Integrating molecular-caged nano-hydroxyapatite into post-crosslinked PVA nanofibers for artificial periosteum
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Periosteum
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The final goal of regenerative periodontal therapy is to restore the structure and function of the periodontium destroyed or lost due to periodontitis. However, the role of periosteum in periodontal regeneration was relatively neglected while bone repair in the skeleton occurs as a result of a significant contribution from the periosteum. The aim of this study is to understand the histological characteristics of periosteum and compare the native periosteum with the repaired periosteum after elevating flap or after surgical intervention with flap elevation.
Periosteum
Periodontium
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Periosteum
Immunosuppression
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AIM To observe the effects of subtotal periosteal stripping on the architecture of the rabbits' tibia. METHODS A comparison was conducted between the tibia of the rabbit that had been stripped of a greater part of periosteum and the tibia with an intact periosteum, with regard to the length, density, strength and histological findings in 8 and 12 wk after operation. RESULTS The studies revealed similar measurements of the intact periosteum and the stripped one, suggesting the compromise of the vascularization at the donor site had been fully compensated by the invasion of metaphyseal vessels and vessels of the remaining periosteum, resulting in unchanged morphology, density and strength of the donor site bone. Furthermore, regeneration of periosteum at the donor site was observed and the operated periosteum had the same structure as the untouched periosteum 8wk post operation. CONCLUSION Large area periosteum harvesting will not affect the architecture of the bone at donor site.
Periosteum
Stripping (fiber)
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To reconstruct tracheal defect after tumor excision, we used the contralateral musculo-periosteum flap of the sternocleidomastoideus with clavicular periosteum.The contralateral musculo-periosteum flap of the sternocleidomastoideus with clavicular periosteum was used to reconstruct the tracheal defect when the blood supply to the ipsilateral sternocleidomastoideus was destroyed because of lymphonode clearing or radiotherapy. The pedicle of the musculo-periosteum flap was dissected adequately and the blood supply was protected carefully.All flaps survived with epithelization and osteogenesis. The endotracheal tubes were pulled out safely without trachea stenosis in all the patients.The contralateral musculo-periosteum flap of the sternocleidomastoideus with clavicular periosteum could reconstruct the tracheal defect when the ipsilateral blood supply was damaged. This method extends the application of the musculo-periosteum flap.
Periosteum
Blood supply
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Although many different materials, techniques and methods, including artificial or engineered bone substitutes, have been used to repair various bone defects, the restoration of critical-sized bone defects caused by trauma, surgery or congenital malformation is still a great challenge to orthopedic surgeons. One important fact that has been neglected in the pursuit of resolutions for large bone defect healing is that most physiological bone defect healing needs the periosteum and stripping off the periosteum may result in non-union or non-healed bone defects. Periosteum plays very important roles not only in bone development but also in bone defect healing. The purpose of this project was to construct a functional periosteum in vitro using a single stem cell source and then test its ability to aid the repair of critical-sized bone defect in animal models. This project was designed with three separate but closely-linked parts which in the end led to four independent papers.
The first part of this study investigated the structural and cellular features in periostea from diaphyseal and metaphyseal bone surfaces in rats of different ages or with osteoporosis. Histological and immunohistological methods were used in this part of the study. Results revealed that the structure and cell populations in periosteum are both age-related and site-specific. The diaphyseal periosteum showed age-related degeneration, whereas the metaphyseal periosteum is more destructive in older aged rats. The periosteum from osteoporotic bones differs from normal bones both in terms of structure and cell populations. This is especially evident in the cambial layer of the metaphyseal area. Bone resorption appears to be more active in the periosteum from osteoporotic bones, whereas bone formation activity is comparable between the osteoporotic and normal bone. The dysregulation of bone resorption and formation in the periosteum may also be the effect of the interaction between various neural pathways and the cell populations residing within it.
