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232 D. Barolet Figure 10 Current and promising LED applications as a function of wavelengths. effect can be observed.18 It is thus important to establish time- dependent responses to adequately assess photomodulatory effects. Fibroblasts in culture show physiological cyclical patterns of procollagen type I up-regulation and metallo- proteinase-1 (MMP-1) down-regulation that can be empha- sized by LED treatments every 48 hours.19 State of Cells and Tissues The magnitude of the biostimulation effect depends on the physiological condition of the cells and tissues at the moment of irradiation.20 Compromised cells and tissues respond more readily than healthy cells or tissues to energy transfers that occur between LED-emitted photons and the receptive chromophores. For instance, light would only stimulate cell proliferation if the cells are growing poorly at the time of the irradiation. Cell conditions are to be considered because light exposures would restore and stimulate procollagen produc- tion, energizing the cell to its own maximal biological poten- tial. This may explain the variability in results in different studies. Effects of LED LED therapy is known for its healing and antiinflammatory properties and is mostly used in clinical practice as a supple- ment to other treatments such as nonablative thermal tech- nologies. Different LED applications can now be subdivided according to the wavelength or combination of wavelengths used (see Fig. 10). LED therapy can be used as a standalone procedure for many indications, as described herein. A sum- mary of recommended LED parameters for various clinical applications are presented in Table 1. When reviewing the literature, one needs to keep in mind that results from different studies may be difficult to compare because the potential effects of variation of treatment param- eters (eg, wavelength, fluence, power density, pulse/contin- uous mode and treatment timing) may vary from one study to the next. Moreover, there is the possibility that the photobi- omodulatory effects are dissimilar across different cell lines, species and patient types. We will now discuss current LED applications. Wound Healing Early work involving LED mainly focused on the wound healing properties on skin lesions. Visible/NIR-LED light treatments at various wavelengths have been shown to in- crease significantly cell growth in a diversity of cell lines, including murine fibroblasts, rat osteoblasts, rat skeletal muscle cells, and normal human epithelial cells.21 Decrease in wound size and acceleration of wound closure also has been demonstrated in various in vivo models, including toads, mice, rats, guinea pigs, and swine.22,23 Accelerated healing and greater amounts of epithelialization for wound closure of skin grafts have been demonstrated in human studies.24,25 The literature also shows that LED therapy is known to positively support and speed up healing of chronic leg ulcers: diabetic, venous, arterial, pressure.26 According to our experience, LED treatments are also very useful after CO2 ablative resurfacing in reducing the signs of the acute healing phase resulting in less swelling, oozing, crusting, pain, and prolonged erythema thereby accelerating wound healing (see Fig. 11). It is important to keep in mind that to optimize healing of necrotic wounded skin, it may be useful to work closer to the near infrared spectrum as an increase in metalloproteinases (ie, MMP-1, debridment-like effect) production accelerates wound remodeling. Inflammation Free radicals are known to cause subclinical inflammation. Inflammation can happen in a number of ways. It can be the result of the oxidation of enzymes produced by the body’s defense mechanism in response to exposure to trauma such as sunlight (photodamage) or chemicals. LED therapy brings a new treatment alternative for such lesions possibly by coun- teracting inflammatory mediators. A series of recent studies have demonstrated the antiin- flammatory potential of LED. A study conducted in arachi- donic acid-treated human gingival fibroblast suggests that 635 nm irradiation inhibits PGE 2 synthesis like COX inhib- itor and thus may be a useful antiinflammatory tool.27 LED photobiomodulation treatment has also been shown to accel- erate the resolution of erythema and reduce posttreatment discomfort in pulsed dye laser (IPL)-treated patients with photodamage and to prevent radiation-induced dermatitis in breast cancer patients.28,29 Patients with diffuse type rosacea (unstable) (see Fig. 12), keratosis pilaris rubra, as well as postintervention erythema (eg, IPL, CO2) (Fig. 11) can ben- efit from a quicker recovery with complementary LED ther- apy. (See also section on wound healing). Because LED is known to reduce MMPs, it might be useful in conditions in which MMPs are implicated. One such case is lupus erythematosus (LE). LE is a heterogeneous autoim- mune disease associated with aberrant immune responses including production of autoantibodies and immune com- plexes and specific MMPs have been implicated in its etiol-PDF Image | (LEDs) in Dermatology
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