Small molecular compounds efficiently convert human fibroblasts directly into neurons.

No effective treatment is currently available for neurodegenerative diseases, and existing pharmacotherapy is inconsistent with severe side effects. Cell replacement therapy is promising for neurodegenerative disease treatment, and the induction of neurons is an unmet need for such therapy. The present study investigated the potential of a combined medium composed of conditioned medium and eight small molecular compounds in reprogramming human foreskin fibroblasts (HFFs) into neurons. HFFs were cultured from foreskin and then induced by small molecules to generate neurons. The results demonstrated that the conditioned medium containing forskolin, RepSox, SP600125, CHIR99021, Go6983, Y‑27632, IXS9 and I‑BET151 effectively induced human fibroblasts to change into neurons in vitro. Following a 30‑day induction, the cells exhibited neuronal properties as determined by morphological and phenotypical alterations. The induced cells exhibited expression of neuronal markers, including class III β‑tubulin, microtubule‑associated protein 2, vesicular glutamate transporter 1 and γ‑aminobutyric acid, accompanied by increased expression of neuronal transcription factors, including neuronal differentiation 1 and achaete‑scute family bHLH transcription factor 1, and decreased expression levels of fibroblast‑specific genes. Furthermore, these cells also exhibited electrophysiological properties of neurons. Notably, the course of cell morphological alterations demonstrated the differentiation of fibroblasts into neurons. The present study provided a novel combination of existing small molecular compounds that efficiently reprogramed human fibroblasts into neurons.