Cystine Crystals Research Articles

Cystine crystal nucleation and decay in the context of cystinuria pathogenesis and treatment.

Cystinuria is a rare disease which results in the precipitation of cystine in the renal filtrate, which may cause acute kidney injury due to mechanical trauma. In this work, we attempt to explore the origin of supersaturated cystine in this context to understand disease pathogenesis. This has enabled us to reproduce the clinical habit of cystine following a comprehensive study of cystine nucleation and growth in saline, artificial and human urine. Then, we describe the physical behaviour of these crystals in the presence of: cysteamine, sodium bicarbonate, captopril, tiopronin, penicillamine, glutathione and α-lipoic acid. Surprisingly, we observe that, in vitro, only cysteamine and saturated sodium bicarbonate dissolve crystals at a faster rate than saline, and that when solution pH is adjusted to physiological conditions, crystal dissolution for all agents is reduced to the rate of saline alone. We highlight that the conventional hypothesis of mixed disulphide formation in cysteamine is not the fastest mechanism of cystine dissolution, but rather that cystine dissolution (in the order of hours) is dominated by pH effects. This, combined with cysteamine's ability to take part in disulfide exchange reactions may explain cysteamine's effectiveness in this condition. Overall, our findings not only contribute to an understanding of cystinuria pathogenesis but also offer insights into how we should evaluate emerging treatments.

B-173 Cystine Analysis in Urine Sample Using the Laser Diode Thermal Desorption technique “LDTD”/Mass Spectrometry (Luxon)

Abstract Background Cystine is a polar amino acid found in the urine of healthy individuals; however, a genetic defect in renal transport can lead to cystine crystals and stones. A usual laboratory approach for diagnosing and monitoring cystinuria is to measure cystine concentration in 24-hour urine. The disease is rare, affecting around 1 in every 10,000 live births. The objective of this study was to develop a rapid assay using Tandem Mass Spectrometry methodology with an internal standard of Cystine derivatized in a urine sample, Luxon Ion Source®, Laser Diode Thermal Desorption (LDTD) technology. Methods The Luxon is a sample introduction and ionization source with a coupled laser diode, providing thermal uniformity, precision, accuracy and speed. Thermally desorbed neutral molecules are analyzed by mass spectrometry (MS). Initially, the sample was derivatized to make the cystine thermally vaporize, followed by liquid-liquid extraction assisted by salting out (SALLE). The isotope-labeled internal standard (Cystine-d4), homemade calibration curve and water quality controls were used for quantification. The analysis was performed using a Sciex 6500+ Triple Quad in APCI (Atmospheric Pressure Chemical Ionization) positive mode. The ratio of peak area to internal standard (ISTD) was used to normalize the signal. A linear regression model with 1/X2 weighting was used to obtain the calibration curve equation and determine the correlation coefficient (r2). Parallelism was assessed by comparing the (r2) of calibration curves prepared in water with six curves prepared with biological matrices. Intra- and interassay precision and accuracy were determined by measuring control samples ranging from low to high concentration in five replicates over 3 consecutive days. For urine analysis, aqueous calibration curves in the concentration range of 1 to 100 mg/L (n=3) showed excellent linearity. The following parameters were evaluated for quantitative analysis: linearity, precision, accuracy, carryover and parallelism.​ Results The calibration curve resulted in a linear response across the entire concentration range, the correlation coefficient (r) was 0.99. For each quality control concentration, CVs were <10%, meeting desirable imprecision and precision specifications. The intraassay CVs were 1.0-2.56% and the interassay CVs were 2.15-4.58% for precision, which reflects the agreement between repeated measurements. Precision results showed similar results, intra-assay CVs were 2.23-3.66% and inter-assay CVs were 1.0-2.77% Conclusions The new LDTD-MS/MS method for the determination of urinary Cystine was accepted after verification and validation of quality control parameters. The technique proved to be effective for reliably and quickly quantifying cystine in urinary samples from human patients, being a valuable tool in the diagnosis and prevention of cystine kidney stones. The assay developed, using the Luxon Ion Source®, based on LDTD (Laser Diode Thermal Desorption) technology, proved to be ultrafast for measuring derivatized cystine in urine

