Circular parietal defects from 3 to 12 mm in diameter were made in 45 6-month old skeletally mature guinea pigs, and animals were sacrificed after survival periods of 3 days to 12 weeks. The original defect was harvested in continuity with a rim of surrounding bone and the adjacent dura and pericranium. After 12 weeks, all 3 and 5 mm defects were completely covered by a bridge of bone, while residual defects were noted within the 8 and 12 mm wounds. Percentage of new bone formation was significantly higher within 3 mm defects, than in all larger defects at each time interval from 1 week on (P < .05), reaching a mean of 93% in 3 mm defects and remaining below a mean of 31% in the remaining defect sizes. Immunolocalization demonstrated an osteogenic front in which the osteoblasts stained strongly for all isoforms of TGF-beta, with the intensity decreasing after the majority of the defects had reossified; this front was located at the advancing bone edge of the defect as well as the endocranial side adjacent to the dura. In conclusion, isoforms of TGF-beta are upregulated during a limited "window" of time corresponding to the period of calvarial reossification, and are localized to osteoblasts within an osteogenic front at the periphery and dural surfaces of the defects.
View details for Web of Science ID 000169712600019
View details for PubMedID 11482629