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

4 years ago

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

Tomonari Suda, Sophannary Kong, Shizuko Ichinose, Kengo Iwasaki, Verica Pavlic, Mayumi Ogita, Koji Mizutani, Akira Aoki, Yuichi Izumi, Sayaka Katagiri

We investigated the biological effects of Er:YAG laser (2,940-nm; DELight®, HOYA ConBio, USA) irradiation at fluences of 3.6, 4.2, 4.9, 6.3, 8.1, or 9.7 J cm−2 at 20 or 30 Hz for 20 or 30 s on primary human gingival fibroblasts (HGFs). Irradiation at 6.3 J cm−2 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) 3 h post-irradiation at 6.3 J cm−2, and the changes subsided after 24 h, 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 RT-qPCR. Surface temperature measurement confirmed that 6.3 J cm−2 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−2 strongly potentiated HGF proliferation via photo-thermal stress, suggesting potential wound-healing benefit.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/jbio.201700157