Treatment of long bone defects and non-unions: from research to clinical practice

Cell Instructive Behavior of Composite Scaffolds in a Co-Culture of Human Mesenchymal Stem Cells and Peripheral Blood Mononuclear Cells

The in vitro evaluation of 3D scaffolds for bone tissue engineering in mono-cultures is a common practice; however, it does not represent the native complex nature of bone tissue. Co-cultures of osteoblasts and osteoclasts, without the addition of stimulating agents for monitoring cellular cross-talk, remains a challenge. In this study, a growth factor-free co-culture of human bone marrow-derived mesenchymal stem cells (hBM-MSCs) and human peripheral blood mononuclear cells (hPBMCs) has been established and used for the evaluation of 3D-printed scaffolds for bone tissue engineering. The scaffolds were produced from PLLA/PCL/PHBV polymeric blends, with two composite materials produced through the addition of 2.5% w/v nanohydroxyapatite (nHA) or strontium-substituted nanohydroxyapatite (Sr-nHA). Cell morphology data showed that hPBMCs remained undifferentiated in co-culture, while no obvious differences were observed in the mono- and co-cultures of hBM-MSCs. A significantly increased alkaline phosphatase (ALP) activity and osteogenic gene expression was observed in co-culture on Sr-nHA-containing scaffolds. Tartrate-resistant acid phosphatase (TRAP) activity and osteoclastogenic gene expression displayed significantly suppressed levels in co-culture on Sr-nHA-containing scaffolds. Interestingly, mono-cultures of hPBMCs on Sr-nHA-containing scaffolds indicated a delay in osteoclasts formation, as evidenced from TRAP activity and gene expression, demonstrating that strontium acts as an osteoclastogenesis inhibitor. This co-culture study presents an effective 3D model to evaluate the regenerative capacity of scaffolds for bone tissue engineering, thus minimizing time-consuming and costly in vivo experiments.

The early posterior cortex pixel value ratio: a novel reliable indicator for distraction osteogenesis

Aims

We aimed to explore the associations of the early PVR in four cortices with Healing Index (HI), Lengthening Index (LI), and External Fixator Index (EFI) in the bone union and non-union groups.

Methods

A total of 52 patients, including 39 bone union and 13 bone non-union subjects, were recruited in this study. The general characteristics and PVR in four cortices in each group were explored. Afterward, the early PVR in four cortices, including medial, lateral, anterior, and posterior sides, were compared. Finally, the associations of the early PVR in four cortices with HI, LI, and EFI were also investigated.

Results

The general characteristics of these patients were consistent, except for HI (31.54 ± 12.24 vs. 45.08 ± 27.10, P = 0.018) and EFI (57.63 ± 18.15 vs. 71.29 ± 24.60, P = 0.046). The growth of regenerated callus was asymmetrical in the bone union group (the posterior PVR seems to grow faster), whereas no statistical difference was obtained in the bone non-union group. Furthermore, the posterior PVR in the bone union group was significantly higher than that in the bone non-union group (the first month: 0.96 ± 0.17 vs. 0.86 ± 0.06, p = 0.047; the second month: 0.98 ± 0.14 vs. 0.89 ± 0.09, p = 0.041; the third month: 1.00 ± 0.12 vs. 0.92 ± 0.09, p = 0.039). Most importantly, the posterior PVR was inversely associated with HI, LI, and EFI (the first month: r = -0.343, p = 0.041; r = -0.346, p = 0.042; r = -0.352, p = 0.041; the second month: r = -0.459, p = 0.004; r = -0.277, p = 0.101; r = -0.511, p = 0.002; the third month: r = -0.479, p = 0.003; r = -0.398, p = 0.018; r = -0.551, p = 0.001) in the bone union group, respectively. However, this finding was lost in the bone non-union group.

Conclusion

The early posterior cortex PVR seems to grow faster than the medial, lateral, and anterior sides in the bone union group, which represents an asymmetrical development pattern. Moreover, the posterior cortex PVR was negatively associated with HI, LI, and EFI, respectively. The posterior cortex PVR may be a novel and reliable detection index in the process of DO.

Bone Marrow Stem Cells with Tissue-Engineered Scaffolds for Large Bone Segmental Defects: A Systematic Review

Critical-sized bone defects (CSBDs) represent a significant clinical challenge, stimulating researchers to seek new methods for successful bone reconstruction. The aim of this systematic review is to assess whether bone marrow stem cells (BMSCs) combined with tissue-engineered scaffolds have demonstrated improved bone regeneration in the treatment of CSBD in large preclinical animal models. A search of electronic databases (PubMed, Embase, Web of Science, and Cochrane Library) focused on in vivo large animal studies identified 10 articles according to the following inclusion criteria: (1) in vivo large animal models with segmental bone defects; (2) treatment with tissue-engineered scaffolds combined with BMSCs; (3) the presence of a control group; and (4) a minimum of a histological analysis outcome. Animal research: reporting of in Vivo Experiments guidelines were used for quality assessment, and Systematic Review Center for Laboratory animal Experimentation's risk of bias tool was used to define internal validity. The results demonstrated that tissue-engineered scaffolds, either from autografts or allografts, when combined with BMSCs provide improved bone mineralization and bone formation, including a critical role in the remodeling phase of bone healing. BMSC-seeded scaffolds showed improved biomechanical properties and microarchitecture properties of the regenerated bone when compared with untreated and scaffold-alone groups. This review highlights the efficacy of tissue engineering strategies for the repair of extensive bone defects in preclinical large-animal models. In particular, the use of mesenchymal stem cells, combined with bioscaffolds, seems to be a successful method in comparison to cell-free scaffolds.

Cyclic mechanical stretch pre-stimulated bone marrow mesenchymal stem cells promote the healing of infected bone defect in a mouse model

Cyclic mechanical stretch (CMS) is an effective method to accelerate mesenchymal stem cells (MSCs) differentiation. Here, CMS pre-stimulated bone marrow MSCs (CMS-BMSCs) was investigated, characterized and evaluated the therapeutic potential of CMS-BMSCs on the treatment of infected bone defect in mouse model. BMSCs were obtained from C57BL/6J mice and then subjected to CMS. The osteogenic differentiation capacity of BMSCs was evaluated by alkaline phosphatase (ALP) assay, Alizarin Red staining, qRT-PCR, and Western blot. The pre-stimulated BMSCs were transplanted into infected bone defect mice, osteogenesis, antibacterial effects, and inflammatory responses were examined. CMS significantly increased ALP activity and the expression of osteoblastic genes (col1a1, runx2, and bmp7) and enhanced osteogenic differentiation and nrf2 expression of BMSCs. Transplantation of CMS pre-stimulated BMSCs promoted the healing of infected bone defect in mice, enhanced antibacterial effects, and reduced inflammatory responses in the mid-sagittal section of the fracture callus. CMS pre-stimulated BMSCs enhance the healing of infected bone defects in a mouse model, suggesting a potential therapeutic strategy for treating infected bone defects.

Effect of silk fibroin scaffold loaded with 17-β estradiol on the proliferation and differentiation of BMSCs

In this study, different concentrations of 17-β estradiol silk fibroin (SF)porous scaffolds (SFPS) were prepared using freeze-drying technique, with a hope for optimal concentration and apply it locally to the bone defect area. In this study, the porous scaffold morphology structure was characterized by SEM, FTIR and universal capacity testing machines, and the in vitro cytocompatibility and biological activity of scaffold materials were studied by cell adhesion, viability and proliferation experiments. The results showed that SFPS boasts better physicochemical properties, while 17-β estradiol SF scaffolds with low concentrations of 10-10 mol/L and 10-12 mol/L had more growth and proliferation of SF scaffolds with higher concentrations, and 10-10 mol/L was the optimal concentration of 17-β estradiol SFPS, which was more conducive to cell adhesion and proliferation. On the other hand, after osteogenesis induction of BMSCs inoculated on 17-β estradiol SFPS at different concentrations, it was found that the expression of alkaline phosphatase in BMSCs on different concentrations of 17-β estradiol porous scaffolds was not large. No conflict of interest exits in the submission of this manuscript.

