Inhibition of Dll4/Notch1 pathway promotes angiogenesis of Masquelet's induced membrane in rats

Optimisation and Validation of an Induced Membrane Technique Model to Assess Bone Regeneration in Rats

Background: The induced membrane (IM) preclinical models have been described in small animals, but few studies have looked at bone regeneration achievement. The optimisation and validation of such a preclinical model, considering the results obtained after the use of biomaterials as a substitute for bone grafting, could lead to simplifying the surgical procedure and enhance the clinical results. Methods: An in vivo model of the IM technique was developed on the femur of Lewis rats after a 4-mm critical bone defect stabilised with an osteosynthesis plate. A first optimisation phase was performed by evaluating different osteotomy methods and two different osteosynthesis plate sizes. The efficiency of the model was evaluated by the failure rate obtained 6 weeks after the first operative time. Thereafter, bone regeneration was evaluated histologically and radiologically at 24 weeks to confirm the critical nature of the bone defect (negative control), the effectiveness of the IM with a syngeneic bone graft (positive control) and the possibility of using a biomaterial (GlassBone Noraker) in this model. Results: Sixty-three rats were included and underwent the first surgical step. Nineteen rats subsequently underwent the second surgical step. The results obtained led to select piezotomy as the best osteotomy technique and 1-mm-thick plates with 2.0-mm-diameter screws as osteosynthesis material. Twenty-four weeks after the second surgical step, solely the group with both surgical steps and a syngeneic bone graft showed complete ossification of the bone defect. In contrast, the group without a graft did not present a suitable ossification, which confirms the critical nature of the defect. IM produced an incomplete bone regeneration using GlassBone alone. Conclusions: A piezotome osteotomy with an osteosynthesis plate of sufficient stiffness is required for this two-stage bone regeneration model in rats. The 4-mm bone defect is critical for this model and suitable for biomaterial evaluation.

Engineering the bone reconstruction surgery: the case of the masquelet-induced membrane technique

The reconstruction of large bone defects remains challenging for orthopedic surgeons. Autologous bone grafts (ABGs) are the gold standard treatment for limited size defects, but larger bone defects (> 5 cm) require the use of more sophisticated techniques, such as the Masquelet technique. Over the last three decades, the Masquelet or induced membrane technique (IMT) has become increasingly popular as it does not require high-precision microsurgery skills and the time taken to achieve bone consolidation is independent of the length of the defect. IMT is a two-stage procedure. In the first stage, a polymethylmethacrylate (PMMA) cement spacer is implanted into the bone lesion and a physiological immune reaction initiates the formation of a fibrotic induced membrane (IM) with both angiogenic and osteogenic properties. The second stage, performed several weeks later, involves removal of the spacer followed by the implantation of a standard ABG in the preserved IM cavity for subsequent bone repair. In this extensive review, we explain how the success of this surgical procedure can be attributed to the synergy of four key components: the inducer (the PMMA cement), the recipient (the IM), the effector (the bone graft) and the modulator (the mechanical environment). Conversely, we then explain how each key component can contribute to the failure of such treatment. Finally, we discuss existing or emerging innovative and biotechnology-oriented strategies for optimizing surgical outcome with respect to the four components of IMT described above.

Construction of a 3D Degradable PLLA/β-TCP/CS Scaffold for Establishing an Induced Membrane Inspired by the Modified Single-Stage Masquelet Technique

