WITHDRAWN: Ameloblast-like characteristics of human Hertwig's epithelial rest of Malassez/epithelial rest of Malassez cells via interaction with stem cells from human exfoliated deciduous teeth.

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Effects of ethanol washing and storage duration on primary culture of stem cells from human exfoliated deciduous teeth.

Purpose: Since the oral environment harbors various microorganisms, the removal of contaminants during the primary culture process of stem cells from human exfoliated deciduous teeth (SHEDs) is very important. We investigated optimal methods for primary culture of SHEDs with minimal contamination rates. Materials and methods: Three different storage conditions for deciduous teeth were utilized:1) storing teeth in Hank's Balanced Salt Solution (HBSS) with 3% penicillin and streptomycin (P/S), 2) storing teeth in HBSS with 3% antibiotics and antimycotics (A-A), and 3) storing teeth in HBSS with A-A, and additional washing with 70% ethanol just before primary culture of dental pulp. In addition, the storage time from the extraction of teeth to the primary culture was measured. Results: The contamination rates were about 70% for HBSS with P/S, 40% for HBSS with A-A, and less than 10% for HBSS with A-A and additional washing with 70% ethanol. When the primary culture was conducted within 12 h after teeth extraction, the contamination rate was the lowest in all conditions. Furthermore, when the teeth were delivered in HBSS with A-A and an additional 70% ethanol washing was performed, the contamination rate was 0% until 48 h after teeth extraction. Ethanol washing had little effect on the cellular characteristics and stemness of SHEDs, including their morphology, growth rate, expression of surface markers, and differentiation potential. Conclusions: We suggested that both delivering teeth in HBSS with A-A and additional 70% ethanol washing are critical considerations for the successful culture of SHEDs without contamination.

Non-Syndromic Dentinogenesis Imperfecta Caused by Mild Mutations in COL1A2.

Hereditary dentin defects can be categorized as a syndromic form predominantly related to osteogenesis imperfecta (OI) or isolated forms without other non-oral phenotypes. Mutations in the gene encoding dentin sialophosphoprotein (DSPP) have been identified to cause dentinogenesis imperfecta (DGI) Types II and III and dentin dysplasia (DD) Type II. While DGI Type I is an OI-related syndromic phenotype caused mostly by monoallelic mutations in the genes encoding collagen type I alpha 1 chain (COL1A1) and collagen type I alpha 2 chain (COL1A2). In this study, we recruited families with non-syndromic dentin defects and performed candidate gene sequencing for DSPP exons and exon/intron boundaries. Three unrelated Korean families were further analyzed by whole-exome sequencing due to the lack of the DSPP mutation, and heterozygous COL1A2 mutations were identified: c.3233G>A, p.(Gly1078Asp) in Family 1 and c.1171G>A, p.(Gly391Ser) in Family 2 and 3. Haplotype analysis revealed different disease alleles in Families 2 and 3, suggesting a mutational hotspot. We suggest expanding the molecular genetic etiology to include COL1A2 for isolated dentin defects in addition to DSPP.

The Significance of SDF-1α-CXCR4 Axis in in vivo Angiogenic Ability of Human Periodontal Ligament Stem Cells.

Periodontal ligament stem cells (PDLSCs) are multipotent stem cells derived from periodontium and have mesenchymal stem cell (MSC)-like characteristics. Recently, the perivascular region was recognized as the developmental origin of MSCs, which suggests the in vivo angiogenic potential of PDLSCs. In this study, we investigated whether PDLSCs could be a potential source of perivascular cells, which could contribute to in vivo angiogenesis. PDLSCs exhibited typical MSC-like characteristics such as the expression pattern of surface markers (CD29, CD44, CD73, and CD105) and differentiation potentials (osteogenic and adipogenic differentiation). Moreover, PDLSCs expressed perivascular cell markers such as NG2, αsmooth muscle actin, platelet-derived growth factor receptor ß, and CD146. We conducted an in vivo Matrigel plug assay to confirm the in vivo angiogenic potential of PDLSCs. We could not observe significant vessel-like structures with PDLSCs alone or human umbilical vein endothelial cells (HU-VECs) alone at day 7 after injection. However, when PDLSCs and HUVECs were co-injected, there were vessel-like structures containing red blood cells in the lumens, which suggested that anastomosis occurred between newly formed vessels and host circulatory system. To block the SDF-1α and CXCR4 axis between PDLSCs and HUVECs, AMD3100, a CXCR4 antagonist, was added into the Matrigel plug. After day 3 and day 7 after injection, there were no significant vessel-like structures. In conclusion, we demonstrated the peri-vascular characteristics of PDLSCs and their contribution to in vivo angiogenesis, which might imply potential application of PDLSCs into the neovascularization of tissue engineering and vascular diseases.

