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Uniaxial Static Strain Promotes Osteoblast Proliferation and Bone Matrix Formation in Distraction Osteogenesis In Vitro.

ABSTRACT: Objective:We aimed at investigating the effects of uniaxial static strain on osteoblasts in distraction osteogenesis (DO). Methods:To simulate the mechanical stimulation of osteoblasts during DO, 10% uniaxial static strain was applied to osteoblasts using a homemade multiunit cell stretching and compressing device. Before and after applying strain stimulation, the morphological changes of osteoblasts were observed by inverted phase-contrast microscopy, Coomassie blue staining, and immunofluorescence. Alkaline phosphatase (ALP) activity, mRNA levels (proliferating cell nuclear antigen [PCNA], ALP, Runx2, osteocalcin [OCN], collagen type I, hypoxia-inducible factor- [HIF-] 1?, and vascular endothelial growth factor [VEGF]), and protein levels (Runx2, OCN, collagen type I, HIF-1?, and VEGF) were evaluated by using ALP kit, real-time quantitative reverse transcription-polymerase chain reaction, western blot, and enzyme-linked immunosorbent assay. Results:After the mechanical stimulation, the cytoskeleton microfilaments were rearranged, and the cell growth direction of the osteoblasts became ordered, with their direction being at an angle of about 45° from the direction of strain. The proliferation of osteoblasts and the expression levels of mRNA and protein of ALP, Runx2, OCN, collagen type I, HIF-1?, and VEGF were significantly higher than in the nonstretch control groups. Conclusion:Our homemade device can exert uniaxial static strain and promote the proliferation of osteoblasts and bone matrix formation. It can be used to simulate the mechanical stimulation of osteoblasts during DO.

SUBMITTER: Li Z

PROVIDER: S-EPMC7443025 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Uniaxial Static Strain Promotes Osteoblast Proliferation and Bone Matrix Formation in Distraction Osteogenesis In Vitro.

Li Zhengqiang Z Zheng Junfa J Wan Di D Yang Xiaoqin X

BioMed research international 20200812

<h4>Objective</h4>We aimed at investigating the effects of uniaxial static strain on osteoblasts in distraction osteogenesis (DO).<h4>Methods</h4>To simulate the mechanical stimulation of osteoblasts during DO, 10% uniaxial static strain was applied to osteoblasts using a homemade multiunit cell stretching and compressing device. Before and after applying strain stimulation, the morphological changes of osteoblasts were observed by inverted phase-contrast microscopy, Coomassie blue staining, and ...[more]

PMID: 32855965

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Project description:Background: Interfragmentary movements have benefits in the improvement of bone formation during distraction osteogenesis (DO). Although several clinical studies reported positive outcomes regarding the application of the cyclic distraction-compression (CDC) dynamization technique in cases with poor bone formation during DO, they are mostly anecdotal without a detailed description. The purpose of this study was to investigate the effectiveness and potential mechanism of different amplitudes and rates of the CDC technique on bone regeneration in a rat femur DO model. Methods: A total of 60 adult male Sprague-Dawley rats underwent right femoral mid-diaphysis transverse osteotomy and were randomly and evenly divided into Control (no manipulation), Group1 (CDC therapy), Group2 (CDC therapy with larger amplitude), and Group3 (CDC therapy with a slower rate) after distraction. The CDC technique was performed during the middle phase of the consolidation period according to different protocols. Animals were sacrificed after 4 and 6 weeks of consolidation. The process of bone formation was monitored by digital radiographs, and the regenerate bone was evaluated by micro-computed tomography (micro-CT), biomechanical test, and histological analysis. The serum contents of hypoxia-inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF) were measured by enzyme-linked immunosorbent assay (ELISA). Results: Bone regeneration after the CDC technique was improved significantly during DO. The digital radiograph, micro-CT, histomorphological analysis, and biomechanical evaluation showed better effects regarding volume, continuity, and mechanical properties of the regenerate bone in Group2 and Group3 when compared to Group1. The angiogenic and osteogenic markers were more highly expressed in Group2 and Group3 than in Group1 according to the immunohistochemical analysis. As for ELISA, the serum contents of HIF-1α and VEGF were also increased after the CDC technique, especially in Group2 and Group3. Conclusion: The CDC dynamization technique has benefits on the improvement of bone formation during DO, and the mechanism may be due to tissue hypoxia activating the HIF pathway followed by the augmentation of osteogenic-angiogenic coupling. Better outcomes may be achieved by moderately increasing the amplitude and slowing down the rate of the CDC technique.

