Cyclosporine induces elevated procollagen alpha 1 (I) mRNA levels in the rat renal cortex

Biomarkers in Progressive Chronic Kidney Disease. Still a Long Way to Go

The traditional chronic kidney disease (CKD) biomarkers (eGFR based on serum creatinine, sex and age and albuminuria) cannot predict a patient's individual risk for developing progressive CKD. For this reason, it is necessary to identify novel CKD biomarkers that will be able to predict which patients are prone to develop progressive disease and discriminate between disease processes in different parts of the nephron (glomeruli or tubules). A good biomarker should change before or simultaneously with lesion development and its changes should correlate strongly with lesion development. Also, there should be a close relationship between severity of injury and amount of detectable biomarker and its levels should decrease with diminishing injury. Among the large number of molecules under investigation, we have reviewed the most promising ones: NGAL and KIM-1, MCP-1, MMP-9, clusterin, MMP-9, TIMP-1, Procollagen I alpha 1 and suPAR. All these, have been studied as biomarkers for prediction of CKD progression in cohorts of patients with chronic kidney disease of different stages and various aetiologies (proteinuric and non-proteinuric, glomerulonephritides, diabetic, hypertensive and polycystic kidney disease). There is evidence that these molecules could be useful as biomarkers for progressive chronic kidney disease, however, the available data are not enough to draw final conclusions. Further studies with large cohorts and long follow-up are required to identify appropriate biomarkers, that will be able to accurately and reliably define the risk for progressive chronic kidney disease.

Cyclosporin A Administration during Pregnancy Induces a Permanent Nephron Deficit in Young Rabbits

ABSTRACT. Cyclosporin A (CsA) is an immunosuppressive agent used to prevent graft rejection and to treat autoimmune disorders. Successful pregnancies can be achieved among CsA-treated women, although it is known that CsA is nephrotoxic and crosses the human placenta. The aim of this study was to evaluate the harmlessness of CsA toward the embryonic kidney. Twenty-one pregnant rabbits were divided into four groups. Groups of six and four female animals were subjected to daily injections of 10 mg/kg per d CsA (administered subcutaneously) for 5 d, from day 14 to day 18 of gestation or from day 20 to day 24 of gestation, respectively. In the third group, five female animals received the CsA diluent (Cremophor) from day 14 to day 18 of gestation. The fourth group consisted of six untreated female animals. Pregnancy outcomes among CsA-treated does demonstrated a reduced number of living pups, which were also growth-retarded, with exposure to CsA from day 20 to day 24 of gestation. However, pups exposed to CsA from day 14 to day 18 of gestation exhibited normal fetal growth, and blood concentrations of CsA matched human data. Examinations of kidneys at birth demonstrated vacuolation of proximal and collecting tubules and ureteric bud ends. Increased glomerular volumes and decreased nephron densities suggested nephron mass reduction, which was quantitatively evaluated in 1-mo-old animals. The nephron numbers were reduced by 25 and 33% in day 14 to 18 CsA-treated and day 20 to 24 CsA-treated animals, respectively, which displayed compensatory adaptation of the existing nephrons. However, foci of segmental glomerular sclerosis were already present, which would possibly jeopardize renal function later in life.

Characterization of a DNA binding site that mediates the stimulatory effect of cyclosporin-A on type III collagen expression in renal cells

BACKGROUND

Previous work from our laboratory demonstrated upregulation of type III collagen by cyclosporin A (CsA) in a cellular model of renal fibroblasts 'in vitro', suggesting that a mechanism of gene transcriptional activation might be responsible for collagen accumulation in renal fibrosis resulting from chronic CsA treatment.

METHODS

We analysed in the same cellular model: (i) COL3A1 mRNA expression by RT-PCR; (ii) COL3A1 promoter activity by transfection of renal fibroblasts with constructs containing promoter fragments of different length fused to a reporter gene; (iii) expression of transcription factors by western blot analysis; (iv) DNA-protein binding by gel retardation assays with nuclear extracts from CsA-treated and untreated cells; and (v) site-directed mutagenesis of COL3A1 promoter to verify the role of a short DNA segment as CsA responsive element.