Promotion of In Vitro Osteogenic Activity by Melt Extrusion-Based PLLA/PCL/PHBV Scaffolds Enriched with Nano-Hydroxyapatite and Strontium Substituted Nano-Hydroxyapatite

Bone tissue engineering has emerged as a promising strategy to overcome the limitations of current treatments for bone-related disorders, but the trade-off between mechanical properties and bioactivity remains a concern for many polymeric materials. To address this need, novel polymeric blends of poly-L-lactic acid (PLLA), polycaprolactone (PCL) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) have been explored. Blend filaments comprising PLLA/PCL/PHBV at a ratio of 90/5/5 wt% have been prepared using twin-screw extrusion. The PLLA/PCL/PHBV blends were enriched with nano-hydroxyapatite (nano-HA) and strontium-substituted nano-HA (Sr-nano-HA) to produce composite filaments. Three-dimensional scaffolds were printed by fused deposition modelling from PLLA/PCL/PHBV blend and composite filaments and evaluated mechanically and biologically for their capacity to support bone formation in vitro. The composite scaffolds had a mean porosity of 40%, mean pores of 800 µm, and an average compressive modulus of 32 MPa. Polymer blend and enriched scaffolds supported cell attachment and proliferation. The alkaline phosphatase activity and calcium production were significantly higher in composite scaffolds compared to the blends. These findings demonstrate that thermoplastic polyesters (PLLA and PCL) can be combined with polymers produced via a bacterial route (PHBV) to produce polymer blends with excellent biocompatibility, providing additional options for polymer blend optimization. The enrichment of the blend with nano-HA and Sr-nano-HA powders enhanced the osteogenic potential in vitro.

Solid locked intramedullary nailing for expeditious return of bone-setting-induced abnormal fracture union victims to work in South-western Nigeria

Wage earning in low- and middle-income countries (LMICs) is predominantly through physical labour. Consequently, limb-related disabilities caused by abnormal fracture unions (AFUs) preclude gainful employment and perpetuate the cycle of poverty. Many AFUs result from traditional bone-setting (TBS), a pervasive treatment for long bone fractures in LMICs. The objective of this study was to accentuate the expediency of solid locked intramedullary nail in the early restoration of victims of TBS-induced abnormal fracture unions (AFUs) to their pre-injury functioning, including work. One hundred AFUs in 98 patients treated with a solid locked intramedullary nail in our center over a period of 7 years were prospectively studied. We found the mean age to be 47.97 years. Males constituted 63.9% of the patients' population. Atrophic non-union accounted for 54.1% of the AFUs. The mean fracture-surgery interval was 21.30 months. By the 12th post-operative week, more than 75% of the fractures had achieved knee flexion/shoulder abduction beyond 90°, were able to squat and smile (or do shoulder abduction-external rotation), and were able to bear weight fully. The study demonstrated the expediency of solid locked nail in salvaging TBS-induced abnormal fracture unions in a way that permitted early return to pre-injury daily activities and work, thereby reducing fracture-associated poverty.

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

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

A comparative study of bone union and nonunion during distraction osteogenesis

BACKGROUND

The clinical characteristics of bone nonunion during distraction osteogenesis (DO) were rarely discussed. This study was employed to specify the difference between bone union and nonunion during DO.

METHODS

The patients with bone lengthening were recruited in our study. The bone union cases indicated the ones that remove the external fixator successfully, whereas the bone nonunion represented the bridging callus did not appear even after 9 months (an absence of bridging callus for at least three out of four cortices on plain radiographs) that needs autogenous bone transplantation. The differences in the pixel value ratio (PVR) growth of regenerated callus, lengthening index (LI), healing index (HI), external fixation index (EFI) and blood biochemical indexes between bone union and nonunion were analyzed.

RESULTS

A total of 8 bone nonunion and 27 bone union subjects were included in this study. The PVR growth in bone nonunion was significantly lower than that in bone union (0.19 ± 0.06 vs. 0.32 ± 0.16, P = 0.048). Interestingly, the HI and EFI in bone nonunion was significantly higher than that in bone union (62.0 ± 31.4 vs. 37.0 ± 27.4, P = 0.036; 75.0 ± 30.9 vs. 49.9 ± 16.1, P = 0.006). However, no significant difference with regard to LI was identified (0.76 ± 0.52 vs. 0.77 ± 0.32, P = 0.976). Moreover, the circulating level of urea and lymphocyte count in bone union was significantly lower than that in bone nonunion (4.31 ± 1.05 vs. 5.17 ± 1.06, P = 0.049; 2.08 ± 0.67 vs. 2.73 ± 0.54, P = 0.018). On the contrary, the circulating level of magnesium in bone union was significantly higher than that in bone nonunion (0.87 ± 0.07 vs. 0.80 ± 0.07, P = 0.014).

CONCLUSION

Compared to the bone union, the PVR growth was significantly lower, whereas the HI and EFI was significantly higher in the bone nonunion. Moreover, the circulating level of urea, magnesium and lymphocyte count was also different between these two. Therefore, the PVR, HI and EFI seems to be reliable and sensitive indicators to reflect the bone nonunion during DO, which might be considered in bone lengthening. Further prospective studies are still needed to elaborate the concerned issues.

The Combination of Platelet Rich Plasma Gel, Human Umbilical Mesenchymal Stem Cells and Nanohydroxyapatite/polyamide 66 Promotes Angiogenesis and Bone Regeneration in Large Bone Defect

BACKGROUND

In the present study, a novel tissue engineering bone graft including platelet rich plasma gel (PRP gel), human umbilical mesenchymal stem cells (HUMSCs) and nanohydroxyapatite/polyamide 66 (nHA-PA66) was constructed. We explored whether the composite scaffolds could enhance the angiogenesis and bone repair capacity in rat femoral large bone defect (LBD). This study aimed to provide evidence for the clinical application of the composite scaffold in LBD treatment.

METHODS

PRP was prepared, the platelets and growth factors were measured. HUMSCs were isolated and identified. the osteogenic capacity of PRP in vitro was measured. Then HUMSCs-PRP-gel/nHA-PA66 composite scaffolds were synthesized and observed. The proliferation and osteogenesis differentiation of HUMSCs on the composite scaffold was measured. The angiogenic capacity of PRP in vitro was measured by capillary-like tube formation assay. Finally, the angiogenesis and bone repair capacity of the composite scaffolds was measured in rat LBD.

RESULTS

PRP contained high level of platelets and growth factors after activation, and promoted osteogenic and angiogenic differentiation in vitro. The HUMSCs-PRP-gel/nHA-PA66 composite scaffold was porosity and promoted the proliferation and osteogenesis differentiation of HUMSCs. At 12th weeks, more micro-vessels and new bone were formed around the composite scaffolds compared with other groups, the defect was almost repaired.

CONCLUSION

Our study for the first time identified that the combination of PRP gel, HUMSCs and nHA-PA66 scaffold could significantly promote angiogenesis and bone regeneration in rat LBD, which may have implications for its further application in clinical LBD treatment.

A 3D-Printed Polycaprolactone/Marine Collagen Scaffold Reinforced with Carbonated Hydroxyapatite from Fish Bones for Bone Regeneration

In bone tissue regeneration, extracellular matrix (ECM) and bioceramics are important factors, because of their osteogenic potential and cell–matrix interactions. Surface modifications with hydrophilic material including proteins show significant potential in tissue engineering applications, because scaffolds are generally fabricated using synthetic polymers and bioceramics. In the present study, carbonated hydroxyapatite (CHA) and marine atelocollagen (MC) were extracted from the bones and skins, respectively, of Paralichthys olivaceus. The extracted CHA was characterized using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis, while MC was characterized using FTIR spectroscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The scaffolds consisting of polycaprolactone (PCL), and different compositions of CHA (2.5%, 5%, and 10%) were fabricated using a three-axis plotting system and coated with 2% MC. Then, the MC3T3-E1 cells were seeded on the scaffolds to evaluate the osteogenic differentiation in vitro, and in vivo calvarial implantation of the scaffolds was performed to study bone tissue regeneration. The results of mineralization confirmed that the MC/PCL, 2.5% CHA/MC/PCL, 5% CHA/MC/PCL, and 10% CHA/MC/PCL scaffolds increased osteogenic differentiation by 302%, 858%, 970%, and 1044%, respectively, compared with pure PCL scaffolds. Consequently, these results suggest that CHA and MC obtained from byproducts of P. olivaceus are superior alternatives for land animal-derived substances.

