牙源性间充质干细胞及其在牙周组织再生治疗中的应用

牙周病是以牙周支持组织的炎症和破坏为特征的感染性疾病。牙周病基础治疗是通过去除牙菌斑以达到控制炎症的目的。但是,牙周治疗的最终目的在于修复并重建牙周组织的结构和功能,包括牙槽骨、牙周韧带、牙骨质等牙周支持组织的再生。组织工程技术的出现为牙周组织再生治疗提供了新的思路和方法,其中具有增殖分化潜能的种子细胞是目前研究热点之一。间充质干细胞属于成体干细胞,是来源于发育早期中胚层的具有高度自我更新能力和多向分化潜能的干细胞,是理想的种子细胞之一。牙源性间充质干细胞具有再生和分化潜力好、免疫原性低的特点,因而成为牙周组织再生的种子细胞。本文将针对目前研究发现的牙源性间充质干细胞的特性及在牙周组织再生中的应用作一综述。     

实现牙周组织形态与功能重建是牙再生的关键科学问题

组织工程与干细胞技术的发展为成功实现牙再生带来了希望,但牙周组织疾病却阻碍了再生牙体内应用的脚步。目前临床对牙周病的治疗并不能从根本上解决牙周功能重建的问题,主要原因可能在于对维持牙周稳态的重要干细胞-牙周膜间充质干细胞的认识不清。牙周膜间充质干细胞与骨髓间充质干细胞具有十分相似的特性,但更容易被炎症因子破坏正常的再生功能。慢性炎症是诱发牙周病最主要因素,如何应对炎症因子的破坏作用,是牙周膜间充质干细胞再生应用面临的难题。利用组织工程技术,牙周膜间充质干细胞聚合体可以成功在慢性炎症条件下实现牙周组织形态和功能的重建。另外考虑骨髓间充质干细胞对炎症因子的耐受性,在一定的条件刺激下,动员体内的骨髓间充质干细胞亦能实现牙周组织的修复重建。无论是上述外源性的,还是内源性的牙周重建再生方法的发展,对牙再生都具有十分重要的临床研究价值和科学研究意义。     

靶向Wnt信号通路在牙周炎治疗领域的研究现状

牙周炎是由菌斑细菌引起并最终导致牙周支持组织吸收的感染性疾病,其药物治疗主要分为抑制炎症反应和介导牙周组织修复两个方面。 Wnt信号通路是调控胚胎干细胞以及多种组织干细胞自我更新和分化的关键途径,被认为是生物体中最为重要的信号通路之一。一些研究显示,Wnt信号通路在牙周炎的发生和治疗中起到关键作用。本综述从牙周病炎症免疫反应和介导牙周膜细胞成骨分化两个方面介绍了近年来关于Wnt信号通路调控的研究成果,并比较了可能通过激活Wnt通路介导牙周膜细胞成骨分化的潜在药物,为靶向Wnt通路治疗牙周炎提供了依据。     

微环境对牙周膜干细胞分化的抑制和诱导作用

牙周膜干细胞(PDLSC)在牙周组织缺损修复和维持牙周动态平衡中起关键性的作用,是牙周组织再生修复治疗的基础细胞.在不同微环境作用下,PDLSC的增殖分化特性呈现出较大的差别.牙周膜干细胞龛和炎症等微环境对PDLSC的分化有抑制作用,然而,牙本质微环境及发育期根尖微环境能促进PDLSC的分化.研究不同的微环境对PDLSC功能的影响,一方面有助于深入研究PDLSC的生物学功能,另一方面为PDLSC应用于牙周疾病的再生治疗提供理论依据.本文就不同的微环境对PDLSC分化的抑制和诱导作用研究进展作一综述,并展望PDLSC在牙周缺损再生治疗中的应用前景.     

