Photobiomodulation with a 645 nm diode laser. in vitro evaluation of proliferation and differentiation of Saos-2 cell line with or without Platelets Rich Plasma

Objective: This in vitro study aimed to investigate possible outcomes resulting by combined use of mesenchymal stem cells, LLLT and PRP. Choosen wavelength was 645 nm; the study included a case‐control structure. Methods: Experiment was conducted on Saos‐2‐ATT‐HTB‐85TM Human Osteosarcoma Cell Line. LLLT was performed every other day for six times in total. Fluence values of 2 J/cm2, 5 J/cm2, and 10 J/cm2 were applied for 1, 2, or 4 min. Cell viability was assessed by resazurin reduction assay. Cell differentiation was assessed by alizarin‐red assay. Results: For proliferation's rate no main differences between protocols were highlighted. For differentiation's rate was observed that inside control wells stem cells with PRP showed higher concentration of Calcium salts deposits than stem cells without PRP, with a mean concentration of 0.8 mM vs 0.11 mM. Protocols applying 2 J/cm2 showed no significant differences between wells with or without PRP. Highest values of Calcium salt deposition were registered for 5 J/cm2 in 2 min application; same results were obtained applying the protocol of 10 J/cm2 in 4 min. Results were statistically significant (p = 0.017) compared to Calcium salt deposition in not irradiated wells (Fisher's Chi2 test). Conclusions: The combination of LLLT and PRP leads to statistically significant increase of both proliferation and differentiation rates. The laser application of 5 J/cm2 delivered in 2 min with Power Density of 130 mW/cm2, meaning a total Energy of 7.8 J and Power of 65 mW, was proven to be the most effective.