Osseous substitute presenting an activity on osseous regeneration, comprises fucan presenting a weight average molar mass of 5000-100000 g/mol, preferably 10000-40000 g/mol. INDEPENDENT CLAIM are included for: (1) the preparation of osseous substitute comprising covering the biomaterial surface by a coating of fucans； (2) a culture medium for a osteocompetent type cell of bone marrow, bone or periosteum, comprising fucans presenting a weight average molar mass of 5000-100000 g/mol, preferably 10000-40000 g/mol； (3) cell culture of osteocompetent cells of bone marrow, bone or periosteum, comprising cultivating the cells in the culture medium or in the osseous substitute； and (4) a medical device presenting an activity on osseous regeneration, comprising fucans presenting a weight average molar mass of 5000-100000 g/mol, preferably 10000-40000 g/mol.