Role of biomarkers of inflammation and MRI technique for the early detection of cystinosis-associated myopathy

BackgroundCystinosis is an autosomal recessive lysosomal storage disorder caused by cystine crystals accumulation within lysosomes resulting in multi-organ dysfunction. Infantile nephropathic cystinosis is the most common phenotype of the disease. Cystinosis distal myopathy was first described in 1994 with a 24% prevalence in cystinosis adult patients.MethodsWe prospectively evaluated the clinical, biochemical, and radiological data of 22 nephropathic cystinosis pediatric patients from 19 unrelated families (17 males and 5 females, their ages 105.7 ± 41.5 months) recruited at the cystinosis clinic at Cairo University Children’s Hospital. Biochemical assessment included several inflammatory biomarkers, such as CRP, ESR, chitotriosidase, and galectin-3. We further performed conventional MRI for the muscles of both upper and lower limbs for potential detection of early myopathic involvement. We compared these findings with 44 CKD children as pathological controls and 22 healthy pediatric controls.ResultsClinically, no evidence of neuromuscular involvement was detected in our cystinosis pediatric cohort. Chitotriosidase was elevated significantly in cystinosis patients compared to CKD controls. Regarding MRI, morphologically, there were no significant differences between the muscles of cystinosis patients and healthy controls.ConclusionA significantly higher chitotriosidase activity in cystinosis patients seems to better represent the overall disease burden and cannot be linked to neuromuscular involvement. MRI findings in muscles of the cystinosis cohort are not striking and indicate no early changes at a younger age. Follow-up and further studies for higher age groups are required to accurately elucidate the MRI’s role in assessing cystinosis myopathy.

Intermediate type cystinosis with a novel CTNS variant in a child: a case report

Cystinosis is a rare lysosomal storage disorder caused by a variant in the CTNS gene that leads to the accumulation of cystine in the body’s tissues. It has been classified into three subtypes based on its clinical presentation: severe infantile nephropathic cystinosis, intermediate mild form, and ocular non-nephropathic adult form. We report a teenage girl who presented with end stage kidney disease as her first presentation and was found to have corneal cystine crystals upon ophthalmic evaluation. Genetic testing confirmed that she has a CTNS variant, a CTNS variant c.520A > C p.(Ser174Arg) never described in the literature previously. Full family genetic screening supported the diagnosis. She was started on oral and ocular cysteamine and maintained on peritoneal dialysis for a few months and eventually underwent a successful deceased donor kidney transplantation. These findings expand the spectrum of CTNS gene variants and highlight the potential of atypical and severe presentations of this variant during adolescence.

Intermediate cystinosis: a case report of 10-year treatment with cysteamine

BackgroundCystinosis is a lysosomal storage disorder characterized by an autosomal recessive phenotype. Intermediate cystinosis, which progresses slowly and causes renal failure, accounts for approximately 5% of all cystinosis cases. Patients with intermediate cystinosis may not exhibit the typical symptoms of cystinosis, such as Fanconi syndrome and ocular symptoms. Because of its diverse clinical presentation and rarity, intermediate cystinosis can be difficult to diagnose. Additionally, few patients can tolerate cystine-depleting drugs, such as cysteamine, because of their complicated administration schedules and side effects. We report a case of intermediate cystinosis that was treated with cysteamine for 10 years.Case presentationUrinary abnormalities were first diagnosed when the patient was 3 years of age during a health examination specifically for 3-year-old children, which is unique to Japan. Cystinosis was diagnosed when the patient was 12 years of age. Cysteamine therapy was initiated and regular cystine concentration measurements were performed. Although proteinuria persisted, the patient’s renal function progressed slowly. Two renal biopsies were performed, and multinucleated podocytes and cystine crystals without focal segmental glomerulosclerosis lesions were observed in the biopsy specimens. The patient’s renal function remained stable.ConclusionsThis case of intermediate cystinosis was treated with cysteamine over the course of 10 years. Intermediate cystinosis requires an appropriate diagnosis and long-term treatment.

