| Objective: To compare the effects of 10600nm CO2 fractional laser and topical retinoic acid formulation on the skin histological and ultrastructural changes of Wistar rats, to preliminary explore the long-term effectiveness and efficiency of 10600nm CO2 fractional laser and topical retinoic acid, and to provide a scientific treatment basis for clinical practice.Methods: Depilating dorsum skins of 45 female Wistar rats, randomly divided into nine groups, and divided the back skins into 4 groups: nearly the left side of the head is the normal control group (A); nearly the left side of the tail is the retinoic acid group (B); nearly the right side of the tail is the combination treatment group(C); nearly the right side of the head is the fractional laser group (D). Area C and D were irradiated with 10600nm CO2 fractional laser in the first week, parameter settings: micro pulse energy, 15mJ; density, 5%; frequency, 300Hz; with a figure of square,10mm×10mm area B and C were wiped with 0.025% retinoic acid cream daily after laser irradiation ,for 3 weeks. Specimens were collected on day 3 and in weeks 1-8 after CO2 fractional laser irradiation, and then histological detection,hydroxyproline kits, and Real-time PCR method were used for detection of the changes of dermis thickness, content of hydroxyproline and the expression level of type ? precollagen mRNA in the four regions of the back of rats. The ultrastructural changes of rat skin were observed by transmission electron microscope (TEM) at 3 weeks after irradiation.Results: ? 3 to 8 weeks later, the dermal thickness of the Wistar rats in the treatment groups (B, C, D) increased compared with the normal control group(A) (P< 0.05); 2 -4 weeks later,the dermal thickness of the fractional laser group (D)increased significantly compared with the retinoic acid group (B) , the difference was statistically significant (P <0.05); 2 ?6 weeks later,the dermal thickness of the combination treatment group (C) increased significantly compared with the retinoic acid group (B)(P < 0.05).? On the third day, the hydroxyproline content of the treatment groups (B, C, D) was lower than the normal control group(A); at 1 week , the hydroxyproline content of the treatment groups (B, C, D) was higher than the normal control group(A) and continued to rise, the maximum of the combination treatment group (C) and the fractional laser group (D) were at 5 weeks and the retinoic acid group (B) were at 6 weeks; at 8 weeks, the hydroxyproline content of the combination treatment group (C) was still significantly higher than other groups(P < 0.05); the difference of the hydroxyproline content of the fractional laser group(D) and the retinoic acid group (B) in 1 ?4 weeks after irradiation was statistically significant (P < 0.05); ?3 days to 1 weeks after irradiation, the expression of III collagen mRNA in the fractional laser group (D) were lower than the normal control group (A); after 1 weeks the III collagen mRNA expression of the treatment groups(B, C, D) were increased than before, especially the combination treatment group (C)which reached peak fastest (3 weeks up to peak,5.61 ± 0.7);?3 weeks later,when rat skin was observed by transmission electron microscopy ,a denser arrangement of collagen was found in the rat skin of the treatment groups (B, C, D) than that in the normal control group (A),and the number of collagen per unit was increased significantly.Conclusion: Collagen synthesisi and remodeling were accurred both topical retinoic acid and irradiate 10600nm CO2 fractional laser, and the effect could last for at least 8 weeks; Compared with retinoic acid preparations, the tender skin effect of 10600nm CO2 fractional laser work more quickly but maintain shorter;Combined use of CO2 fractional laser and retinoic acid preparations could produce synergy.Objective: To compare the expression level of miR-29a, Akt, TGF - ? mRNA and the expression of phosphorylated Akt and TGF - ? protein in Wistar rats' skin with 10600nm CO2 fractional laser and topical retinoic acid formulation , further explore the possible molecular mechanisms of miR - 29a / Akt/TGF - ? signaling pathways in inducing the skin collagen synthesis.Methods: The hair on the back of 10 female Wistar rats was removed and the back was divided equally to four regions with the cross-streaking method: nearly the left side of the head is the normal control group (A); nearly the left side of the tail is the retinoic acid group (B); nearly the right side of the tail is the combination treatment group (C); nearly the right side of the head is the fractional laser group (D). Area C and D were irradiated with 10600nm CO2 fractional laser in the first week,parameter settings: micro pulse energy, 15mJ; density, 5%; frequency, 300Hz;with a figure of square, 10mm×10mm; area B and C were wiped with 0.025%retinoic acid cream daily after laser irradiation,for 3 weeks.Specimens of 4 areas were collected in week 3 after CO2 fractional laser irradiation , respectively using Western blot method to detect he expression of phosphorylated Akt and TGF - ?protein and Real - time PCR method to detect the expression level of miR - 29a,Akt, TGF - ? mRNA.Results:?At week 3 the expression level of Akt and TGF - ? protein in rats skin tissue were significantly higher than the control group,the increase of the combination group was the most significant (P < 0.05). ?Real - time PCR detection results showed that up regulation of Akt and TGF-? mRNA expression and down regulation of miR-29a mRNA expression were observed by the treatment groups (B, C, and D); which the difference in the combination treatment group (C)was the most significant (P<0.05).Conclusion: Retinoic acid formulation and CO2 fractional laser both could the active miR-29a/Akt/TGF-P signal pathways; miR-29a/Akt/TGF-? signal pathways may play a certain role in the promotion of collagen synthesis and proliferation;combined use of CO2 fractional laser and retinoic acid preparations may produce the most significant role in the activation of miR-29a/Akt/TGF-? signal pathways. |
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