Effect of low level laser irradiation on human adult adipose derived stem cells: an in vitro study

M. Tech.Stem cells are defined as undifferentiated cells that can proliferate indefinitely and have the capacity of both self-renewal and differentiation to one or more types of specialised cells. Traumatic tissue injury and age-related degenerative diseases are a major problem in South Africa and worldwide. Stem cells could be used for tissue engineering and reconstructive surgery. In treating these conditions, the main principle of stem cell therapy is the replacement of damaged and dead cells in injured tissues and organs with new healthy ones expanded in vitro from stem cells (Orlic et al., 2002). These cells can be isolated from adipose tissue in significant numbers and exhibit stable growth and proliferation kinetics in culture and could be differentiated into bone, fat, cartilage and muscle when treated with established lineage-specific factors (Zuk et al., 2002). Low Level Laser Therapy (LLLT) is currently applied in the treatment of numerous diseases and pathological conditions (Gasparyan et al., 2004). LLLT produces positive effects on irradiated cells and tissues such as proliferation of cells, capillary growth and adenosine triphosphate (ATP) activation (Schindl et al., 1998). Low level laser radiation at different intensities has been shown to stimulate as well as to inhibit cellular processes (Moore et al., 2005). Epidermal growth factor (EGF) is a growth factor that plays important roles in the regulation of cell growth, proliferation and differentiation. This study investigated the effect of low level laser radiation alone as well as in combination with EGF on adult adipose derived stem cells (ADSCs) isolated from human adipose tissue. ADSCs were isolated from human adipose tissue through collagenase digestion and cultured in DMEM-F12 containing 10% FBS and antibiotics and incubated at 37°C in a humidified atmosphere of 5% CO2 (Zuk et al., 2001). iii Semi-confluent monolayers of ADSCs were exposed to low level laser at 5 J/cm2 using 636 nm diode laser with a power density of 12.1 mW/cm2 at room temperature in the dark. Cell morphology was monitored at 0, 24 and 48 h using an inverted light inverted microscope. Cell viability was evaluated at 0, 24 and 48 h using the Trypan Blue exclusion test and an adenosine triphosphate (ATP) luminescence assay. bFGF (basic fibroblast growth factor) indirect ELISA and optical density assays were used to monitor cell proliferation at 0, 24 and 48 h post irradiation. In addition the expressions of stem cell markers, β1-integrin and Thy-1, were monitored by immunocytochemical live cell surface labelling and Western blot analysis. Cells were incubated with EGF to enhance proliferation and differentiation and the cell morphology, viability and proliferation were monitored as well as the expressions of stem cell markers, β1-integrin and Thy-1. Morphology of the cells was not altered by irradiating them with 5 J/cm2 using diode laser at 0, 24 and 48 h. Cell viability and proliferation showed an increase at 24 and 48 h post irradiation. At 0 h, there was no significant difference between irradiated and non-irradiated cells in cell viability and proliferation. There was an increase in the expression of β1-integrin and Thy-1 after irradiation as shown by Western blot analysis and immunocytochemical live cell surface labelling. Cell viability and proliferation showed a significant increase at all time points post irradiation with the addition of EGF. There was no noticeable change in cellular morphology at any time point. Low level laser irradiation of human ADSC’s at 636 nm with 5 J/cm2 and 12.1 mW/cm2 increased the viability and proliferation of these cells in vitro. Furthermore, low level laser irradiation appeared to increase the expression of stem cell markers, β1-integrin and Thy-1. In addition, laser irradiation did not alter the morphology of the cultured cells. The addition of EGF to the cells also increased their viability and proliferation as well the expression of the markers, β1-integrin and Thy-1. The study showed that laser irradiation stimulates two important cellular responses namely cell viability and proliferation which indicates that ADSCs may be suitable for tissue engineering and future cell differentiation studies