New small isoform of glial cell line-derived neurotrophic factor djGDNF47 promotes neuronal viability, differentiation, and adult neurogenesis: Evidence from in vitro and in vivo models.

Neurodegenerative diseases are characterized by progressive neuronal loss, and current therapies provide only symptomatic relief. Parkinson's disease (PD), a leading example, is marked by progressive dopaminergic neuron loss. Although glial cell line-derived neurotrophic factor (GDNF) supports dopaminergic neuron survival, its poor blood-brain barrier (BBB) permeability limits clinical application. Neuron-like SH-SY5Y and PC12 cell lines were used to assess metabolic and proliferative effects of djGDNF47 using MTS and 5-ethynyl-2'-deoxyuridine (EdU) assays, while neuroinductive properties were evaluated in PC12 cells and rat hippocampal neurons by measuring neurite length. Neuroprotective effects were examined in an MPP+-induced dopaminergic neurotoxicity model in SH-SY5Y cells by analyzing cell viability and apoptosis-related gene expression. In vivo, assess adult neurogenesis via 5-bromo-2'-deoxyuridine (BrdU) and doublecortin (DCX) immunohistochemistry in the olfactory bulb and dentate gyrus. djGDNF47 induced concentration- and time-dependent metabolic effects, with early responses in both cell lines and sustained effects in PC12 cells at higher concentrations. Proliferation increased in SH-SY5Y cells but decreased in PC12 cells, consistent with djGDNF47-induced differentiation, accompanied by enhanced neurite outgrowth, which was confirmed by increased MAP2+ neurite length in hippocampal neurons. In the dopaminergic neurotoxicity model, djGDNF47 pretreatment improved cell viability and reduced p53 and caspase-3 expression. Intranasally delivered Cy3-djGDNF47 reached the olfactory bulb and persisted for 24 h, while repeated administration increased BrdU+/DCX+ newborn neurons in neurogenic brain regions. Together, these findings identify djGDNF47 as a noninvasively deliverable GDNF-derived peptide with neuroinductive and neuroprotective activity, supporting its further investigation as a candidate neurotrophic therapy for neurodegenerative disorders, including Parkinson's disease.