Oral administration activity determination of recombinant osteoprotegerin from silkworm larvae.

Osteoprotegerin (OPG) regulates the formation of osteoclasts and is involved in the regulation of bone resorption and remodeling. To investigate the feasibility of using silkworm (Bombyx mori) larvae to produce recombinant osteoprotegerin as a oral administration drug, the rh-OPG was expressed in the larvae of silkworm through the silkworm baculovirus expression system, and was orally administered to mice. Compared with the control, oral administration of rh-OPG was effective to decrease serum calcium concentration in normal mice, and block the bone loss induced by the loss of estrogen in ovariectomized mice. These results indicated that oral administration of rh-OPG expressed in silkworm larvae had the proper bioactivity.