Induced Pluripotent Stem Cells: How iPSCs Are Made and Used

This presentation by Ryan Hicks from AstraZeneca's Stem & Primary Cell Group demonstrates how 3D kidney organoids derived from human induced pluripotent stem cells (iPSCs) provide physiologically relevant cellular models for drug discovery, overcoming limitations of traditional 2D cell culture by incorporating multiple cell types (podocytes, proximal tubules, endothelial cells) into organized structures that better predict human responses; the team validates these models using CRISPR/Cas9 genome editing, next-generation sequencing, and functional assays to enable applications in target identification, validation, and safety screening for chronic kidney disease and other therapeutic areas.

Organoids represent an advanced preclinical model bridging traditional 2D tissue culture and whole animal models. Unlike 2D cultures using monocellular populations on plastic, organoids are multicellular 3D structures with self-organized cytoarchitecture. They can be generated from cancer biopsies, adult stem cells, embryonic stem cells, or induced pluripotent stem cells (iPSCs)—cells reprogrammed back to pluripotency using four genes. Organoids demonstrate superior predictive validity across multiple disease contexts: glioblastoma organoids show greater temozolomide resistance than 2D cultures; only 3D organoids recapitulate Zika virus-induced microcephaly and interferon inhibition; Alzheimer's organoids develop both amyloid-beta and tau pathologies (unlike most animal models); and PSEN1 knockout organoids show amyloid-beta accumulation absent in 2D cultures. These examples establish that 3D cellular context is essential for accurate disease modeling.

Researchers modeled human retinoblastoma by generating retinal organoids from patient-specific iPSCs. The protocol was optimized using reporter lines to efficiently differentiate iPSCs from 15 different individuals into retinal organoids with good yield and morphology. Functional validation showed retinal pigment epithelial cells juxtaposed with photoreceptors (indicating functional photoreceptor signaling) and wavelength-specific light responses from retinal ganglion cells when recorded on multi-electrode arrays. In xenograft studies, dissociated retinal organoids from 15 RB1-mutant patients were injected into immunocompromised mice. Seven out of 15 patient-specific organoid-derived tumors developed, clustering with patient-derived tumors and xenografts in DNA methylation profiles and single-cell RNA-seq analysis regarding cell type identity and proliferation markers.

Scientists can take a small skin sample from a patient, generate induced pluripotent stem cells, and then differentiate them into specific cell types to model diseases. For example, in premature aging syndromes affecting children, researchers discovered that patient-derived brain organoids showed abnormal cell division patterns where cells prematurely differentiated into nerve cells rather than dividing properly, leading to smaller brains and severe neurological deficits.

Organoids are 3D cellular structures grown from adult or pluripotent stem cells that accurately model patient-specific tumors and tissues, enabling faster and more predictive drug testing compared to traditional 2D cell lines; they are revolutionizing precision medicine by allowing researchers to test therapies on personalized models derived from actual patient samples, thereby improving preclinical trial efficiency and enabling more targeted clinical interventions.

Since Yamanaka's 2006 breakthrough, iPSC technology has rapidly advanced through multiple generations of improvement. Early methods used retroviruses, which raised oncogenic concerns due to c-Myc inclusion. Subsequent advances replaced retroviruses with adenoviruses, direct protein delivery, modified RNA, and finally small molecule/chemical approaches achieving reprogramming without genetic manipulation. The first clinical trial began in September 2014 at RIKEN Institute in Japan, treating macular degeneration with patient-derived iPSC-derived retinal pigment epithelial cells. While initial results showed vision improvement, genetic abnormalities halted the study. Meanwhile, Doug Melton's lab at Harvard has developed iPSC-derived pancreatic beta cells that survive and regulate glucose in diabetic mice. Beyond therapy, iPSCs enable revolutionary disease modeling and drug screening for Parkinson's, Alzheimer's, cardiomyopathy, and muscular dystrophy in vitro.

iPSC technology faces significant clinical translation challenges: extensive safety testing requirements including genomic sequencing to detect mutations, high costs limiting accessibility, personalized therapy logistics, and immune compatibility concerns. While autologous transplantation avoids rejection, universal donor iPSCs through genetic modification offer potential off-the-shelf solutions. The oncogenic potential of reprogramming factors, particularly c-Myc, remains a concern, though rigorous genomic screening helps identify problematic mutations. Long-term iPSC culture can lead to genomic instability requiring routine karyotype analysis. All tissues contain mosaicism, meaning donor cell mutations carry forward into iPSC lines. Telomere maintenance through telomerase reactivation allows unlimited proliferation, distinguishing iPSCs from aged somatic cells. Brief partial reprogramming with Yamanaka factors can reverse cellular aging markers, sparking interest in anti-aging therapies. Interspecies chimerism research explores generating human organs in animals, though significant technical and ethical challenges remain.

