Increased human dermal microvascular endothelial cell survival induced by cysteamine

Residual Cystine Transport Activity for Specific Infantile and Juvenile CTNS Mutations in a PTEC-Based Addback Model

Cystinosis is a rare, autosomal recessive, lysosomal storage disease caused by mutations in the gene CTNS, leading to cystine accumulation in the lysosomes. While cysteamine lowers the cystine levels, it does not cure the disease, suggesting that CTNS exerts additional functions besides cystine transport. This study investigated the impact of infantile and juvenile CTNS mutations with discrepant genotype/phenotype correlations on CTNS expression, and subcellular localisation and function in clinically relevant cystinosis cell models to better understand the link between genotype and CTNS function. Using CTNS-depleted proximal tubule epithelial cells and patient-derived fibroblasts, we expressed a selection of CTNSmutants under various promoters. EF1a-driven expression led to substantial overexpression, resulting in CTNS protein levels that localised to the lysosomal compartment. All CTNSmutants tested also reversed cystine accumulation, indicating that CTNSmutants still exert transport activity, possibly due to the overexpression conditions. Surprisingly, even CTNSmutants expression driven by the less potent CTNS and EFS promoters reversed the cystine accumulation, contrary to the CTNSG339R missense mutant. Taken together, our findings shed new light on CTNS mutations, highlighting the need for robust assessment methodologies in clinically relevant cellular models and thus paving the way for better stratification of cystinosis patients, and advocating for the development of more personalized therapy.

A different approach to cystinosis: ultrasound, doppler, and shear wave elastography findings of thyroid gland

BACKGROUND

While thyroid dysfunction develops in about 50% of untreated children with cystinosis, there is no data about how the sonography of thyroid tissue appears in this disease. Therefore, the purpose of this study was to assess the sonographic appearance, color doppler findings in this disease and to evaluate how cystine crystal accumulation affect tissue stiffness using shear wave elastography (SWE).

METHODS

Sixteen children diagnosed with cystinosis and a control group consisting of 34 healthy children were included in this study. B mode ultrasound, color doppler imaging and real-time SWE of thyroid tissue were performed.

RESULTS

Ultrasound imaging revealed lower echogenicity and diffuse heterogeneous echotexture in 7 of the 16 cystinosis patients. Thyroid gland volumes were lower in cystinosis patients (p 0.005). Doppler ultrasound demonstrated increased flow in 8 patients. On SWE, the thyroid tissue stiffness was established to be lower in patients compared to healthy children (p 0.003).

CONCLUSIONS

This is the first study evaluating thyroid gland B mode, color doppler ultrasonography, and SWE findings in cystinosis. Our findings indicate that cysteamine treatment still cannot completely prevent the disease infiltration process of thyroid gland. The other important finding-that thyroid tissue stiffness was established to be lower than that of the controls-also demonstrates the ongoing disease infiltration process.

Effects of long-term cysteamine treatment in patients with cystinosis

Cystinosis is a rare autosomal-recessive lysosomal storage disease with high morbidity and mortality. It is caused by mutations in the CTNS gene that encodes the cystine transporter, cystinosin, which leads to lysosomal cystine accumulation. Patients with infantile nephropathic cystinosis, the most common and most severe clinical form of cystinosis, commonly present with renal Fanconi syndrome by 6-12 months of age, and without specific treatment, almost all will develop end-stage renal disease (ESRD) by 10-12 years of age. Early corneal cystine crystal deposition is a hallmark of the disease. Cystinosis also presents with gastrointestinal symptoms (e.g., vomiting, decreased appetite, and feeding difficulties) and severe growth retardation and may affect several other organs over time, including the eye, thyroid gland, gonads, pancreas, muscles, bone marrow, liver, nervous system, lungs, and bones. Cystine-depleting therapy with cysteamine orally is the only specific targeted therapy available for managing cystinosis and needs to be combined with cysteamine eye drops for corneal disease involvement. In patients with early treatment initiation and good compliance to therapy, long-term cysteamine treatment delays progression to ESRD, significantly improves growth, decreases the frequency and severity of extrarenal complications, and is associated with extended life expectancy. Therefore, early diagnosis of cystinosis and adequate life-long treatment with cysteamine are essential for preventing end-organ damage and improving the overall prognosis in these patients.

