[Kidney transplant pathology]. / Nierentransplantatpathologie.

Biopsy of the transplanted kidney plays an important role in the care and treatment of patients after kidney transplantation. Today the renal biopsy is a standard procedure which is performed early after renal transplantation in the case of a primary non-functioning graft or a significant rise in serum creatinine. On the other hand, a kidney biopsy is performed if an acute or creeping rise in serum creatinine or acute onset of proteinuria or erythrocyturia is observed during follow-up. Furthermore, zero biopsies or intraoperative biopsies of the graft are important in order to obtain information about the initial quality of the graft. This is particularly important in view of the shortage of donor organs and the resulting necessity to accept increasingly marginal organs, such as for example in the ESP program. In addition, an increasing number of transplant centres perform protocol biopsies, i.e. biopsies that are not based on clinical indication, but are performed at a certain time point after transplantation to detect subclinical rejections as well as histological alterations pointing to chronic allograft damage. Additionally, there is much scientific interest in protocol biopsies.

Increased mycophenolic acid exposure in stable kidney transplant recipients on tacrolimus as compared with those on sirolimus: implications for pharmacokinetics.

The pharmacokinetics of mycophenolic acid (MPA) was studied in 23 kidney transplant recipients with stable, long-term graft function who were receiving mycophenolate mofetil (MMF) in combination with either tacrolimus or sirolimus therapy. After 500 mg MMF, the mean MPA area under the curve (AUC) was significantly lower in sirolimus-treated patients than in those treated with tacrolimus (35.4 +/- 32.3 vs. 77.1 +/- 67.5 mg/l). MPA peak plasma concentration (C(max)) and MPA trough plasma concentration (C(min)) were significantly higher in patients who received tacrolimus than in those who received sirolimus. There were no significant differences between the two groups with respect to MPA time to maximum concentration (T(max)), MPA-glucuronide (MPAG) AUC, MPAG C(max), MPAG C(min), MPAG T(max), MPA-acyl-glucuronide (AcMPAG) AUC, AcMPAG C(max), AcMPAG C(min), and AcMPAG T(max). In conclusion, MPA exposure is greater in tacrolimus-treated patients than in those treated with sirolimus during maintenance immunosuppression after kidney transplant. It is suggested that the influence of tacrolimus on the pharmacokinetics of MPA reflects an interaction of the two agents at the level of their intestinal absorption.

[Infections under immunosuppressive therapy following organ transplantation]. / Infektionen unter immunsuppressiver Therapie nach Organtransplantation.

The risk to acquire opportunistic infections is clearly increased in patients receiving immunosuppressive therapeutic regimens following organ transplantation or during treatment of autoimmune disorders. The modulation of the immune system can alter the clinical symptoms and the course of infectious diseases, including diagnostic signs such as fever or pathological changes in radiographs or blood cell counts. However, a rapid diagnosis and start of treatment is essential in these patients. Thus, a correct interpretation of even mild symptoms in the initial phase of an infectious disease is essential for establishing a diagnosis and initiation of a therapy at an early stage. Therefore, it is necessary that the clinical hallmarks of these diseases are widely known and that physicians treating these patients cooperate closely with transplant centers.

Determination of the pharmacokinetics of cerivastatin when administered in combination with sirolimus and cyclosporin A in patients with kidney transplant, and review of the relevant literature.

OBJECTIVE: Therapy of elevated cholesterol serum concentrations is often necessary in patients with kidney transplants. However, the pharmacokinetics of HMG-CoA reductase inhibitors when administered in combination with sirolimus and cyclosporin A (CsA) have not been determined. The aim of this study was to investigate the pharmacokinetics of cerivastatin when administered in combination with sirolimus in patients with kidney transplants, and to review the literature with regard to the differences in pharmacological behavior between sirolimus, CsA and tacrolimus. METHODS: Patients (n = 7) with a stable and functioning kidney transplant and elevated LDL cholesterol serum concentrations were included in the study. After an observation period of 3 months, and whilst receiving sirolimus and CsA, cerivastatin (0.2 mg daily) was administered for a period of 3 months. Pharmacokinetic parameters were calculated on Day 1 and 3 months after initiation of cerivastatin therapy. Routine laboratory parameters and clinical adverse events were monitored throughout the study period. RESULTS: Single-dose cerivastatin AUC was 2 to 3-fold higher in comparison to published values obtained in healthy subjects. The accumulation ratio of cerivastatin (after 3 months/ Day 1) was 1.6. Sirolimus and CsA trough levels, and the sirolimus AUC did not differ after single dose and multiple doses of cerivastatin. CONCLUSIONS: The combination therapy of cerivastatin with sirolimus and CsA leads to a significant increase in cerivastatin exposure. Additional drug monitoring of sirolimus and CsA is not necessary.

