Is TGF-beta a profibrotic cytokine in human renal transplants?

Value of Pretransplantation Cytokine Profiles for Predicting Acute Rejection in Renal Transplant Recipients

Episodes of acute rejection may represent an important risk factor for the development of chronic allograft nephropathy. Various studies have shown that pretransplant cytokine profiles in recipient blood are associated with transplant outcome. Serum samples were collected 24 hours before transplantation from 57 patients (38 men and 19 women of age 36 +/- 5 years) receiving kidneys from unrelated living donors. Additional samples were collected at 1 and 2 weeks after transplantation, as well as during every rejection episode. The immunosuppression consisted of a cyclosporine, prednisolone, and mycophenolate mofetil. Among the transplanted patients, 19 (33.3%) individuals experienced an acute rejection episode based on an increased level of serum creatinine and blood urea nitrogen during the first 14 days after transplantation. TGF-beta, IL-2 and IFN-gamma serum levels were determined by an ELISA method using Bindermed system kits. The mean concentration of TGF-beta before transplantation tended to be lower among patients with acute rejection episodes compared to those with stable graft (75,265 versus 85,394 pg/mL; P = .34) and at 1 week after transplantation (77,558 versus 84,390 pg/mL), although the differences were not significant. Among patients with rejection the mean IL-2 concentration was significantly higher before, at 1 week, and at 2 weeks after transplantation (15.0 versus 6.8 pg/mL, P = .005; 19.0 versus 4.9 pg/mL, P = .001; and 21.1 versus 4.7 pg/mL, P = .0001). The mean concentration of IFN-gamma was significantly higher pre- and at 1 and 2 weeks posttransplantation in patients with acute rejection episodes (161.1 versus 65.2, 175.6 versus 66.5 and 173.7 versus 77.1 pg/mL, all P < .001). In conclusion, evaluation of Th1 cytokines before transplantation may represent valuable predictive marker for an acute rejection episode.

Donor and recipient-transforming growth factor-beta 1 polymorphism and cardiac transplant-related coronary artery disease

BACKGROUND

Transforming growth factor-beta1 (TGF-beta1) has been implicated in the pathogenesis of coronary vasculopathy following cardiac transplantation. The TGFB1 gene contains polymorphisms at positions +915* (Arg25Pro) and +869* (Leu10Pro) which may influence TGF-beta1 expression. We investigated the relationship between the development of coronary vasculopathy and the prevalence of these alleles in a cardiac transplant population.

METHODS

Vasculopathy was diagnosed at routine surveillance post-transplant coronary angiography. Using sequence-specific polymerase chain reaction we identified the TGFB1 +915* and +869* genotypes in 147 cardiac transplant recipients and 134 cardiac donors.

RESULTS

TGFB1 +915*C allele carriers (low producers) made up 10.5% of the recipient population but were significantly less likely to develop coronary vasculopathy (P=0.03). Median time to diagnosis was 6.0 years (3.9-8.72) in +915*C allele carriers compared to 2.75 years (2.10-4.22) in *G/G homozygotes (p=0.002). Pre- and 1 year post-transplant clinical variables were equivalent between the two groups. Multivariate analysis identified the recipient +915*G/G genotype (hazard ratio 2.96 (95% CI, 1.09-9.98); p=0.039), donor age (hazard ratio 1.05 (95% CI, 1.02-1.09); p=0.008) and number of acute rejection episodes of ISHLT grade 3 or greater in the first year (hazard ratio 1.12 (95% CI, 1.01-1.23); p=0.03) as significant predictors of vasculopathy. The recipient TGFB1 +869*, and both alleles in the donor, had no influence on vasculopathy development.

CONCLUSIONS

Recipient TGFB1 +915* genotype influences the development of cardiac transplant-related coronary vasculopathy. This gives an important insight to the pathophysiology of the disease. On the contrary, donor TGFB1 +915* and TGFB1 +869* polymorphisms do not appear to be important and cannot be used as genetic risk factors.

Fibrosis-associated gene expression in renal transplant glomeruli after acute renal allograft rejection

BACKGROUND

Acute allograft rejection is thought to be a risk factor for chronic allograft nephropathy, the cardinal features of which are vasculopathy, interstitial fibrosis and glomerulosclerosis. Fibrosis-associated genes might act as ad interim surrogate markers for chronic allograft nephropathy. The aim of this study was to determine mRNA expression of fibrosis-associated genes in glomeruli plucked from protocol renal transplant biopsies, in patients with or without a history of acute rejection.

METHODS

A consecutive series of 52 patients (31 male, 21 female) was assessed. Donor categories were cadaveric, living related or asystolic. Transplant recipients received either cyclosporin- or tacrolimus-based immunosuppression. Patients routinely underwent percutaneous needle-core renal transplant biopsy at 1 week, and 3 and 6 months. Acute rejection episodes were confirmed histologically and treated with intravenous methylprednisolone, or antithymocyte globulin if steroid resistant. Individual glomeruli were plucked and total mRNA was extracted. Fibrosis-associated genes were amplified by reverse transcriptase-polymerase chain reaction (PCR) and quantified by enzyme-linked immunosorbent assay.