Although the Masquelet-induced membrane technique (MIMT) is now employed worldwide for bone defects, it often needs to be repeated and autogenous bone graft. This study aims to investigate the theoretical feasibility of replacing PMMA (poly(methyl methacrylate)) bone cement with PLLA (poly-l-lactic acid)/β -TCP (beta-tricalcium phosphate)/CS (calcium sulfate) scaffold for single-stage bone defect reconstruction, which evoke the induced membrane (IM) formation in the early stage and directly acts as the implantation in the second stage to reconstruct the bone defect. We constructed a corn-like PLLA/β -TCP/CS scaffold by the fused deposition 3D printing method. The characterizations of the scaffolds were investigated systematically. The P/T15/S15 scaffolds (the PLLA/β -TCP/CS scaffold with a 15% mass fraction of β-TCP and 15% mass fraction of CS) were filled into the large-segmental radius bone defects of white rabbits to evoke the formation of IMs. HE (hematoxylin-eosin) and VG (van gieson) staining, along with immunofluorescent staining, were performed to analyze the architecture and cellularity, the expression of BMP-2 (bone morphogenetic protein-2), VEGF (vascular endothelial growth factor), and TGF-β1 (transforming growth factor-β1) was evaluated by IHC (immunohistochemistry) and WB (western-blot) respectively, the ALP (alkaline phosphatase) and ARS (alizarin red S) staining was applied to assess the osteogenic potential. The corn-like PLLA/β-TCP/CS scaffolds with excellent physicochemical properties are successfully constructed using the fused deposition 3D printing technique. The HE and VG staining, along with immunofluorescent staining, suggested that the P/T15/S15 scaffold effectively mediated the formation of IM after 6 weeks of placement. A significant presence of M2 macrophages was observed in IM. The results of IHC and WB demonstrated that the IMs derived from the P/T15/S15 scaffolds exhibited elevated levels of VEGF, BMP-2, and TGF-β1, all of which promote the osteogenic differentiation of BMSCs. The results of cellular immunofluorescence, flow cytometry, and WB indicate that P/T15/S15 regulates the phenotypic polarization of M0 macrophages toward the M2 phenotype via the PI3K/AKT/β-Catenin pathway. These findings suggest that the biodegradable PLLA/β-TCP/CS scaffold may serve as a viable alternative to PMMA bone cement for single-stage bone defect reconstruction, owing to its unique ability to stimulate IM formation and promote the polarization of macrophages toward the M2 phenotype. This work presents innovative materials and strategies for the management of bone defects.

Hydrogel-based therapies for diabetic foot ulcers: recent developments and clinical implications

The diabetic foot ulcer is among the most serious diabetes-associated complications, with a long disease course considerably increasing the pain and economic burden of patients, leading to amputation and even death. High blood sugar is characteristic of diabetic foot ulcers, with insufficient blood supply, oxidative stress disorder, and high-risk bacterial infection posing great challenges for disease treatment. Advances in hydrogel dressings have shown potential for the management of diabetic foot ulcers involving multisystem lesions. This study comprehensively reviews the pathogenesis of diabetic foot ulcers and advances in hydrogel dressings in treating diabetic foot ulcers, providing innovative perspectives for assessing the nursing care requirements and associated clinical applications.

The Masquelet induced membrane technique with PRP-FG-nHA/PA66 scaffold can heal a rat large femoral bone defect

BACKGROUND

Masquelet membrane induction technology is one of the treatment strategies for large bone defect (LBD). However, the angiogenesis ability of induced membrane decreases with time and autologous bone grafting is associated with donor site morbidity. This study investigates if the PRP-FG-nHA/PA66 scaffold can be used as a spacer instead of PMMA to improve the angiogenesis ability of induced membrane and reduce the amount of autologous bone graft.

METHODS

Platelet rich plasma (PRP) was prepared and PRP-FG-nHA/PA66 scaffold was synthesized and observed. The sustained release of VEGFA and porosity of the scaffold were analyzed. We established a femur LBD model in male SD rats. 55 rats were randomly divided into four groups depending on the spacer filled in the defect area. "Defect only" group (n = 10), "PMMA" group (n = 15), "PRP-nHA/PA66" group (n = 15) and "PRP-FG-nHA/PA66" group (n = 15 ). At 6 weeks, the spacers were removed and the defects were grafted. The induced membrane and bone were collected and stained. The bone formation was detected by micro-CT and the callus union was scored on a three point system.

RESULTS

The PRP-FG-nHA/PA66 scaffold was porosity and could maintain a high concentration of VEGFA after 30 days of preparation. The induced membrane in PRP-FG-nHA/PA66 group was thinner than PMMA, but the vessel density was higher.The weight of autogenous bone grafted in PRP-FG-nHA/PA66 group was significantly smaller than that of PMMA group. In PRP-FG-nHA/PA66 group, the bone defect was morphologically repaired.

CONCLUSION

The study showed that PRP-FG-nHA/PA66 scaffold can significantly reduce the amount of autologous bone graft, and can achieve similar bone defect repair effect as PMMA. Our findings provide some reference and theoretical support for the treatment of large segmental bone defects in humans.