Laser capture microdissection and real-time PCR for analysis of glomerular endothelin-1 gene expression in mesangiolysis of rat anti-Thy 1.1 and murine Habu Snake Venom glomerulonephritis.

Molecular analysis of pathologic changes in glomeruli requires methods allowing rapid and exact detection of alterations in gene expression. Here, we analyzed endothelin-1 (ET-1) mRNA expression in mesangiolytic glomeruli during the course of a rat and murine model of mesangioproliferative glomerulonephritis (GN). A novel method combining laser capture microdissection (LCM), which permits the precise removal of selected mesangiolytic glomeruli, with a highly sensitive real-time RT-PCR technique was used. Anti-Thy 1.1. GN was introduced in male Sprague-Dawley rats (1.0 mg/kg body weight of OX-7 IV) and Habu Snake Venom GN was introduced in C57BL6 mice (habu snake venom toxin 6 mg/kg body weight IV). The degree of mesangiolysis during both GNs was analyzed using a semiquantitative scoring system. Mesangiolytic glomeruli were microdissected at different days of the diseases (day 2, 6, and 12 in anti-Thy 1.1 GN and days 1, 3, 7, and 14 in Habu Snake Venom GN) and from normal control animals. After RNA extraction and cDNA synthesis, ET-1 gene expression was measured by real-time RT-PCR. In parallel, in anti-Thy 1.1. GN ET-1 mRNA expression was analyzed using semiquantitative nonradioactive in situ hybridization; ET-1 protein expression was investigated by immunohistochemistry. Mesangiolysis peaked at day 6 in anti-Thy1.1 GN and at day 1 in Habu Snake Venom GN. Mesangiolytic glomeruli were easily microdissected on cryostat sections in both models; quantification of mRNA with RT-PCR was reliable and reproducible. Glomerular ET-1 mRNA expression increased during the course of anti-Thy 1.1 GN and Habu Snake Venom GN peaked when mesangiolysis was most pronounced. This was seen by RT-PCR after glomerular LCM and by in situ hybridization; in parallel, glomerular ET-1 protein expression was increased. Combination of LCM and RT-PCR is a reliable method for quantification of localized gene expression in isolated renal structures. The above data argue for an important role of ET-1 in pathogenesis and/or repair of mesangiolysis in experimental mesangioproliferative GN.

Requirement of heat shock protein 90 in mesangial cell mitogenesis.

BACKGROUND: Hyperplasia of mesangial cells (MCs) is a frequent finding in glomerulonephritis. Heat shock protein 90 (HSP90) is a major cellular chaperone that assists protein folding under physiological and stress conditions. METHODS: To identify genes that are potentially involved in the pathogenesis of glomerulonephritis, we analyzed glomerular gene expression in mesangioproliferative rat anti-Thy1.1 nephritis by representational difference analysis (RDA). Expression of HSP90beta in anti-Thy1.1 nephritis was studied by Northern and Western blot analyses and immunohistochemistry. In cultured rat MCs, the requirement of HSP90 for mitogenic signaling steps and MC replication was studied by incubation with the specific HSP90 inhibitor geldanamycin. RESULTS: By RDA, a cDNA fragment homologous to HSP90beta was identified. Glomerular mRNA and protein expression of HSP90beta was markedly and transiently up-regulated during the course of anti-Thy1.1 nephritis, with a maximum at day 6, coinciding with the peak of MC proliferation. By immunohistochemistry, HSP90beta expression in normal glomeruli was detected in podocytes. However, in anti-Thy1.1 nephritis, glomerular HSP90beta protein expression was strongly and transiently increased in mesangial localization. In vitro, mitogenic stimulation of rat MCs led to the induction of HSP90beta mRNA and protein. Incubation of MCs with geldanamycin dose-dependently inhibited DNA synthesis and replication. Moreover, geldanamycin interfered with mitogen-induced phosphorylation of extracellular signal-regulated kinase and transcription of c-fos and Egr-1, but not with transactivation of STAT1 transcription factor. Cell cycle analysis of serum-stimulated MCs revealed that geldanamycin inhibited kinase activity of cyclin D1/CDK4 complexes and blocked progression in the G0/G1 phase and at the S/G2 phase transition. CONCLUSIONS: The up-regulation of HSP90beta in anti-Thy1.1 nephritis may reflect its functional involvement in phenotypical alterations of MCs in mesangioproliferative glomerulonephritis. Our in vitro studies indicate that HSP90 governs the capacity of MCs to respond to proliferative stimuli by regulating critical mitogenic signaling steps necessary for G1 entry and S-phase progression.

