Department of Periodontology, Research Institute for Periodontal Regeneration, College of Dentistry, Yonsei University, Seoul, South Korea.
J Periodontal Res. 2012 Aug;47(4):514-24. doi: 10.1111/j.1600-0765.2011.01463.x. Epub 2012 Feb 6.
Human periodontal ligament stem cells (hPDLSCs) have been reported to play the pivotal role in periodontal regeneration. However, the dynamic cellular healing process initiated by hPDLSCs still remains to be elucidated. In the present study, the sequence of regeneration by hPDLSCs was assessed using histological and immunohistochemical observation in an ectopic transplantation model, which is a well-standardized assessment tool that excludes the innate healing factors from the animals.
Human periodontal ligament stem cells that were isolated and characterized from teeth (n=12) extracted for the purpose of orthodontic treatment were transplanted with carriers into ectopic subcutaneous pouches in immunocompromised mice (n=20). Animals were killed after several different healing periods: 3 d (n=4), 1 (n=4), 2 (n=4), 4 (n=4) and 8 wk (n=4). Histological analysis for regenerated tissues formed by hPDLSCs was conducted using hematoxylin and eosin, Masson's trichrome and picrosirius red staining. In addition, immunohistochemical staining was performed to observe the sequential expression of osteogenic/cementogenic and periodontal ligament tissue-specific markers associated with periodontal regeneration.
The whole healing process by transplanted hPDLSCs could be broadly divided into four distinctive phases. In the first phase, proliferated hPDLSCs migrated evenly all over the carrier, and collagenous tissues appeared in the form of amorphous collagen matrices. In the second phase, collagen fibers were well arranged among the carriers, and cementoid-like tissues were observed. In the third phase, the formation of mature collagen fibers, resembling Sharpey's fibers, was associated with active mineralization of cementum-like tissues, and in the fourth phase, the maturation of cementum-like tissues was observed on carrier surfaces. Various osteogenic/cementogenic markers related to the regeneration processes were expressed in a well-orchestrated time order. Interestingly, well-organized cementum-like and periodontal ligament fiber-like tissues and cells with early and late osteogenic/cementogenic markers were frequently observed in the secluded area of carrier surfaces. We termed this area the cell-rich zone.
The results from this study clearly demonstrated the sequential histological changes during periodontal tissue regeneration by hPDLSCs. Understanding of this process would potentially enable us to develop better cell-based treatment techniques.
人牙周韧带干细胞（hPDLSCs）在牙周再生中起着关键作用。然而，hPDLSCs 启动的动态细胞愈合过程仍有待阐明。在本研究中，我们通过组织学和免疫组织化学观察，在异位移植模型中评估 hPDLSCs 的再生顺序，该模型是一种经过充分标准化的评估工具，排除了动物体内的固有愈合因素。
从正畸治疗中提取的牙齿（n=12）中分离并鉴定出人牙周韧带干细胞，并用载体将其移植到免疫功能低下小鼠的异位皮下囊中（n=20）。在不同的愈合时间后处死动物：3 d（n=4）、1 周（n=4）、2 周（n=4）、4 周（n=4）和 8 周（n=4）。用苏木精和伊红、马松三色和苦味酸红染色对由 hPDLSCs 形成的再生组织进行组织学分析。此外，进行免疫组织化学染色以观察与牙周再生相关的成骨/成牙骨质和牙周韧带组织特异性标志物的顺序表达。
移植的 hPDLSCs 的整个愈合过程可以大致分为四个不同的阶段。在第一阶段，增殖的 hPDLSCs 均匀迁移到载体上，出现无定形胶原基质形式的胶原组织。在第二阶段，胶原纤维在载体之间排列良好，并观察到类牙骨质样组织。在第三阶段，形成类似于 Sharpey 纤维的成熟胶原纤维，与类牙骨质组织的活跃矿化相关，在第四阶段，观察到载体表面类牙骨质样组织的成熟。与再生过程相关的各种成骨/成牙骨质标志物以协调一致的时间顺序表达。有趣的是，在载体表面的隔离区域经常观察到组织良好的类牙骨质样和牙周韧带纤维样组织以及具有早期和晚期成骨/成牙骨质标志物的细胞，我们将该区域称为细胞丰富区。
本研究的结果清楚地显示了 hPDLSCs 牙周组织再生过程中的顺序组织学变化。对这一过程的理解可能使我们能够开发更好的基于细胞的治疗技术。