Antibiotic bone cement accelerates diabetic foot wound healing: Elucidating the role of ROCK1 protein expression

Clinical studies indicate antibiotic bone cement with propeller flaps improves diabetic foot wound repair and reduces amputation rates, but the molecular mechanisms, particularly key proteins' role remain largely unexplored. This study assessed the efficacy of antibiotic bone cement for treating diabetic foot wounds, focusing on molecular impact on ROCK1. Sixty patients were randomized into experimental (EXP, n = 40) and control (CON, n = 20) groups, treated with antibiotic bone cement and negative pressure. Wound healing rate, amputation rate, wound secretion culture and C-reactive protein (CRP) changes, were monitored. Comprehensive molecular investigations were conducted and animal experiments were performed to further validate the findings. Statistical methods were employed to verify significant differences between the groups and treatment outcomes. The EXP group showed significant improvements in wound healing (χ 2 $$ {\chi}^2 $$ = 11.265, p = 0.004) and reduced amputation rates. Elevated levels of ROCK1, fibroblasts and VGF were observed in the trauma tissue post-treatment in the experimental group compared to pre-treatment and the control group (all p < 0.05). Improved trauma secretion culture and CRP were also noted in the EXP group (all p < 0.05). The study suggests that antibiotic bone cement enhances diabetic foot wound healing, possibly via upregulation of ROCK1. Further research is needed to elucidate the underlying molecular mechanisms and broader clinical implications.

Fibromodulin facilitates the osteogenic effect of Masquelet's induced membrane by inhibiting the TGF-β/SMAD signaling pathway

Masquelet's induced membrane (IM) technique is a promising treatment strategy for the repair of substantial bone defects. The formation of an IM around polymethylmethacrylate bone cement plays a crucial role in this technique. Several studies have indicated that IMs have bioactivity because they contain abundant blood vessels, a variety of cells, and biological factors. The bioactivity of an IM increases during the initial stages of formation, thereby facilitating bone regeneration and remodeling. Nevertheless, the precise mechanisms underlying the enhancement of IM bioactivity and the promotion of bone regeneration necessitate further investigation. In this study, we successfully developed a Masquelet IM model of critical femur defects in rats. By employing proteomics analysis and biological detection techniques, we identified fibromodulin (FMOD) as a pivotal factor contributing to angiogenesis and the enhanced bioactivity of the IM. A significant increase in angiogenesis and the expression of bioactive factors in the IM was also observed with the upregulation of FMOD expression. Furthermore, this effect is mediated through the inhibition of the transforming growth factor beta (TGF-β)/SMAD signaling pathway. We also demonstrated that administering recombinant human FMOD enhanced osteogenesis in rat bone marrow mesenchymal stem cells and angiogenesis in human umbilical vein endothelial cells in vitro. Furthermore, the negative regulatory effect of the TGF-β signaling pathway was verified. In conclusion, this study provides a novel theoretical basis for the application of IMs in bone-defect reconstruction and explores possible new mechanisms that may play an important role in promoting the bioactivity and osteogenic potential of IMs.

Systematic literature review of in vivo rat femoral defect models using biomaterials to improve the induced membrane technique: a comprehensive analysis

Purpose

The aim of this study was to conduct a systematic literature review analyzing the results of in vivo rat femoral defect models using biomaterials for improving the induced membrane technique (IMT).

Methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, the PubMed, Embase, and Web of Science databases were searched. Inclusion criteria were studies reporting results of the IMT in in vivo rat femoral critical-sized defect models using a biomaterial possibly combined with molecules. Methodologic quality was assessed with the Animal Research: Reporting In Vivo Experiments guidelines.

Results

Twenty studies met the inclusion criteria. Femoral stabilization with plate and screws was the most frequent. Histologic, biomechanical, and/or radiologic analyses were performed. In two-stage strategies, the PMMA spacer could be associated with bioactive molecules to enhance IM growth factor expression and improve bone formation. Modulating the roughness of spacers could increase IM thickness and accelerate its formation. In one-stage strategies, human tissue-derived membranes combined with bone grafting achieved bone formation comparable to a standard IMT. All calcium phosphate grafts seemed to require a functionalization with growth factors or bone marrow mononuclear cells to improve outcomes compared with non-functionalized grafts.

Conclusion

This systematic review described the main parameters of the in vivo rat femoral defect models using biomaterials to improve the induced membrane technique. Although the studies included had several methodological limitations that may limit the scope of these conclusions, one- and two-stage strategies reported promising results with biomaterials to improve the IMT.

Comparison of osteogenic activity from different parts of induced membrane in the Masquelet technique

BACKGROUND

The Masquelet technique is widely used to treat long-bone segmental defects because of its high success rate and low surgical difficulty. However, the cause of the uneven growth of bone grafts following this procedure remains unclear.

METHODS

Rats were randomly divided into four groups for analysis 2-, 4-, 6- and 8-weeks postoperatively and underwent a uniform surgical procedure to construct a 10 mm bone defect in the right posterior branch of the femur. Induced membrane specimens were harvested at the appropriate time points and divided into segments according to their location. Bone growth activity was assessed by immunohistochemistry, western blotting, and quantitative real-time polymerase chain reaction.

