Changes in lysyl oxidase activity and calcium content during the healing of tooth extraction wounds

The typical wound healing process after tooth extraction includes several important biological reactions. The collagen fiber, which is the main organic component of connective tissue, plays an important role in the formation of granulation tissue and also bone tissue. Maturation of collagen is controlled by the intermolecular crosslinks in the collagen fibers. Lysyl oxidase, which catalyzes the corresponding aldehyde formation from certain lysyl and hydroxylysyl residues in collagen and elastin in the first step of the linking reaction, is the only known enzyme required in the crosslinking process. This study was designed to analyze changes in the lysyl oxidase activity and calcium content during the healing of rabbit tooth extraction wounds and to survey the relationship between them. Healing tissue in the extraction sockets was removed 1, 2, 3, 4, 5, 7, 10, 14, 21, 28, and 56 days postoperatively. After decalcification, lysyl oxidase was extracted from wound tissue, and activity of this enzyme was examined by tritium-release assay. Radiographs and histologic sections were also obtained in each group. The results show that lysyl oxidase activity can be detected on the first day postoperatively and that it increases sharply from days five to seven, reaching the peak value on the seventh day. After that, enzyme activity decreases gradually and returns to normal range on day 14. Histologically, the healing sockets were filled mainly with young fibrous connective tissue at day seven; osteoid tissue could be found on the lateral wall and fundus of the extraction sockets at the same time. Accompanying the formation of new bone, calcium content increased conspicuously from day 7 to day 14. These results indicate that lysyl oxidase predominantly acts to promote cross-linking of the abundantly synthesized collagen in the early stage of healing of rabbit tooth extraction wounds. When minerals were precipitated at a great rate in the newly-formed bone, lysyl oxidase activity was concurrently decreased.