牙囊在牙萌出的作用及其调控机制研究进展

牙齿的萌出是指牙齿从颌骨内向口腔移动,穿透颌骨与口腔黏膜,然后接触对颌牙达到功能位置的复杂过程,这一过程在时间和空间上均受到严格管控。牙囊是围绕在发育中牙胚周围的一层来源于外胚间充质的疏松结缔组织,它通过招募单核细胞以及调控骨吸收和骨形成在牙齿萌出过程中发挥关键作用。国内外学者对牙囊在牙齿萌出中的作用和机制研究甚多,现将研究进展作一综述。     

Expression of angiopoietin‐like protein 4 at the fracture site: Regulation by hypoxia and osteoblastic differentiation

Vascular disruption that occurs as a consequence of bone fracture, leads to hypoxia at the site of damage. Hypoxia regulates the expression of a number of genes that can modulate energy conservation, cell survival, tissue regeneration and angiogenesis. In this study we investigated the expression of Angiopoietin‐like 4, an adipocytokine that has additional roles in angiogenesis, at the fracture site. We demonstrate that Angptl4 mRNA expression increased early during fracture healing (day 3) returning close to baseline at day14. In the callus, Angptl4 mRNA was visualized in areas of condensing mesenchymal cells, callus cartilage and was especially high in mineralizing osteoblasts located in areas of new bone formation. In vitro, Angptl4 mRNA expression in osteoblasts increased under hypoxic conditions and in cells treated with the hypoxia mimetic desferrioxamine. Angptl4 levels were strongly induced at day 14 in differentiating MC3T3‐E1 osteoblastic cells. Exogenous ANGPTL4 increased expression of Runx2, Spp1, vegfa, and Alp mRNA in differentiating osteoblasts. We suggest that the distribution of Angptl4 in the callus may be driven by hypoxia and that Angptl4 may play a role in osteoblastic differentiation, and possibly angiogenesis via regulation of VEGF. Further studies could reveal a dual role for Angptl4 in angiogenesis and osteogenesis. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1364–1373, 2015.     

Biofabrication of a PLGA–TCP‐based porous bioactive bone substitute with sustained release of icaritin

A phytomolecule, icaritin, has been identified and shown to be osteopromotive for the prevention of osteoporosis and osteonecrosis. This study aimed to produce a bioactive poly (l ‐lactide‐co‐glycolide)–tricalcium phosphate (PLGA–TCP)‐based porous scaffold incorporating the osteopromotive phytomolecule icaritin, using a fine spinning technology. Both the structure and the composition of icaritin‐releasing PLGA–TCP‐based scaffolds were evaluated by scanning electron microscopy (SEM). The porosity was quantified by both water absorption and micro‐computed tomography (micro‐CT). The mechanical properties were evaluated using a compression test. In vitro release of icaritin from the PLGA–TCP scaffold was quantified by high‐performance liquid chromatography (HPLC). The attachment, proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) on the composite scaffold were evaluated. Both an in vitro cytotoxicity test and an in vivo test via muscular implantation were conducted to confirm the scaffold's biocompatibility. The results showed that the PLGA–TCP–icaritin composite scaffold was porous, with interconnected macro‐ (about 480 µm) and micropores (2–15 µm). The mechanical properties of the PLGA–TCP–icaritin scaffold were comparable with those of the pure PLGA–TCP scaffold, yet was spinning direction‐dependent. Icaritin content was detected in the medium and increased with time. The PLGA–TCP–icaritin scaffold facilitated the attachment, proliferation and osteogenic differentiation of BMSCs. In vitro cytotoxicity test and in vivo intramuscular implantation showed that the composite scaffold had no toxicity with good biocompatibility. In conclusion, an osteopromotive phytomolecule, icaritin, was successfully incorporated into PLGA–TCP to form an innovative porous composite scaffold with sustained release of osteopromotive icaritin, and this scaffold had good biocompatibility and osteopromotion, suggesting its potential for orthopaedic applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Rush钉矫治成骨不全儿童股骨畸形的疗效观察

目的探讨股骨多段截骨髓内钉固定矫治儿童成骨不全症所致股骨畸形的疗效,分析术后并发症的防治。方法 2007年1月至2013年12月,我院共收治成骨不全所致股骨畸形患儿28例,包括39根畸形股骨。年龄3岁7个月至14岁5个月,平均8岁4个月。术中将弯曲股骨行多段截骨矫形及髓内钉固定,平均截骨1.9(1~3)处,随机分为弹性针组与Rush钉组,其中20根股骨使用弹性髓内钉,19根股骨使用Rush钉。结果随访1年3个月至5年7个月,平均3年8个月。随访后期按Sanders评分标准评定髋关节功能:弹性针组优11例,良2例,中7例,差0例;Rush钉组优16例,良2例,中1例,差0例。结论多段截骨矫形后髓内钉内固定治疗儿童成骨不全所致股骨畸形,能有效矫正股骨弯曲畸形,改善下肢外观及力线关系,防止再骨折,提高患儿生活质量,效果明确。Rush髓内钉内固定效果满意,术后再骨折概率小,股骨不易再次弯曲变形,值得临床推广。     

