# Characteristics of the Dental Pulp and Periodontal Ligament Stem Cells of the Yucatan Miniature Pig
## 4 Discussion  
Research on mesenchymal stem cell-based therapies for tissue regeneration has grown rapidly. Stem cells have been actively studied, as have their characteristics, as important research topics [20; 21; 22]. Comparative studies between stem cells have been active, such as comparing the characteristics of several stem cells in the same species [20; 21; 22; 23; 24; 25] or comparing interspecific differences [26; 27]. The present study is the first attempt to focus on a comparison of the characteristics between the DPSCs and PDLSCs of a Yucatan miniature pig breed and a domestic farm pig breed. Although the two pig breeds are in the same species, comparative studies of mesenchymal stem cells are necessary because they have different phenotypical characteristics, such as weight, size, skin, and physiological mechanisms [28]. Figure 6: The alkaline phosphatase (ALP) activity of the dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PDLSCs) of the miniature pig breed and the domestic farm pig breed, cultured in osteogenic media at one, two, and three weeks. The ALP activity was significantly lower in the DPSCs and PDLSCs of the miniature pig breed than in the DPSCs and PDLSCs of the domestic farm pig breed (* \(p<0.05\)). The scheme used here to compare the characteristics of the dental pulp stem cells and the periodontal ligament stem cells of the Yucatan miniature pig breed to those of the domestic farm pig breed is presented in Figure 1. In a morphology evaluation, the DPSCs and PDLSCs of the miniature pig breed showed fibroblast-like cell morphologies at the passage 3 confluent monolayer under a light microscope, similar to those of the DPSCs and PDLSCs of the domestic farm pig breed. A fibroblast-like cell shape is one of the features found in mesenchymal stem cells [29]. This result demonstrates that mesenchymal stem cells can be separated from the dental pulp and periodontal ligament tissues of a domestic farm pig breed as well as a miniature pig breed, and successful cultivation was demonstrated in this study. The successful cultivation of mesenchymal stem cells from dental pulp and periodontal ligament tissues was also reported in previous studies using human subjects [30; 31]. The results of the high expression patterns of the mesenchymal stem cell-specific surface markers in the FACS analysis support the contention that the cultured cells from the DP and PDL of the miniature pig breed and the domestic farm pig breed in the present study have the characteristics of multipotent MSCs. [PERSON] et al. [32] conducted a comparison of the proliferation of stem cells from various tissues--in that case, the adipose, bone marrow, ear skin, abdominal skin, and lung tissues of Yucatan miniature pigs--but there has been no report of the DPSCs and the PDLSCs of Yucatan miniature pigs. In the present study, it was found that the proliferation rates of the PDLSCs of both the domestic farm pig breed and the miniature pig breed have no significant differences, except for the day five results, whereas the proliferation of DPSCs was significantly higher in the miniature pig breed. Osteogenic differentiation is an important capability because DPSCs and PDLSCs are widely used in dental disease models. An ALP assay and ARS staining showed that the DPSCs and PDLSCs of the miniature pig breed were significantly less able to undergo osteogenic differentiation compared to those of the domestic farm pig breed. In a comparison of the differentiation ability of the MSCs of the miniature pig breed to those of other species' MSCs, [PERSON] et al. [26] reported that the osteogenic differentiation capacity of miniature pig bone-marrow-derived MSCs was also lower compared to that of human bone-marrow-derived MSCs. One of the limitations of this study is that it is difficult to establish a comparable age for the miniature pig breed and the domestic farm pig breed because they are different breeds.