In Vivo Angiogenic Capacity of Stem Cells from Human Exfoliated Deciduous Teeth with Human Umbilical Vein Endothelial Cells.

Dental pulp is a highly vascularized tissue requiring adequate blood supply for successful regeneration. In this study, we investigated the functional role of stem cells from human exfoliated deciduous teeth (SHEDs) as a perivascular source for in vivo formation of vessel-like structures. Primarily isolated SHEDs showed mesenchymal stem cell (MSC)-like characteristics including the expression of surface antigens and in vitro osteogenic and adipogenic differentiation potentials. Moreover, SHEDs were positive for NG2, α-smooth muscle actin (SMA), platelet-derived growth factor receptor beta (PDGFRß), and CD146 as pericyte markers. To prove feasibility of SHEDs as perivascular source, SHEDs were transplanted into immunodeficient mouse using Matrigel with or without human umbilical vein endothelial cells (HUVECs). Transplantation of SHEDs alone or HUVECs alone resulted in no formation of vessel-like structures with enough red blood cells. However, when SHEDs and HUVECs were transplanted together, extensive vessel-like structures were formed. The presence of murine erythrocytes within lumens suggested the formation of anastomoses between newly formed vessel-like structures in Matrigel plug and the host circulatory system. To understand underlying mechanisms of in vivo angiogenesis, the expression of angiogenic cytokine and chemokine, their receptors, and MMPs was compared between SHEDs and HUVECs. SHEDs showed higher expression of VEGF, SDF-1α, and PDGFRß than HUVECs. On the contrary, HUVECs showed higher expression of VEGF receptors, CXCR4, and PDGF-BB than SHEDs. This differential expression pattern suggested reciprocal interactions between SHEDs and HUVECs and their involvement during in vivo angiogenesis. In conclusion, SHEDs could be a feasible source of perivascular cells for in vivo angiogenesis.

Expression profile of the stem cell markers in human Hertwig's epithelial root sheath/Epithelial rests of Malassez cells.

Hertwig's epithelial root sheath/Epithelial rests of Malassez (HERS/ERM) cells are unique epithelial cells in the periodontal ligament. They remain in periodontal tissues through-out the adult life, and it is expected that their functional role is to maintain the homeostasis of the periodontium through reciprocal interactions with other periodontal cells. In this study, we investigated whether HERS/ERM cells have primitive stem cell characteristics: those of embryonic stem cells as well as of epithelial stem cells. Primary HERS/ERM cells had typical epithelial cell morphology and characteristics and they maintained for more than five passages. They expressed epithelial stem cell-related genes: ABCG2, ANp63, p75, EpCAM, and Bmi-1. Moreover, the expression of embryonic stem cell markers such as Oct-4, Nanog, and SSEA-4 were detected. Next, we investigated whether the expression of these stem cell markers was maintained during the sub-culture process. HERS/ERM cells showed different expression levels of these stemness genes at each passage, but their expression was maintained throughout the passages. Taken together, our data suggest that a primary culture of HERS/ERM cells contains a population of primitive stem cells that express epithelial stem cell markers and embryonic stem cell markers. Furthermore, these cell populations were maintained during the sub-culturing process in our culture conditions. Therefore, our findings suggest that there is a strong possibility of accomplishing cementum tissue engineering with HERS/ERM cells.