Adherence to Cysteamine Therapy Among Patients Diagnosed with Cystinosis in Saudi Arabia: A Prospective Cohort Study.

Cystinosis is a rare autosomal recessive disorder in which cystine crystals accumulate within the cellular lysosomes, causing damage to multiple organs. Due to challenges with the stringent cysteamine treatment regimen and side effects, adherence is often sub-optimal. This study aimed to assess the level of adherence to cysteamine therapy among cystinosis patients in Saudi Arabia and its impact on their quality of life. Electronic medical record data of 39 cystinosis patients from the Department of Nephrology at King Faisal Specialist Hospital and Research Center in Saudi Arabia were reviewed, and 25 patients were included in this study. Out of the 25 patients included in the final analysis, 64% (n = 16) were female. The mean age was 19.04 years. Almost all patients (23/25, 92%) were on oral IR cysteamine therapy, and 52% (13/25) were on topical cysteamine eye drop treatment. Of the 15 patients who responded to the Morisky Medication Adherence Scale-8 (MMAS-8) questionnaire, only 4 (26.7%) were highly adherent to cysteamine therapy. Most of the respondents (7/15, 46.7%) showed a medium level of treatment adherence. Based on the medication possession ratio for oral cysteamine, only 6 out of 23 patients (26.1%) were found to be 96-100% adherent. For the cysteamine eye drops, only 5/13 patients (38.4%) were 76-95% adherent. The 36-Item Short Form Health Survey (SF-36) used to assess patients' health-related outcomes showed that their quality of life was affected in the domains of 'social functioning' and 'energy/fatigue.' Despite a small sample size, this study shows sub-optimal adherence to cysteamine treatment in patients from Saudi Arabia. The possible reasons for low treatment adherence could be a high frequency of administration and treatment-related side effects.

Unveiling cystinosis in India

BackgroundCystinosis, a rare autosomal recessive disease, stems from genetic alterations in the CTNS gene, leading to a malfunction of lysosomal ‘cystinosin’ protein. This dysfunction causes intracellular cystine accumulation, resulting in nephropathic and ocular abnormalities. Cystinosis is relatively rare in Asian countries, partly due to underreporting and lack of awareness, and cases often lack sufficient genetic evidence to support their diagnosis. This study presents a descriptive case series involving four Indian patients with cystinosis, elucidating clinical and genetic aspects.MethodsAll four patients underwent comprehensive ophthalmic evaluations. The corneal cystine crystal (CCC) score was determined using anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM). Genetic testing was performed using whole exome sequencing (WES).ResultsCorneal crystal deposition, a hallmark of cystinosis, was evident in all cases. Systemic analysis revealed manifestations such as polyuria, bony abnormalities, growth retardation, hypothyroidism, and developmental delay. Genetic testing in two patients identified a homozygous pathogenic variant c.18_21delGACT (p.Thr7PhefsX7) in the CTNS gene, previously reported to cause cystinosis in different ethnic populations.ConclusionsOur case series sheds light on underrepresented cases of cystinosis in the Indian population. The rarity of this condition poses diagnostic challenges, leading to delayed or inaccurate diagnoses. AS-OCT can serve as a viable alternative to IVCM for assessing corneal crystal density status in cystinosis. Timely recognition and management are crucial in preventing complications, and the inclusion of genetic testing can expedite cystinosis diagnosis.

Cystine Renal Calculi: New Aspects Related to Their Formation and Development.

