Cell generation within the interdental gingival septum of the rat

The aims of this investigation were to determine whether connective tissue progenitor cells in the interdental gingival septum (IGS) have a paravascular origin, and how the distribution of 3HTdR-labelled cells within the IGS changes with time after a single injection. 30 male hooded Lister rats aged 6 weeks, were killed in groups of ten, 3, 75 and 171 h after a single injection of tritiated thymidine. Autoradiographs were examined of 3 transverse Historesin sections of the papilla between second and third mandibular molars in 29 specimens, taken at equidistant intervals between the col and alveolar bone crest. At all times and levels, 73.9-93.0% of labelled cells and 72.0-79.0% of unlabelled cells lay within 50 microns of blood vessels (BVs). The highest percentages of labelled cells (PLCs) occurred within 5 microns of BVs (P < 0.001) although mean nuclear density here was lowest (P < 0.017), and there was a significant diminution of PLC (P < 0.05) with increasing distance from BVs, occurring most precipitously 5-10 microns from vessel walls. Sites of significantly increased PLC at 3 h also approximated to sites in which mean BV densities were greatest. At 3 h, a number of discrete sites with significantly increased PLCs (P < 0.05) were found within two zones, each equivalent to 40% of IGS volume and juxtaposed with each tooth. At later times, additional sites of raised PLC appeared throughout the IGS. Overall PLCs in the upper two levels and within 5 microns of BVs also increased over the time-course (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)