Effects Of Estradiol Benzoate On TGFβ1/Smad3Signal Transduction Pathway In Skin Of Ovariectomized Rats

BackgroundAging is one of the basic law of nature, which scientists are always interested in. In recent ten years, a lot of research has been done to study the skin aging, which is one of hot spots in aging process. For a long time, we know that it would become dry、desquamation、congestion and wounded in the skin of postmenopausal women. Also, the aging skin can easily occur venous ulcer and decubitus after wound, which could be easily cured by using estrogen. Therefore, we consider that skin is sensitive to estrogen. The relationship between the estrogen and skin aging、wound healing has attracted extensive attentions. To eplore the mechanism of estrogen on TGFβ1/Smad3signaltransduction pathway in skin of ovariectomized rats is a significant project.The study of skin aging has showed that collagen is the main structual protein of extracellular matrix in human beings, and90%of the derma fiber is collagen fiber. The research shows, with age growing, collagen fiber and dermis in skin become thinner.70%of collagen in the skin of infants and the youth is type I collagen, and the rest is type II collagen. When the skin aging, the proportion of them inverts, also, the transmission of the stress in collagen, the anti-shear and the total content of collagen has been reduced obviously, especially the reduction of the content of soluble collagen. At the same time, amount of elastic fibers in papillary dermis and reticular dermis has been reduced and degenerated, and the arrangement of collagen fibers and elastic fibers has also been gradually disordered, which leads to wrinkle and dermatolysis. Skin aging can be devided into two types:one is endogenous aging, the other is exogenous aging. Endogenous aging merely refers to the changes of skin due to the age increasing, such as slightly thinning of epithelium, the loss of skin elasticity and certain substances. Exogenous aging which is caused by environmental factors, mainly refers to photoaging because of ultraviolet, thus the skin exogenous aging can also be knew as the skin photoaging. There are some treatments to prevent and cure the photoaging, but the endogenous aging is inevitable and continues. With the social development, people consider that the factors affecting organization senescence are abundance and complicated. Although the skin has strong ability to regenerate, maintaining skin elasticity and postponing aging are still the most important topic to human beings in all ages. A number of studies have shown that estrogen plays a important role in delaying skin aging, the mechanism of which may be related to intracellular signal transduction pathway, even the further study shows that the increasing of the expression of TGFβ1/Smads signaling pathway contributes to ameliorate skin aging. Owing to the diversity of the biological effects of estrogen, the specific mechanism for delaying skin aging of estrogen and its receptors, especially the regulation of signal transduction pathway, is not yet clear, the reports about which are deficient up to the present. Through studying the expression of estrogen receptor and the signaling pathway in aging skin, we come to understand the regulative mechanism of skin aging, which finally offers theoretical basis and practical treatments to delay skin aging and avoid systemic side effects clinically and scientifically.Estrogen that plays a main role in promoting the growth of the female genital organs and the appearance of secondary sexual characteristics and maintaining its normal state, is mainly secreted by the ovaries, and it also affects the function of systemic organ. Estrogen plays a important role in skin, which is the largest non-genital organ. The biological activity of estrogen to each target organ is up to the status of ligand structure and the subtypes of the estrogen receptor. The estrogen targets on the skin tissue, thus it is possible to delay skin aging through estrogen replacement therapy. The main function of estrogen in skin has been shown as:(l)to prevent skin aging.(2)to repair the skin wound.(3)to adjust hair growth.(4)to inhibit the secretion of sebaceous gland.Fibroblast is one of the major cellular components in the dermis, which forms the collagen fibers, elastic fibers, matrix and so on. The decreasing of collagen can lead to the aging appearance in postmenopausal women. Studies has shown that collagen synthesis increases appoximately76%through culturing the fibroblast of rats by using estradiol. The research to rats has found that estrogen is the important regulative factor of connective tissue in photoaging skin and normal skin, which can stimulate the formation of the connective tissue. Someone has investigated the influence of aging and menopause on skin collagen, the results showed that, compared with aging, menopause is more important to collagen, it means that estrogen makes sense to collagen synthesis and its expression.Some studies have confirmed the distribution of estrogen receptor(ER) in human fibroblast. Transforming growth factor(31(TGF(31) is the important regulative factor in wound healing, and also be considered as the most significant factor leading to fibrosis. TGFβ1can promote the collagen synthesis by activating the intracellular signal transduction molecule of Smad3, therefore, we speculate whether estrogen can delaying skin aging by increasing skin collagen through regulating the TGFβ1/Smad3signaling pathway and inhibiting collagen degradation. Whether the estrogen can affect the TGFβ1/Smad3signaling pathway in skin tissue, it is less report at home and abroad. In our study, ovariectomized female rats are targeted, and related mechanism of estrogen for delaying skin aging has been investigated by detecting the expression of TGFβ1and Smad3.Objective(1) To build the animal models of menopausal rats.(2) To investigate the effect of estradiol benzoate on the protein expression of TGFβ1/Smad3signal transduction pathway in skin of ovariectomized rats and the molecular mechanism of estradiol benzoate postponing skin aging.Methods1.Thirty-five healthy female Wistar rats were randomly divided into four groups. Group A was normal control group(n=5). Group B was sham-ovariectomy(n=10). Group C was ovariectomy(n=10). Group D was ovariectomy and estradiol benzoate replacement(n=10). Animal model was made as planning.2.The skin tissue is acquired from executing the rats and is made into paraffin section. The paraffin sections of four groups were stained with HE and TGF(31, SmadS immunohistochemical staining to observe the pathological changes of the rats skin and the expression of TGFβ1, Smad3.3. The sections of four groups were observed at high magnification (20×10) b-y optical microscope.4. The sections were observed with upright fluorescence microscope(model:BX-51,produced in Olympus Ltd.) after im-munohistochemical staining.5. Digital photos of sections were collected and then input computer. MOD(mean optical density) of each photo which were marked TGFβ1and Smad3was measured. Data an-alysis used software SPSS13.0.ResultsThe results showed there was statistical difference between the four groups(P<0.05) both the expression of TGFβ1and Smad3. The expression of TGFβ1and Smad3of group D was statistically higher than that of group A (P<0.05). And the expression of TGFβ1and Smad3of group B was also the same as that of group A (P>0.05). While the expression of TGFβ1and Smad3of group C was statistically lower than that of group A (P<0.05)CnclusionEstradiol benzoate can directly regulate the fibroblast proliferation in the skin tissue of rats through affecting the expression of TGFβ1and Smad3in skin tissue, which may be related to molecular mechanism for postponing skin aging.