Blood-derived human iPS cells generate optic vesicle-like structures with the capacity to form retinal laminae and develop synapses.

Purpose: We sought to determine if human induced pluripotent stem cells (iPSCs) derived from blood could produce optic vesicle-like structures (OVs) with the capacity to stratify and express markers of intercellular communication.

Methods: Activated T-lymphocytes from a routine peripheral blood sample were reprogrammed by retroviral transduction to iPSCs. The T-lymphocyte-derived iPSCs (TiPSCs) were characterized for pluripotency and differentiated to OVs using our previously published protocol. TiPSC-OVs were then manually isolated, pooled, and cultured en masse to more mature stages of retinogenesis. Throughout this stepwise differentiation process, changes in anterior neural, retinal, and synaptic marker expression were monitored by PCR, immunocytochemistry, and/or flow cytometry.

Results: TiPSCs generated abundant OVs, which contained a near homogeneous population of proliferating neuroretinal progenitor cells (NRPCs). These NRPCs differentiated into multiple neuroretinal cell types, similar to OV cultures from human embryonic stem cells and fibroblast-derived iPSCs. In addition, portions of some TiPSC-OVs maintained their distinctive neuroepithelial appearance and spontaneously formed primitive laminae, reminiscent of the developing retina. Retinal progeny from TiPSC-OV cultures expressed numerous genes and proteins critical for synaptogenesis and gap junction formation, concomitant with the emergence of glia and the upregulation of thrombospondins in culture.

Conclusions: We demonstrate for the first time that human blood-derived iPSCs can generate retinal cell types, providing a highly convenient donor cell source for iPSC-based retinal studies. We also show that cultured TiPSC-OVs have the capacity to self-assemble into rudimentary neuroretinal structures and express markers indicative of chemical and electrical synapses.