EXPRESSION OF MATRIX GENES DURING INCORPORATION OF CANCELLOUS BONE ALLOGRAFTS AND AUTOGRAFTS

The healing process of cylindrical metaphyseal bone defects filled wit h fresh autogeneic or frozen allogeneic cancellous bone grafts was stu died using histology, biomechanical testing, and molecular biology, Th e results were compared with the healing pattern observed in nongrafte d defects, where a strong initial expression of Type III collagen was followed by slowly starting expression of osteonectin and Type 1 colla gen genes, Autogeneic or allogeneic cancellous bone grafts considerabl y increased the healing rate of the defects, The sequence of healing w as similar with both types of grafts, but the maximal levels of Type I II and Type I collagen messenger ribonucleic acids (mRNAs) were delaye d by 1 week when allografts were used, Histologically, during the init ial phase the grafts had an invasion of progenitor mesenchymal tissue within 2 weeks followed by intramembranous bone formation and by a gra dual decline in Type I collagen expression, Osteonectin mRNA was prese nt throughout the healing process, but no expression of Type II collag en was seen, Indentation testing showed no significant biomechanical d ifferences between the autografts and allografts, Histology and molecu lar biology testing results revealed that the production of extracellu lar matrix starts slower in allogeneic cancellous bone grafts than in autografts, suggesting a basic difference in the initial host tissue r esponse between autogeneic and allogeneic bone grafts.