RESULTS

Mature blood vessels were more densely distributed at the proximal end of the bone defect than at other locations at all time points. The number of blood vessels on the same side of the longitudinal axis of the femur also varied depending on location. The difference between the proximal-anterior and distal-anterior regions within the induced membranes was most pronounced at 6 weeks postoperatively and decreased by 8 weeks postoperatively. The differences between the proximal-posterior and distal-posterior regions within the induced membranes were more pronounced. The expression of the growth factors bone morphogenetic protein-2 (BMP-2), vascular endothelial growth factor A(VEGFA), and transforming growth factor-β1(TGF-β1) in the proximal-posterior regions of the bone defect was almost always higher than that in other regions at the same time point. The expression of BMP-2 in the posterior regions of the bone defect was always higher than that in the anterior regions at the same end of the femoral longitudinal axis.

CONCLUSION

The number and maturation of vessels in the proximal region of the induced membrane at the bone defect site were higher than those in the distal region, and the expression of growth factors was higher, with the highest induced membrane activity in the proximal-posterior regions of the bone defect. Therefore, there was inhomogeneity in induced membrane activity.

Current status and future trends of reconstructing a vascularized tissue-engineered trachea

Alternative treatment of long tracheal defects remains one of the challenges faced by thoracic surgeons. Tissue engineering has shown great potential in addressing this regenerative medicine conundrum and the technology to make tracheal grafts using this technique is rapidly maturing, leading to unique therapeutic approaches. However, the clinical application of tissue-engineered tracheal implants is limited by insufficient revascularization. Among them, realizing the vascularization of a tissue-engineered trachea is the most challenging problem to overcome. To achieve long-term survival after tracheal transplantation, an effective blood supply must be formed to support the metabolism of seeded cells and promote tissue healing and regeneration. Otherwise, repeated infection, tissue necrosis, lumen stenosis lack of effective epithelialization, need for repeated bronchoscopy after surgery, and other complications will be inevitable and lead to graft failure and a poor outcome. Here we review and analyze various tissue engineering studies promoting angiogenesis in recent years. The general situation of reconstructing a vascularized tissue-engineered trachea, including current problems and future development trends, is elaborated from the perspectives of seed cells, scaffold materials, growth factors and signaling pathways, surgical interventions in animal models and clinical applications. This review also provides ideas and methods for the further development of better biocompatible tracheal substitutes in the future.

Management of wounds with exposed bone structures using an induced-membrane followed by polymethyl methacrylate and second-stage skin grafting in the elderly with a 3-year follow-up

The treatment of traumatic wounds with exposed bone or tendons is often challenging. An induced membrane (IM) is used to reconstruct bone defects, as it provides an effective and sufficient blood supply for bone and soft-tissue reconstruction. This study explored a novel two-stage strategy for wound management, consisting of initial wound coverage with polymethyl methacrylate (PMMA) and an autologous split-thickness skin graft under the IM. Fifty inpatients were enrolled from December 2016 to December 2019. Each patient underwent reconstruction according to a two-stage process. In the first stage, the defect area was thoroughly debrided, and the freshly treated wound was then covered using PMMA cement. After 4-6 weeks, during the second stage, the PMMA cement was removed to reveal an IM covering the exposed bone and tendon. An autologous split-thickness skin graft was then performed. Haematoxylin and eosin (H&E) staining and immunohistochemical analysis of vascular endothelial growth factor (VEGF), CD31 and CD34 were used to evaluate the IM and compare it with the normal periosteal membrane (PM). The psychological status and the Lower Extremity Function Scale (LEFS) as well as any complications were recorded at follow-up. We found that all skin grafts survived and evidenced no necrosis or infection. H&E staining revealed vascularised tissue in the IM, and immunohistochemistry showed a larger number of VEGF-, CD31- and CD34-positive cells in the IM than in the normal PM. The duration of healing in the group was 5.40 ± 1.32 months with a mean number of debridement procedures of 1.92 ± 0.60. There were two patients with reulceration in the group. The self-rating anxiety scale scores ranged from 35 to 60 (mean 48.02 ± 8.12). Postoperatively, the LEFS score was 50.10 ± 9.77. Finally, our strategy for the management of a non-healing wound in the lower extremities, consisting of an IM in combination with skin grafting, was effective, especially in cases in which bony structures were exposed in the elderly. The morbidity rate was low.