牙周内源性再生的策略与展望

牙周病等多种原因造成的牙周支持结构( periodontal supporting apparatus)破坏或丧失是成年人失牙的首要原因,牙周病的治疗和牙周缺损的修复是学者们共同关注的课题,目前还没有哪一种临床治疗方法可以实现真正意义上的牙周组织生理性和功能性再生[1-3].自2004年Seo等[4]从人牙周膜组织中成功分离出牙周膜干细胞( periodontal ligament stem cells,PDLSC)以来,利用干细胞移植技术修复牙周组织缺损已成为牙周组织再生研究的主要策略[3].值得注意的是,无论是动物体内的临床前期研究,还是牙周病患者的临床病例报告,干细胞移植均取得了令人振奋的结果[5-10].然而,干细胞移植需要高标准的体外细胞培养条件、严格的调控措施和复杂的操作规程,其临床转化面临着巨大的人力、物力与财力的挑战,特别在一些非致死性疾病(如牙周组织缺损)的治疗上,"取,,与"舍"仍然存在争议[11].随着干细胞生物学研究的不断深入,利用干细胞在体内的运动和迁移机制,诱导患者自身干细胞募集和"归巢"( cell homing)促进牙周组织自我修复再生有望解决体外干细胞培养与移植面临的"转化困难",具有广阔的研究前景和临床应用空间[12-14].     

牙周膜干细胞表观遗传学研究进展

牙周膜干细胞(periodontal ligament stem cells,PDLSCs)是牙周膜组织中的间充质干细胞,是牙周组织再生和修复的重要细胞群,牙周微环境的变化会影响牙周膜干细胞的生物学特性.表观遗传(epigenetics)是指不基于DNA序列的变化,而出现稳定可遗传的基因表达水平及功能的改变.环境因素是影响表观遗传的重要因素之一,暴露环境的不同可以引起表观修饰改变,进而影响基因表达.表观遗传是干细胞生物学特性的重要内源性调控机制,在干细胞中的变化稳定可遗传,并具有可逆性.近年来牙周膜干细胞的表观遗传调控已成为研究热点,本文通过对表观遗传调控对牙周膜干细胞生物学特性的影响进行综述,以期使牙周膜干细胞更好地应用于牙周再生修复.     

经典Wnt信号通路与牙周膜干细胞成骨分化

牙周炎是口腔最常见的疾病之一,累及牙周支持组织,随着疾病的进展将引起附着丧失、牙周袋形成、牙槽骨吸收,最终导致牙齿松动脱落。因被牙周炎破坏吸收的牙槽骨自愈能力十分有限,所以牙周炎的治疗目标是在彻底清除菌斑生物膜的基础上,争取获得较多的牙周组织再生。牙周膜干细胞作为最适宜进行牙周组织再生的细胞,被广泛研究。Wnt信号通路分为经典Wnt通路和非经典Wnt信号通路,为十分复杂而高度保守的通路传导途径。该通路与牙周膜干细胞成骨分化的关系十分密切,牙周膜干细胞的成骨分化又对牙周组织再生有重要意义。该文对经典Wnt信号通路与牙周膜干细胞成骨分化的研究概况作一综述。     

低强度脉冲超声在牙周组织再生中的作用

牙周病、根面龋以及颌面先天畸形和创伤等都会不同程度地导致牙槽骨、牙龈和牙周膜等牙周支持组织缺损。低强度脉冲超声（LIPUS）的温热效应和机械刺激可促进成骨质细胞、成牙本质细胞和牙周膜细胞（PDLC）的生成和分化。PDLC可分化成中胚层细胞谱系,进而生成牙槽骨、牙骨质和牙周膜等牙周组织。碱性磷酸酶（AKP）和骨钙蛋白（OCN）为骨形成或骨分化的晚期标志物,经LIPUS刺激过的PDLC,其AKP活性和OCN的表达皆提高。经LIPUS刺激可减少正畸过程中牙根的吸收,促进修复牙根缺损的成牙骨质细胞的增殖分化和矿化,促进牙周组织伤口愈合和血管生成的结缔组织生长因子的表达,从而加速牙周软组织的愈合。LIPUS刺激在牙周支持组织再生中为一种安全无创的治疗手段,但其最佳刺激强度和治疗时间尚需继续探索。     

干细胞治疗与牙周组织再生

干细胞是具有自我复制和多向分化潜能的原始细胞,在一定条件下可以分化成多种功能细胞或组织器官,故又称其为"万用细胞",干细胞治疗就是利用其多向分化的特点,以达到修复病变细胞或重建功能正常的细胞和组织的目的。牙周组织再生一直是牙周病治疗中要攻克的难题,干细胞治疗的研究为牙周组织再生提供了新的思路和方法。本文就可用于牙周再生的干细胞和相关治疗技术作一综述。     

