Leendert A. van Es

Endothelial cell chimerism after renal transplantation and vascular rejection

BACKGROUNDnThe blood vessels of a transplanted organ are the interface between donor and recipient. The endothelium in the blood vessels is thought to be the major target for graft rejection. Endothelial cells of a transplanted organ are believed to remain of donor origin after transplantation. We aimed to verify this concept.nnnMETHODSnWe studied biopsy samples from 12 renal transplants for the presence of endothelial cells of recipient origin. We used three different techniques: immunohistochemistry for MHC class-I antigens, immunohistochemistry for ABO-blood-group antigens, and in-situ hybridisation for X and Y chromosomes. After we had confirmed that these techniques did identify endothelial cells of recipient origin, tests were done in a second group of 26 patients to find out whether endothelial chimerism correlated with graft rejection.nnnFINDINGSnWe found a strong correlation between the percentage of recipient endothelial cells in the peritubular capillaries and the type of graft rejection (r = 0.71, p < 0.0001). These cells were found mainly in grafts of patients who had had rejection, especially among patients with vascular rejection. In grafts of patients without rejection only sporadically recipient endothelial cells were detectable.nnnINTERPRETATIONnOur data show that endothelial cells of the recipient can replace those of the donor. This replacement is associated with graft rejection. We postulate that endothelium that is damaged by vascular rejection is repaired by endothelial cells of the recipient.

Interleukin-1α enhances the biosynthesis of complement C3 and factor B by human kidney proximal tubular epithelial cells in vitro

Local production in tubular cells of complement has been shown to occur in several kidney diseases by in situ hybridization, but the regulation at the local site during an inflammation is still unknown. In the present study, we demonstrate that human proximal tubular epithelial cells (PTEC) are able to produce complement components C3 and Factor B under non-stimulated conditions in vitro. The basal production of both was increased by 0.5 ng/ml interleukin-1 alpha (IL-1 alpha) for C3: from 95.5 +/- 4.0 ng/10(6) cells to 416.5 +/- 4.9 ng/10(6), and for Factor B: from 271 +/- 7.0 ng/10(6) cells to 457.5 +/- 7.0 ng/10(6) cells. In contrast cytokines such as TNF-alpha, IFN-gamma, IL-10 and IL-15 had no detectable effect. The upregulation by IL-1 alpha was dose- and time-dependent. The response to IL-1 alpha was shown to be mediated via the IL-1 receptor, as the addition of recombinant interleukin-1 receptor antagonist inhibited the IL-1 alpha induced complement production by more than 80%. IL-1 alpha enhanced mRNA expression of both C3 and Factor B as demonstrated by RT-PCR and dot-blot analysis. This indicated that IL-1 alpha upregulated the expression of the C3 and Factor B at the transcriptional level. We hypothesize that in vivo the production of C3 and Factor B at the local site during an inflammatory response in the kidney may be regulated by IL-1 alpha produced by inflammatory cells.

Effect of danaparoid sodium on hard exudates in diabetic retinopathy

BACKGROUNDnIn diabetes mellitus, both retinopathy and nephropathy represent specific microvascular disease with increased capillary permeability resulting in hard exudates, foveal oedema, and albuminuria. The decrease of heparan-sulphate content of the glomerular-basement membrane is quantitatively related to the rate of proteinuria in nephropathy associated with insulin-dependent diabetes mellitus (IDDM). Several short-term studies in patients with IDDM and non-IDDM have shown that a reduction of microalbuminuria and macroalbuminuria can be achieved with the supplementation of glycosaminoglycans. After completion of a study on the effect of danaparoid sodium on albumin excretion in patients with IDDM and macroalbuminuria, we hypothesised that treatment with danaparoid sodium also influenced retinal leakage in the patients in that trial.nnnMETHODSnIn this retrospective study nine patients with nephropathy received 750 anti-Xa units danaparoid sodium once a day for 6 weeks in a placebo-controlled double-blind cross-over study. Fundus photographs, done at baseline and at the end of the study, were semiquantitatively scored for the severity of hard exudates.nnnFINDINGSnAt baseline 14 eyes had grade 1 to 5 severity of hard exudates and four eyes were without hard exudates (grade 0). There was no progression in the latter four eyes. In ten eyes an improvement was observed: four patients showed a favourable response to treatment in both eyes and two patients showed improvement in one eye. We found improvement of hard exudates after 6 weeks of treatment with danaparoid sodium.nnnINTERPRETATIONnOur uncontrolled observation indicates that the supplementation of danaparoid sodium influences both the permeability of retinal vessels as well as of glomerular vessels. Danaparoid-sodium therapy as a systemic adjuvant is worth considering for treatment strategies for foveal oedema and hard exudates in diabetic maculopathy.

