Background Human bone marrow mesenchymal stem cells (hMSCs) present a promising cell source with the potential to be used for curing various intractable diseases, and it is expected that the development of regenerative medicine employing cell‐based therapy would be significantly accelerated when such methods are established. For that, powerful methods for selective growth and differentiation of hMSCs should be developed. Methods We developed an efficient method for hMSC proliferation and differentiation into osteoblasts and adipocytes using gravity‐controlled environments. Results The results indicate that the average doubling time of hMSCs cultured in a regular maintenance medium under microgravity conditions (0.001 G) was 1.5 times shorter than that of cells cultured under natural gravity conditions (1.0 G). Furthermore, 99.2% of cells grown in the microgravity environment showed the expression of hMSC markers, as indicated by flow cytometry analysis. Osteogenic and adipogenic differentiation of hMSCs expanded in the microgravity environment was enhanced under microgravity and hypergravity conditions, respectively, as evidenced by the downregulation of hMSC markers and upregulation of osteoblast and adipocyte markers, respectively. Most cells differentiated into osteoblasts in the microgravity environment after 14 days (~80%) and adipocytes in the hypergravity environment after 12 days (~90%). Conclusions Our results indicate that hMSC proliferation and selective differentiation into specific cell lineages could be promoted under microgravity or hypergravity conditions, suggesting that cell culture in the gravity‐controlled environment is a useful method to obtain cell preparations for potential clinical applications.
Surface wettability is one of most important indexes for understanding the interfacial characteristics between a solid surface and a liquid, especially such physico-chemical properties as hydrophilicity and water repellency. Recently, non-contact wettability assessment by monitoring the behavior of liquid covering a sample surface by jet-flow application to the liquid has been proposed. This method is applicable to the in-liquid assessment of high wettability materials for which it is difficult to measure the contact angle, such as cultured cells in a liquid culture medium. However, when the flow is dirty, the contamination of the cell culture system by particles (e.g. microorganisms, virus, and aerosols) may occur. To solve this problem, we developed a contamination-free non-contact wettability assessment system that is composed of a clean-air source having a particle filter and an automated system for image processing instrumentation and motorized alignment device for sample positioning. We confirmed that the filtered air-jet contained no particles, although over ten thousand particles had been included in the air source. Furthermore, we detected no microorganisms on agar culture plates, which had been exposed to the air-jet before being incubated. With the image instrumentation, we automatically measured the liquid-squeezed size, which was the main index of surface wettability. The motorized alignment device allowed us to control the sample position without human direct operation. This developed system is compatible with wettability assessment in a high-level clean environment such as quality control of culture cells for regenerative medicine and in vitro assay of drug efficacy and safety.
This study proposed a concept for evaluating biological functions by its physico-chemical properties such as surface wettability. To realize the concept, we have to prepare two elements; (1) systems for assessing the physico-chemical properties of biological objects and (2) a database connecting physico-chemical properties to biological functions. In this study, non-contact wettability assessment system was used as an apparatus for assessing surface wettability, one of the most common physico-chemical properties. Because this system can eliminate a physical contact between a probe and an object, there is an advantage on contamination reduction. Furthermore, in-liquid evaluation is feasible by the system. Therefore, this study aimed to the evaluation of cellular functions via the surface wettability on the cultivated cellular tissues.
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