| ObjectiveDiabetes mellitus is a highly prevalent disease in the world. Meanwhile the skin lesions which are one of the complications in diabetes harm the health of humans seriously. Previous studies have confirmed that histochemical and cytobiology changes have already been occurred in diabetic skin before injury-"underlying disorder" of diabetes. The thickness of epithelium and dermis in diabetic rats were decreased. The features of mutilayer epithelium structure disappeared in epidermis. The dermis layer became thinner with tenuous collagen distributing disorderly and the part of the collagen fibers in dermis became atrophic, swollen and degenerated.OLETF rats are a spontaneous type2diabetic model. LETO rats and OLETF rats which were taken rosiglitazone, were enrolled as controls, respectively.The histological changes of the skin, the biological behavior of dermal fibroblasts and the expression of Advanced Glycosylation End products (AGEs) and Bcl-xL were observed to research the effect and mechanism of rosiglitazone on the skin in type2diabetic rat.MethodsBlood glucose was determined by oral glucose tolerance test (OGTT) for20male OLETF rats. The diabetes was confirmed with blood glucose peak level>16.7mmol/L and blood glucose level>11.1mmol/L taken glucose120minutes later. Up to30weeks, the12of20OLETF rats were developed T2DM. They were randomly divided into diabetes mellitus control (DM) group and rosiglitazone (RGZ) group (n=6per group). The8male LETO rats were used as a normal control (NC) group. DM group and NC group were watered intragastrically for12weeks. RGZ group was taken the rosiglitazone (3mg/kg-d) intragastrically for12weeks.After12weeks of treatment, the rats were sacrificed and the abdominal skins were obtained from each rat. One part of the tissues was fixed in4%formaldehyde solution and another part of the tissues was frozen at-70℃. The skins which were fixed in4%formaldehyde solution were paraffin embedded, cut into5-μm-thick slices. The slices were stained with Hematoxylin-eosin dye, Azure Ⅱ-eosin Y-Wright’ s staining, acridine orange (AO), Masson trichrome staining and immunohistochemis-try assay to observe the histological changes of epidermis and dermis of skin, determ-ination of fibroblasts and fibrocytes, the quantity of cell apoptosis in dermal, changes of collagen fibers and detection of expression of AGEs and Bcl-xL, respectively.The parts which were frozen at-70℃were changed into tissue homogenates to determine the relative amounts of the collagen. All results were performed with analysis software for multimedia pathological image.Results1. Obervation of the general conditions of ratsOLETF rats drank much, ate much, had polyuria and felt significantly bleak, and were dull coat. The activity of OLETF rats was worse than LETO rats. LETO rats’ drinking and eating were normal. The skin thickness of OLETF rats were decreased.2. Comparison of the histological changes of skinGroup NC rats displayed intact skin tissue structure, with clear epidermal layers characterised by the typical multilayer epithelium structure and an abundant number of epidermal cells. In contrast, the rats in DM group had unclear epidermal layers, an absence of the multilayer epithelium structure in parts of the skin and a marked decr-ease in the number of epidermal cells. Additionally, some of the collagen fibres beca-me atrophic, swollenand degenerated. However such changes were not detected in RGZ group.3. Comparison of thickness of epidermis and dermis of skinCompared with NC group[(28.18±4.64) μm], the thickness of epidermis of DM group[(12.84±2.01) μm] decreased(P<0.01) and the thickness of RGZ group [(26.37±3.65) μm] was near to NC group(P>0.05). Compared with NC group[(1007.05±167.18) μm], the thickness of dermis of DM group[(591.32±66.77) μm] decreased(P<0.01) and the thickness of RGZ group[(957.60±106.34) μm] was near to NC group(P>0.05).4. Comparison of the quantity of fibroblasts and fibrocytesThe nuclear and cytoplasmic of fibroblasts were blue and gray. respectively. The nuclear and cytoplasmic of fibrocytes were deep blue and red. The quantity of fibroblasts of DM group (3.75±0.597) and RGZ group (5.56±1.230) decreased significantly compared to NC group (7.025±0.705)(P<0.01). The quantity of fibrocytes of DM group (4.75±1.398) increased significantly compared to NC group (3.4±0.668)(P<0.01), but there was no difference between NC group(3.4±0.668) and RGZ group (3.6±0.529)5. Expression of cell apoptosis in dermisWhen normal cells were stained by the AO, the nuclears were green or kelly, and the RNA of cytoplase and nucleoluse saffron were yellow or yellowish red. But apoptotic cells were compact kelly because of apoptotic bodies. Compared to NC group [(4.0000±0.7560)%], the positive expression rates of apoptotic cells of DM group [(9.6667±0.8165)%]and RGZ group [(6.8333±0.7528)%] were increased significantly (P<0.01).6. Comparison of changes of collagen fibresCompared to NC group which were rich in collagen fibres and arranged regularly. The number of collagen fibers decreased and some of the collagen fibres became atrophic, swollen and degenerated in DM group, but there was no difference betw-een NC group and RGZ group.7. Comparison of the expression of Bcl-xLCompared with the NC group(0.253±0.037), DM group(0.119±0.034) had lower intensity of positive expression of Bcl-xL(P<0.01) and RGZ group(0.349±0.027)had higher intensity of it(P<0.01).8. Comparison of the expression of AGEsCompared with the NC group(0.128±0.032), DM group(0.362±0.070) and RGZ group(0.228±0.051)had higher intensity of positive expression of AGEs (P<0.01).9. Compare of the relative amounts of collagenCompared with the NC group (266.0±54.8mg/g), DM group (149.9±18.4mg/g) and RGZ group (209.7±45.2mg/g) had lower contents of collagen. There was no statistically significant difference between NC group and RGZ group(P>0.05). But there was a significant difference between NC group and DM group (P<0.05) as well as DM group and RGZ group(P<0.01).Conclusions 1. The rat model is obesity, and can be the ideal animal model for study on diabetic dermatopathy under type2diabetes.2. T2DM’s rats have had unclear epidermal layers, an absence of the multilayer epithelium structure in parts of the skin and a marked decrease in the number of epidermal cells. Additionally, some of the collagen fibres became atrophic, swollena-nd degenerated. This may arise from accumulation of AGEs which cause the cells to the survival of the internal environment disorder and then make the structure and function of cells change.3. Apoptotic cells increase and the expression of Bcl-xL decrease in dermis of T2DM’s rats.It shows that it could increase the amounts of apoptotic cells through decreasing the expression of Bcl-xL in type2diabetes.4. The contents of collagen decrease resulting from that the number of fibroblasts reduces, which may be due to the increase of apoptosis of fibroblasts, or that the fibroblasts are inhibited synthetizing collagen by AGEs stimulation.5. Rosiglitazone decreases diabetic dermatopathy in OLETF rats, so Rosiglitazone may protect type2diabetes skin to some degree. |
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