A method for providing a vascular system in biological tissue in vitro, the method comprising cocultivation of the biological tissue with vascular cells and mesenchymal cells. Biological tissue in which a vascular system has been provided by said method. A method for producing a tissue or organ, the method comprising transplantation of the biological tissue in a non-human animal and inducing differentiation to a tissue or organ in which a vascular network has been constructed. A tissue or organ regeneration or function-restoring method comprising transplantation of the biological tissue in a human or non-human animal and inducing differentiation to a tissue or organ in which a vascular network has been constructed. A method for producing a non-human chimera animal, the method comprising transplantation of the biological tissue to a non-human animal and inducing differentiation to a tissue or organ in which a vascular network has been constructed. A method for evaluating drugs using at least one selected from a group consisting of the biological tissue, tissues and organs produced by said method, and non-human chimera animals produced by said method. A regenerative therapy composition comprising biological tissue in which a vascular system has been provided by said method.La présente invention concerne une méthode de formation dun système vasculaire dans un tissu biologique in vitro, la méthode comprenant la culture conjointe du tissu biologique avec des cellules vasculaires et des cellules mésenchymateuses. Linvention concerne également un tissu biologique, dans lequel un système vasculaire a été formé par ladite méthode. Linvention concerne également une méthode de production dun tissu ou dun organe, la méthode consistant à transplanter le tissu biologique chez un animal non humain et à induire une différenciation dans un tissu ou un organe dans lequel a été formé un réseau vasculaire. Linvention concerne également une méthode de régénération de tissus ou dorganes
