Immunohistochemical localization of latent transforming growth factor-beta binding protein in IgA nephropathy

It has been demonstrated that cultured mesangial cells (MC) express latent transforming growth factor (TGF)-beta binding protein (LTBP) mRNA, and that LTBP might be essential for the extracellular matrix (ECM) accumulation stimulated by TGF-beta in cultured MC. We performed a study to test the pathophysiological role of LTBP in mesangial ECM accumulation in human glomerulonephropathies. The expression of LTBP in 64 renal biopsies of patients with renal diseases was examined by immunohistochemical staining with the specific antibody raised against human LTBP. The biopsy specimens were divided into three groups: Group 1, IgA nephropathy; Group 2, IgA negative mesangial proliferative glomerulonephritis, which mainly consisted of diabetic nephropathy and lupus nephritis; and Group 3, non-proliferative nephropathy, which consisted of minimal change and membranous nephropathy. Immunohistochemical staining of LTBP was significantly detected in mesangial/paramesangial area of glomerulus in Group 1, but not observed in Group 2 or Group 3. The intensity of staining was well related to the grade of mesangial ECM accumulation in Group 1. These findings suggest that the LTBP-TGF-beta complex may play a pivotal role in ECM accumulation in IgA nephropathy, and that modification of LTBP-ECM interaction might provide a new therapeutic strategy against the progression of glomerulosclerosis.