Rare earth smart nanomaterials for bone tissue engineering and implantology: Advances, challenges, and prospects

Bone grafts or prosthetic implant designing for clinical application is challenging due to the complexity of integrated physiological processes. The revolutionary advances of nanotechnology in the biomaterial field expedite and endorse the current unresolved complexity in functional bone graft and implant design. Rare earth (RE) materials are emerging biomaterials in tissue engineering due to their unique biocompatibility, fluorescence upconversion, antimicrobial, antioxidants, and anti-inflammatory properties. Researchers have developed various RE smart nano-biomaterials for bone tissue engineering and implantology applications in the past two decades. Furthermore, researchers have explored the molecular mechanisms of RE material-mediated tissue regeneration. Recent advances in biomedical applications of micro or nano-scale RE materials have provided a foundation for developing novel, cost-effective bone tissue engineering strategies. This review attempted to provide an overview of RE nanomaterials' technological innovations in bone tissue engineering and implantology and summarized the osteogenic, angiogenic, immunomodulatory, antioxidant, in vivo bone tissue imaging, and antimicrobial properties of various RE nanomaterials, as well as the molecular mechanisms involved in these biological events. Further, we extend to discuss the challenges and prospects of RE smart nano-biomaterials in the field of bone tissue engineering and implantology.

Development of Injectable Hydroxyapatite/2-(dimethylamino)Ethyl Methacrylate/Polyvinylpyrrolidone Aqua-Hydrogel System to Repair of the Shoulder Joint Head for Hemiarthroplasty

This study aimed to develop osteogenic structure assembly for modular bone treatment presentations, effect of 2-(dimethylamino)ethyl methacrylate and polyvinyl pyrrolidone combination as cell adhesive molecule with hydroxyapatite-based composite as osteoconductive constituent was inspected on bone fracture repair. The prepared injectable composite hydrogel showed significantly improved mechanical stability. The ternary composite gel was characterized for functional group modifications and chemical interactions using Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Moreover, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses were performed to observe surface appearances of the hydrogel. The hydroxyapatite/2-(dimethylamino)ethyl methacrylate/poly-N-vinyl-2-pyrrolidone hydrogel played key role in supporting osteoblastic cell spread due to their bioactivity and strength abilities. The present findings revealed the significance of hydroxyapatite concentration on proliferation and osteogenic purpose of the cells. The developed performances of hydrogel have been improved cell proliferation and functions to repair bone fracture.

Treatments, cost and healthcare utilization of patients with segmental bone defects

BACKGROUND

Treatment of large segmental defects in skeletal long bones is challenging. Heterogeneity in patient presentation further increase the difficulty in designing and running randomized trials, hence the paucity of published data with large patient numbers. This study was designed to help understand patient presentation, costs and outcomes, using real world data sources.

METHODS

Two data sources (Premier healthcare database (PHD) and IBM® MarketScan® Commercial Claims and Medicaid databases) were utilized, PHD for intraoperative and cost analyses, MarketScan for payer costs and longitudinal (2-year) outcomes. Patients were included in the analysis if they had diagnoses of osteomyelitis, non-union or open (acute) fractures, treated with bone graft and/or spacers, using either the Masquelet or external frames. Patient cohorts were defined by diagnosis at index (acute fracture, osteomyelitis, non-union) and descriptive statistics were conducted for patient variables (demographic, comorbidities) and outcomes. Risk of complications were estimated using logistic regression models. Hospital and payer costs for index and follow-up periods, were estimated using least means square estimators from generalized linear model outputs. All costs and payments were adjusted for inflation to 2019 consumer price-index.

RESULTS

904 patients were identified in PHD (414 fractures, 388 osteomyelitis and 102 nonunion patients). Main comorbidities at time of initial surgery were hypertension (32.7%) followed by obesity (22.1%), diabetes with complications (20.9%) and chronic pulmonary disease (20.6%). Significant variability in surgical operating room time and length of stay were observed, with averages of 484.7 minutes and 11.7 days, respectively. Two-year postoperative infection rates ranged from 33.1% - 58.5%, the highest infection rates being reflective of ongoing infections in patients initially treated for osteomyelitis. Amputation rates ranged from 10.0% in patients with bone loss due to acute factures to 14.5% in patients with osteomyelitis. Osteomyelitis patients were also the costliest, with 12-months hospital costs averaging US$ 156.818 (95%CI: 112,970-217,685).

CONCLUSION

This study identified high complication rates and costs of segmental bone repair surgery. All patients with segmental bone defects had high costs and risks but patients with osteomyelitis were at significant risk for increased cost and complications, including amputation. Medical innovation is particularly important for this high-risk patient group.

Investigation into the effects of leukemia inhibitory factor on the bone repair capacity of BMSCs-loaded BCP scaffolds in the mouse calvarial bone defect model

Leukemia inhibitory factor (LIF) is known to play a major role in bone physiology. In the present study, we examined the in vitro effects of LIF on osteoblast differentiation of bone marrow stem cells (BMSCs) and explored in vivo effects of LIF on the bone repair capacity of BMSCs-loaded biphasic calcium phosphate (BCP) scaffolds in mouse calvarial bone defect model. The mRNA and protein expression levels in the BMSCs were determined by quantitative real-time PCR and western blot, respectively; the in vitro osteoblast differentiation of the BMSCs was evaluated by using Alizarin Red S staining. The bone volume and bone density in the repaired calvarial bone defect were determined by Micro-CT. Bone regeneration was also histologically evaluated by hematoxylin and eosin staining and Masson's trichrome staining. Hypoxia treatment induced the up-regulation of Lif mRNA and LIF protein in the BMSCs. Lif overexpression up-regulated the mRNA expression levels of osteopontin and Runt-related transcription factor 2, and increased intensity of Alizarin Red S staining in the BMSCs; while Lif silence exerted the opposite effects. The in vivo studies showed that implantation of Lif-overexpressing BMSCs-loaded BCP scaffolds significantly increased the bone volume and bone density at 4 and 8 weeks after transplantation, and promoted the regeneration of bone tissues in the mouse calvarial bone defect at 8 weeks after transplantation when compared to the BMSCs-loaded BCP scaffolds group; while Lif-silencing BMSCs-loaded BCP scaffolds had the opposite effects. The present study for the first time demonstrated that LIF promoted the in vitro osteoblast differentiation of hypoxia-treated BMSCs; and further studies revealed that LIF exerted enhanced effects on the bone repair capacity of BMSCs-load BCP scaffolds in mouse calvarial bone defect model. However, future studies are warranted to determine the detailed mechanisms of LIF in the large-scale bone defect repair.

The application of Bonelike® Poro as a synthetic bone substitute for the management of critical-sized bone defects - A comparative approach to the autograft technique - A preliminary study

The effective treatment of non-unions and critical-sized defects remains a challenge in the orthopedic field. From a tissue engineering perspective, this issue can be addressed through the application bioactive matrixes to support bone regeneration, such as Bonelike®, as opposed to the widespread autologous grafting technique. An improved formulation of Bonelike® Poro, was assessed as a synthetic bone substitute in an ovine model for critical-sized bone defects. Bone regeneration was assessed after 5 months of recovery through macro and microscopic analysis of the healing features of the defect sites. Both the application of natural bone graft or Bonelike® Poro resulted in bridging of the defects margins. Untreated defect remained as fibrous non-unions at the end of the study period. The characteristics of the newly formed bone and its integration with the host tissue were assessed through histomorphometric and histological analysis, which demonstrated Bonelike® Poro to result in improved healing of the defects. The group treated with synthetic biomaterial presented bone bridges of increased thickness and bone features that more closely resembled the native spongeous and cortical bone. The application of Bonelike® Poro enabled the regeneration of critical-sized lesions and performed comparably to the autograph technique, validating its octeoconductive and osteointegrative potential for clinical application as a therapeutic strategy in human and veterinary orthopedics.

