Disclosed is a novel net member for supporting one or more cell constructs in the culture chamber of a bioreactor, which comprises an array of impermeable pyramidal elements protruding from the face thereof, wherein each of the corners of the base of each of said impermeable pyramidal elements comprises a circular opening. This net member provides for uniform and unobstructed flow of culture medium through 3D cell constructs in culture.Also disclosed are a bioreactor and bioreactor system incorporating said net member.The bioreactor and bioreactor system may be used in the bioproduction of therapeutic proteins and stem cell expansion.