RESULTS

CsA induced a 3-5-fold increase in COL3A1 mRNA that was paralleled by a stimulation of the COL3A1 promoter. Degradation of COL3A1 mRNA was comparable in CsA-treated and -untreated cells. The target region was first limited to a 178 bp fragment from -117 to +61 (pFV1). By gel retardation, utilizing several oligonucleotides that covered the whole length of pFV1, we detected a factor able to bind the promoter DNA (oligo 31) in nuclear extracts after 3 h treatment with CsA. The binding was absent in untreated cells and it was not detected when a 10-base mutation was introduced in oligonucleotide 31. Finally, the same substitution mutation at the site of binding of this factor abolished the stimulatory effect of CsA on COL3A1 promoter. Some transcription factors, whose potential binding sites are included in the above promoter fragment, were induced by CsA treatment either soon (3 h) or late (24-72 h) after treatment and were detected by western blot analysis.

CONCLUSIONS

CsA induces the synthesis of type III collagen by stimulating a pathway leading to activation of COL3A1 promoter and upregulation of COL3A1 mRNA. A short promoter fragment, proximal to the transcription start site, is the target of CsA stimulation.

Unique changes in interstitial extracellular matrix composition are associated with rejection and cyclosporine toxicity in human renal allograft biopsies

Renal allograft loss from chronic rejection or cyclosporine toxicity (CsAT) is characterized by progressive interstitial fibrosis, yet the protein composition of these lesions is unknown. The normal tubular basement membrane (TBM) contains laminin (LM), collagen IV (containing collagen IV alpha chain 1 [COL4A1] and COL4A2), thrombospondin (TSP), and fibronectin (FN). Only TSP and FN extend beyond the TBM into the interstitial space. Very scanty amounts of interstitial collagens (I and III) are detected in the interstitium. In a pilot study of human renal allograft biopsy specimens, three patterns of extracellular matrix (ECM) composition were identified. Pattern 1 showed no change in ECM composition; pattern 2 showed generalized accumulation of collagens I and III in the interstitium; and pattern 3 showed new expression of COL4A3 and LM-beta2 in the proximal TBM. Criteria were established for the clinicopathological diagnosis of CsAT and rejection. These diagnoses were correlated with the ECM composition in 22 renal allograft biopsy specimens. Control groups were examined in a similar manner and included native kidney biopsy specimens from patients with other allografts (n = 7), renal biopsy specimens from patients with glomerular disease (n = 9), and renal allograft biopsy specimens from patients without clinicopathological evidence of renal disease. These data show that rejection is associated with pattern 3 and CsAT is associated with pattern 2. Thus, detection of ECM composition may be a useful adjunct to standard microscopy in distinguishing rejection from CsAT in renal allograft biopsy specimens. These data suggest that interstitial fibrosis associated with rejection and CsAT result from different pathogenic mechanisms.

Differential response of glomerular epithelial and mesangial cells after subtotal nephrectomy

Recent studies in both human and experimental chronic renal disease suggest that there is a linkage between glomerular hypertrophy and glomerulosclerosis. To further define these relationships, we studied the changes in glomerular hypertrophy, procollagen alpha 1(IV) mRNA levels and glomerulosclerosis in rats undergoing 1 2/3 nephrectomy (Nx) or sham nephrectomy (SNx). Glomerular hypertrophy, measured biochemically by RNA/DNA and protein/DNA ratios, was significantly increased in Nx compared to SNx two days after subtotal renal ablation (RNA/DNA: Nx = 133 +/- 8%, SNx = 100 +/- 3% of the mean control value, P < 0.01; protein/DNA: Nx = 164 +/- 22%, SNx = 100 +/- 10%, P < 0.05) and remained elevated after 7 and 15 days (RNA/DNA: seven days Nx = 155 +/- 3%, SNx = 100 +/- 13%, P < 0.01; 15 days Nx = 303 +/- 21%, SNx = 100 +/- 24%, P < 0.001; protein/DNA: seven days Nx = 228 +/- 57%, SNx = 100 +/- 18%, P < 0.05; 15 days Nx = 341 +/- 23%, SNx = 100 +/- 18%, P < 0.01). Light microscopic measures of glomerular tuft volume (GTV) were too insensitive to detect glomerular enlargement until 15 days postoperatively, but GTV measured ultrastructurally demonstrated a 20% increment in Nx compared to SNx as early as two days postoperatively (P < 0.01). The latter increment in GTV was due exclusively to glomerular visceral epithelial cell (GVEC) expansion. Glomerular procollagen alpha 1(IV) mRNA levels were significantly elevated only 15 days after nephrectomy (Nx = 265 +/- 58% of the mean control value, SNx = 100 +/- 12%, P < 0.05; corrected for beta-actin mRNA levels). As this time, exuberant mesangial expansion measured ultrastructurally contributed to a 1.6 +/- 0.1-fold increase in GTV (P < 10(-5)), and to a relative decrement in the GVEC contribution to glomerular cells plus matrix (P < 0.01). Segmental sclerosis was observed only 15 days postoperatively in Nx (Nx = 1.3 +/- 0.4% of glomeruli evaluated, SNx = 0.0%, P < 0.05), and there was a strong correlation between the prevalence of segmental sclerosis and the procollagen alpha 1(IV) mRNA levels in Nx at 15 days (r = 0.93, P < 0.01). There was no significant correlation between the RNA/DNA and protein/DNA ratios and procollagen alpha 1(IV) mRNA levels. Thus, glomerular regions responded differentially to subtotal nephrectomy. Early epithelial cell expansion was followed by later mesangial expansion. Glomerular procollagen alpha 1(IV) mRNA levels were elevated only during the second (mesangial) phase of glomerular hypertrophy, when it correlated with glomerulosclerosis, but not during the initial (epithelial) phase, a pattern consistent with a mesangial origin of the procollagen alpha 1(IV) mRNA.