Project description:Objective The aim of the study was to report our experience with placed allogenic acellular bone matrix and mandibular distraction osteogenesis in Pierre Robin sequence (PRS), and explore the role of distraction in the osteogenesis of acellular bone. Materials and Methods A total of 428 neonates with severe PRS managed with placing allogenic acellular bone and bilateral mandibular distraction osteogenesis were included in the study. The procedure included using oblique-shaped osteotomy, fixing bilateral mandibular distractor, instantly extending a 4–6 mm gap, and placing allogenic acellular bone into the gap. The length of allogenic acellular bone was 4–5 mm. Although the surgical techniques, distraction, and consolidation periods were similar, the allogenic acellular bone matrix we placed was quite different from the traditional distraction. With the technology we used, tracheal intubation could be immediately removed, thus quickly improving breathing conditions compared to traditional methods after the surgery. The jaw extending and oral feeding could begin on the 5th day. The jaw was extended 0.6 mm twice a day until the mandible was overcorrected by 20%. Results All 428 cases included in this study were successfully extubated after the operation, and the difficulty in breathing was instantly relieved. Total mandibular distraction was 15–20 mm. Oral feeding was started at 6 h to 6 days postoperatively, while hospital stay ranged from 18 to 20 days postoperatively. No major complications were reported. Medium to long-term results was good. Mandibular distractors were removed after 3 months. Conclusions Bilateral mandibular distraction osteogenesis combined with placing allogenic acellular bone in the neonate are safe and accurate procedures, which are the primary treatment options for cases of severe PRS. It can be considered that the tension of distraction can promote osteogenesis in acellular bone and thus improve distractive effect of the mandible.

Project description:Introduction: Developmental engineering based on endochondral ossification has been proposed as a potential strategy for repairing of critical bone defects. Bone development is driven by growth plate-mediated endochondral ossification. Under physiological conditions, growth plate chondrocytes undergo compressive forces characterized by micro-mechanics, but the regulatory effect of micro-mechanical loading on endochondral bone formation has not been investigated. Methods: In this study, a periodic static compression (PSC) model characterized by micro-strain (with 0.5% strain) was designed to clarify the effects of biochemical/mechanical cues on endochondral bone formation. Hydrogel scaffolds loaded with bone marrow mesenchymal stem cells (BMSCs) were incubated in proliferation medium or chondrogenic medium, and PSC was performed continuously for 14 or 28 days. Subsequently, the scaffold pretreated for 28 days was implanted into rat femoral muscle pouches and femoral condylar defect sites. The chondrogenesis and bone defect repair were evaluated 4 or 10 weeks post-operation. Results: The results showed that PSC stimulation for 14 days significantly increased the number of COL II positive cells in proliferation medium. However, the chondrogenic efficiency of BMSCs was significantly improved in chondrogenic medium, with or without PSC application. The induced chondrocytes (ichondrocytes) spontaneously underwent hypertrophy and maturation, but long-term mechanical stimulation (loading for 28 days) significantly inhibited hypertrophy and mineralization in ichondrocytes. In the heterotopic ossification model, no chondrocytes were found and no significant difference in terms of mineral deposition in each group; However, 4 weeks after implantation into the femoral defect site, all scaffolds that were subjected to biochemical/mechanical cues, either solely or synergistically, showed typical chondrocytes and endochondral bone formation. In addition, simultaneous biochemical induction/mechanical loading significantly accelerated the bone regeneration. Discussion: Our findings suggest that microstrain mechanics, biochemical cues, and in vivo microenvironment synergistically regulate the differentiation fate of BMSCs. Meanwhile, this study shows the potential of micro-strain mechanics in the treatment of critical bone defects.

