Purpose: To investigate the short-term effects of low-level lasers (LLLs; also known as low-power laser therapy) on the structure, genetic, and phenotype of cultured human retinal pigment epithelial (hRPE) cells from both adult and neonatal sources.

Methods: Cultivated adult and neonatal hRPE cells were irradiated with two types of LLL (630 nm and 780 nm), 1 min daily for five consecutive days.

Results: An increase in doubling time was observed in 630 nm-irradiated adult hRPE cells (P = 0.032). The gene expression profile revealed increased expression of retinoid isomerohydrolase RPE65 (RPE65) (P < 0.01 for 630 nm laser, P < 0.001 for 780 nm laser) and nestin (NES) (P < 0.01 for 630 nm laser) in neonatal hRPE cells, upregulation of RPE65 (P < 0.001 for 780 nm laser) and paired box 6 (PAX6) (P < 0.001 for 780 nm laser) genes in adult hRPE cells, and reduced expression of actin alpha 2 (ACTA2) in 780 nm-irradiated adult hRPE cells (P < 0.001). Except for the significant increase of

Alpha-smooth Muscle Actin, Human Retinal Pigment Epithelial Cells, Low-level Laser, PAX6, Photobiomodulation, RPE65

1. Liu J, Yang L, Wang X, Wang S, Huang Z, Li C, et al. Embryonic stem cell microenvironment enhances proliferation of human retinal pigment epithelium cells by activating the PI3K signaling pathway. Stem Cell Res Ther 2020;11:411.

2. Morten la Cour TT. The retinal pigment epithelium. Adv Oral Biol 2005;10:253–272.

3. Jin ZB, Gao ML, Deng WL, Wu KC, Sugita S, Mandai M, et al. Stemming retinal regeneration with pluripotent stem cells. Stem Cell Res Ther 2019;10:38–56.

4. Atmaca-Sonmez P, Li Y, Yamauchi Y, Schanie CL, Ildstad ST, Kaplan HJ, et al. Systemically transferred hematopoietic stem cells home to the subretinal space and express RPE-65 in a mouse model of retinal pigment epithelium damage. Exp Eye Res 2006;83:1295–1302.

5. Liang CM, Tai MC, Chang YH, Chen YH, Chen CL, Lu DW, et al. Glucosamine inhibits epithelial-tomesenchymal transition and migration of retinal pigment epithelium cells in culture and morphologic changes in a mouse model of proliferative vitreoretinopathy. Acta Ophthalmol 2011;89:e505–14.

6. Laventhal NT, Rivkees SA, Opipari VP. Hope vs. caution: Ethical and regulatory considerations for neonatal stem cell therapies. Pediatr Res 2018;83:557–558.

7. MacLaren RE, Pearson RA, MacNeil A, Douglas RH, Salt TE, Akimoto M, et al. Retinal repair by transplantation of photoreceptor precursors. Nature 2006;444:203–207.

8. Grigoryan EN, Markitantova YV. Molecular strategies for transdifferentiation of retinal pigment epithelial cells in amphibians and mammals in vivo. Russ J Dev Biol 2021;52:220–243.

9. Tang W, Wang H, Zhao X, Liu S, Kong SK, Ho A, et al. Stem cell differentiation with consistent lineage commitment induced by a flash of ultrafast-laser activation in vitro and in vivo. Cell Rep 2022;38:110486.

10. Dang Y, Wu W, Xu Y, Mu Y, Xu K, Wu H, et al. Effects of low-level laser irradiation on proliferation and functional protein expression in human RPE cells. Lasers Med Sci 2015;30:2295–2302.

11. Atasoy KT, Korkmaz YT, Odaci E, Hanci H. The efficacy of low-level 940 nm laser therapy with different energy intensities on bone healing. Braz Oral Res 2017;31:e7.

12. Avci P, Gupta A, Sadasivam M, Vecchio D, Pam Z, Pam N, et al. Low-level laser (light) therapy (LLLT) in skin: Stimulating, healing, restoring. Semin Cutan Med Surg 2013;32:41–52.

13. Hashmi JT, Huang YY, Osmani BZ, Sharma SK, Naeser MA, Hamblin MR. Role of low-level laser therapy in neurorehabilitation. PMR 2010;2:S292–305.