Rat metanephric organ culture in terato-embryology

The development of the permanent mammalian kidney, or metanephros, depends on mesenchymal-epithelial interactions, leading to branching morphogenesis of the ureteric bud that forms the collecting ducts and to conversion of the metanephric mesenchyme into epithelium that forms the nephrons. Rat metanephric organ culture in which these interactions are maintained is a valuable in vitro model system for investigating normal and abnormal renal organogenesis. Methods were designed to evaluate either the capacity of the ureteric bud to branch or that of the mesenchyme to form nephrons. Both are based on specific staining of the ureteric bud and the glomeruli with lectins. Using this approach, we have shown that retinoids are potent stimulating factors of nephrogenesis, acting through an increase in the branching capacity of the ureteric bud. On the other hand, several drugs such as gentamicin and cyclosporin A were found to reduce the number of nephrons formed in vitro. While gentamicin affects the early branching pattern of the ureteric bud, cyclosporin may affect the capacity of the mesenchyme to convert into epithelium. This methodology therefore appears a potentially useful tool for toxicological studies of new drugs.

Role of transforming growth factor-beta 1 in experimental chronic cyclosporine nephropathy

The pathogenesis of fibrosis in chronic cyclosporine (CsA) nephropathy remains unknown. Since TGF-beta 1 plays a key role in the fibrogenesis of a number of renal diseases, we studied a salt-depleted rat model of chronic CsA nephropathy which shows similarity to the structural and functional lesions described in patients. Pair fed rats were treated with either CsA (15 mg/kg/day s.c.) or an equivalent dose of olive oil and sacrificed at 7 and 28 days. Characteristic histologic changes of proximal tubular injury, tubulointerstitial fibrosis and arteriolopathy developed in CsA-treated rats at day 28. They were accompanied by physiologic changes of increased serum creatinine, decreased creatinine clearance, increased enzymuria and decreased concentrating ability. CsA-treated rats showed a progressive increase in mRNA expression of TGF-beta 1 and matrix proteins at days 7 and 28. Most of the changes were in the tubulointerstitial and vascular compartments by immunofluorescence with a predominant involvement of the medulla as compared to cortex. The mRNA expression of plasminogen activator inhibitor, a protease inhibitor stimulated by TGF-beta 1, followed TGF-beta 1 and matrix proteins, suggesting that the fibrosis of chronic CsA nephropathy likely involves the dual action of TGF-beta on matrix deposition and degradation.