ADAM10-a "multitasker" in sepsis: focus on its posttranslational target

BACKGROUND

Sepsis has a complex pathogenesis in which the uncontrolled systemic inflammatory response triggered by infection leads to vascular barrier disruption, microcirculation dysfunction and multiple organ dysfunction syndrome. Numerous recent studies reveal that a disintegrin and metalloproteinase 10 (ADAM10) acts as a "molecular scissor" playing a pivotal role in the inflammatory response during sepsis by regulating proteolysis by cleaving various membrane protein substrates, including proinflammatory cytokines, cadherins and Notch, which are involved in intercellular communication. ADAM10 can also act as the cellular receptor for Staphylococcus aureus α-toxin, leading to lethal sepsis. However, its substrate-specific modulation and precise targets in sepsis have not yet to be elucidated.

METHODS

We performed a computer-based online search using PubMed and Google Scholar for published articles concerning ADAM10 and sepsis.

CONCLUSIONS

In this review, we focus on the functions of ADAM10 in sepsis-related complex endothelium-immune cell interactions and microcirculation dysfunction through the diversity of its substrates and its enzymatic activity. In addition, we highlight the posttranslational mechanisms of ADAM10 at specific subcellular sites, or in multimolecular complexes, which will provide the insight to intervene in the pathophysiological process of sepsis caused by ADAM10 dysregulation.

Ternary regulation mechanism of Rhizoma drynariae total flavonoids on induced membrane formation and bone remodeling in Masquelet technique

CONTEXT

Rhizoma drynariae total flavonoids (RDTF) are used to treat fractures. CD31hiEmcnhi vessels induced by PDGF-BB secreted by osteoclast precursors, together with osteoblasts and osteoclasts, constitute the ternary regulatory mechanism of bone tissue reconstruction.

OBJECTIVE

This study aimed to determine whether RDTF can promote bone tissue remodeling and induce membrane growth in the rat Masquelet model and to explore its molecular mechanism based on the ternary regulation theory.

METHODS

Thirty-six SD rats were randomized to three groups: blank, induced membrane, and RDTF treatment (n = 12/group). The gross morphological characteristics of the new bone tissue were observed after 6 weeks. Sixty SD rats were also randomized to five groups: blank, induction membrane, low-dose RDTF, medium-dose RDTF, and high-dose RDTF (n = 12/group). After 4 weeks, immunohistochemistry and western blot were used to detect the expression of membrane tissue-related proteins. The mRNA expression of key factors of ternary regulation was analyzed by qRT-PCR.

RESULTS

RDTF positively affected angiogenesis and bone tissue reconstruction in the bone defect area. RDTF could upregulate the expression of key factors (PDGF-BB, CD31, and endomucin), VEGF, and HMGB1 mRNA and proteins in the ternary regulation pathway.

DISCUSSION AND CONCLUSION

Although the expected CD31hiEmcnhi vessels in the induction membrane were not observed, this study confirmed that RDTF could promote the secretion of angiogenic factors in the induced membrane. The specific mechanisms still need to be further studied.

A homogalacturonan from Lonicera japonica Thunb. disrupts angiogenesis via epidermal growth factor receptor and Delta-like 4 associated signaling

A homogeneous polysaccharide named as LJW2F2 was extracted and purified from the flowers of Lonicera japonica Thunb. Structural characteristic indicated that LJW2F2 was a homogalacturonan composed of α-1,4-D-galacturonic acid with a molecular weight of 7.2 kDa. Previous investigation suggested that homogalacturonan might impede angiogenesis, however the mechanism is still vague. Here we reported that LJW2F2 significantly disrupted capillary-like tube formation of human microvascular endothelia cells (HMEC-1) on matrigel as well as the cells migration. Mechanism study revealed that LJW2F2 might inactivate phosphorylation of epidermal growth factor receptor (EGFR), subsequently suppress Raf, mitogen-activated protein kinase (MEK) and extracellular-related kinase (ERK) phosphorylation. Moreover, LJW2F2 markedly decreased the expression of Notch1 and Delta-like ligand 4 (Dll4). Therefore, our results suggested that LJW2F2 might be a potential angiogenesis inhibitor via disturbing multiple signaling pathways.

Bone-targeting delivery of platelet lysate exosomes ameliorates glucocorticoid-induced osteoporosis by enhancing bone-vessel coupling

BACKGROUND

Glucocorticoids (GCs) overuse is associated with decreased bone mass and osseous vasculature destruction, leading to severe osteoporosis. Platelet lysates (PL) as a pool of growth factors (GFs) were widely used in local bone repair by its potent pro-regeneration and pro-angiogenesis. However, it is still seldom applied for treating systemic osteopathia due to the lack of a suitable delivery strategy. The non-targeted distribution of GFs might cause tumorigenesis in other organs.