Distinct structural forms of type I collagen modulate cell cycle regulatory proteins in mesangial cells.

BACKGROUND: Extracellular matrix molecules profoundly regulate cell behavior, including proliferation. In glomerulonephritis, type I collagen accumulates in the mesangium and is constantly structurally modified and degraded during the course of the disease. METHODS: We studied how two structurally distinct forms of type I collagen, monomer versus polymerized fibrils, affect cell proliferation, mitogen-activated protein kinase (MAPK) activation, and expression of G1-phase regulatory proteins in cultured rat mesangial cells (MCs). To analyze the possible involvement of collagen-binding integrins in type I collagen-derived growth signals further, distribution patterns of integrin chains were examined by immunocytochemistry. RESULTS: Polymerized type I collagen completely prevented the increase of DNA synthesis and cell replication induced by 5% fetal calf serum (FCS) or 25 ng/mL platelet-derived growth factor (PDGF) in MCs on monomer type I collagen. Protein expression of cyclins D1 and E was markedly down-regulated in MCs plated on polymerized type I collagen for eight hours in 5% FCS, as compared with MCs on monomer type I collagen. Incubation with 5% FCS reduced expression of the cdk-inhibitor protein p27Kip1 on monomer but not on polymerized type I collagen. Moreover, polymerized type I collagen markedly reduced cyclin E-associated kinase activity in the presence of 5% FCS. Polymerized type I collagen diminished the PDGF-induced phosphorylation and nuclear translocation of p42/p44 MAPK, but did not affect phosphorylation of PDGF beta-receptors. In MCs plated on monomer type I collagen, alpha1, alpha2, and beta1 integrin chains were recruited into focal contacts. However, on polymerized type I collagen, alpha2 and beta1, but not alpha1, integrin chains were condensed into focal contacts. CONCLUSIONS: The growth-inhibitory effect of polymerized type I collagen is characterized by rapid changes of expression and/or activation of MAPK and G1-phase regulators and could result from the lack of alpha1beta1 integrin signaling in MCs on polymerized type I collagen. Conceivably, deposition of polymerized type I collagen might reflect a reparative response to control MC replication in glomerular inflammation.

Regulation of mesangial cell proliferation.

Regardless of the source of injury, an imbalance in the control of mesangial cell proliferation appears to play a direct role in the degree of progressive renal injury and glomerulosclerosis. Some of the regulatory mechanisms include specific soluble or non-soluble extracellular factors and a complex array of receptor-mediated signals that control the progression of the cell cycle or cell death. Understanding these regulatory processes could lead to novel therapeutic strategies to alleviate or arrest proliferative glomerular disease.

Alpha8 integrin in glomerular mesangial cells and in experimental glomerulonephritis.

