The Relationship between the Bcl-2/Bax Proteins and the Mitochondria-Mediated Apoptosis Pathway in the Differentiation of Adipose-Derived Stromal Cells into Neurons

Our objective is to study the relationship between the regulatory proteins Bcl-2/Bax and mitochondria-mediated apoptosis during the differentiation of adipose-derived stromal cells (ADSCs) into neurons. Immunocytochemistry and western blotting showed that the cells weakly expressed neuron-specific enolase (NSE) in the non-induced group and expressed NSE more strongly in the groups induced for 1 h, 3 h, 5 h and 8 h. NSE expression peaked at 5 h (P < 0.05), although there was no significant difference between 5 and 8 h (P > 0.05). Bcl-2 expression gradually decreased over time in the non-induced group (P < 0.05). However, Bax, caspase-9, Cyt-c and caspase-3 expression gradually increased and peaked at 8 h (P < 0.05). Transmission electron microscopy revealed karyopyknosis, chromatin edge setting, mitochondria swelling and cavitation in cells at 5 h, and the mitochondrial membrane potential decreased over time, as demonstrated by laser scanning confocal microscopy. After a 5 h induction, cells differentiated into typical neurons and expressed Bcl-2, which inhibited apoptosis. Bax showed a strong apoptosis-promoting capacity, leading to changes in the mitochondrial membrane potential and structure, and then triggered the caspase-independent apoptotic response through the mitochondrial pathway. At the same time, Cyt-c was directly or indirectly released from the mitochondria to the cytoplasm to trigger the caspase-dependent apoptotic response through the mitochondrial pathway. Therefore, Bcl-2/Bax play an important role in regulating caspase-dependent and caspase-independent apoptosis mediated by the mitochondrial pathway during the differentiation of ADSCs into neurons.