Project description:BackgroundHypoxia is the critical driving force for angiogenesis and can trigger the osteogenic-angiogenic coupling followed by the enhancement of bone regeneration. While lots of studies showed that hypoxia administration can accelerate bone formation during distraction osteogenesis (DO), the therapeutic timing for the osteogenic purpose was concentrated on the distraction phase. The outcomes of hypoxia administration in the consolidation phase stay uncertain. The purpose of this study was to determine the osteogenic effectiveness of hypoxia therapy during the consolidation phase, if any, to enhance bone regeneration in a rat femoral DO model.MethodsA total of 42 adult male Sprague-Dawley rats underwent right femoral mid-diaphysis transverse osteotomy and were randomly divided into Control (NS administration, n = 21) and Group1 (deferoxamine therapy, n = 21) after distraction. During the consolidation phase, Group1 was treated with local deferoxamine (DFO) injection into the distraction zone, while the Control underwent the same dosage of NS. Animals were sacrificed after 2, 4, and 6 weeks of consolidation. The process of bone formation and remodeling was monitored by digital radiographs, and the regenerated bone was evaluated by micro-computed tomography (micro-CT), biomechanical test, and histological analysis. The serum content of hypoxia-inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) were measured by enzyme linked immunosorbent assay (ELISA) for further analysis.ResultsBone regeneration was significantly enhanced after hypoxia therapy during the consolidation phase. The digital radiograph, micro-CT, and biomechanical evaluation showed better effects regarding volume, continuity, and mechanical properties of the regenerated bone in Group1. The histomorphological evaluation also revealed the hypoxia treatment contributed to accelerate bone formation and remodeling during DO. The higher positive expression of angiogenic and osteogenic markers were observed in Group1 after hypoxia administration according to the immunohistochemical analysis. The serum content of HIF-1α and VEGF was also increased after hypoxia therapy as evidenced from ELISA.ConclusionHypoxia administration during the consolidation phase of distraction osteogenesis has benefits in enhancing bone regeneration, including accelerates the bone formation and remodeling.

Project description:Rationale: Angiogenesis and osteogenesis are highly coupled processes which are indispensable to bone repair. However, the underlying mechanism(s) remain elusive. To bridge the gap in understanding the coupling process is crucial to develop corresponding solutions to abnormal bone healing. Epidermal growth factor-like protein 6 (EGFL6) is an angiogenic factor specifically and distinctively up-regulated during osteoblast differentiation. In contrast with most currently known osteoblast-derived coupling factors, EGFL6 is highlighted with little or low expression in other cells and tissues. Methods: In this study, primary bone marrow mesenchymal stem cells (MSCs) and osteoblastic cell line (MC3T3-E1) were transduced with lentiviral silencing or overexpression constructs targeting EGFL6. Cells were induced by osteogenic medium, followed by the evaluation of mineralization as well as related gene and protein expression. Global and conditional knockout mice were established to examine the bone phenotype under physiological condition. Furthermore, bone defect models were created to investigate the outcome of bone repair in mice lacking EGFL6 expression. Results: We show that overexpression of EGFL6 markedly enhances osteogenic capacity in vitro by augmenting bone morphogenic protein (BMP)-Smad and MAPK signaling, whereas downregulation of EGFL6 diminishes osteoblastic mineralization. Interestingly, osteoblast differentiation was not affected by the exogenous addition of EGFL6 protein, thereby indicating that EGFL6 may regulate osteoblastic function in an intracrine manner. Mice with osteoblast-specific and global knockout of EGFL6 surprisingly exhibit a normal bone phenotype under physiological conditions. However, EGFL6-deficiency leads to compromised bone repair in a bone defect model which is characterized by decreased formation of type H vessels as well as osteoblast lineage cells. Conclusions: Together, these data demonstrate that EGFL6 serves as an essential regulator to couple osteogenesis to angiogenesis during bone repair.

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Uniaxial Static Strain Promotes Osteoblast Proliferation and Bone Matrix Formation in Distraction Osteogenesis In Vitro.

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Uniaxial Static Strain Promotes Osteoblast Proliferation and Bone Matrix Formation in Distraction Osteogenesis In Vitro.

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