performed after 3 months, and samples were collected for examination using micro-CT and histological evaluation of both hard and soft tissue. Intravital CT examinations revealed minor changes in radiographic density from 4 to 12 weeks postoperatively. In the group treated with rhBMP-2, radiographic density shifted from 2513 ± 128 (mean ± SD) to 2606 ± 115 Hounsfield units (HU), while the group without rhBMP-2 showed a change from 2430 ± 131 to 2601 ± 67 HU. Prior to implantation, the radiological density of samples measured 1508 ± 30 mg HA/cm³, whereas post-mortem densities were 1346 ± 71 mg HA/cm³ in the rhBMP-2 group and 1282 ± 91 mg HA/cm³ in the control group (p = 0.045), as indicated by micro-CT measurements. The histological assessment demonstrated successful ossification in all specimens. The newly formed bone area proportion was significantly greater in the rhBMP-2 group (48 ± 10%) compared with the control group without rhBMP-2 (42 ± 9%, p = 0.03). The mean area proportion of remaining TCP foam was 23 ± 8% with rhBMP-2 and 24 ± 10% without rhBMP-2. Successful bone regeneration was accomplished by implanting hybrid scaffolds into critical-size mandibular defects. Loading these scaffolds with rhBMP-2 led to enhanced bone regeneration and a uniform distribution of new bone formation within the hybrid scaffolds. Further studies are required to determine the adaptability of hybrid scaffolds for larger and potentially segmental defects in the maxillofacial region.

Enhanced osteogenicity of the demineralized bone-dermal matrix composite by the optimal partial demineralization for sustained release of bioactive molecules

Allogenic demineralized bone matrix (DBM), processed to expose bioactive proteins imbedded by calcium salts, is widely used for bone repair and regeneration as an alternative to the autologous bone graft. However, demineralized bone matrices from tissue banks vary significantly in residual calcium content and osteogenicity for clinical bone regeneration. The present study produced DBM with various residual calcium contents by partial demineralization using ethylenediaminetetraacetic acid disodium (EDTA) and hydrochloric acid. Compositional analysis reveals that, as the percent weight loss of bone materials increases from 0% to 74.9% during demineralization, the residual calcium content of DBM decreases from 24.8% to 0.2% and collagen content increases from 29.7% to 92.6%. Calorimetrical analysis and Fourier transform infrared (FTIR) analysis demonstrated that demineralization to the residual calcium content of <4% enables the complete exposure and/or release of bone collagen fibers and other bioactive molecules. In order to evaluate the relationship between the extent of demineralization and the osteogenicity of DBM, DBM particles were fabricated with the aid of acellular dermal matrix (ADM) microfibers to form flexible foam-like DBM/ADM composites. Proteomic analysis identified various type collagens and bone formation-related bioactive molecules in both ADM and DBM. Using the rat bilateral Φ = 5 mm calvarium defect repair model, the study had shown that the DBM/ADM composite with ~20% DBM residual calcium (e.g., ~40% calcium being removed) maximized the osteogenicity for bone defect repair after 4 and 8 weeks. DBM with ~40% calcium removal had the maximal osteogenicity presumably through the sustained release of bioactive molecules during the process of bone regeneration.

Demineralized Bone Matrix and Fibers in Spinal Fusion

Formation of bony fusion after arthrodesis depends on osteoinduction, osteoconduction, and osteogenesis. Traditionally, the patient's own bone, or autograft, has been used to provide biological material necessary for these steps. However, the amount of autograft obtainable is often inadequate. Modern spine surgery has adopted the use of many autograft extenders or replacements, such as demineralized bone matrix or fibers. The present article covers the history of bone grafting, the production and technical details of demineralized bone matrix, and the evidence supporting its use in spine fusions.

Bone Grafting Options for Single-Level TLIF: So Many Options, What Is the Evidence?

BACKGROUND

This review seeks to investigate the clinically relevant bone graft materials in single-level transforaminal lumbar interbody fusion (TLIF) procedures as defined by (1) primary outcomes (ie, fusion rates and complication rates) and (2) patient-reported outcomes (ie, visual analog scale [VAS] and Oswestry disability index [ODI]). Because of the advantages in stimulating bone growth, autologous bone grafts such as the iliac crest bone graft (ICBG) have been the gold standard. Numerous alternatives to ICBG have been introduced. Understanding the risks and benefits of bone graft options is vital to optimizing patient care.

METHODS

A PubMed search was performed for all clinical studies published between January 2008 and March 2023 that referenced the single-level TLIF procedure as well as one of the following grafts: autograft, allograft, bone morphogenetic protein (BMP), demineralized bone matrix, or mesenchymal stem cells (MSCs). Case studies and reports were excluded.

RESULTS

Twenty-eight studies met the inclusion criteria. Studies from the PubMed search demonstrated similarly high fusion rates across nearly all graft materials, the lone exception being MSCs, which showed lower fusion rates. ICBG grafts experienced higher rates of postoperative graft site pain. The BMP graft material had high rates of radiculitis, heterogeneous ossification, and vertebral osteolysis. Patients saw an overall improvement in VAS and ODI scores with all graft materials.

CONCLUSION

Local autografts and ICBG have been the most studied. Fusion rates during single-level TLIF were similar across all graft materials except MSCs. Patient-reported pain levels improved after TLIF surgery regardless of the type of grafts used. While BMP implants have shown promising benefits, they have introduced a new array of complications not normally seen in ICBG implants. The study is limited by the lack of evidence of certain graft materials as well as nonuniformity in metrics evaluating the efficacy of graft materials.

