This study was conducted to understand the cellular proliferative effect of Photobiomodulation Therapy (PBMT) on thawed dental pulp stem cells (DPSCs) stored for 2 years. For this purpose, cells were exposed to PBMT for short period of time to evaluate the most appropriate PBMT parameter for stimulating cellular proliferation that can be used for future tissue engineering therapies. Fully characterized DPSCs were seperated into three groups according to the laser energy densities (5J/cm² or 7J/cm²) applied and a group was served as control in which cells did not receive any laser irradiation. The cells in laser-irradiated groups were further divided into two subgroups according to the period of application (24h and 0h) and exposed to Gallium–Aluminum–Arsenide diode laser irradiation. Cell viability and the proliferation rate of the cells were analyzed with the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, any PBMT related cellular cytotoxicity were determined by performing a lactate dehydrogenase assay (LDH) and statistical analysis of data were performed. The percentage of proliferation seemed to increase upon laser therapy in both different doses of irradiation (5J/cm² and 7J/cm²). DPSCs showed significantly higher proliferation rate upon 7J/cm² irradiation in both 0h and 24h when compared to control groups. However, DPSCs irradiated with 5J/cm² dose induced relatively lower proliferation rate when compared to 7J/cm² dose of irradiation. According to the LDH data, PBMT exposure did not show any significant cytotoxicity at both energy densities in all different time periods. PBMT at 7J/cm² should be an effective parameter to stimulate proliferation of long-term cryopreserved DPSCs in a short term time period. Photobiomodulation therapy may be an upcoming tool for future tissue enngineering and regenerative dentistry applications.

中文翻译：

---

光生物调节疗法对解冻牙髓干细胞的生物刺激效果

本研究旨在了解光生物调节疗法 (PBMT) 对储存 2 年的解冻牙髓干细胞 (DPSC) 的细胞增殖作用。为此，将细胞短时间暴露于 PBMT 以评估最合适的 PBMT 参数，以刺激可用于未来组织工程疗法的细胞增殖。根据激光能量密度（5焦/厘米²或 7J/cm ² ) 施加，一组作为对照，其中细胞没有接受任何激光照射。激光照射组中的细胞根据应用时间进一步分为两个亚组（24h 和 0h) 并暴露于镓-铝-砷化物二极管激光照射。用 3-[4,5-dimethylthiazol-2-yl]-2,5 二苯基溴化四唑 (MTT) 测定法分析细胞活力和细胞增殖率，通过执行乳酸脱氢酶测定任何 PBMT 相关的细胞细胞毒性进行了测定（LDH）和数据的统计分析。在两种不同剂量的照射下，激光治疗后增殖的百分比似乎都增加了（5J/cm ²和 7焦/厘米² )。DPSCs 在 7 岁时表现出显着更高的增殖率J/cm ²辐照均在 0h 和 24h 与对照组相比。然而，DPSCs 用 5与 7 相比， J/cm ²剂量诱导的增殖率相对较低J/cm ²照射剂量。根据 LDH 数据，PBMT 暴露在所有不同时间段的两种能量密度下均未显示出任何显着的细胞毒性。PBMT 在 7J/cm ²应该是在短期内刺激长期冷冻保存的DPSCs增殖的有效参数。光生物调节疗法可能是未来组织工程和再生牙科应用的一个即将到来的工具。