Effects of transforming growth factor-beta 1 on renal extracellular matrixcomponents and their regulating proteins

Transforming growth factor-beta 1 (TGF-beta 1) is widely regarded as a pote nt fibrogenic renal growth factor. In cell culture, TGF-beta 1 has been sho wn to increase various extracellular matrix (ECM) proteins and tissue inhib itors of metalloproteinases (TIMP), while decreasing matrix metalloproteina ses (MMP), providing the optimum environment for progressive ECM accumulati on. This study, which uses the isolated perfused rat kidney (IPRK), describ es for the first time in a whole kidney preparation the action of TGF-beta 1 on factors associated with ECM processing. This model allows the study of the intact rat kidney with physiologic cell-cell interactions in the absen ce of confounding systemic influences. Left kidneys were removed from male Wistar rats by a nonischemic technique and perfused with a sterile, apyroge nic, endotoxin-free perfusate, based on the plasma volume expander Hemaccel (polygeline), at constant pressure in a recirculating IPRK system. Kidneys were perfused for 1 h either with (n = 3) or without (n = 3) recombinant h uman TGF-beta 1 (20 ng/ml). The effects of perfusion were controlled by com parison with the nonperfused contralateral kidney (n = 6). TGF-beta 1 was m easured in the perfusate and urine, at the start and end of the experiment using an enzyme-linked immunosorbent assay to its biologically active form. After perfusion, sections of the kidneys were analyzed for changes in mRNA by Northern blotting. Significant increases in mRNA for fibronectin (7.5-f old, P < 0.01), heparan sulfate proteoglycan core protein (53-fold, P < 0.0 01), laminin beta 1 (12-fold, P < 0.001), collagen alpha 1(IV) (17-fold, P < 0.001), collagen alpha 1(III) (fourfold, P < 0.001), and MMP9 (twofold, P < 0.05) were observed after perfusion with TGF-beta 1. Measurement of TIMP 1, TIMP2, TIMP3, MMP1, and MMP2 mRNA demonstrated no detectable change, whe reas determination of mRNA for tissue transglutaminase, an enzyme capable o f cross-linking many ECM components, showed an eightfold increase (P < 0.01 ). This study suggests that in the IPRK and in the absence of other exogeno us growth factors, TGF-beta 1 selectively increases the synthesis of ECM an d tissue transglutaminase without changes that would result in the reductio n of ECM degradation.