The antifibrogenic effect of hepatocyte growth factor (HGF) on renal tubular (HK-2) cells is dependent on cell growth.

Although several reports suggest an antifibrogenic effect of hepatocyte growth factor (HGF), an increased deposition of matrix induced by HGF has also been reported. These conflicting effects could result from a diverse proliferative state of the target cells. Aim of the present study was to evaluate HGF effects on growth arrested (quiescent) and actively proliferating renal tubular epithelial (HK-2) cells. HK-2 cells were cultured in RPMI medium either on agarose gel or on plastic surface in order to inhibit or to allow cell proliferation. Cells were incubated with RPMI containing HGF (50 ng/ml) for 24 h at 37 degrees C. Untreated HK-2 were used as control. After 24 h of incubation, cells were counted by Coulter counter. (alpha2)IV collagen, transforming growth factor-beta (TGF-beta), Tissue inhibitor of metalloproteases (TIMP1 and 2) mRNA levels were determined by RT-PCR. The production of type IV collagen, c-met, proliferating cell nuclear antigen (PCNA), and SnoN, a transcriptional Smad corepressor and thus a TGF-beta inhibitor, was evaluated by ELISA or western blotting. MMP-9 and 2 gelatinolytic activity was studied by zymography. Treatment with HGF did not increase HK-2 cell number and PCNA synthesis when the cells were grown on agarose as it did for cells grown on plastic surface. HGF increased (alpha2)IV collagen in proliferating cells whereas it reduced (alpha2)IV collagen and c-met synthesis in growth arrested cells. HGF treatment increased TGF-beta and TIMP-2 in proliferating cells while reduced TIMP-1 mRNA levels of quiescent cells. Furthermore, production of the co repressor SnoN was significantly decreased by HGF in proliferating cells. Quiescent and proliferating HK-2 showed a different pattern of metalloproteases activity with a prevalence of MMP2 in quiescent and MMP9 in proliferating cells. In summary, HGF showed opposite effects on growth arrested and proliferating HK-2 cells favouring matrix deposition in the latter with increasing expression of collagen, TIMP-1 and TGF-beta. Our results demonstrate that the proliferative state of target cells may influence the effects of HGF on extracellular matrix turnover in HK-2 cells.

Renal function and functional reserve in healthy elderly individuals.

BACKGROUND: Aging is characterized by a decline in renal function and by a susceptibility to renal diseases. However it is not clear whether the observed changes are solely hemodynamic, structural or both. We evaluated renal function, functional reserve (RFR) and morphology in healthy elderly individuals. METHODS: Healthy participants (n=19) were divided into young (n=6, age range 25-37 years), middle-aged (n=6, 44-74 years) and elderly (n=7, 81-96 years). Nitric oxide (NO), plasma renin activity (PRA) and aldosterone, renal plasma flow (RPF) by p-aminohippurate clearance (CPAH) and glomerular filtration rate (GFR) by inulin clearance (CIN) were determined before and during maximal vasodilating stimuli, induced with the infusion of dopamine and amino acids. Glomerular sclerosis, lumen area and wall thickness of afferent arterioles were determined by kidney biopsy from 36 healthy kidney donors and from 6 nephrectomies for renal carcinoma. RESULTS: GFR and RPF were slightly reduced in elderly individuals whereas filtration fraction (FF) was increased. GFR and RPF did not increase in the elderly after maximal vasodilating stimuli as in young and middle-aged subjects suggesting a reduction of RFR. NO, increased at baseline, did not increase further after vasodilating stimuli; while on the contrary, PRA, similar in the 3 groups at baseline, was not reduced by vasodilating stimuli in the elderly. Sclerotic glomeruli but not glomerular volume were significantly increased by aging. Afferent arteriole lumens were reduced by aging whereas wall thickness was unchanged. CONCLUSIONS: Renal function is preserved with aging in healthy subjects at the expense of a complete reduction of RFR. RFR may be wasted to compensate for the increased number of sclerotic glomeruli. Vascular changes, suggested by reduced arteriolar lumen, may be so advanced that even in the presence of high levels of vasodilatory molecules, kidneys are not responsive anymore to maximal vasoactive stimuli.

Risk factors for chronic renal dysfunction in lung transplant recipients.

Several factors predispose to renal dysfunction (RD), a common complication of solid organ transplants. We evaluated the impact of clinical and laboratory parameters on the decline of renal function in lung and heart-lung transplant recipients. We enrolled 45 patients who survived more than 6 months after transplantation, had normal renal function and urinalysis before the surgery. The prognostic value of variables for the occurrence of RD was calculated by univariate analysis. Thirty patients developed RD, defined as doubling of serum creatinine or creatinine steadily >1.5 mg/dL after a median time of 12 months. Serum creatinine above 0.9 mg/dL during the month preceding lung transplant, systolic blood pressure above 130 mmHg, and pretransplant idiopathic pulmonary hypertension were significantly associated with the development of RD. Our findings indicate that increased systolic blood pressure, reduced glomerular filtration rate, and idiopathic pulmonary hypertension are risk factors for chronic RD in lung transplant recipients.

