Laser Photobiomodulation of Gene Expression and Release of Growth Factors and Cytokines from Cells in Culture: A Review of Human and Animal Studies

Aim: The aim of this paper was to review experimental studies of laser irradiation of human and animal cells in culture to assess the photobiomodulatory effects of such irradiation on gene expression and release of growth factors and cytokines. Background: Previous studies have reported that the release of certain growth factors and cytokines by various types of cells can be modulated by laser irradiation. A review of recent studies may provide further insight into the clinical effects brought about by laser irradiation of cells and tissues, including changes in inflammation and cellular proliferation. Methods: A systematic review was completed of original research papers investigating the effects of laser phototherapy on gene expression and release of these mediators from human and animal cells in culture (January 2002 to September 2009). Relevant papers were retrieved primarily from PubMed and Medline databases. The search terms were "growth factors", "cytokines", "laser therapy", "laser irradiation", "laser phototherapy," and "phototherapy". Results: A total of 17 relevant papers were included in the review, comprising studies on a variety of cell types. Considerable variation occurred in research design, methodology, and irradiation parameters employed, limiting comparison of research findings between studies. Results demonstrated that laser irradiation at green, red, or infrared wavelengths at a range of dosage parameters can cause significant changes in the cellular gene expression and release of these mediators, and that such effects depend upon wavelength and radiant exposure. Conclusion: Findings from the reviewed studies clearly demonstrate the ability of laser irradiation to modulate gene expression and the release of growth factors and cytokines from cells in culture. Further work is indicated at the clinical level to elucidate the putative clinical relevance of these cellular-level effects.