Induced pluripotent stem cells enable revolutionary applications in personalized medicine, including disease modeling, drug screening, and regenerative therapy. Cells can be generated from patients through simple skin biopsies, expanded indefinitely, and differentiated into any cell type, with reprogramming efficiency remaining comparable across ages. However, clinical translation faces significant barriers: generating patient-specific cells is expensive and time-consuming, requiring approximately 3 months total, conflicting with urgent clinical needs. Safety assessment is critical due to teratoma risk from residual undifferentiated cells. Comparative studies show mouse iPSCs are largely indistinguishable from genuine embryonic stem cells in differentiation capacity, but significant variability exists between iPSC lines: some behave identically to ES cells and are safe, while others contain refractory populations prone to teratoma formation. This quality heterogeneity requires careful screening protocols before therapeutic application.

iPSCs are created by reprogramming adult cells back to an embryonic-like state using four transcription factors, enabling differentiation into any cell type. They enable personalized medicine by creating patient-specific cells from small biopsies, eliminating immune rejection. iPSCs are in clinical trials for macular degeneration (replacing retinal pigment epithelium) and diabetes (creating insulin-producing beta cells). Safety challenges include ensuring complete differentiation, preventing teratoma formation, and verifying correct genetic delivery. iPSCs enable modeling of neurodegenerative diseases like Parkinson's by differentiating them into specific neuron types. Neural development follows strict spatial gradients of signaling factors that determine cell fate. Scientists attempt to recreate these gradients in culture to produce specific neuron types.

This comprehensive section traces the evolution of induced pluripotent stem cell technology from its 2006 discovery by Shinya Yamanaka to current clinical translation efforts. It covers fundamental concepts including stem cell classification (embryonic, adult, and induced pluripotent), iPSC generation methods (integrating vs. non-integrating approaches including viral vectors, episomal vectors, and Sendai virus), and the three major applications: disease modeling, drug screening, and therapeutic development. The presentation analyzes global clinical trial data revealing approximately 4,673 unique stem cell trials worldwide, with the US accounting for nearly half. Only 35 represent actual therapeutic iPSC trials, with most being Phase I/II studies under 50 patients. Critical safety concerns including tumorigenicity risks from mutations during reprogramming and differentiation are emphasized, requiring rigorous monitoring at each manufacturing stage. Regulatory frameworks operating through three hierarchical levels (legislative laws, administrative regulations, and voluntary guidelines) are examined, with significant international variations between Japan's conservative policies and the US's more progressive approach.

This webinar explains how combining human induced pluripotent stem cells (iPSCs) with CRISPR-Cas9 gene editing enables powerful drug target identification and validation by allowing researchers to perform unbiased genetic screens in physiologically relevant cell models, overcoming limitations of traditional immortalized cell lines and accelerating the drug discovery pipeline.

CRISPR-Cas9 gene editing combined with human induced pluripotent stem cells (hiPSCs) enables more physiologically relevant drug discovery by allowing researchers to create specific cell types for disease modeling, perform unbiased genetic screens to identify drug targets, and study therapeutic responses in human-relevant cellular contexts, addressing the limitations of traditional immortalized cell lines and animal models.

Induced pluripotent stem cells (iPSCs) combined with CRISPR-Cas9 gene editing enable the creation of isogenic cell pairs to study complex diseases like Parkinson's, allowing researchers to functionally validate genetic risk variants and screen for therapeutic compounds by comparing cells with protective versus risk alleles in a controlled experimental system.

This comprehensive workflow combines human induced pluripotent stem cells with CRISPR-Cas9 technology to generate isogenic cell lines differing only in the edited gene. The process involves creating stable KASAN-expressing iPSC lines, introducing precise mutations through CRISPR, and achieving high editing efficiencies with high survival rates after single-cell sorting. Extensive characterization includes morphology assessment, karyotype verification, and pluripotency confirmation. The indefinite expansion capability of iPSCs enables cryopreservation of engineered line banks for reproducible disease modeling studies.

Induced pluripotent stem cells (iPSCs) revolutionize disease modeling by converting patient fibroblasts or blood cells into pluripotent stem cells using Yamanaka factors. These cells can differentiate into virtually any cell type, enabling access to human tissues impossible to obtain otherwise. Combined with CRISPR-Cas9 genome editing, researchers can create isogenic cell lines—comparing corrected versus uncorrected versions or introducing specific risk factors—to isolate genetic effects. This approach addresses limitations of animal models by capturing human genetic diversity and enabling drug discovery that bridges preclinical success and clinical failure.