The tubular epithelium of the kidney is susceptible to injury from a number of different causes, including inflammatory and immune disorders, oxidative stress, and nephrotoxins, among others. Primary renal epithelial cells remain one of the few tools for studying the biochemical and physiological characteristics of the renal tubular system. Nevertheless, differentiated primary cells are not suitable for recapitulation of disease properties that might arise during embryonic kidney formation and further maturation. Thus, cellular systems resembling kidney characteristics are in urgent need to model disease as well as to establish reliable drug-testing platforms. Induced pluripotent stem cells (iPSCs) bear the capacity to differentiate into every cell lineage comprising the adult organism. Thus, iPSCs bring the possibility for recapitulating embryonic development by directed differentiation into specific lineages. iPSC differentiation ultimately allows for both disease modeling in vitro and the production of cellular products with potential for regenerative medicine. Here, we describe the rapid, reproducible, and highly efficient generation of iPSCs derived from endogenous kidney tubular renal epithelial cells with only two transcriptional factors, OCT4 and SOX2. Kidney-derived iPSCs may provide a reliable cellular platform for the development of kidney differentiation protocols allowing drug discovery studies and the study of kidney pathology.

Mammalian target of rapamycin (mTOR) inhibition has been associated with gonadal dysfunction. The aim of this study was to characterize the effect of sirolimus (SRL) on male gonadal function in an experimental model. Male Wistar rats were treated with intraperitoneal administration of vehicle or SRL. Vehicle group was treated for 12 weeks. Rats treated with SRL were killed at 4, 8, and 12 weeks. A group of rats was treated with SRL for 4 weeks and then observed during 8 weeks to analyze the possible reversibility of the effect of mTOR inhibition. Body and testicular weight, testosterone, follicle-stimulating hormone level, and luteinizing hormone level were measured and testicular histology was analyzed including proliferation and apoptosis analysis. Testicular weight was significantly lower in all SRL groups. After SRL withdrawal testicular weight had partially recovered. The expression of steroidogenic acute regulatory protein decreased during SRL treatment, which could explain the reduction of testosterone levels, because steroidogenic acute regulatory protein is crucial for testosterone synthesis. Spermatogenesis was blocked on the spermatogonial level by SRL treatment. Withdrawal of SRL treatment led to complete recovery. mTOR inhibition in healthy animals produces sexual hormone dysfunction, seminiferous tubule dystrophy and spermatogenesis blockade. Furthermore, the spermatogenesis blockade produced by SRL is reversible.

The aim was to study the influence of sirolimus (SRL) on body weight in a rat model and in kidney transplant patients. Wistar rats (15 weeks old) were either treated with vehicle (VEH; n = 8) or SRL (n = 7) 1.0 mg/kg three times per week for 12 weeks. Body mass and food intake were measured weekly. Adipocyte diameter was determined in hematoxylin–eosin stains. The body mass index (BMI) obtained from clinical kidney transplant trials comparing SRL‐based with cyclosporine‐based therapy was analyzed. Animals: SRL produced a decrease of the weight gain curve. At the end of the study, mean body weight in the SRL group was lower than in the VEH group (356 vs. 507 g, P < 0.01) in spite of comparable food intake normalized for body weight was not different. Mean adipocyte diameter was 36 μm in VEH and 25 μm in SRL rats (P = 0.009). Mean SRL blood trough concentration was 38 ng/ml. Kidney transplant patients: Two years after transplantation, BMI was significantly lower in the SRL‐based treatment arm compared to cyclosporine (24.17 ± 2.99 vs. 25.97 ± 5.01 kg/m², P = 0.031). SRL treatment leads to less body mass. Adipocyte cell diameter was reduced in SRL‐treated animals. A possible explanation may be the effects of SRL on metabolic regulation and cell growth.

Introduction. Despite advances in therapeutics, graft loss associated with chronic allograft dysfunction (CAD) remains high. Urinary proteomic analysis is a noninvasive method that could be used to detect and evaluate CAD in renal transplant recipients. This study was aimed to establish the normal proteome map of stable transplant patients and to validate the utility of two-dimensional difference gel electrophoresis (2DE-DIGE) in identifying new candidates as urinary biomarkers of CAD. Methods. Morning spot urine samples that were collected from kidney transplant recipients with biopsy-proven interstitial fibrosis and tubular atrophy (IFTA) stages 0-I-II/III (n=8/group) under immunosuppressive treatment with tacrolimus plus mycophenolate with or without prednisone. 2DE silver staining and mass spectrometry analyses were used to establish the normal proteome map, and 2DE-DIGE and mass spectrometry were used to identify proteins exhibiting differential abundance. Results and Conclusions. This study defines the normal proteome of stable renal transplant patients, which is composed of several plasma proteins, as well as of immunologic proteins that are probably specific to transplant recipients. The 2DE-DIGE study showed 19 proteins with differential concentrations, depending on the IFTA histologic score. These 19 proteins could be used as urinary biomarkers of the severity of IFTA in renal transplant recipients.