Background: Crystallization experiments of renal-calculi-forming compounds (calcium oxalate, calcium phosphates, uric acid) are normally performed by monitoring these processes during periods of time similar to the residence of urine inside the kidney. Nevertheless, cystine requires high supersaturation for its crystallization, and most experiments last for longer periods. It must be considered that at high supersaturation, the inhibitors of crystalline development have poor effects. Methods: The induction time of crystallization (ti) of cystine in experimental conditions similar to those of the formation of cystine renal calculi and the effect of different cystine-binding thiol agents was determined through turbidimetric measurements. We also studied the macro- and microstructure of 30 cystine kidney stones through stereoscopic microscopy and scanning electron microscopy. Results: Under the studied conditions, the ti in absence of crystallization inhibitors was 15 min, and the presence of 9 mM of penicillamine, tiopronin, or N-acetylcysteine totally inhibited crystallization, as their effects relate to the formation of complexes with cystine, although N-acetylcysteine also delayed cystine crystalline development and modified cystine crystal morphology. Cystine stones have traditionally been classified as smooth and rough. The study of their structure shows that all of them begin their formation from a few crystals that generate a compact radial structure. Their subsequent growth, depending on the renal cavity where they are located, gives rise to the rough structure in the form of large blocks of cystine crystals or the smooth structure with small crystals. Conclusions: To prevent the development of cystine renal stones, the formation of small crystals must be avoided by reducing urinary cystine supersaturation, with N-acetylcysteine being the most effective among the studied cystine-binding thiol agents. Also, the removal of cystine crystals through increased water intake and physical activity can be a very important preventive measure.

Comparison of Scheimpflug Corneal Tomography and Anterior Segment Optical Coherence Tomography Measurements in Corneal Cystinosis: A Case Series.

To report the clinical course and compare the utility of Scheimpflug tomography (ST) and anterior segment optical coherence tomography (AS-OCT) for central corneal thickness (CCT) and corneal densitometry (CD) assessment in patients with corneal crystals owing to nephropathic cystinosis. A retrospective chart analysis of three patients with nephropathic cystinosis and the presence of corneal cystine crystals in both eyes was performed. All patients underwent clinical examination and anterior segment photography, ST, and AS-OCT scans. Corneal densitometry was exported from built-in proprietary software for ST and from custom-made validated software for AS-OCT. Anterior segment optical coherence tomography images were rescaled to grayscale units from 0 (maximum transparency) to 100 (minimum transparency) to match built-in ST densitometry readings. Furthermore, the mean pixel intensity, representative of CD, was calculated from the pixels corresponding to the segmented cornea. All three patients had pathognomonic cystine crystals deposits in the cornea and were treated with cysteamine medications that resulted in clinical improvement. The CCT measured using ST exhibited a range from 560 to 958 μm. Conversely, when assessed with AS-OCT, the CCT varied within the range of 548 to 610 μm. Both examinations could be performed, but in the more severe cases, AS-OCT showed far greater utility to estimate CD. In four of six eyes examined, ST showed disproportionate CCT values, compared with the AS-OCT, whereas reliable CD measurements were only available in AS-OCT. The AS-OCT could be considered a baseline ocular measurement in cystinosis and in the evaluation of disease progression and treatment efficacy.

Nlrp2 deletion ameliorates kidney damage in a mouse model of cystinosis.

