論文

Hyperthermia has been studied as a noninvasive cancer treatment. Cancer cells show stronger thermal cytotoxicity than normal cells, which is exploited in hyperthermia. However, the absence of methods evaluating the thermal cytotoxicity in cells prevents the development of hyperthermia. To investigate the thermal cytotoxicity, culture temperature should be regulated. We, thus, developed a culture system regulating culture temperature immediately and accurately by employing metallic culture vessels. Michigan Cancer Foundation-7 cells and normal human dermal fibroblasts were used for models of cancer and normal cells. The findings showed cancer cells showed stronger thermal cytotoxicity than normal cells, which is quantitatively different from previous reports. This difference might be due to regulated culture temperature. The thermal stimulus condition (43 °C/30 min) was, further, focused for assays. The mRNA expression involving apoptosis changed dramatically in cancer cells, indicating the strong apoptotic trend. In contrast, the mRNA expression of heat shock protein (HSP) of normal cells upon the thermal stimulus was stronger than cancer cells. Furthermore, exclusively in normal cells, HSP localization to nucleus was confirmed. These movement of HSP confer thermotolerance to cells, which is consistent with the different thermal cytotoxicity between cancer and normal cells. In summary, our developed system can be used to develop hyperthermia treatment.

In this study, we proposed an in vitro tumor model to simulate the mechanical microenvironment and investigate the effect of compressive stress on the invasion process of malignant tumors. It has been pointed out that the biomechanical environment, as well as the biochemical environment, could affect the transformation of cancer cell migration, invasion, and metastasis. We hypothesized that the solid stress caused by the exclusion of surrounding tissue could transform tumor cells from noninvasive to invasive phenotypes. Colorectal cell spheroids were embedded and cultured in agarose gels of varying concentrations to simulate the earliest stages of tumor formation and invasion. The spheroids embedded in gels at higher concentrations showed peculiar growth after 72 h of culture, and the external compressive loading imposed on them caused peculiar growth even in the gels at lower concentrations. In conclusion, the mechanical microenvironment caused the transformation of tumor cell phenotypes, promoting the growth and invasion of tumor cell spheroids.

Static mechanical compression is a biomechanical factor that affects the progression of melanoma cells. However, little is known about how dynamic mechanical compression affects the progression of melanoma cells. In the present study, we show that mechanical intermittent compression affects the progression rate of malignant melanoma cells in a cycle period-dependent manner. Our results suggest that intermittent compression with a cycle of 2 h on/2 h off could suppress the progression rate of melanoma cells by suppressing the elongation of F-actin filaments and mRNA expression levels related to collagen degradation. In contrast, intermittent compression with a cycle of 4 h on/4 h off could promote the progression rate of melanoma cells by promoting cell proliferation and mRNA expression levels related to collagen degradation. Mechanical intermittent compression could therefore affect the progression rate of malignant melanoma cells in a cycle period-dependent manner. Our results contribute to a deeper understanding of the physiological responses of melanoma cells to dynamic mechanical compression.

Various culture devices have been developed as fundamental technologies for facilitating bioengineering studies. Culture devices are designed to prepare specific culture environments. Thus, both macrostructures and surface micromorphology should be considered in the device design. Although fabricating devices with elaborate designs incurs high production costs, disposable materials are typically used for culture devices. However, some metallic materials are strong, stable, and biocompatible. Bioengineers have not applied these materials to culture devices because of the difficulty of processing. An emerging technology using three-dimensional (3D) printing has been developed, which can produce complex designs using metal. We demonstrate the applicability and potential of metal 3D printing for fabricating culture devices toward the development of the bioengineering discipline. As a specific example, we fabricated metallic culture devices where the environment of cultured tissues can be improved. One of the biggest factors determining the culture environment is active media supply. To attain active media supply to the tissue, devices having culture surfaces with mesh structures having holes far larger than cells were proposed. Cell sheets were cultured as tissue models, realizing tissue culture with such structures. The cultured tissue showed increased metabolism, indicating enhanced media supply owing to mesh surfaces. The biocompatibility of the 3D printed metal device was confirmed by viability assays on cultured cells, and reusability of the device was confirmed by mechanical and biochemical evaluations. We believe this study serves as a reference for using metallic 3D printing as an option for fabricating culture devices, which will promote bioengineering research.