The Therapeutic Potential of Pericytes in Bone Tissue Regeneration

Pericytes, as perivascular cells, are present in all vascularized organs and tissues, and they actively interact with endothelial cells in capillaries and microvessels. Their involvement includes functions like blood pressure regulation, tissue regeneration, and scarring. Studies have confirmed that pericytes play a crucial role in bone tissue regeneration through direct osteodifferentiation processes, paracrine actions, and vascularization. Recent preclinical and clinical experiments have shown that combining perivascular cells with osteogenic factors and tissue-engineered scaffolds can be therapeutically effective in restoring bone defects. This approach holds promise for addressing bone-related medical conditions. In this review, we have emphasized the characteristics of pericytes and their involvement in angiogenesis and osteogenesis. Furthermore, we have explored recent advancements in the use of pericytes in preclinical and clinical investigations, indicating their potential as a therapeutic resource in clinical applications.

BMP-2 promotes fracture healing by facilitating osteoblast differentiation and bone defect osteogenesis

OBJECTIVE

To investigate the role of bone morphogenetic protein-2 (BMP-2) in promoting fracture healing in animal models.

METHODS

Mouse models with muscle bag heterotopic osteogenesis (HO) were divided into a HO control group (not implanted with 250 μg rhBMP-2 bone repairing material), and a HO observation group (implanted with 250 μg rhBMP-2 bone repairing material); while rat models with bone defect (BD) were divided into a BD control group (not implanted with 250 μg rhBMP-2 bone repairing material) and a BD observation group (implanted with 250 μg rhBMP-2 bone repairing material). At 4 weeks after HO establishment, the new bone formation at the operation site was observed through visual inspections and X-ray scanning. The content of serum alkaline phosphatase (ALP) was detected by automatic biochemical analyzer. The formation of new bone at the operative sites was observed by Hematoxylin and eosin staining and Masson staining. At 0, 2, 4 and 8 weeks after operation, the growth of the defect area and its surrounding callus were observed by X-ray scanning. At 4 and 8 weeks after bone defect establishment in the mouse models, the histological changes and osteogenesis of the bone defect site were observed.

RESULTS

The heterotopic osteogenesis experiment showed that at 4 weeks after operation, the mass at the muscle bag in the HO observation group became larger in contrast to the HO control group. X-ray scanning showed that there was obvious irregular bone shadow at the back muscle bag of mice from the HO observation group. The content of serum ALP in the HO observation group was significantly higher than that in the HO control group (all P<0.05). The muscle pocket in the HO observation group showed higher ectopic osteogenic activity comparing with the HO control group. Histological staining showed that bone tissue structure was visible in the newly regenerated bone, forming bone trabeculae and bone marrow tissue. Under the microscope, a large number of osteoblasts arranged neatly in a cubic shape presented at the edge of the new bone, and there were bone lacunae formed, and the bone tissue was in a relatively mature stage. In the rat bone defect models, X-ray scanning showed that the high-density development area was further increased. There was a large amount of callus formation in the bone defect area of the BD observation group, while the BD control group still had no high-density development. At 8 weeks after operation, the high-density development area decreased, indicating that there was partial absorption of callus, while there was still no high-density development in the BD control group. The callus of the bone defect area in the BD observation group was reduced and the defect area was gradually repaired, while the bone defect in the BD control group was still obvious and the bone repair was not completed.

CONCLUSIONS

BMP-2 could promote osteoblast differentiation and bone defect osteogenesis in vivo. Thus, it is worthy of clinical application.

Comparison of demineralized bone matrix with different cycling crushing times in posterolateral fusion model of athymic rats

Decalcified bone matrix (DBM) is a widely used alternative material for bone transplantation. In the DBM production process, an effective particle size and the highest utilization rate of raw materials can be achieved only through multiple high-speed circulating comminution. The rat posterolateral lumbar fusion model (PLF) is the most mature small animal model for the initial evaluation of the efficacy of graft materials for bone regeneration and spinal fusion. To evaluate the differences in the in vivo osteogenic effects of DBM pulverization through 1, 5, 9, and 14 high-speed cycles, sixty athymic rats were divided into six groups: single cycling crushing (CC1), 5 cycles of crushing (CC5), 9 cycles of crushing (CC9), 13 cycles of crushing (CC13), autogenous bone graft (ABG) and negative control (NC). Posterolateral lumbar fusion was performed. Six weeks after surgery, the bilateral lumbar fusion of athymic rats was evaluated through manual palpation, X-ray, micro-CT and histological sections. Rank data were tested by the rank-sum test, and nonparametric data were tested by the Kruskal‒Wallis H test. The manual palpation and X-ray results showed that the fusion rate did not significantly differ between the CC1, CC5, CC9, CC13 and ABG groups. However, cavities appeared in CC9 and CC13 on the micro-CT image. The bone mass (BV/TV) of CC1, CC5, CC9 and CC13 was better than that of the ABG group, while almost no osteogenesis was observed in the NC group. Histologically, there was no obvious difference between the four groups except that the CC9 group and CC13 group had more fibrous tissues in the new bone. In conclusion, DMB with different cycling crushing times has no obvious difference in fusion rate of PLF, but it is slightly better than the ABG group.

