Location of progenitor cells in periodontal ligament of mouse molar stimulated by wounding.

Wounds were made in the alveolar process overlying the mesial root of the mandibular first molar of 35-g mice to expose periodontal ligament. Dividing cells were arrested in metaphase by injection of vinblastine sulphate three hours before death three, five and seven days after wounding. Serial 1-micron plastic sections of the wound were stained with hematoxylin and eosin. The distance between the mitotic figures and the nearest blood vessel, bone and cementum was measured in every fourth section. No mitotic figure was measured twice. The distances of at least 500 interphase cells from the closest blood vessel were measured in each wound. At all time periods the distribution of mitotic cells was significantly closer to blood vessels than that of interphase cells (p less than 0.01). From three days to seven days after wounding there was a significant shift of mitotic activity away from the bone side of the ligament, but not away from blood vessels (p less than 0.05). Approximately 10% of all mitotic cells lay close to cementum, but not close to blood vessels. The majority of the dividing cells were confirmed to be paravascular, and appeared to belong to two populations, one adjacent to bone, the other in the body of the ligament. A third population, not paravascular, lay adjacent to cementum.