Department of Pediatric Dentistry, School of Stomatology, Fourth Military Medical University, Xi'an, China.
Bone. 2011 Jun 1;48(6):1417-26. doi: 10.1016/j.bone.2011.02.016. Epub 2011 Mar 1.
Dental follicle cells (DFCs) are believed contain the precursor cells of the periodontium and can form cell sheets by secreting extracellular matrix (ECM) proteins. Cell sheet engineering has been recently developed and applied successfully in the field of tissue regeneration. However, research on the in vitro characteristics of DFC sheets is lacking and an assessment of whether DFC sheets can produce periodontal tissues in vivo has not been reported. To test the characteristics and applicability of DFC sheets in this field, we established a co-culture system of rat DFCs and Hertwig's epithelial root sheath (HERS) cells in vitro, and included the following controls: a co-culture of DFCs and alveolar mucosa epithelial cells, DFCs with no cells in the upper chamber, and DFCs cultured without an upper chamber. After 3 weeks of co-culturing the cells, the DFC sheets were transplanted into adult male rats' omenta. One week after co-culturing DFCs with HERS cells, mRNA levels of collagen type I (COL-1), alkaline phosphatase (ALP), runt related transcription factor 2 (Runx 2) and bone sialoprotein (BSP) were increased significantly. In addition, after 3 weeks of co-culturing the cells, the numbers of ALP-, osteocalcin (OCN)-, BSP- and osteoprotegerin (OPG)-positive DFCs increased. The DFCs also produced more calcified nodules and exhibited an increased number of subcellular organelles, which are important for protein synthesis and secretion. Moreover, gap junctions were found between the experimental DFCs within the sheet. Five weeks of in vivo growth of DFC sheets pre-exposed to HERS cells led to the formation of cementum-like tissues, which were positive for OCN, BSP and OPG, as well as the formation of periodontal ligament-like tissues, which were positive for COL-1. In contrast, control cells only produced fibrous tissues. These results indicate that the DFC sheets induced by HERS cells are able to produce periodontal tissues through epithelial-mesenchymal interactions. Therefore, DFC sheets may be useful in the field of periodontium regeneration.
牙囊细胞（DFCs）被认为包含牙周组织的前体细胞，并能通过分泌细胞外基质（ECM）蛋白形成细胞片。细胞片工程最近得到了发展，并成功应用于组织再生领域。然而，DFC 片的体外特性研究尚缺乏，DFC 片是否能在体内产生牙周组织也尚未有报道。为了检验 DFC 片在这一领域的特性和适用性，我们在体外建立了大鼠 DFCs 和 Hertwig 上皮根鞘（HERS）细胞的共培养体系，并设置了以下对照：DFCs 与牙槽黏膜上皮细胞的共培养、上室无细胞的 DFCs 以及上室无细胞培养的 DFCs。共培养 3 周后，将 DFC 片移植到成年雄性大鼠的大网膜中。与 HERS 细胞共培养 1 周后，DFCs 中胶原 I（COL-1）、碱性磷酸酶（ALP）、 runt 相关转录因子 2（Runx 2）和骨涎蛋白（BSP）的 mRNA 水平显著增加。此外，共培养 3 周后，ALP、骨钙素（OCN）、BSP 和骨保护素（OPG）阳性的 DFC 数量增加。DFCs 还产生了更多的钙化结节，并表现出更多的亚细胞细胞器，这对蛋白质的合成和分泌很重要。此外，在实验性 DFC 片中发现了细胞片之间的缝隙连接。预先暴露于 HERS 细胞的 DFC 片在体内生长 5 周后，形成了牙骨质样组织，该组织对 OCN、BSP 和 OPG 呈阳性，同时也形成了牙周韧带样组织，该组织对 COL-1 呈阳性。相比之下，对照细胞仅产生纤维组织。这些结果表明，HERS 细胞诱导的 DFC 片通过上皮-间充质相互作用能够产生牙周组织。因此，DFC 片可能在牙周组织再生领域有应用价值。
