The following facts 1) to 3) are found; 1) when a tissue extract which is extracted from an isolated skin graft is administered intravenously, a bone-marrow-derived pluripotent stem cell can be induced in a peripheral blood; 2) the substance which can recruit the bone-marrow-derived pluripotent stem cell contained in the isolated skin graft into the peripheral blood is HMGB1; and 3) HMGB1 which has an activity to recruit the bone-marrow-derived pluripotent stem cell into the peripheral blood can be purified readily from cells in culture.