Figure 2.

Time-lapse images of the autonomic and continuous compressive force–induced [Ca²⁺]_i responses in isolated hPDL fibroblasts. A) Schematic diagram showing the isolation procedure of primary hPDL fibroblasts. B) The primary hPDL fibroblasts 3 d after isolation. C) Schematic diagram of the delivery of continuous compressive force to the cells. D) Pseudocolor images of the fluorescence-labeled hPDL fibroblasts. The numbered cells represent the cells described in plot E. E) Representative traces of [Ca²⁺]_i dynamics in individual hPDL fibroblasts under static conditions. Each color trace indicates the time course of the [Ca²⁺]_i response of the individual cell represented with the same color. F) Serial pseudocolor images of the fluorescence-labeled hPDL fibroblasts taken at 0, 15, 51, 141, 195, 219, and 282 s after the initiation of monitoring. The vertical color scale reflects the relative fluorescence intensity. A movie of the serial pseudocolor images can also be seen in the supplemental data (Supplemental Video S2). G) Fluorescence pseudocolor images of the hPDL fibroblasts’ response to continuous compressive force. The numbers coded to each cell indicate the cells represented in plot H. H) Representative traces of [Ca²⁺]_i dynamics in individual hPDL fibroblasts in response to the continuous compressive force. The elevation of the relative fluorescence intensity was defined by the mean intensity observed before the application of compressive force. Individual color lines of plot in H represent the [Ca²⁺]_i-responsive hPDL fibroblasts in the corresponding plot in G. I) Sequential images of the hPDL fibroblasts taken at 0, 21, 60, 90, 120, 150, 210, and 300 s during the application of MS. A movie of the serial pseudocolor images can also be seen in the supplemental data (Supplemental Video S3). J) The [Ca²⁺]_i profile of all investigated hPDL cells under MS treatment. The average profile is indicated by the block line in black. K) Representative fluorescent images of isolated hPDL fibroblasts labeled with calcein or propidium iodide (PI: arrowhead). L) Quantification results of hPDL viability tests. All data are expressed as means ± sd. The comparison between control and continuous compressive force groups is determined by unpaired Student’s t test (n = 10 per group). Scale bars, 50 µm.