Biological effects of Er:YAG laser irradiation on the proliferation of primary human gingival fibroblasts

Abstract

We investigated the biological effects of Er:YAG laser (2940-nm; DELight, HOYA ConBio, Fremont, California) irradiation at fluences of 3.6, 4.2, 4.9, 6.3, 8.1 or 9.7 J cm at 20 or 30 Hz for 20 or 30 seconds on primary human gingival fibroblasts (HGFs). Irradiation at 6.3 J cm promoted maximal cell proliferation, determined by WST-8 assay and crystal violet staining, but was accompanied by lactate dehydrogenase release, on day 3 post-irradiation. Elevation of ATP level, Ki67 staining, and cyclin-A2 mRNA expression confirmed that Er:YAG affected the cell cycle and increased the number of proliferating cells. Transmission electron microscopy showed alterations of mitochondria and ribosomal endoplasmic reticulum (ER) at 3 hours post-irradiation at 6.3 J cm , and the changes subsided after 24 hours, suggesting transient cellular injury. Microarray analysis revealed up-regulation of 21 genes involved in heat-related biological responses and ER-associated degradation. The mRNA expression of heat shock protein 70 family was increased, as validated by Real-time PCR. Surface temperature measurement confirmed that 6.3 J cm generated heat (40.9°C post-irradiation). Treatment with 40°C-warmed medium increased proliferation. Laser-induced proliferation was suppressed by inhibition of thermosensory transient receptor potential channels. Thus, despite causing transient cellular damage, Er:YAG laser irradiation at 6.3 J cm strongly potentiated HGF proliferation via photo-thermal stress, suggesting potential wound-healing benefit.

Effects of Low-Level Er:YAG Laser Irradiation on Proliferation and Calcification of Primary Osteoblast-Like Cells Isolated From Rat Calvaria

“…It is conceivable that the disparities in results are caused by differences in irradiation conditions (pulse energy and time) and/or cells used. In addition, although we previously reported that Er:YAG irradiation at 6.3 J/cm 2 promoted cell proliferation of human gingival fibroblasts, surface temperatures increased to 40.9 • C with upregulating genes of heat shock protein family proteins (Kong et al, 2018). The difference in temperature may also affect proliferation.…”

“…We also evaluated cell proliferation using the Cell Counting Kit-8 (CCK-8, Dojindo, Kumamoto, Japan) at 1, 2, and 3 days after laser irradiation as described previously (Aleksic et al, 2010;Kong et al, 2018). Laser irradiation was performed in the absence of medium after a 24 h-starvation.…”

Evaluation of Skin Response After Erbium:Yttrium– Aluminum–Garnet Laser Irradiation: A Network Analysis Approach

“…Effect of laser irradiation on cell cycle and proliferation is reported by several researchers. 16,17 It seems that microtubule destabilization is a significant process that is affected by laser irradiation. Down-regulation of TP53 and activation of this anti-tumor protein indicates that control of cell proliferation after laser irradiation is a prominent point regarding using laser therapy.…”

Laser irradiation decreases sclerostin expression in bone and osteogenic cells

“…Laser irradiation was performed perpendicularly to the bottom of the culture dish at a distance of 25 cm, with the handpiece fixed using a stand as performed previously. 21,22 Neither cover sleeve nor contact tip mounting was used with the handpiece to completely irradiate the 35-mm dish and cover more than the dish area. The medium was removed immediately before irradiation, and all irradiations were performed in the absence of culture medium.…”