Micro Magnetic Resonance Relaxometry (MRR) for Rapid and Non-invasive Detection of iPSC Quality and Differentiation

Technology

MRR measures the spin-spin (T2) relaxation time of microlitre samples using the same principles as Magnetic Resonance Imaging and Nuclear Magnetic Resonance, but with minimal cell number requirements (~110 - ~180k cells per test), making it suitable for cell therapy applications. T2 measurements are highly sensitive to the paramagnetic content of the sample, which is correlated with the iron (Fe3+) content in cells. Over a 10-day differentiation of human iPSCs into spinal cord progenitor cells (SCPCs), the inventors demonstrated that T2 readouts obtained via MRR correlate with the phenotypic transition from iPSCs to SCPCs. iPSCs exhibit higher intracellular Fe3+ and therefore lower T2 values, establishing T2 as a reliable surrogate for the label-free measurement of intracellular Fe3+ content. Batches of SCPCs containing higher levels of pluripotent markers, such as OCT4, exhibited lower T2 values than batches with lower levels of these markers. Furthermore, groups with lower levels of neural progenitor markers, such as SOX1, or stem cell markers, such as Nestin, also showed lower T2 than normally differentiated SCPCs. Importantly, the inventors showed that the general quality of iPSCs at Day 1, quantified by MRR T2 measurement, correlated with the quality of SCPCs at Day 10 based on OCT4+ cell percentages, demonstrating this method’s potential for early prediction of likelihood for successful differentiation.  

Problem Addressed

iPSCs enable regenerative therapies for conditions such as Parkinson’s disease, macular degeneration, heart failure, and spinal cord injury (SCI). In SCI treatment, iPSCs can be differentiated into SCPCs and implanted to restore damaged neuronal and glial populations. However, even a small number of residual undifferentiated iPSC-like cells can pose significant tumorigenicity risks and ensuring the quality of these progenitor cells remains a major bottleneck for iPSC‑based therapies. Current assays to quantify phenotypes of iPSCs and progenitor cells employ label-based fluorescent markers, which often perturb or destroy the cells, making them unusable for subsequent applications. Furthermore, these assays are expensive, laborious, and time-consuming, limiting their use for quality control in bioproduction processes. Biochemical, omics-based methods provide deeper characterization, but usually involve averaging signals across populations, limiting the detection of low‑abundance, high‑risk cells. Although intracellular iron has gained interest as a relevant biological marker, conventional Fe2+/Fe3+ detection methods are largely inaccurate and require additional chemical processing. In contrast, the present technology’s label-free approach supports rapid, nondestructive assessment of cell batch quality, making them suitable for large-scale cell manufacturing and validation of quality phenotypes for iPSC derived SCPCs.  

Advantages

• Provides a label‑free, live‑cell readout that correlates with fixed‑cell markers such as OCT4, SOX1, and Nestin
• No chemical or biological processing required, preserving cells for downstream functional assays
• Small cell number requirement (<2×10⁵)
• Low‑cost instrumentation (approximately $2,500), significantly cheaper than conventional NMR systems
• Enables early critical quality attribute measurements for identification of high‑ and low‑quality batches in iPSC manufacturing as early as Day 1