Endothelin in organ transplantation

Solid organ allografts are often compromised by ischemia, acute rejection episodes associated with hemodynamic changes, and chronic rejection typically characterized by the development of obliterative vasculopathy, and in the case of the kidney, and glomerulosclerosis. Recent in vivo data indicate that endothelin (ET) production is locally upregulated in rejecting allografts, and that, in addition to endothelial cells, ET is also produced by graft-infiltrating mononuclear cells (monocytes/macrophages). In vitro data also indicate that ET production is regulated, at least in part, by certain T cell-and monocyte/macrophage-derived cytokines, which are abundant in rejecting allografts. These data and the findings of elevated plasma levels of ET after transplantation (in particular during rejection processes), the effects of immunosuppressive drugs (cyclosporine and tacrolimus in particular) on ET production, and the profound vasoconstrictive and mitogenic properties of this peptide suggest that endothelin may be involved in the initiation and propagation of posttransplantation complications; including systemic hypertension, acute allograft dysfunction, and perhaps most importantly, chronic allograft dysfunction. These observations provide the rational to use ET receptor antagonists to formally address the potential role of ET in these processes, and to develop therapeutic strategies that ameliorate or possibly prevent these complications.

Cellular proliferation and macrophage influx precede interstitial fibrosis in cyclosporine nephrotoxicity

Chronic cyclosporine (CsA) nephrotoxicity is a major complication of solid organ transplantation, and is characterized histologically by striped tubulointerstitial fibrosis, tubular atrophy, and hyalinization of the afferent arteriole, a highly specific finding in cyclosporine injury. The salt-depleted rat model of chronic cyclosporine nephropathy mimics these lesions in humans. We conducted sequential studies of this model in groups of pair fed rats (N = 6) treated with CsA (15 mg/kg, s.q.) or an equivalent dose of olive oil. Proliferation of tubular and interstitial cells was documented early in the medulla by day 5 (3.2 +/- 2.1 vs. 0.81 +/- 0.4 cells/HPF in CsA vs. control, P < 0.02), and was maximal in areas of interstitial fibrosis by day 35 (7.9 +/- 3.7 vs. 0.52 +/- 0.2 cells/HPF in CsA vs. control, P < 0.005). The interstitial fibrosis was associated with a significant macrophage influx by day 35 (13.9 +/- 3.5 vs. 1.5 +/- 0.32 cells/HPF, CsA vs. control, P < 0.005), which correlated with increased cortical tubular staining for the macrophage adhesion protein, osteopontin. Elevated serum creatinine correlated with interstitial fibrosis at day 35 (0.85 +/- 0.11 vs. 0.40 +/- 0.03 mg/dl Cr, CsA vs. control, P < 0.005) by linear regression (r = 0.9, P < 0.05). Medullary proliferation and interstitial fibrosis correlated with decreased tubular concentrating ability, and higher urinary volume. Cortical interstitial fibrosis was maximal at day 35 and was associated with an increase in type I and type IV collagen deposition, while tubular injury was associated with increased vimentin expression. Tubular interstitial cells also expressed increased vimentin early in the medulla (day 10) and later in the cortex. Both groups remained normotensive despite significantly elevated juxtaglomerular (JG) apparatus renin expression in CsA treated animals, implicating the intrarenal-renal renin-angiotensin system in this disease. We conclude that cyclosporine nephrotoxicity is associated with early tubular and interstitial cell proliferation, and a significant macrophage influx that precedes the development of cortical interstitial fibrosis and afferent arteriolar hyalinosis. These early cellular changes correlate with functional abnormalities including decreased creatinine clearance (CCr) and decreased medullary concentrating ability, which stabilized despite progressive fibrosis. These cellular events may be important in the pathogenesis of chronic CsA nephrotoxicity.

Insulin-like growth factor I induces mesangial proliferation and increases mRNA and secretion of collagen

Insulin-like growth factor I (IGF-1) is a peptide growth factor that is synthesized in cultured mesangial cells and induces hyperplasia. We tested whether incubation with IGF-1 at concentrations of 7 nM, 70 nM, and 350 nM stimulates mesangial cell extracellular matrix mRNA and protein levels, and whether it influences mesangial cell growth. Mesangial cells incubated with IGF-1 demonstrated a statistically significant increase in procollagen alpha 1(I) (100 +/- 13% vs. 147 +/- 12%, 154 +/- 10%, and 173 +/- 21%) and alpha 1(IV) 100 +/- 9% vs. 112 +/- 9%, 125 +/- 8%, and 172 +/- 28%) mRNA. Furthermore, IGF-1 also stimulated a statistically significant increment in alpha 1(IV) mRNA in isolated glomeruli when measured by Northern hybridization and corroborated by in situ hybridization experiments. In addition, mesangial cells incubated with IGF-1 induced a statistically significant increase in both secreted and cell associated type I (secreted: 100 +/- 5% vs. 127 +/- 9%, 148 +/- 5%, 178 +/- 11%; and cell-associated: 100 +/- 19 vs. 132 +/- 17%, 198 +/- 24%, and 314 +/- 17%) and type IV (secreted: 100 +/- 19% vs. 138 +/- 11%, 192 +/- 17%, 379 +/- 16%, and cell-associated: 100 +/- 8% vs. 139 +/- 10%, 206 +/- 16%, 310 +/- 15%) collagen. Thus, mRNA and collagen levels increased in a dose dependent fashion after incubation with IGF-1. Furthermore, IGF-1 stimulated hyperplasia but not hypertrophy in this in vitro system. These data suggest that IGF-1 may contribute to glomerular sclerosis by increasing mesangial matrix production as well as proliferation.

