Evaluation of Outgrowth Potential of Rat Pheochromocytoma Cells Supplied with Highly Purified Rapidly Expanding Clones and Potential Application to Trigeminal Nerve Regeneration

BACKGROUND: Mesenchymal stem/stromal cells (MSCs) are non-hematopoietic, plastic-adherent, and self-renewing cells capable of in vitro trilineage differentiation into fat, bone, and cartilage tissue. Suggestively, MSCs have additional plasticity, as demonstrated by their ability to differentiate in vitro into myocytes, neuron-like cells, and hepatocytes. MSCs are ideal for therapeutic application owing to their numerous advantages; they exhibit limited growth and differentiation abilities, leading to heterogeneous cell populations with inconsistent functions. However, highly purified MSCs, namely, rapidly expanding clones (RECs) that are isolated by single-cell sorting, display uniform functionality. RECs have the potential to offer many benefits, such as transplantable cells for treating several disorders of bone, heart, peripheral nerves, brain, and other organs. This study aimed to assess the effects of RECs on the pheochromocytoma (PC12) cell line, a well-known neuronal cell model. METHODS: PC12 cells were cultured under the following conditions: co-culture with RECs, treatment with REC-derived conditioned medium (CM), or co-culture with RECs using Transwell inserts for 7 days. The cells were stained with anti-βIII-tubulin antibody; the lengths of neurites were measured by image analysis. RESULTS: Regarding the co-culture with RECs, PC12's outgrowth was significantly increased. The RECs expressed nerve growth factor (NGF), a neurotrophic factor that could act on PC12 cells to trigger cellular differentiation. CONCLUSIONS: Our findings suggest that RECs via direct culture, intercellular communication in Transwell culture, and RECs CM promoted PC12 cell survival and outgrowth via NGF signaling.