Composite porous membrane and process for producing the same

A process for co-culturing cells of a first cell group and cells of a second cell group while partitioning the first and second cell groups by a cell culture diaphragm in a cell culture solution so that the cells of the two kinds of cell groups can come into contact with each other,

• said cell culture diaphragm comprising a composite porous membrane which comprises at least one porous membrane comprising an organic polymer and at least one supporting porous membrane adjacent thereto, the supporting porous membrane having continuous pores with an average pore diameter between 1 and 100 μm, and a density of 0.1 to 0.5 g/cm3,
• wherein, when a membrane flat surface of the porous membrane is observed using a photomicrograph, the porous membrane has an opening ratio between 10% and 90%, an average pore diameter D (μm) of 0.1≦D≦50, a standard deviation σd (μm) of pore diameter of 0≦σd/D≦0.6, and the percentage of through-pores to all the pores of the porous membrane is 30% or more;
• and when a membrane section thereof is observed using a photomicrograph, the porous membrane has an average membrane thickness T (μm) defined by 0.05≦T/D≦2 and a structure in which pores adjacent to one another communicate with one another therein;
• the process comprising:
• inoculating the cells of the first cell group on the side of the supporting porous membrane,
• inoculating the cells of the second cell group on the side of the porous membrane, and
• co-culturing the cells of the first and second cell groups while laying the side of the porous membrane up.