Degradable calcium deficient hydroxyapatite/PLGA bilayer scaffold through integral molding 3D printing for bone defect repair

A novel method was developed for calcium deficient hydroxyapatite (CDHA) scaffold 3D printing, through which a bilayer scaffold was fabricated by integral molding of individual CDHA and PLGA. The hydration reaction of α-TCP was utilized to form CDHA, and a mixed solution of gelatin, glycerine, glutaraldehyde was applied as the dispersant and adhesive. The concentration of the glutaraldehyde (1 ‱(v/v)) and the mixing ratio of α-TCP (0.6, 0.8, 1.0, 1.2(g/mL)) was studied in the effect on the forming ability of the CDHA ink. The influence of α-TCP proportion (0.6, 0.8, 1.0, 1.2 (g/mL)) on the formation of CDHA was also researched in phase analysis, morphology and compressive strength measurements. The CDHA/PLGA bilayer scaffold was fabricated with a good combination of the two components by 3D printing. The in vitro degradation, cytotoxicity, and cell proliferation behavior were studied. Meanwhile the in-vivo performances in terms of surgical safety, biodegradation, and osteogenic capacity were investigated with a cortical bone defect model in a rabbit femur. The results showed that the CDHA/PLGA bilayer scaffold had excellent biocompatibility and no cytotoxicity. The scaffolds were successfully implanted and presented remarkable osteogenic capacity within 6 months through analyses in radiography and histology. In conclusion, the method has a potential clinical application in diverse bone repair practices by varied 3D-printing fabrication.

In Vivo Validation of Spray-Dried Mesoporous Bioactive Glass Microspheres Acting as Prolonged Local Release Systems for BMP-2 to Support Bone Regeneration

Bone morphogenetic protein-2 (BMP-2) is a known key mediator of physiological bone regeneration and is clinically approved for selected musculoskeletal interventions. Yet, broad usage of this growth factor is impeded due to side effects that are majorly evoked by high dosages and burst release kinetics. In this study, mesoporous bioactive glass microspheres (MBGs), produced by an aerosol-assisted spray-drying scalable process, were loaded with BMP-2 resulting in prolonged, low-dose BMP-2 release without affecting the material characteristics. In vitro, MBGs were found to be cytocompatible and to induce a pro-osteogenic response in primary human mesenchymal stromal cells (MSCs). In a pre-clinical rodent model, BMP-2 loaded MBGs significantly enhanced bone formation and influenced the microarchitecture of newly formed bone. The MBG carriers alone performed equal to the untreated (empty) control in most parameters tested, while additionally exerting mild pro-angiogenic effects. Using MBGs as a biocompatible, pro-regenerative carrier for local and sustained low dose BMP-2 release could limit side effects, thus enabling a safer usage of BMP-2 as a potent pro-osteogenic growth factor.

Nanostructured Biomaterials for Bone Regeneration

This review article addresses the various aspects of nano-biomaterials used in or being pursued for the purpose of promoting bone regeneration. In the last decade, significant growth in the fields of polymer sciences, nanotechnology, and biotechnology has resulted in the development of new nano-biomaterials. These are extensively explored as drug delivery carriers and as implantable devices. At the interface of nanomaterials and biological systems, the organic and synthetic worlds have merged over the past two decades, forming a new scientific field incorporating nano-material design for biological applications. For this field to evolve, there is a need to understand the dynamic forces and molecular components that shape these interactions and influence function, while also considering safety. While there is still much to learn about the bio-physicochemical interactions at the interface, we are at a point where pockets of accumulated knowledge can provide a conceptual framework to guide further exploration and inform future product development. This review is intended as a resource for academics, scientists, and physicians working in the field of orthopedics and bone repair.

A preclinical large-animal model for the assessment of critical-size load-bearing bone defect reconstruction

Critical-size bone defects, which require large-volume tissue reconstruction, remain a clinical challenge. Bone engineering has the potential to provide new treatment concepts, yet clinical translation requires anatomically and physiologically relevant preclinical models. The ovine critical-size long-bone defect model has been validated in numerous studies as a preclinical tool for evaluating both conventional and novel bone-engineering concepts. With sufficient training and experience in large-animal studies, it is a technically feasible procedure with a high level of reproducibility when appropriate preoperative and postoperative management protocols are followed. The model can be established by following a procedure that includes the following stages: (i) preoperative planning and preparation, (ii) the surgical approach, (iii) postoperative management, and (iv) postmortem analysis. Using this model, full results for peer-reviewed publication can be attained within 2 years. In this protocol, we comprehensively describe how to establish proficiency using the preclinical model for the evaluation of a range of bone defect reconstruction options.

[Development of CRISPR technology and its application in bone and cartilage tissue engineering]

The CRISPR/Cas9 system, consisting of Cas9 nuclease and single guide RNA (sgRNA), is an emerging gene editing technology that can perform gene reprogramming operations such as deletion, insertion, and point mutation on DNA sequences targeted by sgRNA. In addition, CRISPR/dCas9 (a mutant that loses Cas9 nuclease activity) still retains the ability of sgRNA to target DNA. The fusion of dCas9 protein with transcriptional activator (CRISPRa) can activate the expression of the target gene, and fusion transcriptional repressors (CRISPRi) can also be used to suppress target gene expression. Efficient delivery of the CRISPR/Cas9 system is one of the main problems limiting its wide clinical application. Viral vectors are widely used to efficiently deliver CRISPR/Cas9 elements, but non-viral vector research is more attractive in terms of safety, simplicity, and flexibility. In this review, we summarize the principles and research advances of CRISPR technology, including CRISPR/ Cas9 delivery vectors, delivery methods, and obstacles to the delivery, and review the progress of CRISPR-based research in bone and cartilage tissue engineering. Finally, the challenges and future applications of CRISPR technology in bone and cartilage tissue engineering are discussed.

Gingival mesenchymal stem cells as an alternative source to bone marrow mesenchymal stem cells in regeneration of bone defects: In vivo study

Healing of critical sized bone defects represents a challenging issue in clinical and research fields. Current therapeutic techniques, such as bone grafts or bone grafts substitutes, still have limitations and drawbacks. Therefore, stem cell-based therapy provides a prospective approach to enhance bone regeneration. The present study aimed to assess the regenerative capacity of Gingival mesenchymal stem cells (GMSCs) as well as Bone marrow mesenchymal stem cells (BMSCs) loaded on NanoBone scaffold, in comparison to the unloaded one, in surgically created bone defects in rabbits' tibiae. To achieve this aim, critical sized bone defects, of 6-mm diameter each, were unilaterally created in tibiae of adult New Zeeland male white rabbits (n = 27). The rabbits were then divided randomly into three groups (9 each) and received the following: Group I: Unloaded NanoBone Scaffold, Group II: GMSCs Loaded on NanoBone Scaffold, and Group III: BMSCs Loaded on NanoBone Scaffold. Three rabbits from each group were then sacrificed at each time point (2, 4 and 6 weeks postoperatively), tibiae were dissected out to evaluate bone healing in the created bony defects; both histologically and histomorphometrically. The findings of this study indicate that both GMSCs and BMSCs exhibited fibroblast morphology and expressed phenotypic MSCs markers. Histologically, local application of GMSCs and BMSCs loaded on NanoBone scaffold showed enhanced the pattern of bone regeneration as compared to the unloaded scaffold. Histomorphometrically, there was astatistically insignificant difference in the new bone area % between the bony defects treated with GMSCs and BMSCs. Thus, GMSCs can be considered as a comparable alternative source to BMSCs in bone regeneration.

