Influence of Low Intensity Laser Irradiation on Isolated Human Adipose Derived Stem Cells Over 72 Hours and Their Differentiation Potential into Smooth Muscle Cells Using Retinoic Acid

Introduction: Human adipose derived stem cells (hADSCs), with their impressive differentiation potential, may be used in autologous cell therapy or grafting to replace damaged tissues. Low intensity laser irradiation (LILI) has been shown to influence the behaviour of various cells, including stem cells. Aims: This study aimed to investigate the effect of LILI on hADSCs 24, 48 or 72 h post-irradiation and their differentiation potential into smooth muscle cells (SMCs). Methodology: hADSCs were exposed to a 636 nm diode laser at a fluence of 5 J/cm ². hADSCs were differentiated into SMCs using retinoic acid (RA). Morphology was assessed by inverted light and differential interference contrast (DIC) microscopy. Proliferation and viability of hADSCs was assessed by optical density (OD), Trypan blue staining and adenosine triphosphate (ATP) luminescence. Expression of stem cell markers, β1-integrin and Thy-1, and SMC markers, smooth muscle alpha actin (SM-αa), desmin, smooth muscle myosin heavy chain (SM-MHC) and smoothelin, was assessed by immunofluorescent staining and real-time reverse transcriptase polymerase chain reaction (RT-PCR). Results: Morphologically, hADSCs did not show any differences and there was an increase in viability and proliferation post-irradiation. Immunofluorescent staining showed expression of β1-integrin and Thy-1 72 h post-irradiation. RT-PCR results showed a down regulation of Thy-1 48 h post-irradiation. Differentiated SMCs were confirmed by morphology and expression of SMC markers. Conclusion: LILI at a wavelength of 636 nm and a fluence of 5 J/cm ² does not induce differentiation of isolated hADSCs over a 72 h period, and increases cellular viability and proliferation. hADSCs can be differentiated into SMCs within 14 days using RA.