14. Rochkind S. Phototherapy (photobiomodulation) for peripheral nerve and muscle injury. Laser Ther J 2023;30.

15. Kushibiki T, Hirasawa T, Okawa S, Ishihara M. Low reactive level laser therapy for mesenchymal stromal cells therapies. Stem Cells Int 2015;2015:974864.

16. Amid R, Kadkhodazadeh M, Ahsaie MG, Hakakzadeh A. Effect of low level laser therapy on proliferation and differentiation of the cells contributing in bone regeneration. J Lasers Med Sci 2014;5:163–170.

17. Merry GF, Munk MR, Dotson RS, Walker MG, Devenyi RG. Photobiomodulation reduces drusen volume and improves visual acuity and contrast sensitivity in dry age-related macular degeneration. Acta Ophthalmol 2017;95:e270–7.

18. Ivandic BT, Ivandic T. Low-level laser therapy improves vision in a patient with retinitis pigmentosa. Photomed Laser Surg 2014;32:181–184.

19. Joshua A, Chu-Tan MR. Kartik Saxena, Yunlu Wu, Lauren Howitt, Krisztina Valter, Jan Provis, Riccardo Natoli. Efficacy of 670 nm light therapy to protect against photoreceptor cell death is dependent on the severity of damage. Int J Photoenergy 2016;2016:12.

20. Akrami H, Soheili ZS, Khalooghi K, Ahmadieh H, Rezaie- Kanavi M, Samiei S, et al. Retinal pigment epithelium culture; A potential source of retinal stem cells. J Ophthalmic Vis Res 2009;4:134–141.

21. Nasrabadi N, Soheili ZS, Bagheri A, Ahmadieh H, Amizadeh Y, Sahebjam F, et al. The effects of electromagnetic fields on cultured human retinal pigment epithelial cells. Bioelectromagnetics 2018;39:585–594.

22. Balagholi S, Rezaei Kanavi M, Alizadeh S, Dabbaghi R, Karami S, Kheiri B, et al. Effects of fibrin glue as a threedimensional scaffold in cultivated adult human retinal pigment epithelial cells. J Biomater Appl 2018;33:514– 526.

23. Norren DV, Vos JJ. Spectral transmission of the human ocular media. Vision Res 1974;14:1237–1244.

24. Oliveira ME, Santos FM, Bonifácio RP, Freitas MF, Martins DO, Chacur M. Low level laser therapy alters satellite glial cell expression and reverses nociceptive behavior in rats with neuropathic pain. Photochem Photobiol Sci 2017;16:547–554.

25. Michael R. Hamblin TA, Marcelo de Sousa. Handbook of low-level laser therapy. 1st ed. Jenny Stanford Publishing; 2016. 1170 p.

26. Islam MR, Nakamura K, Casco-Robles MM, Kunahong A, Inami W, Toyama F, et al. The newt reprograms mature RPE cells into a unique multipotent state for retinal regeneration. Sci Rep 2014;4:6043.

27. Grigoryan EN. Competence factors of retinal pigment epithelium cells for reprogramming in the neuronal direction during retinal regeneration in newts. Biol Bull Russ Acad Sci 2015;42:1–11.

28. Luz-Madrigal A, Grajales-Esquivel E, McCorkle A, DiLorenzo AM, Barbosa-Sabanero K, Tsonis PA, et al. Reprogramming of the chick retinal pigmented epithelium after retinal injury. BMC Biol 2014;12:28.

29. Zupin L, Ottaviani G, Rupel K, Biasotto M, Zacchigna S, Crovella S, et al. Analgesic effect of Photobiomodulation Therapy: An in vitro and in vivo study. J Biophotonics 2019;12:e201900043.

30. Pastor JC, Rojas J, Pastor-Idoate S, Di Lauro S, Gonzalez-Buendia L, Delgado-Tirado S. Proliferative vitreoretinopathy: A new concept of disease pathogenesis and practical consequences. Prog Retin Eye Res 2016;51:125–155.

31. Martignago CC, Oliveira RF, Pires-Oliveira DA, Oliveira PD, Pacheco Soares C, Monzani PS, et al. Effect of low-level laser therapy on the gene expression of collagen and vascular endothelial growth factor in a culture of fibroblast cells in mice. Lasers Med Sci 2015;30:203– 208.

32. Anders JJ, Lanzafame RJ, Arany PR. Low-level light/laser therapy versus photobiomodulation therapy. Photomed Laser Surg 2015;33:183–184.