Migration and division of progenitor cell populations in periodontal ligament after wounding

Abstract

Connective tissue cells responding to wounding of the periodontal ligament of the lower first molar in mice were studied using the techniques of radioautography and grain counting. Animals were given an intraperitoneal injection of 2 uCi 1g 3H‐Tdr 1 hr before being killed at either 30, 72 or 120 hr after wounding. The ligament in 1 um plastic sections was divided into compartments on the basis of distance from the wound, and the relative number of labelled cells in each compartment was assessed at 30, 72 and 120 hours after wounding. The distance of each labelled cell from the closest blood vessel was also measured at each time to detect relative movement of labelled cells away from blood vessels. In a Parallel experiment, haematogenous progenitors of macrophages were depleted by irradiating the animals with 800rads prior to woundilng to determine if mistakes in identification between fibroblasts and marophages could significantly affect the results. The ultrastructural characteristics of 150 of the 3H‐Tdr labelled cells was examined in thin sections of wounded periodontal ligament prepared for elctron microcope radioautography, The majority of cells lebelled 30 hours after wounding were confirmed to be paravascular, and most of them were found to be located within 200 μ of the wound margin. Some of these cells appreared to have divided a number of times between 30 and 72 hours after wounding, and to have migrated into the wound between 70 and 120 hours after wounding. Examination of the irradiated material and the electron microscope radio‐autographs suggested that significant numbers of macrophages had not been included in the counts of labelled cells. The elctron microscope radioautographs also suggested that cells which exhibited different degrees of cytodifferentiation had incorporated 3H‐Tdr.

Morphological, Functional and Biochemical Characterization of Canine Gingival Fibroblasts

“…Fibroblasts are responsible for the normal growth of the organism and are essential in cases where tissue repairs are necessary, being one of the first cells to appear at injured sites. The current concept that both, gingival fibroblasts (15,16) and periodontal ligament fibroblasts (17)(18)(19)(20)(21), have the capacity to regenerate the periodontium has stimulated an interest in the development of clinical methods for the regularization of these cell types (6).…”

A cell line with characteristics of the periodontal ligament fibroblasts is negatively regulated for mineralization and Runx2/Cbfa1/Osf2 activity, part of which can be overcome by bone morphogenetic protein-2

“…Therefore, PDL fibroblastic cells have been suggested to be multipotent cells (McCulloch and Bordin, 1991) or composed of heterogenous cell populations that have the capacity to differentiate into either osteoblasts or cementoblasts depending on the microenvironment (Gould et al, 1980;Roberts et al, 1982;McCulloch and Melcher, 1983). Indeed, recent studies…”

Periodontal Stem Cells: a Historical Background and Current Perspectives

“…To the best of our knowledge this was the first attempt to show that the perivascular zone might be the niche for periodontal ligament stem cells, similar to adult mesenchymal stem cells located in bone marrow, fat and other tissues [8,[21][22][23]]. Melcher's group also found a pool of mitotic cells in the vicinity of blood vessels following wounding of the alveolar bone and periodontal ligament that shifted within the repopulated wound area [24,25]; this provided evidence for the presence of progenitor/stem cells within the perivascular niche in the periodontal ligament that respond to wounding.…”