Bone Allograft Acid Lysates Change the Genetic Signature of Gingival Fibroblasts

Bone allografts are widely used as osteoconductive support to guide bone regrowth. Bone allografts are more than a scaffold for the immigrating cells as they maintain some bioactivity of the original bone matrix. Yet, it remains unclear how immigrating cells respond to bone allografts. To this end, we have evaluated the response of mesenchymal cells exposed to acid lysates of bone allografts (ALBA). RNAseq revealed that ALBA has a strong impact on the genetic signature of gingival fibroblasts, indicated by the increased expression of IL11, AREG, C11orf96, STC1, and GK-as confirmed by RT-PCR, and for IL11 and STC1 by immunoassays. Considering that transforming growth factor-β (TGF-β) is stored in the bone matrix and may have caused the expression changes, we performed a proteomics analysis, TGF-β immunoassay, and smad2/3 nuclear translocation. ALBA neither showed detectable TGF-β nor was the lysate able to induce smad2/3 translocation. Nevertheless, the TGF-β receptor type I kinase inhibitor SB431542 significantly decreased the expression of IL11, AREG, and C11orf96, suggesting that other agonists than TGF-β are responsible for the robust cell response. The findings suggest that IL11, AREG, and C11orf96 expression in mesenchymal cells can serve as a bioassay reflecting the bioactivity of the bone allografts.

Delivery of Growth Factors to Enhance Bone Repair

The management of critical-sized bone defects caused by nonunion, trauma, infection, malignancy, pseudoarthrosis, and osteolysis poses complex reconstruction challenges for orthopedic surgeons. Current treatment modalities, including autograft, allograft, and distraction osteogenesis, are insufficient for the diverse range of pathology encountered in clinical practice, with significant complications associated with each. Therefore, there is significant interest in the development of delivery vehicles for growth factors to aid in bone repair in these settings. This article reviews innovative strategies for the management of critical-sized bone loss, including novel scaffolds designed for controlled release of rhBMP, bioengineered extracellular vesicles for delivery of intracellular signaling molecules, and advances in regional gene therapy for sustained signaling strategies. Improvement in the delivery of growth factors to areas of significant bone loss has the potential to revolutionize current treatment for this complex clinical challenge.

Development of photoreactive demineralized bone matrix 3D printing colloidal inks for bone tissue engineering

Demineralized bone matrix (DBM) has been widely used clinically for dental, craniofacial and skeletal bone repair, as an osteoinductive and osteoconductive material. 3D printing (3DP) enables the creation of bone tissue engineering scaffolds with complex geometries and porosity. Photoreactive methacryloylated gelatin nanoparticles (GNP-MAs) 3DP inks have been developed, which display gel-like behavior for high print fidelity and are capable of post-printing photocrosslinking for control of scaffold swelling and degradation. Here, novel DBM nanoparticles (DBM-NPs, ∼400 nm) were fabricated and characterized prior to incorporation in 3DP inks. The objectives of this study were to determine how these DBM-NPs would influence the printability of composite colloidal 3DP inks, assess the impact of ultraviolet (UV) crosslinking on 3DP scaffold swelling and degradation and evaluate the osteogenic potential of DBM-NP-containing composite colloidal scaffolds. The addition of methacryloylated DBM-NPs (DBM-NP-MAs) to composite colloidal inks (100:0, 95:5 and 75:25 GNP-MA:DBM-NP-MA) did not significantly impact the rheological properties associated with printability, such as viscosity and shear recovery or photocrosslinking. UV crosslinking with a UV dosage of 3 J/cm2 directly impacted the rate of 3DP scaffold swelling for all GNP-MA:DBM-NP-MA ratios with an ∼40% greater increase in scaffold area and pore area in uncrosslinked versus photocrosslinked scaffolds over 21 days in phosphate-buffered saline (PBS). Likewise, degradation (hydrolytic and enzymatic) over 21 days for all DBM-NP-MA content groups was significantly decreased, ∼45% less in PBS and collagenase-containing PBS, in UV-crosslinked versus uncrosslinked groups. The incorporation of DBM-NP-MAs into scaffolds decreased mass loss compared to GNP-MA-only scaffolds during collagenase degradation. An in vitro osteogenic study with bone marrow-derived mesenchymal stem cells demonstrated osteoconductive properties of 3DP scaffolds for the DBM-NP-MA contents examined. The creation of photoreactive DBM-NP-MAs and their application in 3DP provide a platform for the development of ECM-derived colloidal materials and tailored control of biochemical cue presentation with broad tissue engineering applications.

Additive manufacture of PLLA scaffolds reinforced with graphene oxide nano-particles via digital light processing (DLP)

In this study, 3D printing of poly-l-lactic acid (PLLA) scaffolds reinforced with graphene oxide (GO) nanoparticles via Digital Light Processing (DLP) was investigated to mimic bone tissue. Stereolithography is one of the most accurate additive manufacturing methods, but the dominant available materials used in this method are toxic. In this research, a biocompatible resin (PLLA) was synthetized and functionalized to serve the purpose. Due to the low mechanical properties of the printed product with the neat resin, graphene oxide nanoparticles in three levels (0.5, 1, and 1.5 wt%) were added with the aim of enhancing the mechanical properties. At first, the optimum post cure time of the neat resin was investigated. Consequently, all the parts were post-cured for 3 h after printing. Due to the temperature-dependent structure of GO, all samples were placed in an oven at 85°C for different time periods of 0, 6, 12, and 18 h to increase mechanical properties. The compression test of heat-treated samples reveals that the compressive strength of the printed parts containing 0.5,1, and 1.5% of GO increased by 151,162 ad 235%, respectively. Scaffolds with the designed pore sizes of 750 microns and a porosity of 40% were printed. Surface hydrophilicity test was performed for all samples showing that the hydrophilicity of the samples increased with increasing GO percentage. The degradation behavior of the samples was evaluated in a PBS environment, and it revealed that by increasing GO, the rate of component degradation increased, but the heat treatment had the opposite effect and decreased the degradation rate. Finally, besides improving biological properties, a significant increase in mechanical properties under compression can introduce the printed scaffolds as a suitable option for bone implants.