Bioengineering strategies for bone and cartilage tissue regeneration using growth factors and stem cells

Bone and cartilage tissue engineering is an integrative approach that is inspired by the phenomena associated with wound healing. In this respect, growth factors have emerged as important moieties for the control and regulation of this process. Growth factors act as mediators and control the important physiological functions of bone regeneration. Herein, we discuss the importance of growth factors in bone and cartilage tissue engineering, their loading and delivery strategies, release kinetics, and their integration with biomaterials and stem cells to heal bone fractures. We also highlighted the role of growth factors in the determination of the bone tissue microenvironment based on the reciprocal signaling with cells and biomaterial scaffolds on which future bone and cartilage tissue engineering technologies and medical devices will be based upon.

Multidirectional percutaneous drilling and autologous bone marrow injection for the treatment of femoral diaphyseal nonunions: a prospective interventional study

Background

To examine the outcomes of multidirectional percutaneous drilling and autologous concentrated bone marrow (BM) transplantation for atrophic femoral diaphyseal nonunion characterized by intact hardware and mechanical stability at the nonunion site.

Methods

Fourteen patients (22–63 years of age) were admitted to our hospital with atrophic femoral diaphyseal nonunion. All patients were treated with a combination of multidirectional percutaneous drilling and autologous concentrated BM transplantation. Radiographic evaluation was conducted every month after transplantation until bone healing was achieved.

Results

Bony union was achieved in 13 of the 14 patients (92.9%) after an average of 3.9 months (range: 2.5–6 months). The average radiographic union scale in tibial (RUST) scale score improved significantly from the preoperative period (6.15±1.21) to follow-up (11.23±0.73; P<0.05). The mean follow-up after transplantation was 31.4±9.5 months (range: 18–50 months). At the final follow-up, the quality of function had improved significantly, allowing a return to normal activities.

Conclusion

Combined multidirectional percutaneous drilling and autologous concentrated BM transplantation is an easy, safe, inexpensive, and efficacious method to treat atrophic femoral diaphyseal nonunion characterized by intact hardware and mechanical stability at the nonunion site.

Trial registration number: ISRCTN29808592

3D Printing of Bioceramic Scaffolds-Barriers to the Clinical Translation: From Promise to Reality, and Future Perspectives

In this review, we summarize the challenges of the three-dimensional (3D) printing of porous bioceramics and their translational hurdles to clinical applications. The state-of-the-art of the major 3D printing techniques (powder-based and slurry-based), their limitations and key processing parameters are discussed in detail. The significant roadblocks that prevent implementation of 3D printed bioceramics in tissue engineering strategies, and medical applications are outlined, and the future directions where new research may overcome the limitations are proposed. In recent years, there has been an increasing demand for a nanoscale control in 3D fabrication of bioceramic scaffolds via emerging techniques such as digital light processing, two-photon polymerization, or large area maskless photopolymerization. However, these techniques are still in a developmental stage and not capable of fabrication of large-sized bioceramic scaffolds; thus, there is a lack of sufficient data to evaluate their contribution. This review will also not cover polymer matrix composites reinforced with particulate bioceramics, hydrogels reinforced with particulate bioceramics, polymers coated with bioceramics and non-porous bioceramics.

Iron oxide nanoparticles in liquid or powder form enhanced osteogenesis via stem cells on injectable calcium phosphate scaffold

The objectives of this study were to incorporate iron oxide nanoparticles (IONPs) into calcium phosphate cement (CPC) to enhance bone engineering, and to investigate the effects of IONPs as a liquid or powder on stem cells using IONP-CPC scaffold for the first time. IONP-CPCs were prepared by adding 1% IONPs as liquid or powder. Human dental pulp stem cells (hDPSCs) were seeded. Subcutaneous implantation in mice was investigated. IONP-CPCs had better cell spreading, and greater ALP activity and bone mineral synthesis, than CPC control. Subcutaneous implantation for 6 weeks showed good biocompatibility for all groups. In conclusion, incorporating IONPs in liquid or powder form both substantially enhanced hDPSCs on IONP-CPC scaffold and exhibited excellent biocompatibility. IONP incorporation as a liquid was better than IONP powder in promoting osteogenic differentiation of hDPSCs. Incorporating IONPs and chitosan lactate together in CPC enhanced osteogenesis of hDPSCs more than using either alone.

Advancements and frontiers in nano-based 3D and 4D scaffolds for bone and cartilage tissue engineering

Given the enormous increase in the risks of bone and cartilage defects with the rise in the aging population, the current treatments available are insufficient for handling this burden, and the supply of donor organs for transplantation is limited. Therefore, tissue engineering is a promising approach for treating such defects. Advances in materials research and high-tech optimized fabrication of scaffolds have increased the efficiency of tissue engineering. Electrospun nanofibrous scaffolds and hydrogel scaffolds mimic the native extracellular matrix of bone, providing a support for bone and cartilage tissue engineering by increasing cell viability, adhesion, propagation, and homing, and osteogenic isolation and differentiation, vascularization, host integration, and load bearing. The use of these scaffolds with advanced three- and four-dimensional printing technologies has enabled customized bone grafting. In this review, we discuss the different approaches used for cartilage and bone tissue engineering.

The effect of nacre extract on cord blood-derived endothelial progenitor cells: A natural stimulus to promote angiogenesis?

Angiogenesis is a critical parameter to consider for the development of tissue-engineered bone substitutes. The challenge is to promote sufficient vascularization in the bone substitute to prevent cell death and to allow its efficient integration. The capacity of nacre extract to restore the osteogenic activity of osteoarthritis osteoblasts has already been demonstrated. However, their angiogenic potential on endothelial progenitor cells (EPCs) was not yet explored. Therefore, the current study aimed at investigating if nacreous molecules affect EPC behavior. The gene and protein expression levels of endothelial cell (EC)-specific markers were determined in EPCs cultivated in presence of a nacre extract (ethanol soluble matrix [ESM] at two concentrations: 100 μg/mL and 200 μg/mL (respectively abbreviated ESM100 and ESM200)). Cell functionality was explored by proangiogenic factors production and in vitro tube formation assay. ESM200 increased the expression of some EC-specific genes. The in vitro tube formation assay demonstrated that ESM200 stimulated tubulogenesis affecting angiogenic parameters. We demonstrated that a stimulation with 200 μg/mL of ESM increased angiogenesis key elements. This in vitro study strongly highlights the proangiogenic effect of ESM. Due to its osteogenic properties, previously demonstrated, ESM could constitute the key element to develop an ideal prevascularized bone substitute. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

Injectable mineralized microsphere-loaded composite hydrogels for bone repair in a sheep bone defect model

The efficacy of cell-based therapies as an alternative to autologous bone grafts requires biomaterials to localize cells at the defect and drive osteogenic differentiation. Hydrogels are ideal cell delivery vehicles that can provide instructional cues via their composition or mechanical properties but commonly lack osteoconductive components that nucleate mineral. To address this challenge, we entrapped mesenchymal stromal cells (MSCs) in a composite hydrogel based on two naturally-derived polymers (alginate and hyaluronate) containing biomineralized polymeric microspheres. Mechanical properties of the hydrogels were dependent upon composition. The presentation of the adhesive tripeptide Arginine-Glycine-Aspartic Acid (RGD) from both polymers induced greater osteogenic differentiation of ovine MSCs in vitro compared to gels formed of RGD-alginate or RGD-alginate/hyaluronate alone. We then evaluated the capacity of this construct to stimulate bone healing when transplanting autologous, culture-expanded MSCs into a surgical induced, critical-sized ovine iliac crest bone defect. At 12 weeks post-implantation, defects treated with MSCs transplanted in composite gels exhibited significant increases in blood vessel density, osteoid formation, and bone formation compared to acellular gels or untreated defects. These findings demonstrate the capacity of osteoconductive hydrogels to promote bone formation with autologous MSCs in a large animal bone defect model and provide a promising vehicle for cell-based therapies of bone healing.

pH-Sensitive Nanocarrier-Mediated Codelivery of Simvastatin and Noggin siRNA for Synergistic Enhancement of Osteogenesis