RESULTS

The expression of both collagen type III (mean 0.42 versus 0.31 arbitrary units of PCR products corrected for a housekeeping gene) and collagen IV (mean 0.46 versus 0.42 arbitrary units) at 6 months did not differ between recipients who experienced acute rejection episodes and those who were free from rejection. There was also no significant difference between groups in terms of mRNA expression of collagen IValpha2, matrix metalloproteinase 2, tissue inhibitor of matrix metalloproteinases 1 and 2, transforming growth factor beta or tenascin.

CONCLUSION

These results suggest that acute rejection episodes do not increase the expression of fibrosis-associated genes in glomeruli from renal transplant biopsies.

Urinary amino-terminal propeptide of type III procollagen (PIIINP) as a marker of interstitial fibrosis in renal transplant recipients

BACKGROUND

Interstitial fibrosis in the protocol biopsy specimens of transplanted kidneys is regarded as the most reliable predictor of future impaired renal function. Type I and III collagens are the main components of renal fibrosis. During the synthesis and deposition of type III collagen, an amino-terminal propeptide (PIIINP) of a molecular weight of 44 kDa is degraded from the collagen and secreted into surroundings. Increased circulating PIIINP has been shown to reflect ongoing fibrotic processes.

METHODS

The extent of interstitial fibrosis in 6-month protocol biopsy specimens was recorded, and the urinary excretion of PIIINP in 24-hr urine specimens was measured in 79 graft patients. We also measured the urinary excretion of transforming growth factor (TGF)-beta 1, alpha(1)-microglobulin (alpha(1)M), and albumin and recorded the changes in creatinine clearance during 0.5 to 6 (mean, 4.3) posttransplant follow-up years.

RESULTS

The urinary excretion of PIIINP was significantly lower in patients with no interstitial fibrosis compared with patients with mild or moderate interstitial fibrosis (P<0.01). The urinary PIIINP-to-creatinine ratio correlated closely with the extent of interstitial fibrosis (r=0.410, P<0.001), with TGF-beta 1-to-creatinine (r=0.585, P<0.001) and alpha(1)M-to-creatinine (r=0.438, P<0.001) but not with the albumin-to-creatinine ratio. There was a close correlation between urinary TGF-beta 1 and alpha(1)M (r=0.508, P<0.001), whereas no correlation was found between urinary and serum PIIINP or between urinary PIIINP-to-creatinine ratio and glomerular filtration rate (GFR). During the follow-up, the GFR decreased in 42% of patients with a PIIINP-to-creatinine ratio over 100 ng/mmol, but only in 8% of patients with a ratio less than 100 ng/mmol (P<0.01).

CONCLUSIONS

These findings show that the urinary PIIINP-to-creatinine ratio reflects the ongoing fibrotic processes in the kidney. Tubular epithelial cell injury may initiate the fibrotic processes, and elevated concentrations of urinary TGF-beta 1 and alpha(1)M may associate with the increased production and deposition of collagen type III in the graft. We conclude that measurements of urinary excretion of PIIINP can be used as an early noninvasive indicator of renal fibrosis after kidney transplantation.

Matrix accumulation in mesangial cells exposed to cyclosporine A requires a permissive genetic background

BACKGROUND

Chronic nephrotoxicity is an important adverse effect of cyclosporine A (CsA) therapy. Tubulo-interstitial lesions and arteriolopathy are common histologic findings. Glomerular lesions are also described, but they are of variable severity. The aim of our study is to determine whether CsA has a direct effect on mesangial cells and whether the cellular response depends on the genetic background.

METHODS

We studied mesangial cells isolated from mice susceptible (ROP/Le-+Es1(b)+Es1(a), ROP) and resistant to glomerulosclerosis (B6SJLF1, C57). We previously showed that sclerosis-prone and sclerosis-resistant phenotypes are maintained in vitro. We examined whether CsA exposure directly affected extracellular matrix turnover in mesangial cells and whether the response is determined by the genetic background. Extracellular matrix synthesis and degradation were studied by proline incorporation, ELISA, reverse transcription-polymerase chain reaction, zymography, and reverse zymography. We chose a CsA dose that induced neither cytotoxicity nor apoptosis (1 microg/ml).

RESULTS

At the dose of 1 microg/ml total collagen accumulation was increased in ROP but not in C57 cells. Matrix metalloproteinase (MMP)-2 activity and mRNA levels were selectively decreased in ROP cells. CsA exposure did not affect tissue inhibitors of MMP (TIMP)-1 and -2 activity or TGF-beta1 mRNA expression and protein synthesis in either cell line.

CONCLUSION

CsA increases total collagen accumulation in mesangial cells from sclerosis-prone mice by decreasing MMP-2 activity, but does not affect cells from sclerosis-resistant mice. Thus, CsA directly affects mesangial cells, but only those with a permissive genetic background for glomerulosclerosis.