Chemically Defined Medium Enables GDNF-Driven Early Neuronal-like Phenotype of Human Dental Pulp Stem Cells

Human dental pulp stem cells (hDPSCs) are a promising source of multipotent mesenchymal stem cells (MSCs) for regenerative neurology because of their inherent neurogenic potential. However, robust and reproducible protocols for driving their terminal neuronal maturation in a fully defined, xeno-free environment are lacking.

hDPSCs were isolated from a donor tooth and characterized for mesenchymal (CD105, CD90, CD73, CD13) and stemness-associated markers (SOX2, Oct3/4 and Nanog). Cells were differentiated in a novel, fully chemically defined medium 1% ITS medium (ITS: Insulin, Transferrin, Selenium) supplemented with glial cell line-derived neurotrophic factor (GDNF) or brain-derived neurotrophic factor (BDNF). Neuronal commitment and partial maturation were assessed via immunofluorescence, Western blot, and RT-PCR for markers such as NeuN (Neuronal nuclei) and NF-M (Neurofilament medium chain), and functionally by whole-cell patch-clamp electrophysiology.

Although undifferentiated hDPSCs expressed neural progenitor markers (βIII-tubulin and Nestin), only GDNF treatment in a chemically defined medium significantly upregulated mature neuronal markers (NeuN and NF-M) and downregulated mesenchymal markers. Importantly, GDNF-treated cells exhibited key functional changes, including hyperpolarized resting membrane potentials, increased membrane capacitance, and elevated input resistance, which are electrophysiological hallmarks of neural precursor or early neuronal maturation, compared to control cells cultured in medium containing fetal bovine serum (FBS). Although action potentials were not elicited, this represents a significant advancement toward achieving a functional neuronal state.

This study demonstrates that a fully chemically defined medium enables GDNF to drive hDPSCs beyond the neural progenitor state towards a partially mature neuronal phenotype. This defined medium protocol eliminates serum variability, enhances reproducibility, and provides a critical step towards standardizing hDPSC-derived neuronal cells for disease modeling and cell-based therapy.