BACKGROUND: Mesangial cell (MC) proliferation and extracellular matrix accumulation are typical responses of renal glomeruli to injury. Extracellular matrix components are known to affect MC behavior, which is mediated primarily via integrin receptors of the beta1 family. In addition to alpha1, alpha3, alpha5, and alpha6 chains of beta1 integrins, recent studies have shown the alpha8 chain to be expressed in glomeruli and renal vasculature. alpha8beta1 can serve as a receptor for fibronectin, which is abundant in the mesangium. We investigated the glomerular expression pattern of the alpha8 chain in renal tissues of mouse, rat, and humans as well as in cultured MCs. In addition, the regulation of alpha8 expression in MCs was studied in culture and in nephritic rats. METHODS: The expression of alpha8 protein in kidney tissue and cultured MCs was investigated by immunohistochemistry, immunocytochemistry, and Western blotting. The effects of TGF-beta1 on alpha8 mRNA levels in MCs were studied by Northern blot analysis. In addition, time course studies of glomerular abundance and localization of alpha8 were performed in rats with mesangioproliferative anti-Thy1.1 nephritis. RESULTS: In tissue sections of normal human, rat, and mouse kidney, we found strong immunohistochemical staining for alpha8 in the mesangium and in the media of renal arterioles. Double staining for alpha8 and Thy1.1, a surface antigen of rat MCs, showed alpha8 to be specifically expressed in MCs but not in glomerular endothelial and epithelial cells. In anti-Thy1.1 nephritis of rats, the glomerular abundance of alpha8 protein was reduced in the early mesangiolytic phase but was increased greatly with subsequent MC proliferation, peaking at day 6 of disease. At later stages of this reversible form of nephritis, the number of MCs and the extent mesangial alpha8 staining declined to control levels. Cell culture experiments revealed that freshly plated MCs organize alpha8 into focal contacts within one hour after attachment to fibronectin and vitronectin substrata, showing colocalization with focal contact proteins vinculin and talin. Stimulation of MCs with transforming growth factor-beta1 led to increases of alpha8 mRNA and protein levels. CONCLUSIONS: These results show that in human, rat, and mouse glomeruli, alpha8 integrin is strongly and exclusively expressed in MCs. Gene expression of alpha8 is regulated in cultured MCs, and alpha8 protein abundance is regulated in vivo and in MC culture. It is currently unclear what functional properties this integrin receptor protein has with regard to MC anchorage to extracellular matrix and modulation of the MC phenotype in normal and diseased glomeruli. However, in view of its abundance in the mesangium, alpha8beta1 integrin could be an important MC receptor of matrix ligands and may play a role in the embryology, physiology, and pathophysiology of the glomerular capillary tuft.

[Renal tubular acidosis with severe hypokalemic tetraparesis after ibuprofen intake]. / Renale tubuläre Azidose mit schwerer hypokaliämischer Tetraparese nach Ibuprofeneinnahme.

HISTORY: A 72-year-old woman was admitted because of severe acute tetraparesis, more marked proximally. For six months she had been taking ibuprofen, up to 4800 mg daily, for a painful ulcer of the lower leg. INVESTIGATIONS: Biochemical tests revealed marked hypokalaemia (serum potassium 1.4 mmol/l) with a metabolic acidosis (pH 7.29). The ECG showed changes of hypokalaemia (ST-segment depression and U wave). TREATMENT AND COURSE: Within two days of administering potassium and bicarbonate the pareses completely regressed. Transitorily abnormal renal functions also rapidly normalized after ibuprofen had been discontinued. CONCLUSION: The biochemical findings suggest renal tubular acidosis, type 2, most likely caused by the excess intake of ibuprofen, a drug which can cause renal dysfunctions with life-threatening electrolyte abnormalities.

Mesangial cells and their adhesive properties.

Glomerular mesangial cells play a central role in maintaining structure and function of the glomerular capillary ultrafiltration apparatus. Under physiological and pathological conditions, mesangial cells regulate amount and composition of the surrounding extracellular matrix. Conversely, components of the embedding matrix affect the mesangial cell phenotype. These interactions are mediated via specific cell surface receptors, the best studied group of which is the beta1 integrin family. The beta1 integrins play a role in mesangial cell adhesion, migration, survival and proliferation. Expression and abundance of integrins in healthy and diseased glomeruli and their functions and mediation of signals are discussed in this review. Other factors modulating mesangial cell-matrix interactions, such as antiadhesive proteins, cytokines, disintegrins and nitric oxide, are also considered. The available evidence from in vitro and in vivo studies indicates that receptor-mediated interactions between mesangial cells and the normal or abnormal extracellular matrix regulate the mesangial cell phenotype and thus contribute to normal maintenance of the glomerulus and to remodeling and repair of the glomerular capillary tuft in response to injury.

Regulatory mechanism in glomerular mesangial cell proliferation.