Bone Graft Substitutes and Enhancement in Craniomaxillofacial Surgery

Critical-sized bone defects are a reconstructive challenge, particularly in the craniomaxillofacial (CMF) skeleton. The "gold standard" of autologous bone grafting has been the work horse of reconstruction in both congenital and acquired defects of CMF skeleton. Autologous bone has the proper balance of the protein (or organic) matrix and mineral components with no immune response. Organic and mineral adjuncts exist that offer varying degrees of osteogenic, osteoconductive, osteoinductive, and osteostimulative properties needed for treatment of critical-sized defects. In this review, we discuss the various mostly organic and mostly mineral bone graft substitutes available for autologous bone grafting. Primarily organic bone graft substitutes/enhancers, including bone morphogenic protein, platelet-rich plasma, and other growth factors, have been utilized to support de novo bone growth in setting of critical-sized bone defects. Primarily mineral options, including various calcium salt formulation (calcium sulfate/phosphate/apatite) and bioactive glasses have been long utilized for their similar composition to bone. Yet, a bone graft substitute that can supplant autologous bone grafting is still elusive. However, case-specific utilization of bone graft substitutes offers a wider array of reconstructive options.

Inverse design of anisotropic bone scaffold based on machine learning and regenerative genetic algorithm

Introduction: Triply periodic minimal surface (TPMS) is widely used in the design of bone scaffolds due to its structural advantages. However, the current approach to designing bone scaffolds using TPMS structures is limited to a forward process from microstructure to mechanical properties. Developing an inverse bone scaffold design method based on the mechanical properties of bone structures is crucial. Methods: Using the machine learning and genetic algorithm, a new inverse design model was proposed in this research. The anisotropy of bone was matched by changing the number of cells in different directions. The finite element (FE) method was used to calculate the TPMS configuration and generate a back propagation neural network (BPNN) data set. Neural networks were used to establish the relationship between microstructural parameters and the elastic matrix of bone. This relationship was then used with regenerative genetic algorithm (RGA) in inverse design. Results: The accuracy of the BPNN-RGA model was confirmed by comparing the elasticity matrix of the inverse-designed structure with that of the actual bone. The results indicated that the average error was below 3.00% for three mechanical performance parameters as design targets, and approximately 5.00% for six design targets. Discussion: The present study demonstrated the potential of combining machine learning with traditional optimization method to inversely design anisotropic TPMS bone scaffolds with target mechanical properties. The BPNN-RGA model achieves higher design efficiency, compared to traditional optimization methods. The entire design process is easily controlled.

Efficacy of Modified Lightbulb Technique by Percutaneous Femoral Neck-Head Fenestration Combined With Compacted Artificial Bone Graft for Treating Precollapse Osteonecrosis of the Femoral Head

BACKGROUND

Whether artificial bone provides comparable outcomes to autogenous bone has not been determined for osteonecrosis of the femoral head (ONFH). This study was conducted to compare the clinical outcomes of autogenous and artificial bone grafting (demineralized bone matrix/calcium sulfate [DBM/CaS]) through a modified lightbulb technique by percutaneous femoral neck-head fenestration for treating precollapse ONFH.

METHODS

A total of 73 Association Research Circulation Osseous Stage Ⅱ ONFH patients (81 hips) who had a mean follow-up of 61 months (range, 52 to 74) were included in this retrospective study. Among them were 40 hips treated with autogenous bone and 41 hips treated with DBM/CaS grafting through the percutaneous femoral neck-head fenestration. The Harris scores, radiographic progressions, clinical success rates, and survival analyses were analyzed.

RESULTS

At final follow-up, the mean Harris score was 80 points (range, 63 to 92) in the DBM/CaS group and 76 points (range, 69 to 91) in the autogenous bone group (P = .751). The radiographic progression rate was 29.9% in the DBM/CaS group, without significant difference from the autogenous bone group, which was 37.5% (P = .43). About 73.2% of patients in the DBM/CaS group and 75% in the autologous bone group avoided a total hip arthroplasty (P = .85). Survival analysis for femoral head protection revealed similar outcomes between the 2 groups (P > .05).

CONCLUSION

Percutaneous femoral neck-head fenestration combined with artificial bone (DBM/CaS) grafting had comparable clinical outcomes to autologous bone grafting on preventing femoral head collapse and rescuing THA at a mean of 61-month follow-up for treating early ONFH.

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

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

Advances and Prospects in Materials for Craniofacial Bone Reconstruction

The craniofacial region is composed of 23 bones, which provide crucial function in keeping the normal position of brain and eyeballs, aesthetics of the craniofacial complex, facial movements, and visual function. Given the complex geometry and architecture, craniofacial bone defects not only affect the normal craniofacial structure but also may result in severe craniofacial dysfunction. Therefore, the exploration of rapid, precise, and effective reconstruction of craniofacial bone defects is urgent. Recently, developments in advanced bone tissue engineering bring new hope for the ideal reconstruction of the craniofacial bone defects. This report, presenting a first-time comprehensive review of recent advances of biomaterials in craniofacial bone tissue engineering, overviews the modification of traditional biomaterials and development of advanced biomaterials applying to craniofacial reconstruction. Challenges and perspectives of biomaterial development in craniofacial fields are discussed in the end.