RESULTS

In this study, PL-derived exosomes (PL-exo) were isolated to enrich the platelet-derived GFs, followed by conjugating with alendronate (ALN) grafted PEGylated phospholipid (DSPE-PEG-ALN) to establish a bone-targeting PL-exo (PL-exo-ALN). The in vitro hydroxyapatite binding affinity and in vivo bone targeting aggregation of PL-exo were significantly enhanced after ALN modification. Besides directly modulating the osteogenic and angiogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and endothelial progenitor cells (EPCs), respectively, PL-exo-ALN also facilitate their coupling under GCs' stimulation. Additionally, intravenous injection of PL-exo-ALN could successfully rescue GCs induced osteoporosis (GIOP) in vivo.

CONCLUSIONS

PL-exo-ALN may be utilized as a novel nanoplatform for precise infusion of GFs to bone sites and exerts promising therapeutic potential for GIOP.

Molecular Mechanisms Underlying Pathological and Therapeutic Roles of Pericytes in Atherosclerosis

Pericytes are multipotent mesenchymal stromal cells playing an active role in angiogenesis, vessel stabilisation, maturation, remodelling, blood flow regulation and are able to trans-differentiate into other cells of the mesenchymal lineage. In this review, we summarised recent data demonstrating that pericytes play a key role in the pathogenesis and development of atherosclerosis (AS). Pericytes are involved in lipid accumulation, inflammation, growth, and vascularization of the atherosclerotic plaque. Decreased pericyte coverage, endothelial and pericyte dysfunction is associated with intraplaque angiogenesis and haemorrhage, calcification and cholesterol clefts deposition. At the same time, pericytes can be used as a novel therapeutic target to promote vessel maturity and stability, thus reducing plaque vulnerability. Finally, we discuss recent studies exploring effective AS treatments with pericyte-mediated anti-atherosclerotic, anti-inflammatory and anti-apoptotic effects.

The induced membrane technique: Optimization of bone grafting in a rat model of segmental bone defect

INTRODUCTION

The induced membrane technique (IMT) is a two-stage surgical procedure used to treat fracture nonunion and bone defects. Although there is an increasing number of animal studies investigating the IMT, few have examined the outcomes of bone healing after a second stage grafting procedure. This study aimed at comparing two bone grafting procedures, as part of the IMT, in order to establish a rat model providing consistent healing outcomes.

METHODS

In male Fischer 344 rats, we created a 5 mm defect in the right femur, stabilized the bone with a plate and screws, and inserted a polymethylmethacrylate spacer into the defect. Four weeks later, the spacer was removed. Bone graft was harvested from a donor rat and placed into the defect, followed by membrane and wound closure. Experiments were conducted in two groups. In group 1 (n = 11), the bone graft contained a variable amount of cortical and cancellous bone, the time from donor euthanasia to grafting was up to 240 min, and one donor rat provided graft for 5-6 recipients. In group 2 (n = 12), we reduced the contribution of cortical bone to the graft, included bone marrow, and kept donor euthanasia to grafting time under 150 min. One donor was used per 3-4 recipients. The volume of graft per recipient and all other elements of the protocol were the same across groups. Bone healing at 12 weeks post grafting was compared radiographically by two orthopaedic surgeons in a blinded fashion, based on union status and a modified Lane & Sandhu score.

RESULTS

Healing rates improved from 36.4% in Group 1 to 91.6% in Group 2. There was a significant relationship between the methods and resulting union status (p = 0.004). The odds of achieving full union were significantly higher in group 2 compared to group 1 (odds ratio=19.25, 95% confidence interval [1.77-209.55]; p = 0.009). The average radiographic score was also significantly higher in group 2 (p = 0.005).

CONCLUSION

The revised bone grafting method significantly improved the healing outcomes and contributed to establishing a consistent rat model of the IMT. This model can benefit preclinical investigations by allowing for reliable and clinically-relevant comparisons.

The induced membrane technique in animal models: a systematic review

Objectives:

Data Sources:

Study Selection:

Data Extraction:

Data Synthesis:

Conclusions:

The Basic Science Behind the Clinical Success of the Induced Membrane Technique for Critical-Sized Bone Defects

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The induced membrane technique (IMT) takes advantage of an osteoinductive environment that is created by the placement of a cement spacer into a bone defect.

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Most commonly, a polymethylmethacrylate (PMMA) spacer has been used, but spacers made from other materials have emerged and achieved good clinical outcomes.

