[Problem] To provide a material that can be used as a scaffold for the construction of a large regenerated tissue and has all of the following characteristic properties: (1) the material has a high affinity for cells; (2) the structure of the material is stable under physiological environments; (3) the material can be decomposed rapidly in a living body after being transplanted; (4) the material can carry a blood vessel induction factor in the inside thereof stably without leaking the blood vessel induction factor therefrom; (5) the material has transparency at such a level that the state of cells in culture can be observed in the inside of the gel over time; and (6) the strength of a gel produced from the material can be controlled readily. [Solution] A crosslinkable composition comprising an oligosaccharide oxide having an aldehyde group and a polypeptide or polysaccharide having an amino group in a side chain thereof.
