Two novel mechanisms for maintenance of stemness in mesenchymal stem cells: SCRG1/BST1 axis and cell–cell adhesion through N-cadherin

Summary: Mesenchymal stem cells (MSCs) retain the ability to self-renew and differentiate into mesenchymal cells. Therefore, human MSCs are suitable candidates for use in regenerative medicine and cell therapies. Upon activation by tissue damage, MSCs contribute to tissue repair through a multitude of processes such as self-renewal, migration, and differentiation. However, loss of self-renewal and multi-lineage differentiation potential occurs at a high rate during cell doubling. Effective MSC therapies require the establishment of new techniques that preserve MSC multipotency after lengthy cell expansions. Here, two novel mechanisms are described for maintenance of stemness in MSCs via scrapie responsive gene 1 (SCRG1)/bone marrow stromal cell antigen-1 (BST1) ligand–receptor combination and cell–cell adhesion through N-cadherin. These two mechanisms findings provide a valuable tool for regenerative medicine and cell therapeutic methods that require the ex vivo expansion of human MSCs while maintaining native stem cell potential. Keywords: Mesenchymal stem cells, Stemness, CD271/LNGFR, CD106/VCAM1, SCRG1/BST1 axis, N-cadheri

Vascular Cell-Like Potential of Undifferentiated Ligament Fibroblasts to Construct Vascular Cell-Specific Marker-Positive Blood Vessel Structures in a PI3K Activation-Dependent Manner

Objective: To evaluate whether fibroblasts derived from periodontal ligament (PDL) retain the ability to differentiate into putative vascular cells and construct vascular cell-specific marker-positive blood vessel structures. We also evaluated the morphological features of the structure and investigated the intracellular molecular mechanism underlying the angiogenic activity of these cells. Methods: Single cell-derived cultures (SCDCs) were established from primary rat ligament fibroblast cultures, and their expression of ligament cell-, mesenchymal stem cell (MSC)-, and vascular cell-specific markers was evaluated by RT-PCR and immunocytochemistry. The ability of the cells to construct a blood vessel structure was evaluated in a three-dimensional type I collagen scaffold. The morphological and immunohistological characteristics of the structure were then evaluated. Results: Each SCDC expressed endothelial cell (EC) and smooth muscle cell-specific markers, in addition to MSC- and ligament cell-specific markers. SCDC2 cells, which abundantly expressed the EC markers Flk-1 and Tie-2, vigorously constructed a blood vessel structure in a phosphoinositide 3-kinase activation-dependent manner. Conclusion: PDL fibroblasts have the potential to construct an EC marker-positive blood vessel-like structure. Consequently, the fibroblastic lineage in ligament tissue could be a candidate precursor for construction of a vascular system around damaged ligament tissue to facilitate its regeneration

Novel biological activity of ameloblastin in enamel matrix derivative

Objective Enamel matrix derivative (EMD) is used clinically to promote periodontal tissue regeneration. However, the effects of EMD on gingival epithelial cells during regeneration of periodontal tissues are unclear. In this in vitro study, we purified ameloblastin from EMD and investigated its biological effects on epithelial cells. Material and Methods Bioactive fractions were purified from EMD by reversed-phase high-performance liquid chromatography using hydrophobic support with a C18 column. The mouse gingival epithelial cell line GE-1 and human oral squamous cell carcinoma line SCC-25 were treated with purified EMD fraction, and cell survival was assessed with a WST-1 assay. To identify the proteins in bioactive fractions of EMD, we used proteome analysis with two-dimensional gel electrophoresis followed by identification with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Results Purified fractions from EMD suppressed proliferation of GE-1 and SCC-25. LC-MS/MS revealed that ameloblastin in EMD is the component responsible for inhibiting epithelial cell proliferation. The inhibitory effect of ameloblastin on the proliferation of GE-1 and SCC-25 was confirmed using recombinant protein. Conclusion The inhibitory effects of EMD on epithelial cell proliferation are caused by the biological activities of ameloblastin, which suggests that ameloblastin is involved in regulating epithelial downgrowth in periodontal tissues

Enhancement of Anti-Inflammatory and Osteogenic Abilities of Mesenchymal Stem Cells via Cell-to-Cell Adhesion to Periodontal Ligament-Derived Fibroblasts

Mesenchymal stem cells (MSCs) are involved in anti-inflammatory events and tissue repair; these functions are activated by their migration or homing to inflammatory tissues in response to various chemokines. However, the mechanism by which MSCs interact with other cell types in inflammatory tissue remains unclear. We investigated the role of periodontal ligament fibroblasts (PDL-Fs) in regulating the anti-inflammatory and osteogenic abilities of bone marrow-derived- (BM-) MSCs. The expression of monocyte chemotactic protein- (MCP-)1 was significantly enhanced by stimulation of PDL-Fs with inflammatory cytokines. MCP-1 induced the migratory ability of BM-MSCs but not PDL-Fs. Expression levels of anti-inflammatory and inflammatory cytokines were increased and decreased, respectively, by direct-contact coculture between MSCs and PDL-Fs. In addition, the direct-contact coculture enhanced the expression of MSC markers that play important roles in the self-renewal and maintenance of multipotency of MSCs, which in turn induced the osteogenic ability of the cells. These results suggest that MCP-1 induces the migration and homing of BM-MSCs into the PDL inflammatory tissue. The subsequent adherence of MSCs to PDL-Fs plays an immunomodulatory role to terminate inflammation during wound healing and upregulates the expression stem cell markers to enhance the stemness of MSCs, thereby facilitating bone formation in damaged PDL tissue