A technique of using cells isolated from a tissue in testing or examination is an essential method in the biotechnology-related fields. It is widely used in diagnosing a disease or pathological condition, searching for a new drug and evaluating the efficacy of a drug, or in animal inspection, plant inspection, testing for environmental pollutants, and so on. Thus, cells and the like used in the biotechnology field have been greatly diversified.
In recent years, studies on pluripotent cells, such as embryonic stem cells (ES cells) and induced pluripotent stem cells (iPS cells), have been conducted. The pluripotent cells are cells that can differentiate into all types of cells constituting tissues, parts, and organs which form living organisms. ES cells are used as a potent model system for studying a mechanism underlying the biological properties of pluripotent cells and differentiation in the early embryo. This provides opportunities for genetic operation of mammals and resulting application of business, medicine, and agriculture. Further, techniques for diagnosing a disease or pathological condition, searching for a new drug, and evaluating the efficacy of a drug have been developed by using the appropriate proliferation and differentiation of ES cells.
The isolated cells are sometimes used immediately for testing, but in many cases, operations for causing proliferation and differentiation of cells in a culture dish or a test tube are carrier out. Various examinations are carried out using the cultured cells. Isolated pluripotent cells are required to show drug susceptibility and toxic reaction that are similar to those obtained in a test performed in a living body, that is, a so-called in vivo test, and are also required to differentiate into target cells with high efficiency.
However, the biochemical mechanism for controlling the pluripotency and differentiation of pluripotent cells is barely understood to date. For example, Patent Literature 1 discloses compositions and methods for the production of differentiated mammalian cells as means for causing differentiation of pluripotent cells. Specifically, Patent Literature 1 discloses a cell differentiation method that employs the technique of culturing cells on a feeder layer or under non-feeder conditions in a cell culture, and contacting mammalian cells with an inhibitor of the PI3-kinase signaling pathway and a member of the TGFb family to generate the mammalian cells differentiated from pluripotent mammalian stem cells.
In addition to the methods disclosed above, Non Patent Literature 1 discloses that the differentiation efficiency of pluripotent cells is changed depending on the size of an aggregate of embryoid bodies. Thus, it is an extremely important factor to control the size of the aggregate so as to obtain a uniform endoderm lineage cell, or cells differentiated from the cell, such as hepatic cells or β cells. According to the method disclosed in Non Patent Literature 1, Matrigel having cell adhesion properties and having a diameter of several tens of μm to several hundreds of μm is arranged at regular intervals on a culture bottom surface, thereby forming a cell adhesive region. Cell non-adhesive polymers are coated around the cell adhesive region to allow cells to selectively adhere to the cell adhesive region, thereby controlling the size of an aggregate of embryoid bodies.