Bone disease in nephropathic cystinosis is related to cystinosin-induced osteoclastic dysfunction

Background

Bone impairment is a poorly described complication of nephropathic cystinosis (NC). The objectives of this study were to evaluate in vitro effects of cystinosin (CTNS) mutations on bone resorption and of cysteamine treatment on bone cells [namely human osteoclasts (OCs) and murine osteoblasts].

Methods

Human OCs were differentiated from peripheral blood mononuclear cells (PBMCs) of patients and healthy donors (HDs). Cells were treated with increasing doses of cysteamine in PBMCs or on mature OCs to evaluate its impact on differentiation and resorption, respectively. Similarly, cysteamine-treated osteoblasts derived from murine mesenchymal stem cells were assessed for differentiation and activity with toxicity and proliferation assays.

Results

CTNS was expressed in human OCs derived from HDs; its expression was regulated during monocyte colony-stimulating factor- and receptor activator of nuclear factor-κB-dependent osteoclastogenesis and required for efficient bone resorption. Cysteamine had no impact on osteoclastogenesis but inhibited in vitro HD osteoclastic resorption; however, NC OC-mediated bone resorption was impaired only at high doses. Only low concentrations of cysteamine (50 μM) stimulated osteoblastic differentiation and maturation, while this effect was no longer observed at higher concentrations (200 µM).

Conclusion

CTNS is required for proper osteoclastic activity. In vitro low doses of cysteamine have beneficial antiresorptive effects on healthy human-derived OCs and may partly correct the CTNS-induced osteoclastic dysfunction in patients with NC. Moreover, in vitro low doses of cysteamine also stimulate osteoblastic differentiation and mineralization, with an inhibitory effect at higher doses, likely explaining, at least partly, the bone toxicity observed in patients receiving high doses of cysteamine.

Assessment of a novel mucolytic solution for dissolving mucus in pseudomyxoma peritonei: an ex vivo and in vitro study

Background

Pseudomyxoma peritonei (PMP) is difficult to treat. Intraperitoneal delivery of mucolytic solutions might potentially improve therapy, in addition to surgical cytoreduction and hyperthermic intraperitoneal chemotherapy.

Methods

Comparison of mucolytic effect of two formulations (control: bromelain 300 µg/mL+N-Acetylcystein 250 mM; test: bromelain 200 µg/mL+200 mM cysteamine) in vitro on a mucin producing cell lines (HT29) and ex vivo on mucus obtained from 18 PMP patients. Mucin plugs were classified according to their density into three categories: hard, semi hard and soft. Simulation of peritoneal washing ex vivo using a closed heated circulating pump.

Results

Solubilisation was faster with the test vs. the control formulation (90 vs. 180 min) for dissolving the soft mucin plugs (p < 0.05). The test solution was also more effective in dissolving the hard mucus plugs compared to control (82.5±2.74 % vs. 36.33±3.27 %). All mucin types disintegrated in simulated peritoneal washing. Cytotoxicity of the test solution on HT29 cell line was time-dependent.

Conclusions

The test formulation is more effective and faster than the control formulation in dissolving mucus plugs of various densities. Mucus plugs were all solubilised after 40 min in simulated peritoneal washing. This novel mucolytic formulation might pave the way for an effective and less invasive therapy of PMP in the future.

Improving the prognosis of nephropathic cystinosis

Cystinosis is an autosomal recessive inherited lysosomal storage disease. It is characterized by generalized proximal tubular dysfunction known as renal Fanconi syndrome and causes end-stage renal disease by the age of about 10 years if left untreated. Extrarenal organs are also affected, including the thyroid gland, gonads, pancreas, liver, muscle, and brain. Treatment consists of administration of cysteamine, resulting in depletion of cystine that is trapped inside the lysosomes. Since cysteamine has a short half-life, it should be administered every 6 hours. Recently, a new delayed-release formulation was marketed, that should be administered every 12 hours. The first studies comparing both cysteamine formulations show comparable results regarding white blood cell cystine depletion (which serves as a measure for cystine accumulation in the body), while a slightly lower daily dose of cysteamine can be used.