Efficacy and Safety of Beta-Tricalcium Phosphate/Polylactic-Co-Glycolic Acid for Implantation of Bone Defects

INTRODUCTION

Bone defects are often observed after surgery for fractures and bone tumors. Their treatment is technically difficult and sometimes results in negative clinical and economic outcomes. To repair bone defects, a bone graft is implanted by selecting a transplant material from an autologous or artificial bone. Each method has its advantages and disadvantages. Compared to the gold standard of autologous bone graft, bone graft substitutes are not limited by the amount of harvested graft and avoid complications at the donor site. ORB-03 is a new cotton-like bone graft substitute composed of beta-tricalcium phosphate (β-TCP) and a bioabsorbable polymer, polylactic-co-glycolic acid (PLGA). ORB-03 is easy to mold and can fill various bone defect shapes, and its three-dimensional microfiber scaffold can enhance the differentiation of osteoblasts and promote osteogenesis. We investigated the efficacy, ease of handling, and safety of ORB-03 as a bone graft substitute. A multicenter, open-label, single-group study was conducted at six institutions.

METHODS

Between July 2018 and August 2019, 60 patients with bone defects caused by fracture, benign tumors, or an iliac donor site from bone harvesting were enrolled in this study; 54 patients were finally included for the safety analysis and 48 patients for the image analysis. During surgery, ORB-03 was mixed with the patient's blood and molded into a bone defect. To evaluate the efficacy of ORB-03, radiography and computed tomography (CT) were performed at intervals until 24 weeks after surgery.

RESULTS

The effective rate and its accurate bilateral 95% confidence interval (CI) were calculated based on the efficacy criteria at 24 weeks postoperatively. The ease with which ORB-03 could be handled in surgery was evaluated. Adverse events that occurred after surgery were evaluated, and those associated with ORB-03 were examined. Bone fusion was good in all cases, and the radiography and CT effective rates were 100.0% and 91.5%, respectively. Handling was easy in all cases. There were four adverse events, none of which were clinically problematic.

CONCLUSIONS

ORB-03 was found to be easy to handle, safe, and effective as a bone graft substitute for bone defects.

Clinical and Radiographic Evaluation of Autologous Platelet-Rich Fibrin With or Without Demineralized Bone Matrix in the Treatment of Grade II Furcation Defects

Introduction This study aims to differentiate the employment of demineralized bone matrix (DMBM; Osseograft, Advanced Biotech Products (P) Ltd, Chennai, India) and platelet-rich fibrin (PRF) alone to a composite graft consisting of both materials in the surgical actions toward the anomalies of the human periodontal furcation imperfection. Methods In a split-mouth study, 30 patients with mandibular molars affected by the furcation were allocated without conscious choice to test (PRF + DMBM, n = 30) or control (PRF, n = 30) categories. At the starting point, three months after surgery, and six months later, the following modifiable factors were evaluated: probing pocket depth (PPD), full-mouth plaque scores, full-mouth gingival scores, radiographic defect depth, relative vertical clinical attachment level (RVCAL), and relative horizontal clinical attachment level (RHCAL). Results Results at three and six months demonstrated substantial differences between baseline values for both treatment methods in clinical and X-ray imaging appraisal. Nonetheless, the PRF/DMBM group manifests statistically significantly soaring changes observed in comparison to the PRF group. Overall, the probing depth (PD) in the test site was significantly lower than that in the control site, showing a reduction of 68% (95% CI=41%, 95%, p<0.001). Conclusion Clinical indications significantly improved with PRF and DMBM combined instead of PRF alone. On radiographs, the test group also showed higher bone fill.

Fibrocartilage extracellular matrix augmented demineralized bone matrix graft repairs tendon-to-bone interface in a rabbit tendon reconstruction model

Current tendon/ligament reconstructions integrate via scar tissue rather than proper bone-tendon interface regeneration, which affects graft longevity, changes in bone tunnel size, and functional outcomes. The purpose of this study was to develop a functional demineralized bone matrix (DBM) + fibrocartilage extracellular matrix (FCECM) composite scaffold, characterize its physicochemical properties, and evaluate its efficacy in repairing tendon-bone interface in a rabbit tendon reconstruction model. Solubilized FCECM was loaded and crosslinked on to DBM scaffolds via gamma-irradiation to create DBM + FCECM scaffolds. The resulting scaffold showed interconnected pores coated with FCECM and protein cargo similar to FCECM. The addition of FCECM modified the physicochemical properties of the DBM scaffold, including microstructure, biochemical composition, mechanical strength, thermodynamic properties, and degradation period. The DBM + FCECM scaffold was biocompatible for mesenchymal stem cells (MSCs) and resulted in elevation of fibrochondrogenic gene markers compared to DBM scaffolds in vitro. In vivo implantation of DBM + FCECM scaffold resulted in neofibrocartilage formation, better pullout strength, and less bone tunnel widening compared to DBM only group in a rabbit tendon reconstruction model. In conclusion, the FCECM augmented DBM scaffold repairs the tendon-bone interface with osseous-fibrocartilage tissue, which may be utilized to improve current tendon reconstruction surgeries.

Progress in the application of 3D-printed sodium alginate-based hydrogel scaffolds in bone tissue repair

In recent years, hydrogels have been widely used in the biomedical field as materials with excellent bionic structures and biological properties. Among them, the excellent comprehensive properties of natural polymer hydrogels represented by sodium alginate have attracted the great attention of researchers. At the same time, by physically blending sodium alginate with other materials, the problems of poor cell adhesion and mechanical properties of sodium alginate hydrogels were directly improved without chemical modification of sodium alginate. The composite blending of multiple materials can also improve the functionality of sodium alginate hydrogels, and the prepared composite hydrogel also has a larger application field. In addition, based on the adjustable viscosity of sodium alginate-based hydrogels, sodium alginate-based hydrogels can be loaded with cells to prepare biological ink, and the scaffold can be printed out by 3D printing technology for the repair of bone defects. This paper first summarizes the improvement of the properties of sodium alginate and other materials after physical blending. Then, it summarizes the application progress of sodium alginate-based hydrogel scaffolds for bone tissue repair based on 3D printing technology in recent years. Moreover, we provide relevant opinions and comments to provide a theoretical basis for follow-up research.

