Stem cells from apical papilla promote differentiation of human pluripotent stem cells towards retinal cells

Recently, we have found that human stem cells from apical papilla (SCAP) show a stromal cell-derived inducing activity (SDIA). To examine SDIA competence for retinal cells differentiation, we co-cultured SCAP with human pluripotent stem cells (hPSCs). In comparison with Matrigel-cultured hPSCs, SCAP significantly induces hPSCs to differentiate into rostral neural cells as demonstrated by upregulation of OTX2 and PAX6 and down-regulation of EN1, HOXB4 and HOXC8. Furthermore, the differentiated cells on SCAP significantly expressed eye-field markers, RAX, PAX6, LHX2 and SIX3 and showed five folds pigmented colonies. The generated hPSC-retinal pigmented epithelium (RPE) was hexagonal and highly expressed related markers, ZO-1, RPE65, BEST, CRALBP and MITF. They were able to phagocytose latex beads. Moreover, the assessment of the isolated neural tube-like structures on SCAP showed the expression of retinal progenitor cells (RPCs) - SIX3, RAX, and PAX6. SCAP highly expressed DKK3 and SFRP2, Wnt inhibitor factors and their target genes, Cyclin D1 and c-Myc were down-regulated significantly on SCAP. These results showed SCAP promoted the differentiation of hPSCs into retinal cells (RPE and RPCs) possibly through inhibition of Wnt signaling pathway. This simple and efficient approach provides human RPE generation for developing therapies for diseases such as age-related macular degeneration.