| BackgrandLong-term sun exposure, mainly is the UV damage, can lead to skin aging or accelerated aging occurrence skin photoaging.Skin photoaging performance for the skin rough, relaxation, drying, irregular pigment changes, wrinkles, even can happen benign or malignant tumor. Both intrinsic and extrinsic influences are involved in the process of skin aging.People usually call the factors, which due to such as gravity, the important organ physiological dysfunction which caused by endogenous structure change called natural aging,and extrinsic influences such as pollution,exposure to sunlight,UV,smoking,repetitive muscle movements like squinting or frowning,nutriti-on and sleeping position are called extrinsic skin aging. Because the solar UV radiation is the most important factor in environmental factors resulting in skin aging, it is usually said that extrinsic skin aging is skin photoaging.Intrinsic aging is characterized by smooth, thinned skin with exaggerated expression lines and the occurrence of benign neoplasms such as seborrhoic keratoses and cherry angiomass. In the process of intrinsic aging, the ability of the skin water synthesis and the number of the sebaceous glands is reduced,which aggravate the dry degree, result in corneous layer hardens, breaking out. Temporary water shortage causes facial skin shallow wrinkles. The natural process of aging contributes to the generation of reactive oxygen species (ROS) that stimulate the inflammatory process in the skin, activating transcription factors that regulate the proteolytic degradation of the extracellular matrix (ECM). An interlinked network of enzymes that convert ROS to harmless water and oxygen molecules regulates the antioxidant defense system, which is reduced in the skin of aging individuals.Histological changes include a reduced surface contact between the epidermis and dermis, which results in a reduced exchange of nutrients and metabolites between the two skin layers.Extrinsically aged skin is also called Skin photoaging, which is characterized by signs such as wrinkles, dyspigmented lesions, teleangiectasia and loss of elasticity Histological analysis of photo-damaged skin shows epidermis a thickening or thin, black element cell proliferation or reduce, leather capillary array of disorder, inflammatory cells infiltration and extracellular matrix components change,the major modifications in the dermis including the formation of solar elastosis. UV radiation can down-regulate the expression of TGF-β or TGF-β receptor and result in the reduction or apoptosis of fibroblasts as well as the activation of AP-1by blocking TGF-b/Smad and p38MAPK signaling pathways. The changes of fibroblasts and AP-1respectively increase the expression of MMPs, Cathepsin Qserine proteases,fibroblast elastase,free radicals,ROS etc,which can lead to collagen or elastin production decreasing as well as collagen and ECM breakdown increasing,, leading to epidermal invagination representing the beginning of wrinkles. In aged skin, MMPs may already exist in a more active state because of the decreased levels of tissue inhibitors of MMPs.Thus cause dermal collagen, extracellular matrix component degradation. Additionally, UV light causes the depletion of cellular and enzymatic antioxidants and activates the neuroendocrine system leading to immunosuppression and the release of neuroendocrine mediators. Ultimately, these may contribute to skin photoaging presentation,Thus cause dermal collagen, extracellular matrix component degradation, for the performance of the wrinkles, skin flabby, rough, decreased elasticity, irregular pigment change.Skin photoaging lead to premature loss beauty symptoms, the serious influence people appearance beautiful requirements.Recently, more and more patients with beauty,they demand for minimally invasive treatments to preserve or improve skin smoothness and tonicity is increasing. Traditional ablative laser therapies with CO2-or Er:YAG-lasers are highly effective for the repair of rhytides and photoaged skin. These treatments remove the entire epidermis, allowing for its complete regeneration and extensive remodeling.However, ablative resurfacing requires significant downtime and may involve persistent erythema,hyperpigmentation,infection or scarring.Healing after non-ablative resurfacing techniques takes less downtime, but seems to be less effective even if several treatment sessions are applied.The fractional ablative laser (AFP) emits light in a pixilated fashion onto the skin,producing an array of microthermal zones (MTZs) in the dermis with depths of300-400mm.It has been postulated that columns of cellular debris are eliminated by trans-epidermal elimination and remodeling due to inflammation.At present, the fractional ablative laser has got very good treatment effect in the repair of scar and light aging.But it is also have Fife and Avram MM reported that hypertrophic scarring of neck following Ablativbe Fractional Carbon Dioxide Laser resurfacing,Speculation may be due to the thin skin and lack of skin appendage.In addition, the choice of high energy,caused the postoperative infection may also is one of the important reasons.TGF-β has many biological effects,under normal circumstances, these cytokines are in a network equilibrium to maintain the tissues and organs is