Analysis of the Ability of Different Allografts to Act as Carrier Grafts for Local Drug Delivery

Bone defects and infections pose significant challenges for treatment, requiring a comprehensive approach for prevention and treatment. Thus, this study sought to evaluate the efficacy of various bone allografts in the absorption and release of antibiotics. A specially designed high-absorbency, high-surface-area carrier graft composed of human demineralized cortical fibers and granulated cancellous bone (fibrous graft) was compared to different human bone allograft types. The groups tested here were three fibrous grafts with rehydration rates of 2.7, 4, and 8 mL/g (F(2.7), F(4), and F(8)); demineralized bone matrix (DBM); cortical granules; mineralized cancellous bone; and demineralized cancellous bone. The absorption capacity of the bone grafts was assessed after rehydration, the duration of absorption varied from 5 to 30 min, and the elution kinetics of gentamicin were determined over 21 days. Furthermore, antimicrobial activity was assessed using a zone of inhibition (ZOI) test with S. aureus. The fibrous grafts exhibited the greatest tissue matrix absorption capacity, while the mineralized cancellous bone revealed the lowest matrix-bound absorption capacity. For F(2.7) and F(4), a greater elution of gentamicin was observed from 4 h and continuously over the first 3 days when compared to the other grafts. Release kinetics were only marginally affected by the varied incubation times. The enhanced absorption capacity of the fibrous grafts resulted in a prolonged antibiotic release and activity. Therefore, fibrous grafts can serve as suitable carrier grafts, as they are able to retain fluids such as antibiotics at their intended destinations, are easy to handle, and allow for a prolonged antibiotic release. Application of these fibrous grafts can enable surgeons to provide longer courses of antibiotic administration for septic orthopedic indications, thus minimizing infections.

Time-Dependent Demineralization of Tilapia (Oreochromis niloticus) Bones Using Hydrochloric Acid for Extracellular Matrix Extraction

Tilapia (Oreochromis niloticus) is a widely cultivated fish in tropical and subtropical regions such as the Philippines, generating substantial waste during processing, including bones that are a valuable source of extracellular matrix (ECM). However, the extraction of ECM from fish bones requires an essential step of demineralization. This study aimed to assess the efficiency of tilapia bone demineralization using 0.5 N HCl at different time durations. By evaluating the residual calcium concentration, reaction kinetics, protein content, and extracellular matrix (ECM) integrity through histological analysis, composition assessment, and thermal analysis, the effectiveness of the process was determined. Results revealed that after 1 h of demineralization, the calcium and protein contents were 1.10 ± 0.12% and 88.7 ± 0.58 μg/mL, respectively. The study found that after 6 h, the calcium content was almost completely removed, but the protein content was only 51.7 ± 1.52 μg/mL compared to 109.0 ± 1.0 μg/mL in native bone tissue. Additionally, the demineralization reaction followed second-order kinetics with an R² value of 0.9964. Histological analysis using H&E staining revealed a gradual disappearance of the basophilic components and the emergence of lacunae, which can be attributed to decellularization and mineral content removal, respectively. As a result, organic components such as collagen remained in the bone samples. ATR-FTIR analysis showed that all demineralized bone samples retained collagen type I markers, including amide I, II, and III, amides A and B, and symmetric and antisymmetric CH₂ bands. These findings provide a route for developing an effective demineralization protocol to extract high-quality ECM from fish bones, which could have important nutraceutical and biomedical applications.

One Stage Masquelets Technique: Evaluation of Different Forms of Membrane Filling with and without Bone Marrow Mononuclear Cells (BMC) in Large Femoral Bone Defects in Rats

The classic two-stage masquelet technique is an effective procedure for the treatment of large bone defects. Our group recently showed that one surgery could be saved by using a decellularized dermis membrane (DCD, Epiflex, DIZG). In addition, studies with bone substitute materials for defect filling show that it also appears possible to dispense with the removal of syngeneic cancellous bone (SCB), which is fraught with complications. The focus of this work was to clarify whether the SCB can be replaced by the granular demineralized bone matrix (g-DBM) or fibrous demineralized bone matrix (f-DBM) demineralized bone matrix and whether the colonization of the DCD and/or the DBM defect filling with bone marrow mononuclear cells (BMC) can lead to improved bone healing. In 100 Sprague Dawley rats, a critical femoral bone defect 5 mm in length was stabilized with a plate and then encased in DCD. Subsequently, the defect was filled with SCB (control), g-DBM, or f-DBM, with or without BMC. After 8 weeks, the femurs were harvested and subjected to histological, radiological, and biomechanical analysis. The analyses showed the incipient bony bridging of the defect zone in both groups for g-DBM and f-DBM. Stability and bone formation were not affected compared to the control group. The addition of BMCs showed no further improvement in bone healing. In conclusion, DBM offers a new perspective on defect filling; however, the addition of BMC did not lead to better results.

