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Comparative Study Highlights Optimal Strategy for Retinal Cell Generation from hPSCs

Review of “Systematic Comparison of Retinal Organoid Differentiation from Human Pluripotent Stem Cells Reveals Stage Specific, Cell Line, and Methodological Differences” from STEM CELLS Translational Medicine by Stuart P. Atkinson

Researchers from the laboratory of Majlinda Lako (Newcastle University, UK) recently reported on the production of photoreceptors from human pluripotent stem cells (hPSCs) previously cultured on mouse embryonic fibroblasts under two-dimensional feeder‐free and three-dimensional organoid culture conditions [1, 2]. However, their subsequent studies employing hPSCs adapted to feeder‐free and defined media conditions encountered different results. Importantly, additional studies have underlined that a single defined protocol for organoid generation does not necessarily function for every hPSC line encountered [3-5].

These perplexing findings prompted the team to compare how the retinal organoid differentiation protocol employed and cell background may affect the production of mature and functional photoreceptors. In their new STEM CELLS Translational Medicine article, Mellough et al. now report that cell line‐specific differences and embryoid body generation/organoid maintenance methods both contribute to the differing abilities of hPSCs to produce laminated retinal tissue containing mature and electrophysiologically responsive photoreceptors [6]. 

Can this comparative study highlight the optimal means to produce mature and functional retinal cell types?

Employing transcriptional analysis during the first five weeks of differentiation, the authors discovered that the hPSC-type used represented the most critical variable affecting early differentiation efficiency rather than the specific differentiation method employed. However, later differentiation and maturation of retinal organoids over 22 weeks depended on the embryoid body generation method used and the particular maintenance conditions. 

Overall, the study highlighted that the mechanical method of embryoid body generation under static conditions, followed by Rho-associated protein kinase inhibitor treatment for the first 48 hours of differentiation, and subsequent organoid maintenance under stationary culture conditions provided for the consistent formation of laminated retinal neuroepithelium containing mature and electrophysiologically responsive photoreceptors that closely resembled human embryonic/fetal retina.

In summary, the authors highlight the specific contributions of cell line‐specific differences and embryoid body generation/organoid maintenance methods in the production of laminated retinae. Furthermore, they anticipate that a greater understanding of the events controlling retinal organoid formation will allow the development of improved and standardized protocols for large scale production of, for example, electrophysiologically sensitive photoreceptors from an hPSC line for applications in ophthalmic research and development.

For more on the efficient production of functionally mature retinal cell types from hPSCs, stay tuned to the Stem Cells Portal!

References

  1. Mellough CB, Sernagor E, Moreno-Gimeno I, et al., Efficient Stage-Specific Differentiation of Human Pluripotent Stem Cells Toward Retinal Photoreceptor Cells. STEM CELLS 2012;30:673-686.
  2. Mellough CB, Collin J, Khazim M, et al., IGF-1 Signaling Plays an Important Role in the Formation of Three-Dimensional Laminated Neural Retina and Other Ocular Structures From Human Embryonic Stem Cells. STEM CELLS 2015;33:2416-2430.
  3. Meyer JS, Shearer RL, Capowski EE, et al., Modeling early retinal development with human embryonic and induced pluripotent stem cells. Proceedings of the National Academy of Sciences 2009;106:16698.
  4. Hallam D, Hilgen G, Dorgau B, et al., Human-Induced Pluripotent Stem Cells Generate Light Responsive Retinal Organoids with Variable and Nutrient-Dependent Efficiency. STEM CELLS 2018;36:1535-1551.
  5. Hiler D, Chen X, Hazen J, et al., Quantification of Retinogenesis in 3D Cultures Reveals Epigenetic Memory and Higher Efficiency in iPSCs Derived from Rod Photoreceptors. Cell Stem Cell 2015;17:101-115.
  6. Vawda R, Badner A, Hong J, et al., Early Intravenous Infusion of Mesenchymal Stromal Cells Exerts a Tissue Source Age-Dependent Beneficial Effect on Neurovascular Integrity and Neurobehavioral Recovery After Traumatic Cervical Spinal Cord Injury. STEM CELLS Translational Medicine 2019;8:639-649.