Current cell models for bioengineering a salivary gland: a mini‐review of emerging technologies

Oral Diseases (2013) 19 , 236–244 Saliva plays a major role in maintaining oral health. Patients afflicted with a decrease in saliva secretion (symptomatically, xerostomia) exhibit difficulty in chewing and swallowing foods, tooth decay, periodontal disease, and microbial infections. Despite recent improvements in treating xerostomia (e.g., saliva stimulants, saliva substitutes, and gene therapy), there is a need of more scientific advancements that can be clinically applied toward restoration of compromised salivary gland function. Here we provide a summary of the current salivary cell models that have been used to advance restorative treatments via development of an artificial salivary gland. These models represent initial steps toward clinical and translational research, to facilitate creation of clinically safe salivary glands. Further studies in salivary cell lines and primary cells are necessary to improve survival rates, cell differentiation, and secretory function. Additionally, the characterization of salivary progenitor and stem cell markers are necessary. Although these models are not fully characterized, their improvement may lead to the construction of an artificial salivary gland that is in high demand for improving the quality of life of many patients suffering from salivary secretory dysfunction.     

Dedifferentiated Fat (DFAT) cells: A cell source for oral and maxillofacial tissue engineering

Tissue engineering is a promising method for the regeneration of oral and maxillofacial tissues. Proper selection of a cell source is important for the desired application. This review describes the discovery and usefulness of dedifferentiated fat (DFAT) cells as a cell source for tissue engineering. Dedifferentiated Fat cells are a highly homogeneous cell population (high purity), highly proliferative, and possess a multilineage potential for differentiation into various cell types under proper in vitro inducing conditions and in vivo. Moreover, DFAT cells have a higher differentiation capability of becoming osteoblasts, chondrocytes, and adipocytes than do bone marrow‐derived mesenchymal stem cells and/or adipose tissue‐derived stem cells. The usefulness of DFAT cells in vivo for periodontal tissue, bone, peripheral nerve, muscle, cartilage, and fat tissue regeneration was reported. Dedifferentiated Fat cells obtained from the human buccal fat pad (BFP) are a minimally invasive procedure with limited esthetic complications for patients. The BFP is a convenient and accessible anatomical site to harvest DFAT cells for dentists and oral surgeons, and thus is a promising cell source for oral and maxillofacial tissue engineering.     

Beagle犬脂肪基质干细胞的培养及分化研究

目的：体外培养Beagle犬脂肪基质干细胞（dog adipose-derived stromal cells，dADSCs），定向诱导分化为脂肪、成骨细胞，为口腔组织工程提供种子细胞。方法：取Beagle犬皮下脂肪组织，剪碎，经Ⅰ型胶原酶消化培养犬脂肪基质干细胞，取第3代细胞鉴定其来源及干细胞标记并向脂肪、成骨细胞诱导分化。结果：该细胞波形丝蛋白表达阳性，角蛋白表达阴性，CD44表达阳性；成脂诱导后，经油红O染色可见细胞内脂滴的积累；成骨诱导后，ALP、钙结节、骨钙素、Ⅰ型胶原均阳性表达。结论：Beagle犬脂肪组织中存在着具有能分化为脂肪、成骨细胞的脂肪基质干细胞，此脂肪基质干细胞可作为口腔组织工程种子细胞来源。     

Establishment of a convenient system for the long-term culture and study of non-neoplastic human salivary gland epithelial cells

Epithelial cells appear to play an important role in the initiation and maintenance of autoimmune lesions in the salivary glands of patients with Sjögren's syndrome. Therefore, the detailed study of immunological function of salivary gland epithelial cells (SGEC) may provide useful information for the understanding of Sjögren's syndrome pathogenesis. In this report we aimed to formulate a protocol for the establishment of human non‐neoplastic SGEC lines as a tool for the study of the physiology and pathophysiology of these cells. Pointing towards a practical approach, we sought to establish SGEC lines from quite a limited amount of biopsy tissue obtained during the diagnostic evaluation of patients. Herein, the favorable conditions for the long‐term maintenance of human non‐neoplastic SGEC lines are presented and involve the successive application of a serum‐containing and a serum‐free culture medium, supplemented with essential epithelial growth factors. This protocol has been found reliable and convenient, as attested by the reproducible establishment of non‐neoplastic SGEC lines. The analysis of SGEC phenotypic features, as well as a coculture system for the study of interactions between epithelial cells and lymphocytes, are also described. Such techniques may provide valuable means for the functional and molecular investigation of human SGEC and particularly for the study of Sjögren's syndrome and other disorders of glandular epithelia.     

