OBJECTIVETo study the effect of Q-switched 1 064 nm Nd:YAG laser treatment on the proliferation of dermal collagen and expression of immunoglobulin binding protein/glucose related protein 78 (BiP/GRP78) in rats' skin and the mechanism of endoplasmic reticulum stress.

METHODSDorsal skin of 25 Wistar rats was divided into two parts equally after hair removal. Q-switched 1 064nm Nd:YAG laser was applied to treat rats' dorsal skin for 4 times at an interval of 2 days in the experiment part. The control part received no laser treatments. The rats' dorsal skin samples were taken on the 14th and 30th day after laser treatment to measure the dermis thickness and collagen bundles under HE stain and to measure the hydroxyproline content by alkaline hydrolysis method after laser treatment. The expression of BiP/GRP78 was also detected by immunohistochemical method. Statistics was used to analyze the data.

RESULTSThe dermis thickness increased by 29. 6% on the 14th day and 16.7% on the 30th day after laser treatment. The collagen bundles became thicker and denser. The hydroxyproline in the skin was also raised after laser treatment (P < 0.05). The immunohistochemical result showed the expression of BiP/GRP78 increased to 100% after laser treatment, showing a significant difference from the control group(X2 = 28.76, P < 0.01).

CONCLUSIONSThe Q-switched 1064 nm Nd:YAG laser treatment can induce endoplasmic reticulum stress, so as to enhance the protein folding and synthesizing precisely. The proliferation of dermis collagen is the base of effect of non-ablative skin rejuvenation.