Characterization of Stem Cells in the Orofacial Region

牙科生物科由Songtao Shi博士领导，目前包括Masako Miura，Beng-Moo Seo，Wataru Sonoyama，Yasuo Miura和Carolyn Coppe博士。我们的研究主要集中在牙齿/颅面相关干细胞的分离和鉴定，包括牙髓干细胞，牙周膜干细胞和骨髓基质干细胞。 出生后骨髓基质干细胞（BMSSC）和牙髓干细胞（DPSC）是多能干细胞，能够分化成各种细胞类型，包括但不限于成骨细胞/成牙本质细胞、脂肪细胞和神经细胞。以前的研究也表明BMSSCs能够分化为软骨细胞和肌肉细胞。在体内移植后，BMSSC和DPSC一致地分化成功能性成骨细胞/成牙本质细胞以分别产生骨/骨髓器官结构和牙本质/牙髓复合体。然而，在启动和维护的骨/骨髓器官和牙本质/牙髓复合体的详细机制尚未确定。我们发现，BMSSC和DPSC形成矿化组织的时间相似，导致BMSSC形成骨/骨髓器官，DPSC形成牙本质/牙髓复合体。碱性成纤维细胞生长因子（bFGF）和基质金属蛋白酶9（MMP-9，明胶酶B）的表达升高被认为是与骨髓造血干细胞移植的形成，但不是在结缔组织DPSC移植。牙本质涎蛋白（DSP）的表达特异性地标志着DPSC移植物中的牙本质合成。此外，DPSCs还可以在人牙本质表面形成修复性牙本质样组织。我们的研究提供了直接的证据表明，BMSSCs和DPSCs介导的成骨和牙本质形成，分别可能是由不同的机制，导致矿化和非矿化组织的不同组织。 牙周病是最常见的细菌感染之一，导致牙周组织包括牙周韧带（PDL），牙骨质和骨的破坏。它们是成年人牙齿脱落的主要原因，并在全球范围内造成重大的公共卫生负担。牙周膜（PDL）是一种特殊的结缔组织，连接牙骨质和牙槽骨，以维持牙齿原位、支持牙齿功能并保持组织稳态。我们测试的概念，人类牙周膜含有干细胞，可用于牙周组织再生。我们首次证明PDL干细胞（PDLSC）存在于PDL组织区室中，并且它们表达间充质干细胞标志物STRO-1和CD 146/MUC 18。在确定的培养条件下，PDLSC能够在体外分化为成牙骨质细胞样细胞、脂肪细胞和胶原形成细胞。PDLSC还表现出产生牙骨质/PDL样结构的能力，并有助于体内牙周组织修复，当移植到免疫功能低下的啮齿动物。PDLSC具有在体内生成牙骨质/PDL样组织的潜力。重要的是，人PDLSC可以从容易获得的组织资源获得，并出于治疗目的离体扩增。PDLSC介导的组织再生可能为牙周病破坏的牙齿支持组织的重建提供一种有前途的治疗方法。

The Dental Biology Unit is directed by Dr. Songtao Shi and currently includes Drs. Masako Miura, Byoung-Moo Seo, Wataru Sonoyama, Yasuo Miura and Carolyn Coppe. Our research is focused on isolation and characterization of dental/craniofacial associated stem cells including stem cells derived from Dental Pulp, periodontal ligament and bone marrow stromal. Postnatal bone marrow stromal stem cells (BMSSCs) and dental pulp stem cells (DPSCs) are multipotent stem cells, capable of differentiating into various cell types including, but not limited to, osteoblasts/odontoblasts, adipocytes, and neural cells. Previous studies also demonstrated that BMSSCs were able to differentiate into chondrocytes and muscle cells. Upon in vivo transplantation, BMSSCs and DPSCs consistently differentiate into functional osteo/dontoblasts to generate a bone/marrow organ structure and a dentin/pulp complex, respectively. However, the detailed mechanisms involved in the initiation and maintenance of the bone/marrow organ and dentin/pulp complex have yet to be determined. We revealed that BMSSCs and DPSCs share a similar timing for forming mineralized tissue, leading to the establishment of a bone/marrow organ for BMSSCs and a dentin/pulp complex for DPSCs. Elevated expression of basic fibroblast growth factor (bFGF) and matrix metalloproteinase 9 (MMP-9, gelatinase B) was found to be associated with the formation of hematopoietic marrow in BMSSC transplants, but not in the connective tissue of DPSC transplants. The expression of dentin sialoprotein (DSP) specifically marked dentin synthesis in DPSC transplants. Moreover, DPSCs were found to be able to generate reparative dentin-like tissue on the surface of human dentin in vivo. Our study provided direct evidence to suggest that osteogenesis and dentinogenesis mediated by BMSSCs and DPSCs, respectively, may be regulated by distinct mechanisms, leading to the different organization of the mineralized and non-mineralized tissues. Periodontal diseases are one of the most common bacterial infections leading to the destruction of periodontal tissues including periodontal ligament (PDL), cementum, and bone. They are the major cause of tooth loss in adults and post a significant public health burden worldwide. Periodontal ligament (PDL) is a specialized connective tissue that connects cementum and alveolar bone to maintain teeth in situ, support teeth for function, and preserve tissue homeostasis. We tested the notion that human PDL contains stem cells that may be utilized for periodontal tissue regeneration. We demonstrated for the first time that PDL stem Cells (PDLSCs) subsisted within PDL tissue compartment and they expressed the mesenchymal stem cell markers, STRO-1 and CD146/MUC18. Under defined culture conditions, PDLSCs were able to differentiate into cementoblast-like cells, adipocytes, and collagen-forming cells in vitro. PDLSCs also exhibited the capacity to generate a cementum/PDL-like structure and contribute to periodontal tissue repair in vivo, when transplanted into immunocompromised rodents. PDLSCs have potentials to generate cementum/PDL-like tissue in vivo. Importantly, human PDLSCs can be obtained from an easily accessible tissue resource and expanded ex vivo for therapeutic purposes. PDLSC-mediated tissue regeneration may provide a promising therapy for the reconstruction of tooth supporting tissues destroyed by periodontal diseases.