Identification of a Novel Periodontal Ligament Stem Cell Marker

Objectives: Periodontal ligament stem cells (PDLSCs) have been expected to be the useful cell source for periodontal tissue regeneration. However, it is difficult to isolate these cells from PDL cell population. One of the reasons includes that the efficient method to isolate PDLSCs is not established, because the essential markers of PDLSCs are very few. Thus, we focused on mesoderm specific transcript (MEST), which is known as an imprinted gene, and highly expressed in some adult human tumors. In this study, we examined whether this factor was involved in keeping the stemness of PDLSCs.
Methods: We have established two immortalized human PDL fibroblast cell lines; 2-23 strongly expressed the mesenchymal stem cell (MSC) markers (CD90, CD105, and CD146), and possessed the potential to differentiate into osteoblasts and adipocytes in vitro, while 2-52 exhibits low differentiation potential into these cells. We compared the expression of MEST between 2-23 and 2-52 by Western blotting. Furthermore, we examined the effects of MEST siRNA on the expression of MSC markers in 2-23 by flow cytometry, and osteoblastic and adipogenic differentiation of 2-23 by quantitative RT-PCR.
Results: The expression level of MEST in 2-23 was much higher than that in 2-52. The knockdown of MEST in 2-23 decreased the expression of CD90, CD105, and CD146. Furthermore, the knockdown of MEST suppressed the expression of bone-related genes (ALP, BSP, and Osterix) and adipocyte-related genes (PPARγ, LPL, and CEBPA) in 2-23 cultured under the respective inductive condition.
Conclusions: MEST was highly expressed in 2-23 that showed the stem cell-like characteristic. The knockdown of MEST decreased the stemness of 2-23. Therefore, MEST may play a critical role in keeping the stemness of PDLSCs, and be a novel periodontal ligament stem cell marker.