Urinary endothelin and renal vasoconstriction with cyclosporine or FK506 after liver transplantation

Transplant immunosuppression using either cyclosporine (CsA) or FK506 leads to renal vasoconstriction. To examine the role of endothelin (ET) in this process, we measured plasma and urinary ET before and at intervals for two years after liver transplantation. Urinary prostacyclin (as 6-keto-PG-F1 alpha), thromboxane, glomerular filtration rate and renal plasma flow were also measured. Forty-four patients were treated with CsA-based regimens and 31 patients with FK506-based regimens. Prednisone doses after one year were lower with FK506 (5.5 +/- 0.5 vs. 10.5 +/- 0.5 mg/day) by study design. Circulating plasma ET remained above normal, but not different from pre-transplant levels. Urinary ET was elevated before transplant (24.6 +/- 3.4 ng/day vs. normal 16 +/- 1.5 ng/day, P < 0.05) and rose further after transplantation (48.5 +/- 13 ng/day, P < 0.05), remaining elevated for two years. 6-keto-PG-F1 alpha fell from 2567 +/- 338 ng/day to subnormal levels and remained suppressed (1158 +/- 128 ng/day, P < 0.01). Over the same period GFR fell (84 +/- 3 ml/min to 60 +/- 3 ml/min, P < 0.01) and renal vascular resistance index rose (11,119 +/- 561 to 23,279 +/- 1692 d.s.cm-5.m-2, P < 0.01). Similar changes were observed both with CsA and FK506-based immunosuppression. No changes in ET were attributable to dihydropyridine calcium channel blockers. These results demonstrate that urinary ET changes independently from plasma ET after transplantation. Elevated ET and suppression of endothelium-derived prostacyclin persist with intense renal vasoconstriction for at least two years after transplant.

Prevention of glomerulosclerosis by early cyclosporine treatment of experimental lupus nephritis

The influence of cyclosporine A (CsA) treatment on the development of glomerulonephritis and glomerulosclerosis was investigated in chronic graft-versus-host disease (GvHD), a murine model for lupus nephritis. The renal disease is characterized by the formation of IgG-containing electron-dense deposits along the glomerular basement membrane (GBM) and in the mesangium, followed by the onset of proteinuria which starts, varying per individual mouse, about six weeks after the induction of the disease. Glomerular mRNA levels for matrix molecules were increased from week 4, preceding mesangial matrix expansion and GBM thickening which occurred from week 6. These initial events finally led to development of glomerulosclerosis, and end-stage renal failure. Groups of mice received three intraperitoneal (i.p.) injections per week with different doses of CsA, and treatment was started 2, 4, or 6 weeks after induction of the disease. Treatment with 10 or 50 mg CsA/kg/week did not influence the development of glomerulonephritis or glomerulosclerosis. Injection of 100 mg CsA/kg/week delayed the onset of proteinuria only when treatment was started in week 2. In week 6 some mice had already developed proteinuria whereas others had not. Treatment with 250 mg CsA/kg/week starting in week 6 abrogated glomerulonephritis and glomerulosclerosis only in those animals which were not yet proteinuric at that time. This, despite comparable increased autoantibody levels against DNA, GBM, and renal tubular epithelium (RTE) in both treated and untreated GvHD mice. Further increase in proteinuria and development of glomerulosclerosis could not be prevented if the mice already had developed proteinuria when CsA treatment was started. Dot blot analysis and in situ hybridization showed significantly decreased mRNA levels for alpha 1(I) and alpha 1(IV) collagen in kidneys of CsA-treated mice as compared to those of untreated mice 12 weeks after induction of the disease, if the highest dose of CsA was administered before the onset of proteinuria. No effect on these whole-kidney mRNA levels was observed in mice which had already developed proteinuria before CsA injections were started. Increased mRNA expression for matrix molecules in this group and in untreated GvHD mice was observed mainly in the interstitium. The kidneys of the treated GvHD mice and those of mice injected with 250 mg CsA/kg/week without induction of GvHD showed no morphological signs of CsA nephrotoxicity. We conclude that treatment with 250 mg CsA/kg/week prevents the development of glomerulonephritis and glomerulosclerosis in this model of lupus nephritis, if started before the onset of proteinuria.(ABSTRACT TRUNCATED AT 400 WORDS)

