Functional sensory neurons derived from human stem cells from apical papilla

Objectives: This study aimed to investigate the sensory maturation–enhancing effects of co-culturing human stem cells from apical papilla (hSCAPs)-derived neural stem cells (NSCs) with chick embryonic dorsal root ganglia (DRG) under three-dimensional (3D) neurosphere conditions. The ultimate goal was to assess whether this co-culture approach promotes the generation of functional sensory neurons suitable for future sensory neuropathy transplantation applications. Methods: hSCAPs were isolated from the apical papilla of impacted third molars obtained from healthy Thai donors (n = 3; ages 18–21). The isolated hSCAPs were expanded and characterized for mesenchymal stem cell markers and multipotency. These cells were induced into NSCs via 3D-neurosphere formation. Embryonic chick DRG (E9) were dissected and co-cultured with NSCs under three experimental conditions: Co-culture, NeuroMat, and Control, for 7 days. Neuronal differentiation and maturation were evaluated by Cresyl violet staining, immunofluorescence staining for neuronal and glial markers, and intracellular calcium oscillation assays to assess functional activity. Results: hSCAPs exhibited MSC-like characteristics and successfully differentiated into NSCs under 3D-neurosphere conditions, expressing Nissl substance and early neurogenic markers (Nestin, SOX2). Co-culture with chick embryonic DRG significantly enhanced the differentiation of NSCs into functional sensory neurons. These neurons expressed neuronal-associated proteins including βIII-tubulin, MAP2, GFAP, and Brn3a, and demonstrated calcium oscillation activity indicative of mature, functional neurons. On day 7, the co-culture group exhibited the highest proportion of pseudounipolar sensory neurons (Cresyl violet positive), confirming the sensory maturation–enhancing effect of DRG co-culture on hSCAP-derived NSCs. Conclusions: Co-culture with embryonic DRG promotes the sensory neurogenic maturation of NSCs derived from hSCAPs, yielding functional pseudounipolar neurons. This model highlights the potential of hSCAPs as a promising stem cell source for neural regeneration and sensory neuropathy treatment.