Cystinosis is a rare autosomal recessive disorder caused by mutations in the CTNS gene that encodes cystinosin, a ubiquitous lysosomal cystine/H+ antiporter. The hallmark of the disease is progressive accumulation of cystine and cystine crystals in virtually all tissues. At the kidney level, human cystinosis is characterized by the development of renal Fanconi syndrome and progressive glomerular and interstitial damage leading to end-stage kidney disease in the second or third decade of life. The exact molecular mechanisms involved in the pathogenesis of renal disease in cystinosis are incompletely elucidated. We have previously shown upregulation of NLRP2 in human cystinotic proximal tubular epithelial cells and its role in promoting inflammatory and profibrotic responses. Herein, we have investigated the role of NLRP2 in vivo using a mouse model of cystinosis in which we have confirmed upregulation of Nlrp2 in the renal parenchyma. Our studies show that double knock out Ctns-/- Nlrp2-/- animals exhibit delayed development of Fanconi syndrome and kidney tissue damage. Specifically, we observed at 4-6 months of age that animals had less glucosuria and calciuria and markedly preserved renal tissue, as assessed by significantly lower levels of inflammatory cell infiltration, tubular atrophy, and interstitial fibrosis. Also, the mRNA expression of some inflammatory mediators (Cxcl1 and Saa1) and the rate of apoptosis were significantly decreased in 4-6-month old kidneys harvested from Ctns-/- Nlrp2-/- mice compared to those obtained from Ctns-/-mice. At 12-14 months of age, renal histological was markedly altered in both genetic models, although double KO animals had lower degree of polyuria and low molecular weight proteinuria and decreased mRNA expression levels of Il6 and Mcp1. Altogether, these data indicate that Nlrp2 is a potential pharmacological target for delaying progression of kidney disease in cystinosis.

Event-related potential (ERP) evidence for visual processing differences in children and adults with cystinosis (CTNS gene mutations)

BackgroundCystinosis, a rare lysosomal storage disease caused by mutations in the CTNS gene, is characterized by cystine crystallization and accumulation within multiple tissues, including kidney and brain. Its impact on neural function appears mild relative to its effects on other organs during early disease, but since therapeutic advances have led to substantially increased life expectancy, neurological implications are of increasing interest, necessitating deeper understanding of the impact of cystinosis on neurocognitive function. Behavioral difficulties have been reported in cystinosis in the visual domain. Very little is known, however, about how the brains of people living with cystinosis process visual information. This is especially interesting given that cystine accumulation in the cornea and posterior ocular structures is a hallmark of cystinosis.MethodsHere, high-density scalp electrophysiology was recorded to visual stimuli (during a Go/No-Go task) to investigate visual processing in individuals with cystinosis, compared to age-matched controls. Analyses focused on early stages of cortical visual processing.ResultsThe groups differed in their initial cortical response, with individuals with cystinosis exhibiting a significantly larger visual evoked potential (VEP) in the 130–150 ms time window. The groups also differed in the associations between neural responses and verbal abilities: While controls with higher IQ scores presented larger neural responses, that relationship was not observed in cystinosis.ConclusionsThe enlarged VEP in cystinosis could be the result of cortical hyperexcitability and/or differences in attentional engagement and explain, at least partially, the visual and visual-spatial difficulties described in this population.

Neurologic involvement in cystinosis: Focus on brain lesions and new evidence of four-repeat (4R-) Tau immunoreactivity

Nephropathic cystinosis is a rare autosomal recessive storage disorder caused by CTNS gene mutations, leading to autophagy-lysosomal pathway impairment and cystine crystals accumulation. Neurologic involvement is highly variable and includes both neurodevelopmental and neurodegenerative disturbances, as well as focal neurologic deficits. By presenting longitudinal data of a 28-year-old patient with a large infratentorial lesion, we summarized the pathology, clinical and imaging features of neurological involvement in cystinosis patients. Brain damage in form of cystinosis-related cerebral lesions occurs in advanced disease phases and is characterized by the accumulation of cystine crystals, subsequent inflammation with vasculitis-like features, necrosis, and calcification. Epilepsy is a frequent comorbidity in affected individuals. Steroids might play a role in the symptomatic treatment of “stroke-like” episodes due to edematous-inflammatory lesions, but probably do not change the overall prognosis. Lifelong compliance to depleting therapy with cysteamine still represents the main therapeutic option. However, consequences of CTNS gene defects are not restricted to cystine accumulation. New evidence of four-repeat (4R-) Tau immunoreactivity suggests concurrent progressive neurodegeneration in cystinosis patients, highlighting the need of innovative therapeutic strategies, and shedding light on the crosstalk between proteinopathies and autophagy-lysosomal system defects. Eventually, emerging easily accessible biomarkers such as serum neurofilament light chains (NfL) might detect subclinical neurologic involvement in cystinosis patients.