GRP78 induction by cyclosporin A in human HeLa cells

Immunosuppressive drugs such as cyclosporin A (CsA) and FK506 are known to have pleiotropic effects on cells. Here we demonstrate that treatment of HeLa cells with low concentrations of CsA (but not of FK506) induces the synthesis of a stress protein, GRP78, located inside the endoplasmic reticulum. High concentrations of CsA lead to a general decrease in protein synthesis. When cells are stressed (heat-shocked) during the CsA treatment, the synthesis of heat shock proteins is reinforced. FK506 has no detectable effects at any concentration. The mechanism of induction of GRP78 by CsA remains presently unknown. Whatever the mechanism involved, GRP78 overexpression might be responsible for some of the physiological effects of CsA.

Immunohistochemical study of 30 cases of cyclosporin A-induced gingival overgrowth

Immunohistochemical techniques were used to study the presence of cyclosporin A (CsA) and leukocyte subsets in 30 gingival biopsies of renal transplant subjects with gingival overgrowth (GO). Statistical analysis revealed significant differences in the total number of inflammatory cells determined by monoclonal antibody CD45, the monocyte/macrophage (CD68) subset, the plasmatic cells (EMA), and the total of T-lymphocytes (CD3) (P < 0.001, Student t test) between the treated subjects and the healthy control group. Differences were found in the helper/inducer T lymphocytes CD4 (P < 0.001 Student t test) and cytotoxic/suppressor T lymphocyte (CD8) (P < 0.01, Student t test) subsets between both groups. The CD4/CD8 ratio was greater in the transplant subjects than in the control group (1.82 +/- 0.16 versus 1.35 +/- 0.05 respectively) (P < 0.05 Student t test). There was no significant difference in the populations CD16+, CD57+, and CD20+. The CD45+ CD4+, and CD68+ cells increased in number along with the degree of GO. The number of epithelial cells/mm2 which displayed a deposit of CsA increased in accordance with the degree of GO (P < 0.05, Kruskal-Wallis's test). Likewise, the intraepithelial deposit of CsA in the GO region was found to be related to the inflammatory infiltrate CD4+, CD8+, and CD68+ (r = 0.7432; r = 0.7346; r = 0.77005, respectively). Our findings suggest that the intraepithelial deposit of CsA and the inflammatory infiltrate play a predominantly pathogenic role and are both related to the degree of GO.

Interstitial fibrosis in obstructive nephropathy

Interstitial fibrosis and tubular basement membrane (TBM) thickening are evident within 16 days of unilateral ureteral obstruction (UUO) in the rabbit, and resemble the changes previously reported in hydronephrotic human kidneys. The cortical interstitial volume fraction in this rabbit model at 16 days is 43.3 +/- 6.1% (+/- 1 SD) in UUO kidneys, 4.9 +/- 3.1% in contralateral kidneys (CLK), and 2.8 +/- 0.8% in kidneys from sham-operated animals (ANOVA, P < 0.0001). Immunohistochemically, UUO is associated with increased interstitial collagens I and III, fibronectin, heparan sulfate proteoglycan and tubulointerstitial nephritis antigen. Aberrant collagen expression is also evident as interstitial collagen IV becomes prominent. Focal, peritubular accumulation of collagens I and II also appear to encircle the TBM. These changes are accompanied by an early, transient increase in renal cortical mRNA encoding the alpha 1 monomers of collagens I, III and IV, implicating increased matrix synthesis in the pathogenesis of obstructive nephropathy. In situ hybridization localized increased expression of alpha 1 (I) and alpha 1 (IV) mRNA to cells in the interstitial space, with clusters of alpha 1(I) positive cells associated with dilated tubules, muscular arteries and the periglomerular interstitium.

