Preparation of Absorption-Resistant Hard Tissue Using Dental Pulp-Derived Cells and Honeycomb Tricalcium Phosphate.

In recent years, there has been increasing interest in the treatment of bone defects using undifferentiated mesenchymal stem cells (MSCs) in vivo. Recently, dental pulp has been proposed as a promising source of pluripotent mesenchymal stem cells (MSCs), which can be used in various clinical applications. Dentin is the hard tissue that makes up teeth, and has the same composition and strength as bone. However, unlike bone, dentin is usually not remodeled under physiological conditions. Here, we generated odontoblast-like cells from mouse dental pulp stem cells and combined them with honeycomb tricalcium phosphate (TCP) with a 300 µm hole to create bone-like tissue under the skin of mice. The bone-like hard tissue produced in this study was different from bone tissue, i.e., was not resorbed by osteoclasts and was less easily absorbed than the bone tissue. It has been suggested that hard tissue-forming cells induced from dental pulp do not have the ability to induce osteoclast differentiation. Therefore, the newly created bone-like hard tissue has high potential for absorption-resistant hard tissue repair and regeneration procedures.

Geometrical Structure of Honeycomb TCP to Control Dental Pulp-Derived Cell Differentiation.

Recently, dental pulp has been attracting attention as a promising source of multipotent mesenchymal stem cells (MSCs) for various clinical applications of regeneration fields. To date, we have succeeded in establishing rat dental pulp-derived cells showing the characteristics of odontoblasts under in vitro conditions. We named them Tooth matrix-forming, GFP rat-derived Cells (TGC). However, though TGC form massive dentin-like hard tissues under in vivo conditions, this does not lead to the induction of polar odontoblasts. Focusing on the importance of the geometrical structure of an artificial biomaterial to induce cell differentiation and hard tissue formation, we previously have succeeded in developing a new biomaterial, honeycomb tricalcium phosphate (TCP) scaffold with through-holes of various diameters. In this study, to induce polar odontoblasts, TGC were induced to form odontoblasts using honeycomb TCP that had various hole diameters (75, 300, and 500 µm) as a scaffold. The results showed that honeycomb TCP with 300-µm hole diameters (300TCP) differentiated TGC into polar odontoblasts that were DSP positive. Therefore, our study indicates that 300TCP is an appropriate artificial biomaterial for dentin regeneration.

Impact of the Stroma on the Biological Characteristics of the Parenchyma in Oral Squamous Cell Carcinoma.

Solid tumors consist of the tumor parenchyma and stroma. The standard concept of oncology is that the tumor parenchyma regulates the tumor stroma and promotes tumor progression, and that the tumor parenchyma represents the tumor itself and defines the biological characteristics of the tumor tissue. Thus, the tumor stroma plays a pivotal role in assisting tumor parenchymal growth and invasiveness and is regarded as a supporter of the tumor parenchyma. The tumor parenchyma and stroma interact with each other. However, the influence of the stroma on the parenchyma is not clear. Therefore, in this study, we investigated the effect of the stroma on the parenchyma in oral squamous cell carcinoma (OSCC). We isolated tumor stroma from two types of OSCCs with different invasiveness (endophytic type OSCC (ED-st) and exophytic type OSCC (EX-st)) and examined the effect of the stroma on the parenchyma in terms of proliferation, invasion, and morphology by co-culturing and co-transplanting the OSCC cell line (HSC-2) with the two types of stroma. Both types of stroma were partially positive for alpha-smooth muscle actin. The tumor stroma increased the proliferation and invasion of tumor cells and altered the morphology of tumor cells in vitro and in vivo. ED-st exerted a greater effect on the tumor parenchyma in proliferation and invasion than EX-st. Morphological analysis showed that ED-st changed the morphology of HSC-2 cells to the invasive type of OSCC, and EX-st altered the morphology of HSC-2 cells to verrucous OSCC. This study suggests that the tumor stroma influences the biological characteristics of the parenchyma and that the origin of the stroma is strongly associated with the biological characteristics of the tumor.

Preliminary study on the apoptosis mechanism of microwave ablation in tongue cancer Cal-27 cell transplanted tumor in nude mice / 实用口腔医学杂志

Objective: To study the apoptosis mechanism of microwave ablation (MA) in tongue cancer Cal-27 cell transplanted tumor in nude mice. Methods: 20 nude mice with Cal-27 cell subcutaneously transplanted tumor were randomly divided into blank control group, 50 ℃ 1 min MA group, 50 ℃ 2 min MA group and 55 ℃ 2 min MA group (n = 5) respecitvely, and were treated with MA with indiated perameters respectively. The apoptosis of tumor cells was observed by HE staining. The expression of Caspase-3 and PCNA protein was detected by immunohistochemical SP method. Results: HE staining showed that microwave ablation induced apoptosis of the tumor cells. Immunohistochemical results showed that the expression of Caspase-3 protein was significantly up-regulated in the microwave ablation groups compared with the control group (P ＜ 0. 05), and the expression of PCNA protein was significantly decreased (P ＜ 0. 05) . In microwave ablation 55 ℃ 2 min group, the expression of Caspase-3 protein was increased more (P ＜0. 01), and the expression of PCNA protein was decreased more (P ＜ 0. 01) . Conclusion: Microwave ablation may inhibite the proliferation of tongue cancer cells by inducing apoptosis of the cells. The mechanism may be related to the up-regulation of Caspase-3 signaling pathway and down-regulation of PCNA signaling pathway.