Photobiomodulation of human adipose-derived stem cells using 810nm and 980nm lasers operates via different mechanisms of action.
Level 5 - mechanism / opinion, no new human data
In vitro bench study on cultured human cells
PubMed 27751953 · doi:10.1016/j.bbagen.2016.10.008
What was done
Researchers exposed human adipose-derived stem cells in vitro to near-infrared photobiomodulation at either 810 nm or 980 nm across various fluences. They assessed cell proliferation at 24 hours and measured changes in cytosolic and mitochondrial calcium levels. To probe the mechanism of action, they evaluated the effects of calcium channel blockers (capsazepine for TRPV1 and SKF96365 for TRPC channels) and temperature manipulations (adding 4°C medium during light exposure or pre-incubating cells at 42°C).
What was found
Both wavelengths showed a biphasic dose response for cell proliferation at 24 hours. The peak dose for 810 nm was 3 J/cm², whereas the peak dose for 980 nm was 10 to 100 times lower at 0.03 or 0.3 J/cm². Treatment with 980 nm, but not 810 nm, increased cytosolic calcium while decreasing mitochondrial calcium. The effects of 980 nm were blocked by capsazepine, SKF96365, cold medium (4°C), and 42°C pre-incubation, none of which affected the response to 810 nm.
Why it matters
This study provides evidence that 810 nm and 980 nm near-infrared lasers stimulate stem cells through distinct primary pathways: 810 nm via mitochondrial cytochrome c oxidase and 980 nm via temperature-gated calcium ion channels. These findings indicate that optimal dosing fluences can vary by orders of magnitude depending on the chosen laser wavelength.
Limits
The study is entirely in vitro in cell culture without in vivo or clinical testing. The abstract does not state the number of donors, cell lines, or biological replicates (n). Absolute values for proliferation rates, calcium concentration shifts, and variance or statistical significance metrics are not reported in the abstract.