One of the most important aspects in periosteum engineering is how to introduce new blood vessels into the engineered periosteum to help form vascularized bone tissues in bone defect areas. The second part of this study was designed to investigate the possibility of differentiating bone marrow stromal cells (BMSCs) into the endothelial cells and using them to construct vascularized periosteum. The endothelial cell differentiation of BMSCs was induced in pro-angiogenic media under both normoxia and CoCl2 (hypoxia-mimicking agent)-induced hypoxia conditions. The VEGF/PEDF expression pattern, endothelial cell specific marker expression, in vitro and in vivo vascularization ability of BMSCs cultured in different situations were assessed. Results revealed that BMSCs most likely cannot be differentiated into endothelial cells through the application of pro-angiogenic growth factors or by culturing under CoCl2-induced hypoxic conditions. However, they may be involved in angiogenesis as regulators under both normoxia and hypoxia conditions. Two major angiogenesis-related growth factors, VEGF (pro-angiogenic) and PEDF (anti-angiogenic) were found to have altered their expressions in accordance with the extracellular environment. BMSCs treated with the hypoxia-mimicking agent CoCl2 expressed more VEGF and less PEDF and enhanced the vascularization of subcutaneous implants in vivo.
Based on the findings of the second part, the CoCl2 pre-treated BMSCs were used to construct periosteum, and the in vivo vascularization and osteogenesis of the constructed periosteum were assessed in the third part of this project. The findings of the third part revealed that BMSCs pre-treated with CoCl2 could enhance both ectopic and orthotopic osteogenesis of BMSCs-derived osteoblasts and vascularization at the early osteogenic stage, and the endothelial cells (HUVECs), which were used as positive control, were only capable of promoting osteogenesis after four-weeks. The subcutaneous area of the mouse is most likely inappropriate for assessing new bone formation on collagen scaffolds. This study demonstrated the potential application of CoCl2 pre-treated BMSCs in the tissue engineering not only for periosteum but also bone or other vascularized tissues.
In summary, the structure and cell populations in periosteum are age-related, site-specific and closely linked with bone health status. BMSCs as a stem cell source for periosteum engineering are not endothelial cell progenitors but regulators, and CoCl2-treated BMSCs expressed more VEGF and less PEDF. These CoCl2-treated BMSCs enhanced both vascularization and osteogenesis in constructed periosteum transplanted in vivo.
Periosteum
Long bone
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In the oral and maxillofacial area, we often encounter cases in which the periosteum involved in bone defects cannot be preserved. Therefore, porous hydroxyapatite (HAP) blocks are inserted into the bone defect in such cases. The purpose of this experiment was to investigate the influence of the periosteum on the porous HAP block implants. Bone defects measuring 5×5mm were made at the region of the inferior border of the mandible in 15 mature domestic rabbits, and a porous HAP block (pore size 200μm ; porosity rate 70±3% ; firing temperature 1200℃) was inserted. In one group, the periosteum was preserved, and in other groups, the periosteum had been removed before the HAP block was inserted. These specimens were examined histopathologically at 3, 5, 7, 14, 21, 30, 60 and 90 days after operation. Histomorphometrical analysis of bone formation within the HAP pores was performed at 14, 21, 30, 60 and 90 days after operation. The following results were obtained : 1. On histopathological examination, the whole healing process and new bone formation within the HAP pores were more rapid in the periosteum-preserved group than that in the groups without periosteum. 2. On histomorphometrical analysis, the average of bone formation within HAP pores did not vary much during the short term, however it was larger in the periosteum-preserved group than that in the groups without periosteum during the long term. 3. In the periosteum-preserved group, new bone extending from the bone stump covered almost all of the HAP surface and the bone surface developed smoothly. However, new bone was not well formed in some regions of the HAP surface and the bone surface was rough in the groups without periosteum. 4. In this experiment, wound healing around HAP implantation was better in the periosteum-preserved group than that in the groups without periosteum. However, bone formation average tended to increase gradually even in the groups without periosteum. It is suggested that the bone conductivity of HAP provides a good influence on the healing of bone defect whether the periosteum exists.
