HEALING OF A SEGMENTAL DEFECT IN THE RAT FEMUR WITH USE OF AN EXTRACTFROM A CULTURED HUMAN OSTEOSARCOMA CELL-LINE (SAOS-2) - A PRELIMINARY-REPORT

Devitalized extracts from cultured human osteosarcoma cells (Saos-2) c an induce ectopic bone formation. The ability of an extract from Saos- 2 cells to stimulate healing of an operatively created four-millimeter defect in the femoral diaphyses of rats was compared with that of col lagen and that of autogenous bone graft. Forty adult rats were randomi zed into four groups of ten each. In Group 1 (controls), no material w as placed in the defect; in Group 2, the defect was filled with pure b ovine collagen; in Group 3, it was filled with autogenous graft obtain ed by morseling of the resected segment of the femur; and in Group 4, it was filled with ten milligrams of extract from Saos-2 cells that wa s mixed with an equal amount of bovine collagen. Five rats from each g roup were killed at four weeks and the remaining five, at eight weeks. Each femoral defect was analyzed radiographically and histologically for osseous healing. There was no evidence of healing at either four o r eight weeks in Groups 1 and 2. Although there was some new-bone form ation in Group 3, none of the defects had united at eight weeks. There was early, almost complete union in all five four-week specimens in G roup 4 and complete healing of the defect in four of the five rats ass essed at eight weeks. The Saos-2 cell extract was found to be the most effective agent, promoting union by mature lamellar bone within eight weeks. CLINICAL RELEVANCE: Potential clinical applications of Saos-2- cell bone-inducing extract include the promotion of bone growth in fra cture non-unions, in large operatively created defects, and in spinal arthrodeses. It is possible that a bone-inducing extract could enhance osteointegration of porous prosthetic implants.