牙周膜干细胞巢与牙周组织再生

牙周膜干细胞巢是牙周膜干细胞周围的微环境,由干细胞周围的支持细胞、黏附分子和基质组成,其在牙周组织的发育、牙周病的发生与发展以及牙周组织再生等方面具有重要的作用。本文将从影响巢结构稳定的因素及其在牙周组织再生中的作用等方面作一综述。     

New attachment following surgical treatment of human periodontal disease

Abstract The present experiment was undertaken to test the hypothesis that new connective tissue attachment may form on a previously periodontitis involved root surface provided cells originating from the periodontal ligament are enabled to repopulate the root surface during healing. A mandibular incisor with advanced periodontal disease of long standing (the distance between the cemento-enamel junction and the alveolar bone crest was 9 mm) was subjected to periodontal surgery using a technique which during healing prevented the dentogingival epithelium and the gingival connective tissue from reaching contact with the curetted root surface. Preference was hereby given to the periodontal ligament cells to repopulate the previously diseased root surface. After 3 months of healing a block biopsy containing the incisor and surrounding tissue was sampled. The histological analysis revealed that new cementum with inserting principal fibers had formed on the previously diseased root surface. This new attachment extended in coronal direction to a level 5 mm coronal to the alveolar bone crest. This finding suggests that new attachment can be achieved by cells originating from the periodontal ligament and demonstrates that the concept that the periodontitis affected root surface is a major preventive factor for new attachment is invalid.     

Cellular therapy in periodontal regeneration

Periodontitis is a chronic inflammatory condition leading to destruction of the tooth supporting tissues, which if left untreated may cause tooth loss. The treatment of periodontitis mainly aims to arrest the inflammatory process by infection control measures, although in some specific lesions a limited periodontal regeneration can also be attained. Current regenerative approaches are aimed to guide the cells with regenerative capacity to repopulate the lesion and promote new cementum and new connective tissue attachment. The first phase in periodontal tissue regeneration involves the differentiation of mesenchymal cells into cementoblasts to promote new cementum, thus facilitating the attachment of new periodontal ligament fibers to the root and the alveolar bone. Current regenerative approaches limit themselves to the confines of the lesion by promoting the self‐regenerative potential of periodontal tissues. With the advent of bioengineered therapies, several studies have investigated the potential use of cell therapies, mainly the use of undifferentiated mesenchymal cells combined with different scaffolds. The understanding of the origin and differentiation patterns of these cells is, therefore, important to elucidate their potential therapeutic use and their comparative efficacy with current technologies. This paper aims to review the in vitro and experimental studies using cell therapies based on application of cementoblasts and mesenchymal stem cells isolated from oral tissues when combined with different scaffolds.     

Identification of multipotent stem cells from adult dog periodontal ligament

Periodontal diseases, which are characterized by destruction of the connective tissues responsible for restraining the teeth within the jaw, are the main cause of tooth loss. Periodontal regeneration mediated by human periodontal ligament stem cells (hPDLSCs) may offer an alternative strategy for the treatment of periodontal disease. Dogs are a widely used large-animal model for the study of periodontal-disease progression, tissue regeneration, and dental implants, but little attention has been paid to the identification of the cells involved in this species. This study aimed to characterize stem cells isolated from canine periodontal ligament (cPDLSCs). The cPDLSCs, like hPDLSCs, showed clonogenic capability and expressed the mesenchymal stem cell markers STRO-1, CD146, and CD105, but not CD34. After induction of osteogenesis, cPDLSCs showed calcium accumulation in vitro. Moreover, cPDLSCs also showed both adipogenic and chondrogenic potential. Compared with cell-free controls, more cementum/periodontal ligament-like structures were observed in CB-17/SCID mice into which cPDLSCs had been transplanted. These results suggest that cPDLSCs are clonogenic, highly proliferative, and have multidifferentiation potential, and that they could be used as a new cellular therapeutic approach to facilitate successful and more predictable regeneration of periodontal tissue using a canine model of periodontal disease.     