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The IMT has demonstrated good results for long-bone repair; however, more research is required in order to optimize union rates as well as delineate more precise indications and surgical timing.

Masquelet's induced membrane technique: Review of current concepts and future directions

Masquelet's induced membrane technique (MIMT) is a relatively new, two-stage surgical procedure to reconstruct segmental bone defects. First performed by Dr. Masquelet in the mid-1980s, MIMT has shown great promise to revolutionize critical-sized bone defect repair and has several advantages over its alternative, distraction osteogenesis (DO). Also, its success in extremely challenging cases (defects > 15 cm) suggests that its study could lead to discovery of novel biological mechanisms that might be at play during segmental defect healing and fracture non-union. MIMT's advantages over DO have led to a world-wide increase in MIMT procedures over the past decades. However, MIMT often needs to be repeated and so the average initial success rate in adults lags significantly behind that of DO (86% vs 95%, respectively). The autologous foreign-body membrane created during the first stage by the immune system's response to a polymethyl methacrylate bone cement spacer is critical to supporting the morselized bone graft implanted in the second stage. However, the biological and/or physical mechanisms by which the membrane supports graft to bone union are unclear. This lack of knowledge makes refining MIMT and improving the success rates through technique improvements and patient selection a significant challenge and hinders wider adoption. In this review, current knowledge from basic, translational, and clinical studies is summarized. The dynamics of both stages under normal conditions as well as with drug or material perturbations is discussed along with perspectives on high-priority future research directions.

Promotion of Aerobic Exercise Induced Angiogenesis Is Associated With Decline in Blood Pressure in Hypertension: Result of EXCAVATION-CHN1

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Pathophysiological Changes and the Role of Notch-1 Activation After Decompression in a Compressive Spinal Cord Injury Rat Model

Surgical decompression is the primary treatment for cervical spondylotic myelopathy (CSM) patients with compressive spinal cord injury (CSCI). However, the prognosis of patients with CSCI varies, and the pathophysiological changes following decompression remain poor. This study aimed to investigate the pathophysiological changes and the role of Notch-1 activation after decompression in a rat CSCI model. Surgical decompression was conducted at 1 week post-injury (wpi). DAPT was intraperitoneally injected to down-regulate Notch-1 expression. Basso, Beattie, and Bresnahan scores and an inclined plane test were used to evaluate the motor function recovery. Hematoxylin and eosin staining was performed to assess pathophysiological changes, while hypoxia-inducible factor 1 alpha, vascular endothelial growth factor (VEGF), von Willebrand factor (vWF), matrix metalloproteinase (MMP)-9, MMP-2, Notch-1, and Hes-1 expression in the spinal cord were examined by immunohistochemical analysis or quantitative PCR. The results show that early decompression can partially promote motor function recovery. Improvements in structural and cellular damage and hypoxic levels were also observed in the decompressed spinal cord. Moreover, decompression resulted in increased VEGF and vWF expression, but decreased MMP-9 and MMP-2 expression at 3 wpi. Expression levels of Notch-1 and its downstream gene Hes-1 were increased after decompression, and the inhibition of Notch-1 significantly reduced the decompression-induced motor function recovery. This exploratory study revealed preliminary pathophysiological changes in the compressed and decompressed rat spinal cord. Furthermore, we confirmed that early surgical decompression partially promotes motor function recovery may via activation of the Notch-1 signaling pathway after CSCI. These results could provide new insights for the development of drug therapy to enhance recovery following surgery.

Induced membrane technique: a critical literature analysis and proposal for a failure classification scheme

The reconstruction of long-bone segmental defects remains challenging, with the three common methods of treatment being bone transport, vascularized bone transfer, and the induced membrane technique (IMT). Because of its simplicity, replicability, and reliability, usage of IMT has spread all over the world in the last decade, with more than 300 papers published in the PubMed literature database on this subject so far. Most of the clinical studies have reported high rates of bone union, yet some also include more controversial results with frequent complications and revision surgeries. At the same time, various experimental research efforts have been designed to understand and improve the biological properties of the induced membrane. This literature review aims to provide an overview of IMT clinical results in terms of bone union and complications and to compare them with those of other reconstructive procedures. In light of our findings, we then propose an original classification scheme of IMT failures distinguishing between preventable and nonpreventable failures.

