The Role Of Decorin In The Tubulointerstitial Damage

Glomerulosclerosis and tubulointerstitial fibrosis are common pathological features of most end-stage kidneys. Accumulation of glomerular extra cellular matrix is a prominent feature of most forms of progressive glomerular disease. But recently years, the importance of tubulointerstitial fibrosis is underscored by the striking correlation between the severity of matrix deposition and the progression of renal insufficiency culminating in eventual organ failure. Tubulointerstitial fibrosis (TIF) is an irreversible pathologic process that arises by all kinds of primary or secondary renal diseases, culminating in the destruction of renal normal tissue structure and the accumulation of extra cellular matrix. No matter renal glomerulus's ailments or renal blood vessel diseases and tubulointerstitial diseases, the degree of renal function damage was intimate correlation with the degree of tubulointerstitial damage. In a word, the degree of tubulointerstitial damage is an important indicator that reflects the severity of kidney insufficiency and judges the severity of kidney prognosis. Infiltration of blood mononuclear cells, proliferation of interstitial mesenchymal cells, transdifferentiation and apoptosis of tubular epithelial cells are considered to be important processes which influenced renal inflammation and fibrosis. Among the many profibrotic factors, transforming growth factor TGFβ₁ plays a pivotal role. TGFβ₁ increases deposition of ECM, resulting in TIF through multi-pathways. So, it is important to explore the reseaons that may inhibit the excess expressions or the activities of TGFβ₁.Decorin is a small leucine-rich extra cellular matrix proteoglycan composed of a core protein with a single glycosaminoglycan (GAG) chain near the N-terminus. Metabolism disorders or formation changes of Decorin have the intimate relation with pathologic process of kidney diseases. Its expression supports capillary formation and cell survival, influences fibril stability, and interacts with extra cellular matrix molecules to influence cells adhesion. Increasing evidences show that Decorin plays an important role in fibro genesis by regulating TGFβ₁. It is not only a factor of extra cellular matrix, but also a natural antagonist of transforming growth factor and may accommodate the process and delay the development of renal fibrosis induced by some cytokines, collagen, fibroblasts, macrophages, and so on. In order to illustrate the mechanism between Decorin and TGFβ₁, especially the effects of Decorin on the transdifferentiation and the expression ofⅠandⅢcollagen in human renal tubular epithelial cells induced by TGFβ₁ in vitro, we performed the following two-part study in vitro.PartⅠ: Expression and orientation of Decorin in renal tissue and correlation with tubulointerstitial damageObjective: Discuss the expression and the orientation of Decorin in renal biopsy. At the same time, discuss the correlation between Decorin with tubulointerstitial damage or TGFβ₁.Methods: Collect pathological dates and clinic dates of thirty six patients by the renal tissue with various glomerulonephritis and tubulointerstitial diseases. Classify the cases to different groups: mild damage group was ten cases; moderate damage group was thirteen cases and density damage group was thirteen cases. Detect the expression and the orientation of Decorin and TGFβ₁ in the renal tissue by Immunochemistry.Results: Decorin expressed in renal tubular epithelial cells, the places of the tubulointerstitial fibrosis and the surroundings of glomerulosclerosis. With the severity of tubulointerstitial lesions, the expression of Decorin increased. They had significant differences in mild damage group, moderate damage group and density damage group (P＜0.05). The expressions of TGFβ₁ also assembled in renal tubular epithelial cells, the places of the tubulointerstitial lesions and the surroundings of glomerulosclerosis. The expression of TGFβ₁ also increased with the severity of tubulointerstitial lesions. A positive correlation was found between Decorin and TGFβ₁ in renal tissue.Conclusion: (1) With the increased severity of tubulointerstitial lesions, the expressions of Decorin improved homologically and a positive correlation was found between Decorin and TGFβ₁.PartⅡ: The effects of core proteoglycan on the transdifferentiation and the expressions ofⅠandⅢcollagen in human renal tubular epithelial cells induced by TGFβ₁ in vitroObjective: Study the effects of Decorin on the transdifferentiation of human renal tubular epithelial cells induced by TGFβ₁ in vitro; explore the roles of Decorin and TGFβ₁ on the expressions ofⅠ,Ⅲcollagen in human renal tubular epithelial cells.Methods: The cultured HK-2 cells were divided into six groups: A. negative control group; B.10ng/ml TGFβ₁ group; C. 10ng/ml Decorin treated group; D. 100ng/ml Decorin treated group; E. 10ng/ml TGFβ₁＋10ng/ml Decorin group; F. 10ng/ml TGF∞₁＋100ng/ml Decorin group. After being stimulated 48 hours, observe the morphological changes of HK-2 cells. At the same time, the expressions of keratin,α-smooth muscle actin, vimentin,ⅠandⅢcollagen mRNAs were detected by RT-PCR after being stimulated 48 hours as before. The expressions ofⅠandⅢcollagen proteins were detected by Western-blot and Immunochemistry after being stimulated 48 hours.Results: (1) In A group, C group and D group, morphology of cells had no changes, the expressions ofα-smooth muscle actin, vimentin had no differences in these three groups. Compare to A group, B group cells took great changes, most cells converted into spindle shape, the mRNA expressions ofα-smooth muscle actin, vimentin had significant advanced, keratin had reduced significantly (P＜0.05). Compare B group, spindle shape cells of E group and F group reduced significantly, especially F group; In E group and F group, a-smooth muscle actin, vimentin expression reduced significantly, keratin expression up-regulated (P＜0.05). (2) Compare B group with A group, the expressions ofⅠandⅢcollagen mRNA and protein increased significantly; But after TGFβ₁ and Decorin treated jointly, the expressions of them decreased in some degree; E group and F group had significant differences (P＜0.05)Conclusion: (1) In HK-2 cells, TGFβ₁ could stimulate the transdifferentiation of human renal tubular epithelial cells and Decorin could inhibit the transdifferentiation of human renal tubular epithelial cells induced by TGFβ₁ in some degree in vitro. (2) In I-IK-2 cells, TGFβ₁ up-regulated the expressions ofⅠandⅢcollagen. (3) In HK-2 cells, Decorin could inhibit the expressions ofⅠandⅢcollagen in HK-2 cells induced by TGFβ₁ in vitro.