Omic Studies on In Vitro Cystinosis Model: siRNA-Mediated CTNS Gene Silencing in HK-2 Cells

Cystinosis is an autosomal recessive disease caused by mutations in the CTNS gene encoding a protein called cystinosine, which is a lysosomal cystine transporter. Disease-causing mutations lead to accumulation of cystine crystals in the lysosomes, thereby causing dysfunction of vital organs. Determination of the increased leukocyte cystine level is one of the most used methods for diagnosis. However, this method is expensive, difficult to perform, and may yield different results in different laboratories. In this study, a disease model was created with CTNS gene-silenced HK2 cells, which can mimic cystinosis in cell culture, and multiomics methods (ie, proteomics, metabolomics, and fluxomics) were implemented at this cell culture to investigate new biomarkers for the diagnosis. CTNS-silenced cell line exhibited distinct metabolic profiles compared with the control cell line. Pathway analysis highlighted significant alterations in various metabolic pathways, including alanine, aspartate, and glutamate metabolism; glutathione metabolism; aminoacyl-tRNA biosynthesis; arginine and proline metabolism; beta-alanine metabolism; ascorbate and aldarate metabolism; and histidine metabolism upon CTNS silencing. Fluxomics analysis revealed increased cycle rates of Krebs cycle intermediates such as fumarate, malate, and citrate, accompanied by enhanced activation of inorganic phosphate and ATP production. Furthermore, proteomic analysis unveiled differential expression levels of key proteins involved in crucial cellular processes. Notably, peptidyl-prolyl cis–trans isomerase A, translation elongation factor 1-beta (EF-1beta), and 60S acidic ribosomal protein decreased in CTNS-silenced cells. Additionally, levels of P0 and tubulin α-1A chain were reduced, whereas levels of 40S ribosomal protein S8 and Midasin increased. Overall, our study, through the utilization of an in vitro cystinosis model and comprehensive multiomics approach, led to the way toward the identification of potential new biomarkers while offering valuable insights into the pathogenesis of cystinosis.

Cysteamine Eye Drops in Hyaluronic Acid Packaged in Innovative Single-Dose Systems, Part II: Long-Term Stability and Clinical Ocular Biopermanence.

Cystinosis is a rare genetic disorder characterized by the accumulation of cystine crystals in several tissues and organs causing, among others, severe eye symptoms. The high instability of cysteamine eye drops makes it difficult to develop formulations with an acceptable shelf life to be prepared in hospital pharmacy departments. Previously, a new compounded formulation of cysteamine eye drops in hyaluronic acid (HA) packaged in innovative single-dose systems was developed. Long-term stability at -20 °C of this formulation was studied considering the content of cysteamine, pH, osmolality, viscosity, and microbiological analysis. The oxygen permeability of single-dose containers was also studied and an ocular biopermanence study was conducted in healthy volunteers measuring lacrimal stability and volume parameters. Data confirm that cysteamine concentration remained above 90% for 120 days, all parameters remaining within the accepted range for ophthalmic formulations. The permeability of the containers was reduced over time, while ocular biopermanence was maintained despite the freezing process and storage time. 0.55% cysteamine hydrochloride formulation in HA and packaged in single-dose containers preserved at -20 °C is stable for 120 days protected from light, presenting high potential for its translation into clinical practice when commercial presentations are not available.