Human Hematopoietic Stem Cells Co-cultured in 3D with Stromal Support to Optimize Lentiviral Vector-mediated Gene Transduction

HSC transplantation (HSCT) has emerged as a promising treatment option for hematological and immunological disorders. Unfortunately, many viral vectors are inefficient at transduction, limiting the number of cells available for gene therapy in cord blood HSC transplantation. Combining ex vivo expansion and genetic manipulation of cord blood cells is a potential gene therapy approach. We present a 3D co-culture method using a demineralized bone matrix scaffold to optimize lentiviral vector-mediated gene transduction. pLenti-III-miR-GFP-has-miR-124 was transduced into cord blood HSCs. Transduced CD34 + cells co-cultured on the stromal layer for 72 h under cytokine-free conditions. We performed flow cytometry, colony assays, real-time polymerase chain reaction, and SEM morphological analysis. Seventy-two hours after transduction, when pLentiIII-miR-GFP-has-miR-124 and control vector-transduced expanded cord blood HSCs were compared to non-transduced expanded cord blood HSCs, the findings revealed 15 ± 3.04 and 55 ± 3.05-fold increases in miR-124 mRNA expression, respectively. Compared to a control culture on the same day, the expansion of CD34+, CD38-HSCs in 3D culture increased 544 ± 31.09 fold. This result demonstrated that the 3D-culture system could emerge as a novel approach to overcoming the current limitations of cord blood HSC transduction. In the future, this research could be applied in a therapeutic setting.

A Mechanically Reinforced Super Bone Glue Makes a Leap in Hard Tissue Strong Adhesion and Augmented Bone Regeneration

Existing bone tissue engineering strategies aim to achieve minimize surgical trauma, stabilize the injured area, and establish a dynamic osteogenic microenvironment. The cutting-edge bone glue developed in this study satisfies these criteria. Inspired by the excellent adhesive properties of mussels, herein, a super osteogenic glue (L-DPZ) that integrates poly(vinyl alcohol), L-dopa amino acid, and zeolitic imidazolate framework-8 characterized by catechol-metal coordination is used to successfully adhere to hard tissue with a maximum adhesive strength of 10 MPa, which is much higher than those of commercial and previously reported bone glues. The stable hard tissue adhesion also enables it to adhere strongly to luxated or broken teeth, Bio-Oss (a typical bone graft material), and splice fragments from comminuted fractures of the rabbit femur. Then, it is testified that the L-DPZ hydrogels exhibit satisfactory biocompatibility, stable degradability, and osteogenic ability in vitro. Moreover, the ability to anchor Bio-Oss and sustained osteogenesis of L-DPZ result in satisfactory healing in calvarial bone defect models in rabbits, as observed by increased bone thickness and the ingrowth of new bone tissue. These results are expected to demonstrate solutions to clinical dilemmas such as comminuted bone fracture fixation, bone defect reconstruction, and teeth dislocation replantation.

Open-source perfusion system for medium-scale fabrication of demineralized bone matrix chip grafts

Demineralized bone matrix (DBM) is considered one of the most reliable bone tissue grafts for regular surgical use, as it provides a scaffold that is structurally like native bone, and that enhances bone regeneration. However, commercially available DBM products are not suited for surgical restitutions of large bones. Therefore, each Tissue Bank is urged to implement their own demineralization protocol, which usually does not meet the high demand for bone grafting. In this project, we developed an open source system for medium-scale manufacturing of DBM grafts from human cadaveric donors to automate the demineralization protocol and improve its reproducibility. The device consists in (1) unidirectional flow reaction chamber, where the demineralization protocol takes place; (2) automated syringe pump, which controls the reagent́s inlet and vacuum; and (3) reagent dispenser, for the management of the reagents need for the demineralization protocol. Validation of the device included histological analysis, DNA quantification temperature regulation, electrochemiluminescence and colorimetric protocols, followed by the optimization of physicochemical parameters based on Response Surface Methodology. The results showed values of residual lipids and calcium within standardized ranges, and the maintenance of the structural integrity of the DBM, demonstrating the capacity of the system to support the proposed demineralization protocol.

The differentiation of human induced pluripotent stem cells into hematopoietic stem cells on 3D bone scaffold in a dynamic culture system

Hematopoietic stem cell transplantation is used for cell-based therapy for many hematological disorders. However, difficulty in finding proper donors has limited this source of stem cells. For clinical application, the generation of these cells from induced pluripotent stem cells (iPSs) is a fascinating and endless source. One of the experimental methods to generate HSCs from iPSs is the mimicking of the hematopoietic niche. In the current study, as the first phase of differentiation, embryoid bodies were formed from iPSs. They were then cultured in different dynamic conditions in order to determine the appropriate settings for their differentiation into HSCs. The dynamic culture was composed of DBM Scaffold with or without growth factor. After ten days, the specific HSC markers (CD34, CD133, CD31 and CD45) were assessed using flow-cytometry. Our findings demonstrated that the dynamic conditions were significantly suitable than static ones. In addition, in 3D scaffold and dynamic system the expression of CXCR4, as a homing marker, was increased. These results suggest that the 3D culture bioreactor with DBM scaffold could provide a new approach for differentiation of iPSs into HSCs. Moreover, this system could provide maximum mimicry of bone marrow niche.

Biomedical applications of three-dimensional bioprinted craniofacial tissue engineering

Anatomical complications of the craniofacial regions often present considerable challenges to the surgical repair or replacement of the damaged tissues. Surgical repair has its own set of limitations, including scarcity of the donor tissues, immune rejection, use of immune suppressors followed by the surgery, and restriction in restoring the natural aesthetic appeal. Rapid advancement in the field of biomaterials, cell biology, and engineering has helped scientists to create cellularized skeletal muscle-like structures. However, the existing method still has limitations in building large, highly vascular tissue with clinical application. With the advance in the three-dimensional (3D) bioprinting technique, scientists and clinicians now can produce the functional implants of skeletal muscles and bones that are more patient-specific with the perfect match to the architecture of their craniofacial defects. Craniofacial tissue regeneration using 3D bioprinting can manage and eliminate the restrictions of the surgical transplant from the donor site. The concept of creating the new functional tissue, exactly mimicking the anatomical and physiological function of the damaged tissue, looks highly attractive. This is crucial to reduce the donor site morbidity and retain the esthetics. 3D bioprinting can integrate all three essential components of tissue engineering, that is, rehabilitation, reconstruction, and regeneration of the lost craniofacial tissues. Such integration essentially helps to develop the patient-specific treatment plans and damage site-driven creation of the functional implants for the craniofacial defects. This article is the bird's eye view on the latest development and application of 3D bioprinting in the regeneration of the skeletal muscle tissues and their application in restoring the functional abilities of the damaged craniofacial tissue. We also discussed current challenges in craniofacial bone vascularization and gave our view on the future direction, including establishing the interactions between tissue-engineered skeletal muscle and the peripheral nervous system.