Cyclosporine A has no direct effect on collagen metabolism by cardiac fibroblasts in vitro

BACKGROUND

Cyclosporine A has been implicated in the pathogenesis of myocardial interstitial fibrosis observed in heart transplant recipients. However, other confounding variables such as posttransplantation hypertension and rejection episodes may also be responsible for interstitial fibrosis development and associated abnormalities in ventricular diastolic function. Therefore, we examined whether cyclosporine A directly or indirectly affects fibrillar collagen metabolism by cardiac fibroblasts in vitro.

METHODS AND RESULTS

Rat cardiac fibroblasts were isolated by collagenase digestion. Subconfluent cultures were then maintained (24 hours) in serum-containing or serum-free medium before addition of cyclosporine A (50-1,000 ng/mL). After an additional 24 hours, total procollagen synthesis, accumulation, and degradation were analyzed by measuring hydroxyproline content in the cell monolayer and in the ethanol-soluble and ethanol-precipitable fractions of the culture medium. mRNA levels for alpha 1(I) and alpha 1(III) procollagen polypeptides were assessed 2, 6, 12, and 24 hours after cyclosporine A treatment using Northern blot analysis. The results were compared with control cultures maintained in the absence of cyclosporine A. There were no differences in procollagen gene expression, total procollagen synthesis, accumulation, or degradation in cardiac fibroblasts treated directly with cyclosporine A, in concentrations up to 1,000 ng/mL, compared with untreated cells. In additional experiments, we examined whether cyclosporine A might stimulate the production of collagen regulatory substances by cardiac myocytes in culture. However, addition of conditioned media from neonatal myocytes maintained in the presence and absence of cyclosporine A (1,000 ng/mL) also had no effect on collagen deposition by cardiac fibroblasts.

CONCLUSIONS

We conclude that cyclosporine A has no direct effect on collagen metabolism by cultured cardiac fibroblasts in vitro. In addition, we have excluded a paracrine effect of ventricular myocytes on collagen production in the presence of cyclosporine A. These results suggest that factors other than cyclosporine A are responsible for the interstitial fibrosis observed in cardiac allografts.

Early increased renal procollagen alpha 1(IV) mRNA levels in streptozotocin induced diabetes

Changes in renal procollagen mRNA levels were measured shortly after the induction of streptozotocin induced diabetes in the rat. "Medullary" procollagen alpha 1(IV) levels seven days after diabetes induction was significantly higher in untreated diabetic rats (DM, N = 12; 244 +/- 57% of the mean control value), than in diabetic rats receiving small doses of insulin insufficient to achieve euglycemia (NPH, N = 10; 87 +/- 12%) and in diluent injected nondiabetic control rats (C, N = 15; 100 +/- 12%; P less than 0.01, DM vs. C and DM vs. NPH). "Medullary" procollagen alpha 1(I) mRNA levels were numerically increased in DM to a lesser degree (141 +/- 5%, ANOVA not significant) compared to C (100 +/- 13%), and this small increment was further normalized by insulin treatment (NPH, 120 +/- 11%). A trend for increased beta-actin mRNA levels in DM did not reach significance (P greater than 0.05). Increases in "medullary" procollagen mRNA levels did not correlate with kidney weight, glomerular tuft volume, creatinine clearance, food intake, or body weight gain, and occurred when renal morphology was normal by light microscopy. Statistically significant but weak correlations were noted between the serum glucose levels and "medullary" procollagen alpha 1(IV) mRNA levels (r = 0.43, P less than 0.05). In addition, weak correlations were noted between glycosuria and "medullary" procollagen alpha 1(I) levels (r = 0.38, P less than 0.05). In situ hybridization studies localized the increased procollagen alpha 1(IV) mRNA levels predominantly in the DM group primarily in the deep cortex and medullary outer stripe of proximal tubules. Glomerular procollagen alpha 1(IV), alpha 1(I), alpha 1(III) and beta-actin mRNA levels were not increased in untreated diabetic rats 7 or 28 days after diabetes induction. Thus, tubular procollagen alpha 1(IV) mRNA levels increased prior to any measurable change in glomerular levels and were ameliorated by insulin administration.