Glomerular mesangial cells have a central function in maintaining structure and function of the glomerular capillary ultrafiltration apparatus. Regardless of the type of glomerular injury, imbalances in the control of mesangial cell replication appear to play a key role in the pathogenesis of progressive renal failure. The available evidence from in vitro and in vivo studies indicates that such regulatory mechanisms include specific soluble and non-soluble extracellular factors and a complex array of receptor-mediated signals which control cell proliferation, survival and apoptosis. This review summarizes results from recent investigations concerning regulation of cell cycle progression in mesangial cells. In addition to results from cell culture studies, descriptive findings on expression and regulation of cell cycle-regulatory proteins and their potential role for altered mesangial cell behaviour in glomerular disease are considered. We believe that better understanding of processes which regulate mesangial cell replication could lead to novel diagnostic as well as therapeutic strategies and, thus, help control better proliferative glomerulonephritis.

[Egr-1 transcription factor regulates the growth of glomerular mesangium cells]. / Der Transkriptionsfaktor Egr-1 reguliert das Wachstum glomerulärer Mesangiumzellen.

BACKGROUND: The transcriptional regulator Early growth response gene-1 (Egr-1) is rapidly and transiently induced by various mitogens in cultured rat mesangial cells (MCs). METHOD AND RESULTS: Here we show Egr-1 induction in an in vivo model of mesangioproliferative glomerulonephritis (GN). A 14.9-fold increase in Egr-1 mRNA was observed 6 days after disease induction. A concomitant increase in Egr-1 protein was demonstrated by immunocytochemistry. Egr-1 was mainly localized to the nuclei of cells in mesangial localization. To test whether Egr-1 directly regulated MC proliferation, we preincubated cultured MCs with antisense oligonucleotides directed against Egr-1. The platelet-derived growth factor (PDGF)-induced increase in Egr-1 mRNA and protein levels was inhibited by 75% and 74%, respectively. At the same time Egr-1 antisense oligonucleotides dose-dependently inhibited MC-proliferation as determined by thymidine-uptake by up to 75%. Control oligonucleotides were without effects on Egr-1 mRNA, protein or MC growth. CONCLUSION: We conclude that Egr-1 induction is a necessary step in the mitogenic signaling cascade in glomerular MCs.

Cell-matrix interactions in the glomerular mesangium.

Specific interactions between cells and components of the surrounding extracellular matrix (ECM) or underlying basement membrane have been shown to modulate cell behavior, including cellular responses to soluble regulator molecules. In addition to the long-recognized role of such interactions in cell localization, anchoring and differentiation during embryogenesis, they are also involved in diverse processes such as maintenance of tissue integrity, response of cells to mechanical stress, inflammatory response, wound healing, tumor cell growth and metastasis as well as apoptosis. Over the last several years, evidence has been reported that extensive "cross-talk" between glomerular mesangial cells (MCs), ECM molecules and soluble mediator substances also affects the proliferative and synthetic phenotype of MCs. This is likely to be relevant for the behavior of MCs during embryonic development, tissue repair and disease processes of glomeruli. The potential biologic and clinical relevance of cell-matrix interactions in the glomerulus makes their elucidation a challenging goal in current kidney research. In this brief review, we present selected aspects of recent investigations concerning the mesangial matrix and its interactions with MCs. In addition to results from cell culture studies, descriptive findings on abnormalities of the ECM and their potential role for the altered MC behavior in glomerular disease will also be discussed.

Long latency muscle responses in cerebellar diseases.

Long latency reflexes were measured from the hand muscles of 27 patients suffering from different cerebellar diseases (12 diffuse cerebellar atrophies, 7 cerebellar hemispheric infarcts, 8 Friedreich's disease) and from 45 controls after electrical stimulus of the median nerve at the wrist. The M3 response (latency about 70 ms) was increased in about 50% of cerebellar atrophy cases and occasionally (10 of 12 cases) separated from the M2 response (50 ms). M3 was sometimes (3/7) increased and the M2-3 complex was prolonged ipsilaterally in cases of cerebellar infarcts. In the cases of Friedreich's ataxia M2 was always lost uni or bilaterally because of the disturbance of afferent or efferent fibres. The latencies of the spinal reflex M1 and also of M2 were not always increased strongly enough to be clearly separated from the normal values.