Expression And Significance Of BMP-7 And CTGF In Glomeruli Of Patients With Idiopathic Membranous Nephropathy

Objective: Idiopathic membranous nephropathy (IMN) is a common chronic glomerular disease, which most performance is proteinuria or nephrotic syndrome. IMN is characterized with two quite variable long-term outcome, complete spontaneous remission or progression to renal failure. It is reported that the more Proteinuria the worse prognosis, About 25%-40% of the IMN progress eventually to end-stage renal disease (ESRD) after 5-30 years, therefore it urges people to pay more attention to the formation of proteinuria of IMN and intervention research. Recent years, researchers believe changes of podocyte related proteins have relations with the permeability of glomerular filtration membrane, since podocyte changes in protein levels is associated with proteinuria. Podocyte proteins include the inherent podocyte proteins, cytoskeletal proteins, as well as podocyte synthesis and secretion functional proteins, however, various proteins of podocyte expressing, and their roles, as well as the relationship between proteinuria and the IMN has not yet been fully clarified.Bone morphogenetic protein-7, also called osteogenic protein-1, is one of bone morphogenetic proteins of TGF- superfamily member. It is a pleiotropic cytokine, and mainly exists in the human kidney, and has relationship with kidney development, the maintenance of renal function, and is a protective factor for the kidney. However, relationship among BMP-7 in podocyte, glomerular filtration membrane morphological changes, functional changes in filtration, and proteinuria in IMN have not been studied.Connective tissue growth factor is a cysteine-riched secreted peptide, the molecular weight 36-38 kD, which is one of the immediate-early gene protein CCN gene family member, is the downstream molecules of TGF-β-induced fibrosis, and exist in a variety of tissues and organs in human, including heart, brain, kidney, lung, placenta, pancreas and connective tissue, and at the highest levels in the kidney, and also expressed in Podocyte. The relationship between CTGF in Podocyte with IMN is unknown.The goal of our study is for investigating the expression of BMP-7 and CTGF (by immunohistochemistry) in the glomeruli of patients with idiopathic membranous nephropathy (IMN), And their relationship with albuminuria, serum creatinine and other indicators, in order to deeply understand the contribution of BMP-7 and CTGF to the IMN.Methods: (1) 32 cases of idiopathic membranous nephropathy group (IMN group) were collected from the patients who underwent renal biopsy in Department of Nephrology, the second hospital of Hebei Medical University, from January 2008 to December 2008. The 32 objects were divided into two groups: stageⅠIMN group(n=25), stageⅡ+ⅢIMN group (stageⅡIMN 6例,stageⅢIMN 1例), according to their pathological stages of IMN. (2) 6 cases of control group were collected from the patients who were performed operations for removing benign tumor kidney in Department of Uropoiesis Surgery. (3) Immunohistochemistry was applied to detect the expression of BMP-7 and CTGF in renal glomerulus of patients with stageⅠIMN group, stageⅡ+ⅢIMN group and the control group. (4) 24-hour urine samples and serum specimens were taken from all objects. (5) The estimates of BMP-7 and CTGF expression were mathematically analysed to examine changes of both markers in the various glomerulopathies and the differences between groups were evaluated by one-way analysis of variance test. To determine the significance between group means in the analysis of variance, the nearest significant difference test (SNK-q test) was used as the multiple comparison test. And correlation analysis was processed between immunohistochemical result and clinical index. (6) Use SPSS 13.0 statistical software to analyze the above-mentioned date. Significance was set at p<0.05.Results: 1 clinic experiment indicatrix:1.1 there was no significant difference between control group (50.60±10.12) and 32 patients of IMN group (47.74±11.64) in the age (p>0.05).1.2 24 hours urine protein quantitation and serum creatinine of control group were (0.05±0.03) g/24h,(63.74±8.95)μmol/L respectively. 24 hours urine protein quantitation of stageⅠIMN group,stageⅡ+ⅢIMN group and stageⅠ-ⅢIMN group were (4.29±2.23) g/24h,(5.12±2.16) g/24h,(4.56±2.26) g/24h respectively. Serum creatinine of stageⅠIMN group and stageⅡ+ⅢIMN group and stageⅠ-ⅢIMN group were (72.02±11.87)μmol/L,(76.30±6.50)μmol/L,(72.85±11.08)μmol/L respectively. 24-hour urine protein quantitation of IMN group was significantly higher than control group (p<0.01).2 Immunohistochemistry results:2.1 BMP-7 expressed in podocyte, proximal tubule, a collection of small tubes of control group and IMN group. The rate of positive areas in glomerulus IMN group, stageⅠIMN group, stageⅡ+ⅢIMN group and control group were (18.46±8.25)%,(25.98±3.93)%,(12.56±4.89)%,(30.15±4.19)% respectively. The expression of BMP-7 in glomerulus IMN group, stageⅠIMN group, stageⅡ+ⅢIMN group was a significant reduction than the control group (p<0.01,p<0.05,p <0.01 respectively). The expression of BMP-7 in glomerulus stageⅡ+ⅢIMN group was a significant reduction than stageⅠIMN group (p<0.01).2.2 CTGF expressed in glomerular podocyte, endothelial cells, mesangial cells and tubular epithelial cells of control group and IMN group. The rate of positive areas in glomerulus IMN group, stageⅠIMN group, stageⅡ+ⅢIMN group and control group were: (26.57±10.56)%,(20.49±6.78)%,(32.49±8.75)%,(15.10±3.30)% respectively. The expression of CTGF in glomerulus IMN group, stageⅠIMN group, stageⅡ+ⅢIMN group was a marked higher than the control group (p<0.01). The expression of CTGF in glomerulus stageⅡ+ⅢIMN group was a significant higher than stageⅠIMN group (p<0.01).2.3 In IMN group, the expression of BMP-7 negatively correlated with the expression of CTGF (r=-0.698, p=0.001).2.4 The expression of BMP-7 negatively correlated with 24 hours Urine protein quantitation (r=-0.751, p=0.001), but did not correlated with the level of serum albumin, serum creatinine, blood lipids, immunoglobulin IgG and serum creatinine.2.5 The expression of CTGF positively correlated with 24 hours Urine protein quantitation (r=0.605, p=0.001), but did not correlated with the level of serum creatinine, serum creatinine, blood lipids, immunoglobulin IgG and serum creatinine.Conclusions: 1 BMP-7 was specifically expressed in podocytes. The expression of BMP-7 in glomerulus in every stage IMN was a significant reduction than the control group, and the expression of BMP-7 negatively correlated with 24 hours Urine protein quantitation. That is, with the pathological type progessed, the expression of BMP-7 decrease but the urinary protein gradually increased, prompting BMP-7 is a renal protective factor. 2 CTGF was non-specifically expressed in podocytes. The expression of CTGF in glomerulus IMN group was a significant higher than the control group, and the expression of CTGF positively correlated with 24 hours Urine protein quantitation, prompting CTGF has relationships with Urine protein.