Uremic serum induces proatherogenic changes in human endothelial cells.

BACKGROUND: Cardiovascular complications are the main cause of death in uremic patients. Uremic angiopathy has been regarded as an accelerated form of atherosclerosis. However the mechanism leading to vessel wall injury is still unknown. We hypothesized that uremic serum affects endothelium inducing a proatherogenic state. METHODS: We studied the effects of uremic serum on human endothelial cells (HECs). Cell proliferation and adhesion of mononuclear cells to HEC monolayers were evaluated by cell counting, apoptosis and collagen production by ELISA, and nitric oxide (NO) by measuring the concentration of nitrite/nitrate in the cell supernatant. (alfa2)IV collagen, tissue inhibitor of metalloproteases-1 (TIMP-1) and transforming growth factor-beta (TGF-beta) mRNA levels were measured by reverse transcriptase polymerase chain reaction (RT-PCR). In some experiments cells were preincubated with anti-receptor for advanced glycation end product (anti-RAGE) blocking antibodies. RESULTS: Uremic serum did not modify HEC proliferation but induced apoptosis after 72 hours of incubation. Adhesion of mononuclear cells to HEC monolayers was significantly increased by uremic serum. In addition, uremic serum increased (alfa2)IV collagen, TIMP-1 and TGF-beta mRNA levels. There was no increase in nitric oxide concentration in ure-mic serum-treated endothelial cells, and the expression of TGF-beta was neither modified by L-NAME nor by anti-RAGE antibodies. CONCLUSIONS: Our results indicate that uremic serum affects HEC inducing a proatherogenic state that may be responsible for the accelerated atherosclerosis of uremic patients. Apparently uremic serum effect is not mediated by NO or by AGEs.

Hepatocyte growth factor (HGF) modulates matrix turnover in human glomeruli.

BACKGROUND: The imbalance between synthesis and degradation of mesangial matrix causes glomerulosclerosis and leads to renal failure. Hepatocyte growth factor (HGF) has been shown to reduce the progression in murine models of chronic renal failure. The present study evaluated the effect of HGF on the extracellular matrix turnover and on c-met receptor in human glomeruli. METHODS: Human glomeruli microdissected from donor kidney biopsies before transplantation were incubated with culture media containing HGF (50 ng/mL). After 24 and 48 hours, the expression of c-met, (alpha2) IV collagen, transforming growth factor-beta (TGF-beta), metalloprotease (MMP) 2 and 9 and of the inhibitor of MMP-2, tissue inhibitors of metalloprotease-1 (TIMP-1), was evaluated by polymerase chain reaction (PCR). beta-actin was used as housekeeping gene. The production of collagen type IV and TGF-beta was evaluated by enzyme-linked immunosorbent assay (ELISA) and Western blotting and the activity of MMP by zymography. RESULTS: (alpha2) IV collagen, TGF-beta, and TIMP-1 mRNA levels were markedly decreased in glomeruli treated with HGF at 24 and 48 hours. The expression of c-met was up-regulated by HGF treatment. HGF reduced the production of collagen type IV and TGF-beta. MMP-2 but not MMP-9 mRNA level was increased in HGF-treated glomeruli, although the gelatinolytic activity of the supernatant was not changed. By light microscopic examination kidney biopsies neither showed glomerular hypercellularity nor mesangial expansion. CONCLUSION: HGF reduced expression and synthesis of TGF-beta and collagen type IV and increased MMP-2 mRNA level in normal human glomeruli. These results suggest an antifibrotic effect of HGF on glomerular cells and may explain its beneficial role in glomerulosclerosis.

Development of albuminuria and glomerular lesions in normoglycemic B6 recipients of db/db mice bone marrow: the role of mesangial cell progenitors.

The pathologic hallmarks of diabetic nephropathy are excess mesangial extracellular matrix (ECM) and mesangial cell proliferation. We previously showed that mesangial cell phenotypic changes play an important role in the pathogenesis of diabetic nephropathy. We concluded that phenotypic changes were present in bone marrow (BM)-derived mesangial cell progenitors, as transplantation of BM from db/db mice, a model of type 2 diabetic nephropathy, transferred the db genotype and a nephropathy phenotype to naive B6 mice recipients. The recipients did not develop diabetes; however, they did develop albuminuria and glomerular lesions mirroring those in the donors (i.e., glomerular hypertrophy, increased ECM, and increased cell number with cell proliferation). We found that matrix metalloproteinase 2 (MMP-2) facilitated invasion of the mesangial cells into ECM and proliferation in vitro. Thus, increased MMP-2 activity in db/db mesangial cell progenitors may partially explain increased mesangial cell repopulation and proliferation in B6 recipients of db/db BM. In summary, BM-derived mesangial cell progenitors may play a crucial role in the development and progression of ECM accumulation and mesangial cell proliferation in this model of diabetic nephropathy in type 2 diabetes.