Despite over 100 million units of blood being donated annually, supply remains insufficient, particularly for patients with chronic conditions or in crisis settings. Alloimmunization and blood group incompatibilities further constrain transfusion efficacy. In response, researchers are exploring the use of induced pluripotent stem cells (iPSCs) to generate red blood cells (RBCs) in vitro as a reliable and potentially limitless source of transfusable cells. The journal Blood Science (2025) presents a comprehensive review of the current progress, challenges, and future directions of iPSC-derived erythropoiesis.Developmental Context and Rationale
To understand the rationale behind using iPSCs, it is important to consider how erythropoiesis occurs naturally. Erythropoiesis proceeds through two phases—primitive and definitive—with the latter producing enucleated, functionally mature RBCs. Replicating this process in vitro is complex due to reliance on bone marrow-specific cues. While embryonic stem cells have shown erythroid potential, their use raises ethical concerns. iPSCs bypass such issues by being reprogrammed from adult somatic cells, using Yamanaka’s factors. The ability of iPSCs to mimic ESCs while offering a more ethically acceptable source makes them ideal candidates for RBC generation.
Methods and Differentiation Techniques
Building on this biological foundation, researchers have developed methods to guide iPSCs through erythroid differentiation. Two principal strategies dominate current protocols: co-culture with feeder layers and embryoid body (EB)-based suspension cultures. These involve sequential phases—mesoderm induction, hematopoietic specification, and erythroid maturation—facilitated by growth factors like EPO, IL-3, and SCF.
Comparative studies suggest that feeder-based systems, such as those using OP9 or CH310T1/5 cells, yield higher enucleation rates than EB cultures. However, both approaches face limitations regarding scale, cost, and physiological fidelity.
Results Recent advances have focused on improving both the efficiency and maturity of iPSC-derived RBCs. Progress has been made in enhancing enucleation and adult hemoglobin expression. Techniques incorporating microRNAs (e.g., miR-451, miR-144) and 3D scaffolds have improved maturation. Suspension platforms and spinner flasks enable scalable differentiation, with enucleation rates reaching up to 90% under optimized conditions. Culture media such as R6 and IMIT, which exclude albumin and reduce reliance on transferrin, further support scalability. Nonetheless, variability remains depending on the origin of the reprogrammed cells, with umbilical cord-derived iPSCs showing higher erythroid output than fibroblast-derived lines.
In Vivo Performance and Translational Gaps
To move beyond the lab, in vivo data are critical. Animal studies using NOD-SCID gamma mice have shown that iPSC-derived erythroblasts can complete enucleation and switch from fetal to adult hemoglobin post-transfusion. However, these models lack immune competence and bone marrow integrity, limiting translational value. Alternative preclinical models like non-human primates may offer more reliable insights. A consistent gap remains in determining whether these lab-grown RBCs can achieve physiological lifespans or oxygen-carrying capacity equivalent to native cells.
Obstacles to Clinical Application
These promising findings still face significant clinical and manufacturing hurdles. Despite encouraging lab outcomes, no iPSC-derived RBC therapy has entered clinical trials. Current obstacles include high production costs, insufficient yields, reliance on xenogenic culture components, and inadequate knowledge of molecular differentiation pathways. For clinical use, Good Manufacturing Practice (GMP) standards must be met, demanding chemically defined, serum-free conditions. Engineering scalable bioreactors and optimizing cytokine usage are key future steps. Moreover, more extended in vivo monitoring is required to evaluate cell longevity and function.
Applications and Future Promise
Looking beyond transfusion, iPSC-derived RBCs hold broader therapeutic promise. Their extracellular vesicles (EVs), naturally released during erythroid development, have demonstrated utility in delivering RNA-based therapies to cancer cells. This opens avenues for dual use of iPSC-derived RBCs in regenerative medicine and targeted drug delivery.
Conclusion In summary, while still in early development, the generation of RBCs from iPSCs offers a transformative solution to the global blood shortage. Scientific advancements in reprogramming, culture systems, and in vivo modeling bring this goal closer to clinical translation. However, sustained innovation and rigorous testing are essential to ensure that iPSC-derived RBCs meet the safety, efficiency, and scalability requirements of modern transfusion medicine.
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