人乳牙牙髓干细胞和成人牙髓干细胞研究进展

近年来,成体干细胞不断地从不同的组织中被分离出来,该类细胞具有多向分化潜能、较强的增殖能力和持久的自我更新能力,具备充当组织工程种子细胞的天然优势。2000年和2003年,研究者先后从成人牙髓组织和人乳牙牙髓组织中分离出具有干细胞特征的细胞,这两种细胞的发现对牙组织工程将产生重要的意义。现就这两种成体干细胞的研究进展做一综述,并展望其应用前景。     

Immunohistochemistry and ultrastructure of myoepithelium and modified myoepithelium of the ducts of human major salivary glands: histogenetic implications for salivary gland tumors

The organization of salivary gland ducts, especially the presence or absence of myoepithelial cells, is central to histogenetic approaches to the classification of salivary gland tumors. Striated and excretory ducts are reported to be devoid of myoepithelial cells but do contain basal cells. To investigate the nature of such basal cells, tissue sections of normal human salivary glands were examined by means of immunohistochemical, ultrastructural, and fluorescent microscopic techniques. With the use of a mouse monoclonal anticytokeratin antibody (3 12C8-1) that, in salivary glands, is specific for myoepithelial cells, these cells associated with acini and intercalated ducts were strongly stained, as were the basal cells of striated and excretory ducts in each case. Ultrastructurally, some basal cells of both striated and excretory ducts had narrow, elongated cellular processes or the main portion of the cell containing parallel arrays of microfilaments with linear densities and micropinocytotic vesicles, whereas in other basal cells tonofilament bundles predominated. A similar range of cytoplasmic features existed in myoepithelial cells associated with acinar and intercalated duct cells. In addition, some duct basal cells have a complement of actin filaments similar to classic myoepithelium of acini and intercalated ducts. Striated and excretory ducts of human salivary glands, therefore, contain fully differentiated and modified myoepithelial cells, both of which express a specific cytokeratin polypeptide that is absent from duct luminal and acinar cells. Differentiation patterns in the intralobular and interlobular ducts suggest that these regions of salivary gland parenchyma cannot be excluded as histogenetic sites for the induction of salivary gland tumors in which neoplastic myoepithelial cells have been shown to have a major role.     

Chondrogenic potential of stem cells from human exfoliated deciduous teeth in vitro and in vivo

Objective. The aim of this study was to investigate the chondrogenic potential of stem cells from human exfoliated teeth (SHED). Materials and methods. SHED cultures were isolated from human exfoliated deciduous teeth. Colony-forming capacity, odonto/osteogenic and adipogenic potential were measured. SHED were cultured for 2 weeks in chondrogenic differentiation medium containing dexamethasone, insulin, ascorbate phosphate, TGF-β3 and bFGF. Toluidine blue staining and safranin O staining were used for chondrogenesis analysis. The related markers, type II collagen and aggrecan, were also investigated using immunohistochemistry. SHED were seeded onto the β-TCP scaffolds and transplanted into the subcutaneous space on the back of nude mice. The transplants were recovered at 2, 4 and 8 weeks post-transplantation for analysis. Results. SHED showed colony-forming capacity, odonto/osteogenic and adipogenic differentiation capacity. Chondrogenic differentiation was confirmed by toluidine blue staining, safranin O staining, type II collagen and aggrecan immunostaining. After in vivo transplantation, SHED recombined with β-TCP scaffolds were able to generate new cartilage-like tissues. Conclusions. The ?ndings demonstrate the chondrogenic differentiation capacity of SHED both in vitro and in vivo models, suggesting the potential of SHED in cartilage tissue engineering.     

骨髓基质干细胞片层的制备及其在组织工程骨中应用的初步研究

目的：探讨骨髓基质干细胞（bone marrow stromal cells,BMSCs）片层（cell sheet）的制备方法,并观察其在实验犬体内构建组织工程骨时的成骨作用。方法：密度梯度离心法获取实验犬骨髓基质干细胞,经成骨诱导培养后,利用温度感应性培养皿（temperature-responsive culture dish）制备细胞片层后在体外包裹犬同种异体脱钙骨基质（demineralized bone matrix,DBM）,相差显微镜和扫描电镜观察细胞及片层形态;将复合体植入实验犬背阔肌筋膜下,组织学方法观察术后组织工程骨的骨形成情况。结果：细胞片层成功制备,并与支架材料复合良好,术后16周组织学显示形成类似板层骨的致密骨组织。结论：利用温度反应性培养皿可成功制备BMSC细胞片层,细胞片层包裹支架材料后在实验动物体内可形成具有类似板层骨结构的组织工程骨。     