The inexpensive hypolipidemic drug simvastatin (SIM), which promotes bone regeneration by enhancing bone morphogenetic protein 2 (BMP-2) expression, has been regarded as an ideal alternative to BMP-2 therapy. However, SIM has low bioavailability and may induce the upregulation of the BMP-2-antagonistic noggin protein, which greatly limits the osteogenic effect. Here, a pH-sensitive copolymer, monomethoxy-poly(ethylene glycol)- b-branched polyethyleneimine- b-poly( N-( N', N'-diisopropylaminoethyl)- co-benzylamino)aspartamide (mPEG-bPEI-PAsp(DIP-BzA)) (PBP), was synthesized and self-assembled into a cationic micelle. SIM and siRNA targeting the noggin gene (N-siRNA) were loaded into the PAsp(DIP-BzA) core and the cationic bPEI interlayer of the micelle via hydrophobic and electrostatic interactions, respectively. The SIM-loaded micelle effectively delivered SIM into preosteoblast MC3T3-E1 cells and rapidly released it inside the acidic lysosome, resulting in the elevated expression of BMP-2. Meanwhile, the codelivered N-siRNA effectively suppressed the expression of noggin. Consequently, SIM and N-siRNA synergistically increased the BMP-2/noggin ratio and resulted in an obviously higher osteogenetic effect than did simvastatin or N-siRNA alone, both in vitro and in vivo.

BMP7-overexpressing bone marrow-derived mesenchymal stem cells (BMSCs) are more effective than wild-type BMSCs in healing fractures

Bone fractures are a worldwide public health concern. Previous studies have demonstrated that bone morphogenetic protein-7 (BMP7) gene transfer or mesenchymal stem cells (MSCs) transplantation may be a promising novel therapeutic approach. Therefore, the aim of the present study was to observe the effect of bone BMP7 transfer to MSCs on fracture healing. Bone marrow-derived MSCs (BMSCs) from New Zealand white rabbits were isolated and identified using flow cytometry. A recombinant BMP7 overexpressing adenovirus vector (Adv) was constructed and transfected into BMSCs. The expression of BMP7 was detected by reverse transcription-polymerase chain reaction, immunofluorescence and western blotting. The present study additionally investigated the effect of BMP7 on the differentiation capacity of BMSCs. Finally, tissue-engineered bone was created with support material to verify the effect of BMP7-BMSCs on fracture healing. The results demonstrated that the expression of BMP7 was increased at the mRNA and protein levels in BMSCs following transfection with BMP7 overexpressing Adv. The results additionally demonstrated that the expression of BMP7 enhanced the differentiation capacity of bone marrow mesenchymal stem cells and had a promotional effect on fracture healing. Overall, these data suggest that Adv-BMP7 is useful for introducing foreign genes into BMSCs and will be a powerful gene therapy tool for bone regeneration and other tissue engineering applications in the future.

Technical and clinical feasibility of contrast-enhanced ultrasound evaluation of long bone non-infected nonunion healing

PURPOSE

To assess the technical feasibility of contrast-enhanced ultrasound (CEUS) in the monitoring of non-infected long bone nonunion healing.

METHODS

Twenty-five patients (16 males; mean age: 40.4 ± 11.7) with long bone nonunion were treated using surgery and mesenchymal stem cells and platelet-rich plasma. They performed CEUS up to 15 days before, 7 days, 4 and 8 weeks after treatment. To categorize the angiogenesis around the fracture site, the microvascular blood flow from CEUS was classified into four categories, depending on the portion of the investigated area that was involved in the neovascularization process: grade 0 = 0%; grade 1 = 0-30%; grade 2 = 30-70%; grade 3 = 70-100%. Nonparametric Friedman and Wilcoxon statistics were used.

RESULTS

Before treatment, neovascularization was graded as 0 in 15/25 patients, as 1 in 10/25. Vascularity significantly increased over time (P < 0.001), namely: 1 (25th-75th percentile = 1-2) at 7 days; 2 (1-2) at 4 weeks; 3 (0-2) at 8 weeks. All patients but one showed early progressive increase in neovascularization well identified with CEUS at the fracture site.

CONCLUSION

CEUS is a feasible method to monitor healing in patients with long bone nonunion.

Analgesic Effect of Extracorporeal Shock Wave Treatment Combined with Fascial Manipulation Theory for Adhesive Capsulitis of the Shoulder: A Retrospective Study

Objectives

This study aims to explore whether extracorporeal shockwave treatment (ESWT) based on the theory of fascial manipulation (FM) at select treatment points is superior to traditional local ESWT for pain relief in adhesive capsulitis of the shoulder.

Methods

Data from patients with adhesive capsulitis of the shoulder who received weekly ESWT according to fascial manipulation theory (ESWT-FM) or local extracorporeal shockwave treatment (L-ESWT) during a 5-week treatment period were evaluated. Pain-on-movement numeric rating scale (p-NRS) and range of motion (ROM) testing were performed before the treatment period, after the first treatment, and after the fifth treatment.

Results

There were significant reductions in pain scores in the ESWT-FM group (p < 0.05) after the first treatment, and after the fifth treatment, both groups had marked, significant improvement (p < 0.05), with a significantly greater reduction in pain (p-NRS) in the ESWT-FM group compared to the L-ESWT group (p < 0.05). There was no significant difference in terms of ROM in the L-ESWT group, while there was slight improvement of forward flexion in the ESWT-FM group after the fifth treatment.

Conclusions

ESWT-FM provided faster pain relief and slightly more notable improvement of function compared with L-ESWT for the patients with adhesive capsulitis of shoulder.

Small Ubiquitin-Like Modifier Protein 3 Enhances the Solubilization of Human Bone Morphogenetic Protein 2 in E. coli

Small ubiquitin-like modifier (SUMO) fusion technology is widely used in the production of heterologous proteins from prokaryotic system to aid in protein solubilization and refolding. Due to an extensive clinical application of human bone morphogenetic protein 2 (hBMP2) in bone augmentation, total RNA was isolated from human gingival tissue and mature gene was amplified through RT-PCR, cloned (pET21a), sequence analyzed, and submitted to GenBank (Accession no. KF250425). To obtain soluble expression, SUMO3 was tagged at the N-terminus of hBMP2 gene (pET21a/SUMO3-hBMP2), transferred in BL21 codon+, and ~ 40% soluble expression was obtained on induction with IPTG. The dimerized hBMP2 was confirmed with Western blot, native PAGE analysis, and purified by fast protein liquid chromatography with 0.5 M NaCl elution. The cleavage of SUMO3 tag from hBMP2 converted it to an insoluble form. Computational 3D structural analysis of the SUMO3-hBMP2 was performed and optimized by molecular dynamic simulation. Protein-protein interaction of SUMO3-hBMP2 with BMP2 receptor was carried out using HADDOCK and inferred stable interaction. The alkaline phosphatase assay of SUMO3-hBMP2 on C2C12 cells showed maximum 200-ng/ml dose-dependent activity. We conclude that SUMO3-tagged hBMP2 is more suited for generation of soluble form of the protein and addition of SUMO3 tag does not affect the functional activity of hBMP2.

Upregulation of the BDNF/TrKB pathway promotes epithelial-mesenchymal transition, as well as the migration and invasion of cervical cancer

Brain-derived neurotrophic factor (BDNF) has previously been demonstrated to be associated with several types of cancer. In addition, its receptor, tropomyosin related kinase B (TrkB) is involved in tumor invasion and metastasis. Epithelial-mesenchymal transition (EMT) is associated with metastasis in cancers. Thus, The aim of the present study was to examine whether BDNF/TrKB expression is linked to a poor survival and the acquisition of the EMT phenotype in cervical cancer. We found that a high positive expression of BDNF/TrKB was associated with poor survival in cervical cancer. Our results revealed that high expression levels of BDNF/TrKB were observed in cervical cancer compared to normal cells. Importantly, we demonstrated that the silencing of TrKB suppressed the activation of EMT via the downregulation of N-cadherin, vimentin, matrix metalloproteinase (MMP)2 and MMP9, and the upregulation of E-cadherin and tissue inhibitor of metalloproteinases (TIMP)2, which resulted in suppressed cell proliferation, migration and invasion. Furthermore, high phosphorylation levels of ERK and Akt were observed in the cervical cancer cells, while these levels were decreased in the cells in which TrKB was knocked down. On the whole, these findings suggest that the BDNF/TrKB pathway is a promising target for the prevention of tumor proliferation, invasion, metastasis and EMT in cervical cancer cells.