Zonally Stratified Decalcified Bone Scaffold with Different Stiffness Modified by Fibrinogen for Osteochondral Regeneration of Knee Joint Defect

Articular cartilage is generally known to be a complex tissue with multiple layers. Each layer has different composition, structure, and mechanical properties, making regeneration after knee joint defects a troubling clinical problem. A novel integrated stratified decalcified bone matrix (SDBM) scaffold with different stiffness to mimic the mechanical properties of articular cartilage is presented herein. This SDBM scaffold was modified using fibrinogen (Fg) (Fg + SDBM) to enhance its vascularization ability and improve its repair efficiency for osteochondral defects of knee joints. A Fg + SDBM scaffold with different elastic modulus in each layer (high-stiffness DBM (HDBM) layer, 174.208 ± 44.330 MPa (Fg + HDBM); medium-stiffness DBM (MDBM) layer, 21.214 ± 6.922 MPa (Fg + MDBM); and low-stiffness DBM (LDBM) layer, 0.678 ± 0.269 MPa (Fg + LDBM)) was constructed by controlling the stratified decalcification time with layered embedding paraffin (0, 3, and 5 days). The low- and medium-stiffness layers of the Fg + SDBM scaffold remarkably promoted the cartilage differentiation of bone marrow mesenchymal stem cells in vitro. Subcutaneous transplantation and rabbit knee joint osteochondral defect repair experiments revealed that the low- and medium-stiffness layers of the Fg + SDBM scaffold exhibited wonderful cartilage capacity, whereas the high-stiffness layer of Fg + SDBM scaffold exhibited good osteogenesis ability. Furthermore, this scaffold could promote blood vessel formation in subchondral bone area. This study presents a feasible strategy for osteochondral regeneration of defective knee joints, which is of great clinical value for tissue repair.

Injectable demineralized bone matrix particles and their hydrogel bone grafts loaded with β-tricalcium phosphate powder and granules: A comparative study

Demineralized bone matrix (DBM), has been used as a bone-graft material because of its osteoconductivity and osteoinductivity. However, the previous research report that supports the single use of DBM is limited by its rapid resorption caused by the lack of calcium and phosphate. β-Tricalcium phosphate (TCP) is an enriched calcium phosphate material suitable for bone healing with osteoconductive properties. In this study, we have developed injectable bone graft by the loading two kinds of TCP in DBM particles and thermo-sensitive DBM-derived hydrogel (hDBM). TCP powder (pTCP) and TCP granules (gTCP) were loaded into hDBM and DBM, respectively. The bone formation effect was investigated according to the morphological features of TCP. Residual growth factor concentrations were investigated; microstructure and morphology were characterized by SEM. In-vitro studies showed that hDBM/DBM/pTCP and hDBM/DBM/gTCP bone grafts were biocompatible and could promote osteogenesis by up-regulating the expression of Runx2 and OPN, bone-related genes. In-vivo studies using the rabbit-femur defect model revealed that the implanted hDBM/DBM/pTCP bone graft showed similar histology to that of fibrous dysplasia with the expression of CD68, whereas hDBM/DBM/gTCP showed good bone formation. Loading of gTCP in place of pTCP was noticed as an effective way to improve bone regeneration in an injectable hDBM/DBM hydrogel-based bone graft.

The allogeneic shell technique for alveolar ridge augmentation: a multicenter case series and experiences of more than 300 cases

PURPOSE

Allogeneic cortical bone plates (CP) might be used for alveolar ridge augmentation as an alternative to autogenous grafts (AG) and bone substitutes (BS). We report about a multicenter case series and our experiences of more than 300 cases using CP and the shell technique for reconstruction of the alveolar process to illustrate surgical key steps, variations, and complication management.

METHODS

Different types of alveolar ridge defects were augmented using the shell technique via CP. The space between the CP and the alveolar bone was filled with either autogenous or allogeneic granules (AUG, ALG) or a mixture of both. Implants were placed after 4-6 months. Microscopic and histological assessments were performed. In addition, space filling using AUG, ALG and bovine BS was discussed.

RESULTS

Scanning electron microscopy demonstrated the compact cortical structure of CP and the porous structure of ALG allowing micro-vessel ingrowth and bone remodeling. Histological assessment demonstrated sufficient bone remodeling and graft resorption after 4-6 months. In total, 372 CP cases and 656 implants were included to data analysis. The mean follow-up period was about 3.5 years. Four implants failed, while all implant failures were caused by peri-implantitis. Next, 30 CP complications were seen, while in 26 CP complications implant placement was possible. CP rehydration, stable positioning by adjusting screws, smoothing of sharp edges, and a tension-free wound closure were identified as relevant success factors. Space filling using ALG and a mixture of AUG/ALG resulted in sufficient bone remodeling, graft resorption and stability of the augmented bone.

CONCLUSIONS

CP and the shell technique is appropriate for alveolar ridge augmentation with adequate bone remodeling and low complication rates. Allografts can prevent donor site morbidity and therefore may decrease discomfort for the patient.