Visible light regulates neurite outgrowth of nerve cells

Abstract

The neurite outgrowth of PC12 cells on collagen-coated glass plates under light emitting diode (LED) irradiation at several wavelengths (i.e., 455, 470, 525, 600, 630, 880 and 945 nm) was investigated. No neurite outgrowth was observed during cultivation under irradiation from the lamp of an inverted light microscope through filters (yielding mixed light at ca. 525 nm and more than 800 nm), whereas neurite outgrowth was observed during cultivation in the dark. When these cells were irradiated with monochromatic LED light, neurite outgrowth was slightly, but not completely, suppressed at 455, 525, 600, 630, 880 and 945 nm, as was observed in the case of mixed light. Long connected neuronal outgrowths (e.g., 3 mm length) were observed with LED light at 470 nm and 1.8 mW/cm(2) intensity. No such outgrowths were observed at other LED light wavelengths (i.e., 455, 525, 600, 630, 880 and 945 nm). Irradiation at 470 nm may have caused specific responses to transductional signals in these cells that led to the connection of neuronal outgrowths between cells. Not only suppressed neurite outgrowth but also long connected neurite outgrowths were observed when PC12 cells were cultured under several different wavelengths of light.

Analysis of laser-induced heating in optical neuronal guidance

“…Previous estimates of this effect in the optical neuronal guidance experiments suggested a negligible temperature increase (Albrecht-Buehler, 1991;Carnegie et al, 2008Carnegie et al, , 2009Ehrlicher et al, 2002;Graves et al, 2009;Higuchi et al, 2005Higuchi et al, , 2007Mohanty et al, 2005;Stevenson et al, 2006;Mathew et al, 2010;Koch et al, 2004), but our more detailed simulations show a temperature increase of the order 1 • C/100 mW of laser power, which is in agreement with experimental results and modelling from the field of optical trapping (Schönle and Hell, 1998;Braun and Libchaber, 2002;Peterman et al, 2003;Ebert et al, 2007). Furthermore, we find a temperature gradient of the order 1 • C/typical neuronal growth cone-radius.…”

“…A curious new addition to the field of neuronal guidance is optical neuronal guidance (Carnegie et al, 2008(Carnegie et al, , 2009Ehrlicher et al, 2002;Graves et al, 2009;Higuchi et al, 2005Higuchi et al, , 2007Mohanty et al, 2005;Stevenson et al, 2006;Mathew et al, 2010;Koch et al, 2004) reviewed in Franze and Guck (2010) and Stevenson et al (2010). In 1991 it was first observed that Swiss 3T3 cells (mammalian fibroblast-like cells) would extend pseudopodia towards near-infrared light sources (Albrecht-Buehler, 1991), and in 2002 it was shown that a near-infrared laser spot placed on and in front of the leading edge of growing PC12 and NG108 neurons enhanced the neuronal growth into the laser spot and resulted in laser-guided turns of the growth cone and increased growth speed (Ehrlicher et al, 2002).…”

Neurite growth acceleration of adult Dorsal Root Ganglion neurons illuminated by low-level Light Emitting Diode light at 645 nm

“…780 nm laser irradiation of embryonic rat brain cells embedded in NeuroGel resulted in the development of a much higher number of large size neurons with dense branched interconnected network of neuronal fibers after only 1 week [22]. Contradictory effects of visible light irradiation on neurite growth were reported on PC12 cells: no outgrowth under irradiation of polychromatic microscope light (1 mW/cm 2 , 36 h), outgrowth with cultivation in the dark, unequal decrease of outgrowth under monochromatic LED at 455, 525, 600, 630, 880 or 945 nm (1 mW/cm 2 , 36 h) [23], increase and decrease of the neurite length (at 0.01 mW/cm 2 and 0.006 mW/cm 2 , respectively, at 670 nm) [24], increase of the neurite outgrowth (4 W/cm 2 , 810 nm, 5 s) [25]. Most of these published studies provide mean irradiance at the output of the light source, which does not take into account the real irradiance reaching the cells.…”

“…Enhancement or inhibition effects on neurite growth irradiated by low power visible light from LED or laser have been reported on embryonic primary rat cortical neurons [15,21], embryonic rat brain cells [22] and PC12 cells [23][24][25]. Red and near infra-red light irradiation have been shown to be effective as a non-invasive post-operative therapeutic solution for enhancing nerve regeneration and functional outcome in different animal models of peripheral nerve injury [15,[26][27][28].…”

Influence of distant femtosecond laser pulses on growth cone fillopodia

“…In addition, the attraction efficiency while guiding axons with laser light has been tested for different wavelengths (Stevenson et al 2006). Recently, neurite outgrowth of PC12 cell lines has been observed under LED illumination (Higuchi et al 2007). However this outgrowth only occurred at a specific wavelength (479 nm).…”