Potential of Osteoblastic Cells Derived from Bone Marrow and Adipose Tissue Associated with a Polymer/Ceramic Composite to Repair Bone Tissue

One of the tissue engineering strategies to promote bone regeneration is the association of cells and biomaterials. In this context, the aim of this study was to evaluate if cell source, either from bone marrow or adipose tissue, affects bone repair induced by osteoblastic cells associated with a membrane of poly(vinylidene-trifluoroethylene)/barium titanate (PVDF-TrFE/BT). Mesenchymal stem cells (MSC) were isolated from rat bone marrow and adipose tissue and characterized by detection of several surface markers. Also, both cell populations were cultured under osteogenic conditions and it was observed that MSC from bone marrow were more osteogenic than MSC from adipose tissue. The bone repair was evaluated in rat calvarial defects implanted with PVDF-TrFE/BT membrane and locally injected with (1) osteoblastic cells differentiated from MSC from bone marrow, (2) osteoblastic cells differentiated from MSC from adipose tissue or (3) phosphate-buffered saline. Luciferase-expressing osteoblastic cells derived from bone marrow and adipose tissue were detected in bone defects after cell injection during 25 days without difference in luciferin signal between cells from both sources. Corroborating the in vitro findings, osteoblastic cells from bone marrow combined with the PVDF-TrFE/BT membrane increased the bone formation, whereas osteoblastic cells from adipose tissue did not enhance the bone repair induced by the membrane itself. Based on these findings, it is possible to conclude that, by combining a membrane with cells in this rat model, cell source matters and that bone marrow could be a more suitable source of cells for therapies to engineer bone.

Repair of segmental radial defect with autologous bone marrow aspirate and hydroxyapatite in rabbit radius: A clinical and radiographic evaluation

AIM

Finding an ideal bone substitute to treat large bone defects, delayed union and nonunions remain a challenge for orthopedic surgeons and researchers. Several studies have been conducted on bone regeneration; each has its own advantages and disadvantages. The aim of this study was to evaluate the effect of a combination of hydroxyapatite (HA) powder with autologous bone marrow (BM) aspirate on the repair of segmental radial defect in a rabbit model.

MATERIALS AND METHODS

A total of 36 male and adult New Zealand rabbit with a mean weight of 2.25 kg were used in this study. Approximately, 5 mm defect was created in the mid-shaft of the radius to be filled with HA powder in the control group "HA" (n=18) and with a combination of HA powder and autologous BM aspirate in the test group "HA+BM" (n=18). Animals were observed daily for healing by inspection of the surgical site, and six rabbits of each group were sacrificed at 30, 60, and 90 post-operative days to perform a radiographic evaluation of defect site.

RESULTS

Obtained results revealed a better and more rapid bone regeneration in the test group: Since the defect was rapidly and completely filled with mature bone tissue after 90 days.

CONCLUSION

Based on these findings, we could infer that adding a BM aspirate to HA is responsible of a better regeneration process leading to a complete filling of the defect.

Biomaterial-mediated strategies targeting vascularization for bone repair

Repair of non-healing bone defects through tissue engineering strategies remains a challenging feat in the clinic due to the aversive microenvironment surrounding the injured tissue. The vascular damage that occurs following a bone injury causes extreme ischemia and a loss of circulating cells that contribute to regeneration. Tissue-engineered constructs aimed at regenerating the injured bone suffer from complications based on the slow progression of endogenous vascular repair and often fail at bridging the bone defect. To that end, various strategies have been explored to increase blood vessel regeneration within defects to facilitate both tissue-engineered and natural repair processes. Developments that induce robust vascularization will need to consolidate various parameters including optimization of embedded therapeutics, scaffold characteristics, and successful integration between the construct and the biological tissue. This review provides an overview of current strategies as well as new developments in engineering biomaterials to induce reparation of a functional vascular supply in the context of bone repair.

Clinical evaluation of patients submitted to osteogenic distraction in the lower limb at a university hospital

Objective

To evaluate the clinical characteristics from patients submitted to osteogenic distraction to correct bone gap at a university hospital.

Methods

Retrospective transversal study, with a convenience sample, from 2000 to 2012, evaluating clinical aspects of patients treated, submitted to osteogenic distraction (bone transport) with Ilizarov's external fixation device. The chi-squared, Fisher's, and Mann–Whitney's U tests were used with a 5% level of significance (p < 0.05).

Results

33 patients were studied, of whom 28 men (84.8%). The more frequent age was from 21 to 40 years. Most patients were from the metropolitan region of the capital (57.6%). The leg was the most affected limb (75.8%), and the left side was the most affected (66.7%). The most common cause was infected pseudoarthrosis (75.8%). The most common bone transportation type was bifocal (75.8%). Mean previous surgery at others institutions were 2.62 (1.93 standard deviation), and mean surgeries after treatment were 1.89 (1.29 standard deviation). Ilizarov's external fixation device was used for 1.94 years (1.34 mean deviation), from one to six years. The most common complications were pin infection (57.6%), equinus (30.3%), deep infection (24.2%), and shortening (21.2%).

Conclusion

Osteogenic distraction for bone gaps were more frequent in young adults, men, in the leg, with bifocal transportation, after several previous surgeries, treated for a mean of two years, with many complications (infections were the most common).

Bone Tissue Engineering

Medical advances have led to a welcome increase in life expectancy. However, accompanying longevity introduces new challenges: increases in age-related diseases and associated reductions in quality of life. The loss of skeletal tissue that can accompany trauma, injury, disease or advancing years can result in significant morbidity and significant socio-economic cost and emphasise the need for new, more reliable skeletal regeneration strategies. To address the unmet need for bone augmentation, tissue engineering and regenerative medicine have come to the fore in recent years with new approaches for de novo skeletal tissue formation. Typically, these approaches seek to harness stem cells, innovative scaffolds and biological factors that promise enhanced and more reliable bone formation strategies to improve the quality of life for many. This review provides an overview of recent developments in bone tissue engineering focusing on skeletal stem cells, vascular development, bone formation and the translation from preclinical in vivo models to clinical delivery.

Cell engineering by the internalization of bioinstructive micelles for enhanced bone regeneration

Aim: To direct precursor cells toward the osteoblastic lineage, by using an intracellular nanocarrier releasing dexamethasone. Materials & methods: Biodegradable gelatin-based micelles entrapped dexamethasone (dex-micelles). Internalization efficiency and biocompatibility of dex-micelles and their potency for in vitro osteogenic differentiation and in vivo bone regeneration were assessed. Results: Dex-micelles were internalized by rat bone marrow mesenchymal stem cells and demonstrated a pH-responsive release profile and an enhancement of 2D and 3D in vitro osteogenic differentiation. In vivo implantation of gelatin scaffolds seeded with rat bone marrow mesenchymal stem cells precultured for 24 h with dex-micelles promoted a significant enhancement of de novo bone formation in a rat ulna defect, in a dose-dependent manner. Conclusion: The proposed intracellular delivery system is a powerful tool to promote bone regeneration.

