Nephron reduction is an important factor in the development of glomerulosclerosis. In a study of the oligosyndactyly (Os) mutation that causes a congenital 50% reduction in nephron number , we previously found that ROP Os/؉ mice developed glomerulosclerosis whereas C57B1/6J Os/؉ mice did not. We concluded that the predisposition to glomerulosclerosis depended largely on the genetic background , the ROP being sclerosis-prone whereas the C57 strain was sclerosis-resistant. In the current experiments we asked whether the intensity of the sclerotic response to nephron reduction in the ROP strain was related to the time at which it occurred , ie , a pre-or post-natal event. We also determined whether the absence of lesions in C57 Os/؉ mice was caused by a higher threshold for the induction of a sclerotic response in C57 mice. We further examined the relationship between glomerular hypertrophy and sclerosis. C57 ؉/؉, C57 Os/؉, ROP ؉/؉, and ROP Os/؉ mice were uninephrectomized (NX) at age 10 weeks and followed for 8 weeks. We found no sclerotic changes in NX C57 ؉/؉ and C57 Os/؉ mice , despite a 75% reduction in nephron number in the latter. In contrast, both NX ROP ؉/؉ and NX ROP Os/؉ mice had glomerulosclerosis , which was more severe in the NX ROP Os/؉ mice. Examination of extracellular matrix synthesis and degradation at the mRNA level revealed that synthesis exceeded degradation in ROP Os/؉ mice. The lesions in NX ROP ؉/؉ were less severe than in sham-operated ROP/Os mice , suggesting that the timing of nephron reduction affected the amplitude of the sclerotic response in this strain. Following NX , an increase in glomerular volume was found in C57 ؉/؉, ROP ؉/؉, and ROP Os/؉ mice. However, NX did not lead to a further increase in glomerular volume in C57 Os/؉ mice. We make three conclusions: 1) sclerosis was more severe in the ROP strain when nephron reduction occurred in utero; 2) the absence of glomerulosclerosis in C57 mice was not related to a higher threshold for a sclerosis response in this strain; and 3) whereas glomerular size continued to increase as nephron number decreased in ROP mice, it reached a plateau in C57 mice. (Am J Pathol 1999, 154:891-897)Because the shortage of cadaver kidneys has prompted an increase in the use of kidneys from living donors for transplantation, 1 it is important to know whether this practice places donors at risk. 2-6 Many, 5,6 but not all, [2][3][4] retrospective studies have demonstrated that adult donors do not have a significant decline of renal function in follow-up periods of up to 45 years. It is possible that the risk to the donor depends on their susceptibility to a reduction in renal mass. In fact, patients undergoing unilateral nephrectomy who have a family history of renal disease and hypertension appear to carry a higher risk of long-term renal insufficiency than those without familial antecedents. 7 There is increasing evidence that genetic factors play an important role in the development of a large number of glomerular diseases. 8 -10 Furthermore, we recentl...

Besides its procoagulant activity, thrombin has been shown to stimulate cell proliferation and to regulate the fibrinolytic pathway. We report here the effect of purified human alpha thrombin on the synthesis of tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1) by cultured human mesangial cells. Thrombin (0 to 2.5 U/ml) increased in a time- and dose-dependent manner the production of t-PA and PAI-1 (2- to 3-fold increase of secreted t-PA and PAI-1 release during a 24 hour incubation). This effect was associated with a twofold increase in DNA synthesis measured by 3H-thymidine incorporation. Zymographic analysis and reverse fibrin autography showed that thrombin also increased the level of the 110 Kd t-PA-PAI-1 complex, whereas PAI-1 was present as a free 50 Kd form in the culture medium conditioned by unstimulated and thrombin-stimulated cells. Free t-PA was never observed. Both membrane binding and catalytic activity of thrombin were required since the effects of 1 U/ml thrombin were inhibited by addition 2 U/ml hirudin, which inhibits the membrane binding and catalytic activity of thrombin, and since DFP-inactivated thrombin, which has the ability to bind but which has no enzymatic activity, did not induce t-PA or PAI-1. Gamma thrombin, which does not bind to thrombin receptor, did not increase t-PA and PAI-1 releases. The effects of thrombin were probably mediated by protein kinase C activation since H7, an inhibitor of protein kinases, inhibited significantly thrombin effects on t-PA and PAI-1 production, and since addition of an activator of protein kinase A, 8-bromocyclic AMP (100 microM), induced a significant inhibition of the thrombin effect. The effects of thrombin were also suppressed by 1.25 micrograms/ml alpha amanitin, suggesting a requirement of de novo RNA synthesis. Northern blot analysis indicated that thrombin induced an increase in the mRNA levels of t-PA and of PAI-1. We conclude that thrombin increases DNA synthesis in human mesangial cells and enhances the synthesis of both t-PA and PAI-1. The latter is released in a large excess as compared to t-PA. Hence, thrombin may have a role in provoking a localized hypofibrinolytic state and may contribute to the persistence of glomerular fibrin deposits during proliferative glomerulonephritis.

Thrombomodulin (TM), the endothelial cell surface receptor for thrombin-mediated activation of protein C and of its anticoagulant system, is involved in maintaining vascular nonthrombogenicity, and depressed TM activity may induce intravascular fibrin formation. TM antigen was previously found by immunohistochemical methods in rabbit glomeruli. We therefore attempted to identify the corresponding TM activity in isolated detergent-solubilized rat and human glomeruli. Like purified lung TM, rat glomeruli extracts accelerated the hydrolysis by activated protein C of the chromogenic substrate S-2238 in the presence of 10 nM thrombin, as determined by spectrophotometry. One mg glomerular protein promoted the formation of 681 +/- 115 nmol activated protein C, the equivalent of the amount generated by 845 ng of purified rabbit TM. TM activity correlated with the protein content of the glomerular extracts (r = 0.94). These extracts prolonged rat plasma activated partial thromboplastin time. Incubation of glomeruli with tumor necrosis factor-alpha (TNF) or E. coli lipopolysaccharide depressed their TM-like activity in a dose and time dependent manner. Incubation with TNF suppressed their anticoagulant activity. In human glomeruli, TM activity was also found at a level which corresponded to their TM antigen content, and was determined by ELISA with mouse monoclonal antibody. These results indicate that measurement of glomerular TM activity might help to clarify the mechanisms of intraglomerular fibrin deposition in renal diseases.