Background. Post-transplantation bone disease is associated with a high degree of morbidity including pain and fractures. Glucocorticoid-induced osteoporosis on top of pre-existing renal osteodystrophy is considered the major pathogenic factor, while the role of non-glucocorticoid immunosuppressants is less well defined. Methods. In this study, we investigated the influence of sirolimus (SRL) versus calcineurin inhibitor (CI)-based immunosuppressive regimens on biomarkers of bone resorption in renal transplant patients. In addition, the impact of SRL, tacrolimus and mycophenolate mofetil (MMF) on osteoclast activation and function was assessed in cell culture systems. Results. Using this approach, we demonstrated reduced serum levels of bone resorption markers in patients treated with SRL after kidney transplantation compared to a CI-based regimen. In line with this observation, we detected profoundly reduced osteoclast differentiation and subsequently diminished hydroxyapatite resorption in the presence of SRL compared to MMF and tacrolimus in vitro . Moreover, SRL significantly reduced osteoclast precursor proliferation in vitro compared to tacrolimus and led to augmented apoptosis in osteoclast precursors. Conclusions. Taken together, SRL was shown to inhibit osteoclast formation in vivo and in vitro . SRL thus may have the potential to balance osteoclast promoting effects of glucocorticoids and CI, thereby counteracting the development of accelerated osteoporosis in renal transplant recipients.

Introduction: Nephrogenic systemic fibrosis (NFS) is a generalized disorder occurring in people with kidney failure. This new disease entity can lead to significant disability or even death. Gadolinium-associated systemic fibrosis is related to exposure to contrast agents used for magnetic resonance imaging. The aim of this study was to review the literature in available scientific databases on NFS—complication after gadolinium-containing contrast agents. Methods: PubMed and Cochrane Library databases were searched using adequate key words. A literature review of the described cases of NSF occurrence after exposure to gadolinium-containing contrast agents was performed. A review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A review written protocol was not drafted. Results: Originally, 647 studies were searched in scientific databases. After rejecting the duplicate results, 515 results were obtained. Finally, nine studies were included in the review. A total of 173 cases with NSF were included in the analysis. The majority of patients were undergoing dialysis. The contrast agent used for MRI was most often gadodiamide and gadopentetate dimeglumine. The time from exposure to NSF symptoms was from two days to three years. Three authors pointed out other factors in their papers that could potentially influence the occurrence of NSF. These included: metabolic acidosis, ongoing infection, higher doses of erythropoietin and higher serum concentrations of ionized calcium and phosphate. Since 2008, the number of reported cases of NSF has decreased significantly. More recent guidelines and reports indicate that not all contrast agents are associated with the same risk of developing NSF. Conclusions: Most NSF occurs after exposure to linear contrast agents. Therefore, it is recommended to limit their use, especially in dialyzed patients and patients with a GFR < 30 mL/min.

Hypertensive patients exhibit elevated cancer incidence, especially of cancers of the kidney. Elevated levels of ANG II, the active peptide of the renin-angiotensin system, regulating blood pressure and cardiovascular homeostasis, are known to cause hypertension and kidney diseases. There is evidence that ANG II is an activator of NAD(P)H oxidase, leading to the formation of free radicals, which are known to participate in the induction of DNA damage. This study was undertaken to characterize ANG II-induced DNA damage. DNA damage was measured by comet assay and micronucleus frequency test. Incubation of pig kidney cells (LLC-PK₁) in vitro with ANG II concentrations between 85 and 340 nM led to a 6- to 15-fold increase of DNA damage compared with the control as revealed by comet assay analysis. Micronuclei were induced about fourfold compared with the control in pig and rat kidney cells (LLC-PK₁, NRK) and in human promyelocytic cells (HL-60). ANG II-induced DNA damage could be prevented by coincubation with the ANG II type 1 receptor blocker candesartan and the antioxidants N-acetylcysteine and α-tocopherol. The ANG II type 2 receptor antagonist PD123319 could not reduce ANG II-induced DNA damage. Measurement of reactive oxygen species (ROS) by flow cytometry showed an enhanced formation after exposure to ANG II and a reduction of ROS after candesartan, N-acetylcysteine, and α-tocopherol. The present findings support our hypothesis that ANG II causes DNA damage via ANG II type 1 receptor binding and subsequent formation of oxidative stress.