Cysteamine ophthalmic hydrogel for the treatment of ocular cystinosis

Ocular cystinosis is a rare disease characterised by the deposition on the corneal surface of cystine crystals that hinder the eyesight of patients. Oral cysteamine is administered as cysteamine bitartrate; however, due to the lack of corneal vascularization it does not reach the cornea and must be administered by the topical ocular route. The aim of the present study was to determine the stability of an ophthalmic hydrogel of cysteamine under different preservation conditions during a follow-up of 30 days. This hydrogel could be prepared in hospital pharmacy services.Several physical and chemical parameters were assessed: osmolality, pH, and cysteamine concentration, which was measured using an ultra-performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) method. Descriptive tests were also performed, such as transparency measurements and microbiological assays in order to verify sterility. The results show that cysteamine hydrogel is stable over 30 days and should be preserved under refrigeration.

Chemical Modification of Tiopronin for Dual Management of Cystinuria and Associated Bacterial Infections.

Cystinuria is an inherited autosomal recessive disease of the kidneys of recurring nature that contributes to frequent urinary tract infections due to bacterial growth and biofilm formation surrounding the stone microenvironment. In the past, commonly used strategies for managing cystinuria involved the use of (a) cystine crystal growth inhibitors such as l-cystine dimethyl ester and lipoic acid, and (b) thiol-based small molecules such as N-(2-mercaptopropionyl) glycine, commonly known as tiopronin, that reduce the formation of cystine crystals by reacting with excess cystine and generating more soluble disulfide compounds. However, there is a dearth of simplistic chemical approaches that have focused on the dual treatment of cystinuria and the associated microbial infections. This work strategically exploited a single chemical approach to develop a nitric oxide (NO)-releasing therapeutic compound, S-nitroso-2-mercaptopropionyl glycine (tiopronin-NO), for the dual management of cystine stone formation and the related bacterial infections. The results successfully demonstrated that (a) the antibacterial activity of NO rendered tiopronin-NO effective against the stone microenvironment inhabitants, Escherichia coli and Pseudomonas aeruginosa, and (b) tiopronin-NO retained the ability to undergo disulfide exchange with cystine while being reported to be safe against canine kidney and mouse fibroblast cells. Thus, the synthesis of such a facile molecule aimed at the dual management of cystinuria and related infections is unprecedented in the literature.

Starry-like Cornea: A Case of Ocular Cystinosis

Ocular cystinosis is a rare autosomal recessive disorder caused by mutations in the CTNS gene, which encodes a lysosomal cystine transporter protein. This results in the accumulation of cystine crystals in various ocular structures, leading to a range of ocular manifestations. The incidence of cystinosis is estimated to be 1 in 100,000 to 200,000 live births, with a higher prevalence in certain populations such as those of European descent. We report the case of a 5-year-old child with ocular cystinosis. The ophthalmological examination revealed a photophobic child with a visual acuity of 3/10 in both eyes (Pigassou scale), and diffuse stromal crystal deposits over the entire cornea in both eyes. The rest of the examination was unremarkable. The patient was referred to pediatrics for work-up of storage disease and was diagnosed with ocular and nephrological cystinosis. The patient was able to start general treatment with Mercaptamine with improvement in renal function, but was unable to obtain local treatment due to lack of funds. The patient is still being followed in our clinic with stable corneal involvement. Ocular cystinosis is a very rare genetic disorder. There are three main types of cystinosis: nephropathic cystinosis and non-nephropathic cystinosis. Nephropathic cystinosis divides further on infantile and intermediate. The most common ocular manifestation of cystinosis is corneal cystine crystal deposit, which typically presents in the first year of life and can lead to photophobia, tearing, and decreased visual acuity. The corneal crystals can also cause recurrent erosions, which can be very painful. The severity of corneal involvement can range from mild punctate deposition to severe confluent crystal accumulation that can lead to corneal scarring and vision loss. Cysteamine drops, which are a form of cysteamine hydrochloride, can help dissolve the cystine crystals and improve corneal clarity, prevent further vision loss, and reduce the frequency of recurrent erosions. Early diagnosis and treatment are crucial in preventing further ocular damage in individuals with cystinosis. Regular ophthalmologic examinations should be conducted to monitor for ocular manifestations and initiate treatment as early as possible. A multidisciplinary approach is necessary, involving ophthalmologists, nephrologists, and other specialists, to manage the systemic manifestations of cystinosis.