牵张成骨联合正颌正畸治疗成人严重小下颌畸形

目的：探讨牵引成骨技术联合正颌正畸治疗重度小下颌伴偏颌畸形患者下颌骨严重发育不足及咬合关系紊乱的疗效。方法：对2例继发于儿童时期颞下颌关节损伤的小下颌伴偏颌畸形患者采用牵张成骨技术进行治疗。手术行双侧下颌角处截骨,安置牵引器,延长下颌升支及下颌体。第二期在拆除牵引器后进行正畸治疗,继而采用正颌外科方法进一步矫正颌面畸形及咬合关系,术后正畸治疗矫正咬合关系,排齐牙列。结果：2例患者均顺利完成治疗。下颌骨最小牵引距离25 mm,最大牵引距离30 mm,牵引区成骨良好,SNB角由术前平均67°增加到术后80°,小下颌及偏颌畸形得以矫治。联合正颌外科及正畸治疗后,面形及咬合功能均获得满意效果。术后经过2年6个月随访,未见复发。结论：联合应用牵张成骨和正颌外科技术并配合正畸治疗是矫治成人重度小下颌不对称性牙颌面畸形的有效治疗方案。     

Influence of different intensities of vibration on proliferation and differentiation of human periodontal ligament stem cells

Introduction

To understand the effects of low-magnitude, high-frequency (LMHF) mechanical vibration at different intensities on human periodontal ligament stem cell (hPDLSC) proliferation and osteogenic differentiation.

Material and methods

The effect of vibration on hPDLSC proliferation, osteogenic differentiation, tenogenic differentiation and cytoskeleton was assessed at the cellular, genetic and protein level.

Results

The PDLSC proliferation was decreased after different magnitudes of mechanical vibration; however, there were no obvious senescent cells in the experimental and the static control group. Expression of osteogenesis markers was increased. The expression of alkaline phosphatase (ALP) and osteocalcin (OCN) mRNA was up-regulated at 0.1 g, 0.3 g, 0.6 g and 0.9 g magnitude, with the peak at 0.3 g. The type I collagen (Col-I) level was increased after vibration exposure at 0.1 g, 0.3 g, and 0.6 g, peaking at 0.3 g. The expression levels of both mRNA and protein of Runx2 and osterix (OSX) significantly increased at a magnitude of 0.1 g to 0.9 g, reached a peak at 0.3 g and then decreased slowly. The scleraxis, tenogenic markers, and mRNA expression decreased at 0.05 g, 0.1 g, and 0.3 g, and significantly increased at 0.6 g and 0.9 g. Compared with the static group, the F-actin stress fibers of hPDLSCs became thicker and clearer following vibration.

Conclusions

The LMHF mechanical vibration promotes PDLSC osteogenic differentiation and implies the existence of a magnitude-dependent effect of vibration on determining PDLSC commitment to the osteoblast lineage. Changes in the cytoskeleton of hPDLSCs after vibration may be one of the mechanisms of the biological effects.     

Regenerative Potential of Human Schneiderian Membrane: Progenitor Cells and Epithelial‐Mesenchymal Transition

An innate osteogenic potential of the Schneiderian membrane (SM) is progressively assessed in studies ranging from non‐human species to human subjects. It has relevance for endosteal placement and osseointegration. Nestin‐expressing osteogenic progenitor cells are allegedly involved in bone formation and remodelling. Nestin phenotype was not assessed previously in human SM. We therefore aimed to fill that particular gap in the literature. Bioptic samples of human adult SM were obtained during surgery from eight adult patients, operated for non‐malignant pathologies. Immunohistochemistry on paraffin‐embedded tissue samples used primary antibodies against nestin, CD45, CD146, cytokeratin 7 (CK7), and alpha‐smooth muscle actin (α‐SMA). Nestin expression was consistently found in endothelial cells, and was scarcely encountered in pericytes, putative stromal stem/progenitor cells, as well as in glandular epithelial cells. Moreover, woven bone formation in the periosteal layer of the SM can also be regarded as evidence of the osteogenic potential of this membrane. Nestin and CD45 expression in cells of the primary bone supports the osteogenic potential of SM nestin‐expressing cells and a possible involvement of hematopoietic stem cells in maxillary sinus floor remodeling. CD146, a known inducer of epithelial‐mesenchymal transition (EMT), was expressed in epithelia, as was CK7. Isolated stromal cells were found expressing CD146, CK7 and α‐SMA, suggesting that regenerative processes happening in the SM may also involve processes of EMT which generate stem/progenitor cells. This study provides additional evidence for the regenerative potential of the Schneiderian membrane and identifies potential roles for cells of its stem niche in osteogenesis. Anat Rec, 298:2132–2140, 2015. © 2015 Wiley Periodicals, Inc.