大鼠唾液腺细胞体外原代培养的一种新方法

目的 建立大鼠唾液腺上皮细胞体外原代培养模型,为体外研究唾液腺疾病提供种子细胞。方法 在无菌条件下取出生1~2 d的Wistar大鼠腮腺组织,手术显微镜下去除腺体包膜,以无血清培养基( kerotinocyte-SFM )为培养液,并添加表皮生长因子( rat epidermal growth factor, rEGF )、牛垂体提取物(bovine pituitary extract,BPE)、氢化可的松(hydrocortisone,HC)、转铁蛋白(transferrin,Tf)、胰岛素(insulin,INS)等因子,应用组织块培养法进行培养。用倒置相差显微镜观察培养细胞体外生长的形态特征。用H-E染色及细胞角蛋白、波形蛋白免疫组织化学染色对培养的细胞进行形态学检查和鉴定。结果 培养的腮腺上皮细胞为三角形、多边形、圆形、短梭形,细胞单层生长,连接疏松。H-E染色可见细胞多为圆形,核蓝染,细胞有突起、细胞间桥。细胞角蛋白染色阳性,证实所培养细胞为上皮来源;Vimentin、actin和calponin染色细胞大部分呈阳性,进一步确定细胞主要为肌上皮细胞。原代细胞在3~5 d内保持良好的生长状态,并存活1周左右。结论 组织块培养法可以简捷、快速地获得大鼠腮腺上皮细胞,成功建立Wistar大鼠腮腺上皮细胞的体外模型。     

Long‐Term Results Comparing Xenogeneic Collagen Matrix and Autogenous Connective Tissue Grafts With Coronally Advanced Flaps for Treatment of Dehiscence‐Type Recession Defects

Background: Although connective tissue grafts with coronally advanced flaps (CTG + CAF) have been deemed the gold standard for recession defect treatment, to provide adequate recession coverage, the periodontal profession continues to pursue lower‐morbidity, patient‐preferred substitutes that are more convenient and of unlimited supply. Methods: Using a randomized, controlled, and masked contralateral comparison of matched‐pair, within‐patient recession defects, collagen matrix (CMX) + CAF therapy was compared with CTG + CAF at 6 months and 5 years. The primary efficacy endpoint was percentage of root coverage (RC). Secondary efficacy parameters included width of keratinized tissue (KTw), probing depth (PD), clinical attachment level (CAL), clinician rating of color and texture compared with surrounding tissues, and patient esthetic satisfaction. Results: Seventeen patients were available for the 5‐year recall. Mean RC between 6 months and 5 years changed from 89.5% to 77.6% for CMX + CAF test sites and 97.5% to 95.5% for CTG + CAF control sites. KTw averaged >3 mm for both test and control sites at 5 years. PD was equivalent at all time points. The 6‐month to 5‐year changes for RC, KTw, and PD were not significantly different between therapies. CAL change from 6 months to 5 years was greater for CTG + CAF (0.26 mm) than CMX + CAF (?0.21 mm). Tissue color match to surrounding tissues remained similar for both therapies throughout the study. There was a difference in tissue texture at both 6 months and 5 years, with CMX + CAF sites tending to be “equally firm” and CTG + CAF sites “more firm.” Patient satisfaction was high, with no statistical difference in satisfaction between therapies at any time point. Conclusion: When balanced with patient‐reported satisfaction, clinical rankings of esthetics, and control and historical RC results reported by other investigators, CMX + CAF appears to present a viable and long‐term alternative to traditional CTG + CAF therapy.     

A simple, yet accurate method for detecting and quantifying secretions from human minor salivary glands using the iodine-starch reaction

The lack of published information about the minor salivary glands is due in part to the difficulties experienced in collecting and quantifying their secretions. In fact, no method exists for measuring their secretions that is both simple and accurate. This investigation examined the accuracy of our newly developed method (which simply employs the iodine-starch reaction) in 10 healthy non-medicated adults. A strip painted with a solution of iodine in absolute alcohol then with a fine starch powder mixed with castor oil was placed at a designated location on the lower-lip mucosa for 2 min to collect saliva. Black-stained spots of various sizes corresponding to the individual glands could be accurately visualized. After removal of the strip, the total stained area (mm2) was calculated by digitizing the spot areas using a computer system. The correlation coefficient (r) between known volumes of saliva and stain size was 0.995, indicating a close correlation. The correlation coefficient (r) between area values obtained in the first trial in each subject (Y) and the second (X; 10 min later) was 0.963, and the simple regression equation was close to Y=X, indicating good reproducibility. The mean flow rate microl/cm2 per min) obtained by converting mean total area to volume and thence to flow rate was 0.49+/-0.26, in good agreement with published values obtained by others. These results suggest that our newly developed method allows both the distribution and secretion rate of the minor salivary glands to be observed, and that it should be of practical value due to its simplicity, accuracy, and reproducibility.