Interrelationship of inflammation and tooth mobility (trauma) in pathogenesis of periodontal disease

Abstract A series of studies has investigated interactions between periodontal trauma and marginal periodontitis in relation to the initiation, progression and treatment of periodontal disease. Lesions of trauma in the periodontal ligament consequent to either single or jiggling displacing forces result in morphologic alterations in the ligament and alveolar bone. These changes do not initiate the loss of connective tissue attachment characteristic of marginal periodontitis. Studies conducted in squirrel monkeys and beagle dogs in which jiggling forces have been produced subjacent to an established marginal periodontitis reported increased loss of alveolar bone, but the accelerated loss of attachment which occurred in the dog model did not occur in the monkey model. To clarify the relative importance of inflammation and tooth mobility in the treatment of advanced periodontal disease, periodontal response was evaluated after removing traumatic and/or inflammatory components. Elimination of trauma in the presence of existing marginal inflammation did not reduce tooth mobility or increase bone volume. Osseous regeneration and decreased tooth mobility occurred after resolving both components, however, similar findings occurred after resolving inflammation in the presence of continued tooth mobility. Resolution of marginal inflammation is of prime importance in the management of periodontal disease. After resolution of inflammation, bone regeneration may occur around mobile teeth and, furthermore, any residual tooth mobility does not result in increased loss of connective tissue attachment.     

Stem cells and periodontal regeneration

Periodontitis is an inflammatory disease which manifests clinically as loss of supporting periodontal tissues including periodontal ligament and alveolar bone. For decades periodontists have sought ways to repair the damage which occurs during periodontitis. This has included the use of a range of surgical procedures, the use of a variety of grafting materials and growth factors, and the use of barrier membranes. To date periodontal regeneration is considered to be biologically possible but clinically unpredictable. Recently, reports have begun to emerge demonstrating that populations of adult stem cells reside in the periodontal ligament of humans and other animals. This opens the way for new cell-based therapies for periodontal regeneration. For this to become a reality a thorough understanding of adult human stem cells is needed. This review provides an overview of adult human stem cells and their potential use in periodontal regeneration.     

Cell-seeding of ligament fibroblasts

This study was undertaken to test the hypothesis that seeded periodontal ligament cells are able to create new attachment. In one beagle dog, a premolar was removed and scrapings of the ligament were cultured. Artificial periodontal defects were made and the cultured ligament cells were seeded on the planed root surfaces and covered with muco-periosteal flaps. The opposite side served as control. After 4 months, the dog was sacrificed and histological and electron microscopical sections were prepared. The seeded root surfaces were almost completely covered with cementoblasts, whereas in controls, epithelial down-growth could be observed. We conclude that seeding of periodontal ligament cells could be a promising technique to create new connective tissue attachment.     

非编码RNA调控人牙周膜干细胞成骨向分化的研究进展

牙周炎是一种常见的炎症性疾病,以牙齿支持结构的进行性损伤为特点,是我国成人牙齿丧失的主要原因。治疗牙周炎的目的不仅是通过控制炎症来阻止疾病发展,更重要的是获得牙周再生。人牙周膜干细胞具有成骨向分化潜能,有望在牙周组织修复再生的临床应用上发挥重要作用。非编码RNA(ncRNA)一般是指不编码蛋白质的RNA。伴随高通量检测技术的不断发展,发现了大量的种类丰富的ncRNA,其生物学功能也被不断揭示。越来越多证据显示,ncRNA在分子机制及细胞组织层面对疾病的发生、发展起重要调控作用,因此探索ncRNA调控机制可为牙周再生的研究提供新思路。本综述主要阐述了目前研究较多的几种ncRNA在人牙周膜干细胞成骨向分化中的调控机制。     

牙周膜干细胞的研究进展

牙周组织工程是牙周病治疗研究的热点,牙周膜干细胞是其关键种子细胞之一。本文就牙周组织工程的相关研究和牙周膜干细胞的来源、分离与培养、细胞表型、生物学特性、功能影响因素和分子调控进行综述,并对其面临的挑战和前景作一讨论。