Self-Assembly of Cysteine into Nanofibrils Precedes Cystine Crystal Formation: Implications for Aggregation Inhibition.

The self-association of metabolites into well-ordered assemblies at the nanoscale has significant biological and medical implications. The thiol-containing amino acid cysteine (CYS) can assemble into amyloid-like nanofibrils, and its oxidized form, the disulfide-bonded cystine (CTE), forms hexagonal crystals as those found in cystinuria due to metabolic disorder. Yet, there have been no attempts to connect these two phenomena, especially the fibril-to-crystal transition. Here, we reveal that these are not separated events, and the CYS-forming amyloid fibrils are mechanistically linked to hexagonal CTE crystals. For the first time, we demonstrated that cysteine fibrils are a prerequisite for forming cystine crystals, as observed experimentally. To further understand this mechanism, we studied the effects of thiol-containing cystinuria drugs (tiopronin, TIO; and d-penicillamine, PEN) and the canonical epigallocatechin gallate (EGCG) amyloid inhibitor on fibril formation by CYS. The thiol-containing drugs do not solely interact with monomeric CYS via disulfide bond formation but can disrupt amyloid formation by targeting CYS oligomers. On the other hand, EGCG forms inhibitor-dominant complexes (more than one EGCG molecule per cysteine unit) to prevent CYS fibril formation. Interestingly, while CYS can be oxidized into CTE, the thiol drugs can reduce CTE back to CYS. We thus suggest that the formation of crystals in cystinuria could be halted at the initial stage by targeting CYS fibril formation as an alternative to solubilizing the water-insoluble hexagonal CTE crystals at a later stage. Taken together, we depicted a complex hierarchical organization in a simple amino acid assembly with implications for therapeutic intervention.

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

BackgroundWhile 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).MethodsSixteen 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.ResultsUltrasound 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).ConclusionsThis 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.

The gene therapy for corneal pathology with novel nonsense cystinosis mouse lines created by CRISPR Gene Editing

PurposeCystinosis is an autosomal recessive lysosomal storage disease (LSDs) caused by mutations in the gene encoding cystinosin (CTNS) that leads to cystine crystal accumulation in the lysosome that compromises cellular functions resulting in tissue damage and organ failure, especially in kidneys and eyes. However, the underlying molecular mechanism of its pathogenesis remains elusive. Two novel mice lines created via CRISPR are used to examine the pathogenesis of cystinosis in the kidney and cornea and the treatment efficacy of corneal pathology using self-complimentary Adeno-associated viral (scAAV-CTNS) vector. MethodsThe CRISPR technique generated two novel cystinotic mouse lines, Ctnsis1 (an insertional mutation) and Ctnsis2 (a nonsense mutation). Immune histochemistry, renal functions test and HRT2 in vivo confocal microscopy were used to evaluate the age-related renal pathogenesis and treatment efficacy of the scAAV-CTNS virus in corneal pathology. ResultsBoth mutations lead to the production of truncated Ctns proteins. Ctnsis1 and Ctnsis 2 mice exhibit the characteristic of cystinotic corneal crystal phenotype at four-week-old. Treatment with the scAAV-CTNS viral vector decreased the corneal crystals in the treated mice cornea. Ctnsis 1 show renal abnormalities manifested by increased urine volume, reduced urine osmolality, and the loss of response to Desmopressin (dDAVP) at 22-month-old but Ctnsis2 don't manifest renal pathology up to 2 years of age. ConclusionsBoth Ctnsis1 and Ctnsis2 mice exhibit phenotypes resembling human intermediate nephropathic and ocular cystinosis, respectively. scAAV-CTNS viral vectors reduce the corneal cystine crystals and have a great potential as a therapeutic strategy for treating patients suffering from cystinosis.