A Refined Method for Micro-Scale Blood Cystine Measurement in Preclinical Cystinosis Models

Cystinosis is a rare autosomal recessive lysosomal storage disorder that is caused by mutations in the CTNS gene. The hallmark of this disease is the accumulation of cystine within lysosomes, which functions as a pivotal diagnostic and monitoring biomarker. Cysteamine therapy has been demonstrated to reduce lysosomal cystine and improve outcomes; however, it does not fully halt progression, particularly renal decline. Consequently, preclinical research relies on diverse in vitro and in vivo models to explore mechanisms and test new treatments. Accurate intracellular cystine quantification is vital for clinical and research purposes. Conventional granulocyte cystine measurement, the prevailing standard, is technically intricate and necessitates volumes of samples, which presents challenges for rodent models. Advancements in analytical chemistry, such as the use of liquid chromatography with tandem mass spectrometry (LC-MS/MS), have enhanced the sensitivity of analytical methods. However, the development of optimized methods for analyzing small volumes of biological samples remains a limitation. This study presents a novel micro-quantification protocol for measuring cystine in a minimal volume of whole blood from rodent models. This protocol enhances the sensitivity, reproducibility, and feasibility of longitudinal studies. Addressing this methodological gap is imperative for accelerating translational research and supporting the development of improved therapies for cystinosis.