Periosteum
Mandible (arthropod mouthpart)
Bone Formation
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A 2 cm partial ulnectomy was performed in twelve 4‐month‐old mongrel dogs with experimentally induced radius curvus. In four dogs, the periosteum was left intact; in four dogs, all of the periosteum was excised from the ulnectomy site; and in the remaining four dogs, the periosteum was sewn over the ends of the ostectomized bone. The unoperated limbs of all 12 dogs served as controls. Progress was determined monthly from radiographs until the dogs were 9 months of age. The ulnectomies performed when the periosteum was left in situ at the ulnectomy site healed quickly, resulting in progressive deformity of the foreleg. When the periosteum was excised or sewn over the ends of the bone, the ulnectomy sites did not heal and correction of the radius curvus resulted. Histopathologic examination confirmed the absence of bony healing.
Periosteum
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The regulatory effect of the periosteum on the growth of the mandibular condylar process has previously been investigated by relieving the periosteal tension, e.g. by dividing the periosteum, but no unanimous conclusion has been reached. In the present investigation, a different experimental design was applied in that the growth of the condylar process was observed following a provoked periosteal damage. Using 15-day-old rats, the mandibular ramus on the right side was exposed, and the periosteum subjacent to the condylar cartilage was frozen by a cryotechnique. Controls were treated similarly, with the exception of the freezing. The height of the ramus and the length of the mandibular corpus were measured on separated dry mandibular halves 15 or 30 days postoperatively. The measurements showed that the mandibular halves on which the periosteum had been frozen were significantly smaller than the contralateral ones. A tendency in the same direction was also found in the sham-operated animals. It can be concluded that the presumably increased restriction following damage to the periosteum, and evidently also scarring resulting from the operation, has an inhibitory effect on the growth of the condylar process. However, it is still open to discussion whether the reduced growth is transmitted by mechanical means according to the periosteal-tension hypothesis and/or by here unspecified mitogenic factors.
Periosteum
Mandible (arthropod mouthpart)
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The purpose of this study is to evaluate the role of hydroxyapatite (HA) in the process of osteogenesis. Composite grafts of HA (particles and porous column) and autogenous calvarial periosteum were implanted into the back muscle of 12 rabbits. HA alone and periosteum alone were also implanted as control. Three and 6 months after implantation, the grafts were retrieved and evaluted histologically and microradiographically. There was no significant difference between 3-and 6-month implant periods in any implant group.No calcified tissue was formed when HA alone (both particles and porous column) was implanted. Minute calcified tissues were scattered in the histologic and microradiographic specimens of periosteum alone or particulate HA/periosteum grafts. On the other hand, bone tissue was noted in the specimens of porous-columnar HA/periosteum grafts. Bone tissue was seen only inside of the pores where it adhered intimately to the HA wall of the pores.Although the role of HA in the osteogenic process was not defined in this study, it is very interesting that different calcified tissues were induced by the particulate and porouscolumnar HA/periosteum grafts.
Periosteum
Bone tissue
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Osteogenesis of the periosteum was examined in rats. The periosteum electrically stimulated for 6 days was grafted into the axillar muscle, and new bone tissue was found in 40 out of 44 animals (90.9%). Periosteum without stimulation and that with only 2 days of electrical stimulation did not generate new bone tissue. The periosteum electrically stimulated for 4 days did not show substantial new bone formation in the muscle. The periosteal tissue which was initially electrically stimulated for 6 days was definitely transformed into new bone tissue in the muscle. This shows that boneless bone grafting can be accomplished successfully in rats by electrically stimulating the periosteum before grafting. Periosteal grafting is considered to be potentially valuable as a boneless bone grafting technique.
Periosteum
Bone grafting
Bone tissue
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