relatively stable. When ultraviolet irradiation,the balance will be destroyed, TGF-β was synthesized and releaseaed by many inflammatory cells, and then promoted the fibroblast cells, monocytes and lymphocytes division and proliferation. TGF-β with TGF-β receptor and Smad protein jointly constitute TGF-P/Smad signaling pathway. Through this signaling pathway, TGF-β can facilitate collagen Ⅰ/Ⅲ and elastin synthesis in fibroblasts, repress matrix metalloproteinases (MMPs) activity, enhance fibronectin expression, decrease collagen fibers degradation and heightenECM. Furthermore, TGF-β can also activate mitogen-actived protein kinase (MAPK) to stimulate fibroblasts proliferation, re-strain fibroblasts apoptosis, and improve the expression of collagen fibers,elastic fibers and fibroblasts.TGF-β1is known to be a potent stimulus for fibrosis,which stimulates fibroblast proliferation and dramatically increases the production of collagen and other extracellular matrix proteins,so from fibroblasts activation and new collagen synthesis point of view, we select TGF-β1as the research object to further clarified the mechanism of Ablativbe Fractional Carbon Dioxide Laser.we use rats as experimental animals and we conduct the Ablativbe Fractional Carbon Dioxide Laser experimental research.So, in order to further clarified the mechanism of Ablativbe Fractional Carbon Dioxide Laser,we use rats as experimental animals and we conduct the Ablativbe Fractional Carbon Dioxide Laser experimental research.ObjectiveIn Wistar rats for preparation skin photoaging model, to observe the influence of Ablative fractional CO2laser to photoaging rats.From molecular and tissue pathology aspects to discuss the mechanism of Ablative fractional CO2laser in the treatment of photoaging diseases in order to provide the evidence for the clinical application of Ablative fractional CO2laser.Methods Twenty-four white male Wistar rats, weight250g±10g,were divided randomly:8in blank group,16in model group, Every Wistar rats was shave off on the back for5cm×6cm bare area. Model group were exposed to the stage from the light source30cm and was received continuous irradiation as10min once a day,a week after irradiation, the time extended10min every week until the irradiation time is60min, maintain this time. The irradiation strength were UVB0.12mW/cm2, UVA1.05mW/cm2respectively. While the blank group without irradiation treatment. Observe the histological, antioxidant indexes of MDA, SOD, hydroxyproline contents every two weeks to evaluate the effects of photoaging model. When photoaging skin models were completed, the Wistar rats in model group were divided randomly into two groups:8in photoaging recovery group(A1)and8in photoaging laser intervention group(A2).Each Wistar rats’s back in A2was divided into three areas and recieved different density of laser treatment. The laser is from UltraPulse Encore (Lumenis Inc.SantaClara,Deep FXTM treatment probe,energy:10mJ,Frequency150hz, time interval0.5s, graphics for square. To observe the change of skin histology, antioxidant indexes (MDA, SOD), hydroxyproline, and TGF-β1expression on the time points1day,1week,2week,4week after treatment.Results1.14Wistar rats live in model group,we see skin labby, elastic loss,rough hypertrophy,accompanied by desquamation,skin furrow deepen,skin crest elevation in the area of UV irradiation. The histological,we see the epidermis structure is not very intact,leather fiber organization arrangement disorder and part of the areas have inflammatory cells infiltration.In biochemistry,with the UV illumination, the MDA content in rat skin was elevated in model group,the content of SOD,HYP in rat skin was reduced, the content in the control group was stable. In irradiation after2week, 4week,8weeks,12weeks, the MDA content, SOD content and HYP content in A group compared with the control group, the two groups have significant difference (P<0.05).2. After the fractional laser treatment,compared with the photoaging recovery group(A1),the improvements of photoaging skin is obvious either from eye view or histological in the laser treatment group(A2),Along with the treatment, the MDA content in the laser treatment photoaging group decreased significantly(P<0.05),the SOD and HYP content in the laser treatment photoaging group increased (P<0.05)The express of TGF-β1in skin tissue was over-active,and with the extension of recovery time, the expression of TGF-β1was increased gradually.After the laser treatment of1week,2weeks,4weeks, the expression of TGF-β1in the laser treatment photoaging group is significantly higher than the natural recovery group (P <0.05). Conclution1. In wistar rats as a laboratory animal to UV radiation rats bare skin,in12weeks appear the skin photoaging clinical and characterristics,we construct the skin photoaging model successfully.2.Ablative Fractional CO2laser can improve photoaged skin histological characteristics and help repairing the imbalance anti-oxidant system of photoaging skin.3.Ablative Fractional CO2laser can make the express of TGF-β1was over-active,and with the extension of recovery time,the expression of TGF-β1was increased gradually, this could be one of the possible mechanisms of Ablative Fractional CO2laser repair of photoaging. |
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