Allogeneic HSCT transfers wild-type cystinosin to nonhematological epithelial cells in cystinosis: First human report.

Cystinosis is an autosomal recessive lysosomal storage disorder characterized by the defective transport of the amino acid cystine out of the lysosome due to a deficiency of cystinosin, the lysosomal cystine transporter. Patients have lysosomal cystine accumulation in various tissues, leading to cellular stress and damage, particularly in the kidney, cornea, and other extrarenal tissues. Cysteamine, a cystine-depleting agent, improves survival and delays the progression of disease, but it does not prevent the development of either renal failure or extrarenal complications. Furthermore, the drug has severe adverse effects that significantly reduce patient compliance. Allogeneic hematopoietic stem cell transplantation (HSCT) is currently established as a therapeutic option for many inborn errors of metabolism, where the main pathologic driving factor is an enzyme deficiency. Recent studies in the cystinosis mouse-model suggested that HSCT could be a curative treatment alternative to cysteamine therapy. We treated a 16-year-old boy who had infantile cystinosis and side effects of cysteamine therapy with HSCT. We were able to demonstrate successful transfer of the wild-type cystinosin protein and CTNS mRNA to nonhematological epithelial cells in the recipient, as well as a decrease in the tissue cystine-crystal burden. This is the first report of allogeneic HSCT in a patient with cystinosis, the prototype of lysosomal membrane-transporter disorders.

APOL1 C-Terminal Variants May Trigger Kidney Disease through Interference with APOL3 Control of Actomyosin.

The C-terminal variants G1 and G2 of apolipoprotein L1 (APOL1) confer human resistance to the sleeping sickness parasite Trypanosoma rhodesiense, but they also increase the risk of kidney disease. APOL1 and APOL3 are death-promoting proteins that are partially associated with the endoplasmic reticulum and Golgi membranes. We report that in podocytes, either APOL1 C-terminal helix truncation (APOL1Δ) or APOL3 deletion (APOL3KO) induces similar actomyosin reorganization linked to the inhibition of phosphatidylinositol-4-phosphate [PI(4)P] synthesis by the Golgi PI(4)-kinase IIIB (PI4KB). Both APOL1 and APOL3 can form K+ channels, but only APOL3 exhibits Ca2+-dependent binding of high affinity to neuronal calcium sensor-1 (NCS-1), promoting NCS-1-PI4KB interaction and stimulating PI4KB activity. Alteration of the APOL1 C-terminal helix triggers APOL1 unfolding and increased binding to APOL3, affecting APOL3-NCS-1 interaction. Since the podocytes of G1 and G2 patients exhibit an APOL1Δ or APOL3KO-like phenotype, APOL1 C-terminal variants may induce kidney disease by preventing APOL3 from activating PI4KB, with consecutive actomyosin reorganization of podocytes.

Molecular Basis of Cystinosis: Geographic Distribution, Functional Consequences of Mutations in the CTNS Gene, and Potential for Repair.

Mutations in the CTNS gene encoding the lysosomal membrane cystine transporter cystinosin are the cause of cystinosis, an autosomal recessive lysosomal storage disease. More than 140 CTNS mutations have been reported worldwide. Recent studies have discovered that cystinosin exerts other key cellular functions beyond cystine transport such as regulation of oxidative state, lysosomal dynamics and autophagy. Here, we review the different mutations described in the CTNS gene and the geographical distribution of incidence. In addition, the characteristics of the various mutations in relation to the functions of cystinosin needs to be further elucidated. In this review, we highlight the functional consequences of the different mutations in correlation with the clinical phenotypes. Moreover, we propose how this understanding would be fundamental for the development of new technologies through targeted gene therapy, holding promises for a possible cure of the kidney and extra-renal phenotypes of cystinosis.

Human Urine as a Noninvasive Source of Kidney Cells.

Urine represents an unlimited source of patient-specific kidney cells that can be harvested noninvasively. Urine derived podocytes and proximal tubule cells have been used to study disease mechanisms and to screen for novel drug therapies in a variety of human kidney disorders. The urinary kidney stem/progenitor cells and extracellular vesicles, instead, might be promising for therapeutic treatments of kidney injury. The greatest advantages of urine as a source of viable cells are the easy collection and less complicated ethical issues. However, extensive characterization and in vivo studies still have to be performed before the clinical use of urine-derived kidney progenitors.

Amniotic Fluid Derived Stem Cells with a Renal Progenitor Phenotype Inhibit Interstitial Fibrosis in Renal Ischemia and Reperfusion Injury in Rats.

OBJECTIVES: Mesenchymal stem cells derived from human amniotic fluid (hAFSCs) are a promising source for cellular therapy, especially for renal disorders, as a subpopulation is derived from the fetal urinary tract. The purpose of this study was to evaluate if hAFSCs with a renal progenitor phenotype demonstrate a nephroprotective effect in acute ischemia reperfusion (I/R) model and prevent late stage fibrosis. METHODS: A total of 45 male 12-wk-old Wistar rats were divided into three equal groups;: rats subjected to I/R injury and treated with Chang Medium, rats subjected to I/R injury and treated with hAFSCs and sham-operated animals. In the first part of this study, hAFSCs that highly expressed CD24, CD117, SIX2 and PAX2 were isolated and characterized. In the second part, renal I/R injury was induced in male rats and cellular treatment was performed 6 hours later via arterial injection. Functional and histological analyses were performed 24 hours, 48 hours and 2 months after treatment using serum creatinine, urine protein to creatinine ratio, inflammatory and regeneration markers and histomorphometric analysis of the kidney. Statistical analysis was performed by analysis of variance followed by the Tukey's test for multiple comparisons or by nonparametric Kruskal-Wallis followed by Dunn. Statistical significance level was defined as p <0.05. RESULTS: hAFSCs treatment resulted in significantly reduced serum creatinine level at 24 hours, less tubular necrosis, less hyaline cast formation, higher proliferation index, less inflammatory cell infiltration and less myofibroblasts at 48 h. The treated group had less fibrosis and proteinuria at 2 months after injury. CONCLUSION: hAFSCs contain a renal progenitor cell subpopulation that has a nephroprotective effect when delivered intra-arterially in rats with renal I/R injury, and reduces interstitial fibrosis on long term follow-up.