Human periodontal ligament cells in vitro

This paper reports on ultrastructural features of human periodontal ligament (PDL) cells growing in vitro as primary outgrowths and as continuous lines. The two most striking features of these cells were: 1) their branching bands of micro filaments containing semiperiodic dense nodes; and 2) the massive amounts of glycogen (α and β particles) found in many cells. Both of these features, particularly the glycogen, were found in an earlier study of the human PDL in vivo. In that study, of 22 teeth, glycogen was located universally in the cementoblasts and superjacent fibroblasts but not in the PDL fibroblasts more distant from the cementum.