The effect of induced membranes combined with enhanced bone marrow and 3D PLA-HA on repairing long bone defects in vivo

The repair of large bone defects has always been a challenge, especially with respect to regeneration capacity and autogenous bone availability. To address this problem, we fabricated a 3D-printed polylactic acid (PLA) and hydroxyapatite (HA) scaffold (3D-printed PLA-HA, providing scaffold) loaded with enhanced bone marrow (eBM, providing seed cells) combined with induced membrane (IM, providing grow factors) to repair large radial defects in rabbits. in vitro assays, we demonstrated that 3D-printed PLA-HA had excellent biocompatibility, as shown by co-culturing with mesenchymal stem cells (MSCs); eBM-derived MSCs exhibited considerable differentiation potential, as shown in trilineage differentiation assays. To investigate bone formation efficacy in vivo, the rabbit radial long bone defect model was established. In the first stage, polymethylmethacrylate (PMMA) was inserted into the bone defect to stimulate the formation of IM; in the second stage, iliac crest bone graft (ICBG) with IM, PLA-HA alone with the removal of IM, PLA-HA with IM, and PLA-HA in conjunction with IM and eBM were sequentially applied to repair the long bone defect. At 8, 12, and 16 weeks, X-ray plain radiography, microcomputed tomography, and histological analysis were performed to evaluate the efficacy of bone repair and bone regeneration in each group. We found that IM combined with PLA-HA and eBM prominently enhanced bone repair and reconstruction, equivalent to that of IM/ICBG. Taken together, the data suggest that PLA-HA loaded with eBM combined with IM can be an alternative to IM with bone autografts for the treatment of large bone defects.

The Masquelet technique: Current concepts, animal models, and perspectives

Bone reconstruction within a critical-sized defect remains a real challenge in orthopedic surgery. The Masquelet technique is an innovative, two-step therapeutic approach for bone reconstruction in which the placement of a poly (methylmethacrylate) spacer into the bone defect induces the neo-formation of a tissue called "induced membrane." This surgical technique has many advantages and is often preferred to a vascularized bone flap or Ilizarov's technique. Although the Masquelet technique has achieved high clinical success rates since its development by Alain-Charles Masquelet in the early 2000s, very little is known about how the process works, and few animal models of membrane induction have been developed. Our successful use of this technique in the clinic and our interest in the mechanisms of tissue regeneration (notably bone regeneration) prompted us to develop a surgical model of the Masquelet technique in rats. Here, we provide a comprehensive review of the literature on animal models of membrane induction, encompassing the defect site, the surgical procedure, and the histologic and osteogenic properties of the induced membrane. We also discuss the advantages and disadvantages of those models to facilitate efforts in characterizing the complex biological mechanisms that underlie membrane induction.

Contextual Regulation of Skeletal Physiology by Notch Signaling

PURPOSE OF REVIEW

This article reviews the past 2 years of research on Notch signaling as it relates to bone physiology, with the goal of reconciling seemingly discrepant findings and identifying fruitful areas of potential future research.

RECENT FINDINGS

Conditional animal models and high-throughput omics have contributed to a greater understanding of the context-dependent role of Notch signaling in bone. However, significant gaps remain in our understanding of how spatiotemporal context and epigenetic state dictate downstream Notch phenotypes. Biphasic activation of Notch signaling orchestrates progression of mesenchymal progenitor cells through the osteoblast lineage, but there is a limited understanding of ligand- and receptor-specific functions. Paracrine Notch signaling through non-osteoblastic cell types contributes additional layers of complexity, and we anticipate impactful future work related to the integration of these cell types and signaling mechanisms.

Intervertebral Bridging Ossification After Percutaneous Kyphoplasty in Osteoporotic Vertebral Compression Fractures

BACKGROUND

Percutaneous kyphoplasty (PKP) is effective in treating osteoporotic vertebral compression fractures (OVCFs). Intervertebral bridging ossification can sometimes be detected after surgery, but studies related to its formation mechanism and its influence on outcome are few.

CASE DESCRIPTION

We reviewed patients' radiologic images and found 7 patients in whom intervertebral bridging ossification developed after PKP. Their personal and clinical information was recorded. The 7 patients had an average age of 63.43 ± 4.79 years. Injured levels included L1 (1 patients) and L2 (1 patient). GeneX and PMMA cement were respectively applied. Both the Cobb angle and the VAS scores were significantly improved after surgery, but all surgical vertebrae showed recollapse combined with larger Cobb angle at the last follow-up visits. In 1 patient the new-onset T11 fracture developed 29 months after surgery.

CONCLUSIONS

We deemed that spinal degeneration, mechanical instability, bone cement, and fracture pattern are all potential promoting factors for intervertebral bridging ossification. Solid bridging ossification may increase local spinal stability, but it also increases the risk of adjacent vertebral fractures.