Endogenous lipids in matrix-induced bone morphogenesis.

Demineralized matrix was delipidized with chloroform methanol before and after demineralization and implanted in muscle of allogeneic rats. Because lipids are difficult to separate completely from bone collagen, another preparation was gelatinized and delipidized with either chloroform methanol or acetone or both. Bone matrix demineralized without delipidization induced formation of a spherical-shaped deposit of new bone, which was remodeled to form a shell of cortical bone and central pool of normal hematopoietic bone marrow. When the bone was delipidized, only 20% to 25% was resorbed and replaced by new bone; unresorbed matrix failed to recalcify. Gelatinized bone matrix delipidized before implantation was even less well resorbed or replaced by new bone, but 12% to 44% of the matrix residue recalcified. The new deposits of bone were colonized by blood-borne bone marrow-derived stem cells and developed central pools of normal hematopoietic bone marrow. Recalcified residual matrix did not develop bone marrow. Additional investigations are required to determine whether the host bed adipocytes provide the phospholipids for recalcification of bone matrix. There was no preliminary recalcification in matrix-induced bone development, even though the 2 processes may occur simultaneously under specified experimental and pathologic conditions. Additional investigations are in progress to determine whether certain acetone soluble lipids may form the endogenous delivery system for bone morphogenetic protein and induced bone development.