Representation of laser irradiation system. A. Figure illustrating the experimental set-up with the main technical features of the beam used for red laser in vitro irradiation. Since the portion of the laser beam with homogeneous power is not coincident with the geometric axis of the laser beam, a black mask interposed between laser source and cells was used to obtain the homogeneous fluency of the beam. B. The cell culture substrate, composed of glass coverslip coated with collagen and laminin, is also shown.