Dual-loaded exosomes with fibroblast growth factor 2 and retinoic acid enhance directed neural differentiation of embryonic stem cells

Neural differentiation of embryonic stem cells (ESCs) holds significant therapeutic potential for the treatment of neurodegenerative diseases. A cell conversion strategy was developed to induce neural differentiation of ESCs by utilizing exosomes (Exo) derived from mesenchymal stem cells (MSCs) as efficient delivery vehicles for retinoic acid (RA) and fibroblast growth factor 2 (FGF2). The abundant surface proteins and phospholipid bilayer of Exo provided protective effects for FGF2 and RA, 88 % of RA remained within the Exo, and the residual amount of exosome-bound FGF2 was nearly 5-fold higher than that of free FGF2, after storage at 4 °C for 5 days. Exo co-loaded with RA and FGF2 exhibited excellent biocompatibility and promoted cell proliferation, resulting in a 3.3-fold higher proliferation over the free RA+FGF2 within 3 days. Neural differentiation was enhanced through dual signaling pathways mediated by RA and FGF2, leading to a nearly 3-fold increase in the relative expression of neuronal marker genes and 8.3-fold increase in the number of differentiated neural cells, compared to the RA+FGF2 group by day 7. This approach significantly enhanced both the efficiency and yield of neural differentiation, presenting a promising nanomedicine strategy by applying engineered Exo to guide the neural lineage commitment of ESCs.