Stimulation of bone resorption and cell proliferation in vitro by human gingival fibroblasts from patients with periodontal disease

Indirect co-culture of stem cells from human exfoliated deciduous teeth and oral cells in a microfluidic platform

Oral epithelial-mesenchymal interactions play a key role in tooth development and assist differentiation of dental pulp. Many epithelial and mesenchymal factors in the microenvironment influence dental pulp stem cells to differentiate and regenerate. To investigate the interaction between oral cells during differentiation, we designed a microfluidic device system for indirect co-culture. The system has several advantages, such as consumption of low reagent volume, high-throughput treatment of reagents, and faster mineralization analysis. In this study, stem cells from human exfoliated deciduous teeth were treated with media cultured with human gingival fibroblasts or periodontal ligament stem cells. When human exfoliated deciduous teeth was incubated in media cultured in human gingival fibroblasts and human periodontal ligament stem cells under the concentration gradient constructed by the microfluidic system, no remarkable change in human exfoliated deciduous teeth mineralization efficiency was detected. However, osteoblast gene expression levels in human exfoliated deciduous teeth incubated with human gingival fibroblasts media decreased compared to those in human exfoliated deciduous teeth treated with human periodontal ligament stem cells media, suggesting that indirect co-culture of human exfoliated deciduous with human gingival fibroblasts may inhibit osteogenic cytodifferentiation. This microfluidic culture device allows a co-culture system set-up for sequential treatment with co-culture media and differentiation additives and facilitated the mineralization assay in a micro-culture scale.

Cell populations associated with active probing attachment loss

The purpose of this study was to evaluate the ability of cell populations to differentiate between untreated progressing periodontitis sites (P) and untreated non-progressing sites (NP). Pairs of biopsies were obtained from untreated periodontal patients, one biopsy from a site which had lost probing attachment of 2 mm or more within the previous month, the other biopsy from a non-progressing site. Cell populations were identified on 1 micron sections in a defined connective tissue area at the junctional epithelium. The cell types counted were fibroblasts, mast cells, monocytes/macrophages, polymorphonuclear leukocytes (PMNs), lymphoid cells, plasma cells, endothelial cells, total inflammatory cells, and the total number of cells. The number of fibroblasts, mast cells, monocytes/macrophages, and inflammatory cells, as well as their percentage of the total number of cells, differed significantly between P- and NP-sites. In addition, the actual total counts differed between groups. The difference between groups was more significant for percent fibroblasts than for any other cell type. It appears that cell populations, particularly fibroblast counts, can aid in the histological discrimination between P and NP periodontitis lesions.

In vitro studies on bone resorption in neonatal mouse calvariae using a modified dissection technique giving four samples of bone from each calvaria

Bone resorption in a modified bone culture system, based on incubation of small fragments from neonatal mouse calvarial bones, has been studied. Four bone fragments were dissected out from each mouse calvaria and were thereafter cultured in CMRL 1066 medium in plastic multiwell dishes. Bone resorption was assessed by 45Ca release from prelabeled bones. The rate of bone resorption in response to parathyroid hormone (PTH) was less in the anterior part of the calvaria compared to the posterior part. After removing the anterior region, four parietal bone fragments that showed identical basal and PTH-stimulated release of 45Ca could be dissected out from each mouse. Excretion of lactate dehydrogenase and beta-glucuronidase was the same in bones cultured submerged or on grids. Uptake of [3H]thymidine in bones cultured submerged was 54% of [3H]thymidine uptake in bones cultured on grids. Dose-response curves, established by using parietal bone fragments, showed that the sensitivity and the magnitude of the increase in 45Ca release seen after stimulation with PTH, prostaglandin E2, and 1 alpha-hydroxyvitamin D3 were the same for bones cultured submerged or on grids. The 45Ca release in response to stimulation with PTH, prostaglandin E2, and 1 alpha-OHD3 was the same in calvarial fragments cultured submerged and those previously obtained with calvarial halves cultured on grids. Thus, even though the rate of DNA synthesis was slower in bones cultured submerged, the rate and the magnitude of resorption were the same in bones cultured on grids or submerged. These data show that it is possible to perform studies on bone resorption with small fragments of neonatal mouse parietal bones.