Delayed minimally invasive injection of allogenic bone marrow stromal cell sheets regenerates large bone defects in an ovine preclinical animal model

Cell-based tissue engineering approaches are promising strategies in the field of regenerative medicine. However, the mode of cell delivery is still a concern and needs to be significantly improved. Scaffolds and/or matrices loaded with cells are often transplanted into a bone defect immediately after the defect has been created. At this point, the nutrient and oxygen supply is low and the inflammatory cascade is incited, thus creating a highly unfavorable microenvironment for transplanted cells to survive and participate in the regeneration process. We therefore developed a unique treatment concept using the delayed injection of allogenic bone marrow stromal cell (BMSC) sheets to regenerate a critical-sized tibial defect in sheep to study the effect of the cells' regeneration potential when introduced at a postinflammatory stage. Minimally invasive percutaneous injection of allogenic BMSCs into biodegradable composite scaffolds 4 weeks after the defect surgery led to significantly improved bone regeneration compared with preseeded scaffold/cell constructs and scaffold-only groups. Biomechanical testing and microcomputed tomography showed comparable results to the clinical reference standard (i.e., an autologous bone graft). To our knowledge, we are the first to show in a validated preclinical large animal model that delayed allogenic cell transplantation can provide applicable clinical treatment alternatives for challenging bone defects in the future.

Bone marrow-derived, neural-like cells have the characteristics of neurons to protect the peripheral nerve in microenvironment

Effective repair of peripheral nerve defects is difficult because of the slow growth of new axonal growth. We propose that "neural-like cells" may be useful for the protection of peripheral nerve destructions. Such cells should prolong the time for the disintegration of spinal nerves, reduce lesions, and improve recovery. But the mechanism of neural-like cells in the peripheral nerve is still unclear. In this study, bone marrow-derived neural-like cells were used as seed cells. The cells were injected into the distal end of severed rabbit peripheral nerves that were no longer integrated with the central nervous system. Electromyography (EMG), immunohistochemistry, and transmission electron microscopy (TEM) were employed to analyze the development of the cells in the peripheral nerve environment. The CMAP amplitude appeared during the 5th week following surgery, at which time morphological characteristics of myelinated nerve fiber formation were observed. Bone marrow-derived neural-like cells could protect the disintegration and destruction of the injured peripheral nerve.

Hollow hydroxyapatite microspheres/chitosan composite as a sustained delivery vehicle for rhBMP-2 in the treatment of bone defects

Composite scaffold comprised of hollow hydroxyapatite (HA) and chitosan (designated hHA/CS) was prepared as a delivery vehicle for recombinating human bone morphogenetic protein-2 (rhBMP-2). The in vitro and in vivo biological activities of rhBMP2 released from the composite scaffold were then investigated. The rhBMP-2 was firstly loaded into the hollow HA microspheres, and then the rhBMP2-loaded HA microspheres were further incorporated into the chitosan matrix. The chitosan not only served to bind the HA microspheres together and kept them at the implant site, but also effectively modified the release behavior of rhBMP-2. The in vitro release and bioactivity analysis confirmed that the rhBMP2 could be loaded and released from the composite scaffolds in bioactive form. In addition, the composite scaffolds significantly reduced the initial burst release of rhBMP2, and thus providing prolonged period of time (as long as 60 days) compared with CS scaffolds. In vivo bone regenerative potential of the rhBMP2-loaded composite scaffolds was evaluated in a rabbit radius defect model. The results revealed that the rate of new bone formation in the rhBMP2-loaded hHA/CS group was higher than that in both negative control and rhBMP2-loaded CS group. These observations suggest that the hHA/CS composite scaffold would be effective and feasible as a delivery vehicle for growth factors in bone regeneration and repair.

3D artificial bones for bone repair prepared by computed tomography-guided fused deposition modeling for bone repair

The medical community has expressed significant interest in the development of new types of artificial bones that mimic natural bones. In this study, computed tomography (CT)-guided fused deposition modeling (FDM) was employed to fabricate polycaprolactone (PCL)/hydroxyapatite (HA) and PCL 3D artificial bones to mimic natural goat femurs. The in vitro mechanical properties, in vitro cell biocompatibility, and in vivo performance of the artificial bones in a long load-bearing goat femur bone segmental defect model were studied. All of the results indicate that CT-guided FDM is a simple, convenient, relatively low-cost method that is suitable for fabricating natural bonelike artificial bones. Moreover, PCL/HA 3D artificial bones prepared by CT-guided FDM have more close mechanics to natural bone, good in vitro cell biocompatibility, biodegradation ability, and appropriate in vivo new bone formation ability. Therefore, PCL/HA 3D artificial bones could be potentially be of use in the treatment of patients with clinical bone defects.

Complexation and sequestration of BMP-2 from an ECM mimetic hyaluronan gel for improved bone formation

Bone morphogenetic protein-2 (BMP-2) is considered a promising adjuvant for the treatment of skeletal non-union and spinal fusion. However, BMP-2 delivery in a conventional collagen scaffold necessitates a high dose to achieve an efficacious outcome. To lower its effective dose, we precomplexed BMP-2 with the glycosaminoglycans (GAGs) dermatan sulfate (DS) or heparin (HP), prior to loading it into a hyaluronic acid (HA) hydrogel. In vitro release studies showed that BMP-2 precomplexed with DS or HP had a prolonged delivery compared to without GAG. BMP-2-DS complexes achieved a slightly faster release in the first 24 h than HP; however, both delivered BMP-2 for an equal duration. Analysis of the kinetic interaction between BMP-2 and DS or HP showed that HP had approximately 10 times higher affinity for BMP-2 than DS, yet it equally stabilized the protein, as determined by alkaline phosphatase activity. Ectopic bone formation assays at subcutaneous sites in rats demonstrated that HA hydrogel-delivered BMP-2 precomplexed with GAG induced twice the volume of bone compared with BMP-2 delivered uncomplexed to GAG.

Bone Regeneration Based on Tissue Engineering Conceptions - A 21st Century Perspective

The role of Bone Tissue Engineering in the field of Regenerative Medicine has been the topic of substantial research over the past two decades. Technological advances have improved orthopaedic implants and surgical techniques for bone reconstruction. However, improvements in surgical techniques to reconstruct bone have been limited by the paucity of autologous materials available and donor site morbidity. Recent advances in the development of biomaterials have provided attractive alternatives to bone grafting expanding the surgical options for restoring the form and function of injured bone. Specifically, novel bioactive (second generation) biomaterials have been developed that are characterised by controlled action and reaction to the host tissue environment, whilst exhibiting controlled chemical breakdown and resorption with an ultimate replacement by regenerating tissue. Future generations of biomaterials (third generation) are designed to be not only osteoconductive but also osteoinductive, i.e. to stimulate regeneration of host tissues by combining tissue engineering and in situ tissue regeneration methods with a focus on novel applications. These techniques will lead to novel possibilities for tissue regeneration and repair. At present, tissue engineered constructs that may find future use as bone grafts for complex skeletal defects, whether from post-traumatic, degenerative, neoplastic or congenital/developmental "origin" require osseous reconstruction to ensure structural and functional integrity. Engineering functional bone using combinations of cells, scaffolds and bioactive factors is a promising strategy and a particular feature for future development in the area of hybrid materials which are able to exhibit suitable biomimetic and mechanical properties. This review will discuss the state of the art in this field and what we can expect from future generations of bone regeneration concepts.

Autologous vs. allogenic mesenchymal progenitor cells for the reconstruction of critical sized segmental tibial bone defects in aged sheep

Mesenchymal progenitor cells (MPCs) represent an attractive cell population for bone tissue engineering. Their special immunological characteristics suggest that MPCs may be used in allogenic applications. The objective of this study was to compare the regenerative potential of autologous vs. allogenic MPCs in an ovine critical size segmental defect model. Ovine MPCs were isolated from bone marrow aspirates, expanded and cultured with osteogenic medium for 2weeks before implantation. Autologous and allogenic transplantation was performed using the cell-seeded scaffolds and unloaded scaffolds, while the application of autologous bone grafts served as a control group (n=6). Bone healing was assessed 12weeks after surgery by radiology, microcomputed tomography, biomechanical testing and histology. Radiology, biomechanical testing and histology revealed no significant differences in bone formation between the autologous and allogenic groups. Both cell groups showed more bone formation than the scaffold alone, whereas the biomechanical data showed no significant differences between the cell groups and the unloaded scaffolds. The results of the study suggest that scaffold-based bone tissue engineering using allogenic cells offers the potential for an off-the-shelf product. Thus the results of this study serve as an important baseline for translation of the assessed concepts into clinical applications.