The D-allele of the ACE gene polymorphism predicts a stronger antiproteinuric response to ACE inhibitors

SUMMARY: Angiotensin converting enzyme (ACE) inhibitors have additional renoprotective effects over other antihypertensive drugs in retarding the development and progression of diabetic and non‐diabetic nephropathies. This additional beneficial effect has been attributed to their antiproteinuric action. However, individual antiproteinuric responses to ACE inhibitors vary considerably. the mechanism underlying the variable response is unresolved. the role of the insertion/deletion (I/D) polymorphism of the ACE gene in this response was examined. the case series consisted of 96 patients (69 males, median age 46.5 years) on ACE inhibitors with an initial proteinuria in excess of 1.0 g/24h. A control series consisted of 103 patients (43 males, median age 40 years) with autosomal polycystic kidney disease. A second control series consisted of 82 patients (52 males, median age 39 years) with a diagnosis of insulin‐dependent diabetes mellitus (IDDM) without microalbuminuria after more than 15 years of IDDM. Angiotensin converting enzyme genotyping was performed by polymerase chain reaction (PCR) analysis of chromosomal DNA. the ACE genotype distribution (DD 44%, ID 28%, II 28%) in the case series was not in accordance with the Hardy‐Weinberg equilibrium (χ2= 17.2, P<0.001), whereas it was in both control series. the difference in ACE genotype distribution between the case series and both control series combined was significant as a result of an overrepresentation of patients with the DD genotype (χ2=9.2, P=0.01). the allele frequencies were compared in patients with a reduction of proteinuria above and below the median value of 45%. the antiproteinuric effectiveness of ACEI therapy in the whole group was greater in the presence of the D‐allele (OR 1.6, 95% CI 0.9‐2.9). the effect of the D‐allele was more pronounced in the subgroup of patients with an initial proteinuria in the non‐nephrotic range (relative risk 2.8, 95%CI 1.0‐8.0) and in patients not receiving diuretics (relative risk 2.3, 95% CI 1.1–4.5). In conclusion, the DD genotype seems to predispose the development of proteinuria in the presence of a kidney disorder. the presence of the D‐allele predicts a stronger antiproteinuric efficacy of ACE inhibitor therapy in patients with an initial proteinuria in the non‐nephrotic range and in the patients not requiring comedication with diuretics.

Cytokine-regulated production of the major histocompatibility complex class-III-encoded complement proteins factor B and C4 by human glomerular mesangial cells

Local production of complement within normal or diseased kidneys could be of importance during local inflammatory reactions. In the present study, we demonstrate that human MCs are able to synthesize the MHC class-III-encoded complement proteins factor B and C4 in vitro. This synthesis is strongly upregulated following stimulation with cytokine-containing supernatants of activated peripheral blood mononuclear cells. All primary cell lines tested so far are able to synthesize factor B and C4 after stimulation. To determine more specifically whether defined cytokines are able to enhance factor B and C4 complement production, MCs were stimulated with IL-1 alpha, IFN-gamma, and TNF-alpha. Factor B synthesis was increased in a dose-dependent fashion by IL-1 alpha, TNF-alpha, and IFN-gamma, whereas C4 synthesis was only upregulated by IFN-gamma. Furthermore, factor B synthesis was upregulated after stimulation with IFN-alpha, -beta, and -gamma and C4 synthesis only by IFN-gamma. The synthesis of factor B and C4 was inhibited by cycloheximide, suggesting de novo protein synthesis. The cytoplasmic localization of both components was shown by immunofluorescence studies. Northern and dot blot analysis revealed induction of factor B and C4 mRNA after stimulation with cytokines.

Interleukin‐1α and tumour necrosis factor‐α modulate the production of monocyte chemoattractant protein‐1 by cultured human glomerular visceral epithelial cells

Summary: Mediators released by glomerular macrophages may stimulate glomerular visceral epithelial cells (GVEC) to produce cytokines, growth factors or extracellular matrix components. This study describes that human GVEC produce monocyte chemoattractant protein‐1 (MCP‐1), a monocyte‐specific chemotactic factor, and the effects of interleukin‐lα (IL‐1α) and tumour necrosis factor‐α (TNF‐a) on the production of MCP‐1 by GVEC.