CREB1 Facilitates GABAergic Neural Differentiation of Human Mesenchymal Stem Cells through BRN2 for Pain Alleviation and Locomotion Recovery after Spinal Cord Injury

The transplantation of GABAergic neuron cells has been reported to alleviate nerve pain and improve motor function after spinal cord injury (SCI). However, human mesenchymal stem cell (hMSC) differentiation into GABAergic neuron cells in a sufficient quantity remains to be accomplished. From a database screening, cAMP-responsive element-binding protein 1 (CREB1) was chosen as a potential modulator due to its critical role in the protein-protein interaction of genes related to GABAergic neural differentiation. Here, CREB1 was overexpressed in transfected hMSCs, where CREB1 could induce differentiation into GABAergic neuron cells with an upregulation of Map2 and GAD1 by 2- and 3.4-fold, respectively. Additionally, GABAergic neural differentiation was enhanced, while Notch signaling was inhibited, and BRN2 transcriptional activation played an important role in neuronal maturation. Moreover, transfected hMSCs injected into immunocompromised mice caused by CsA exhibited the neuronal markers Tuj1 and Map2 via the intraspinal route, suggesting an improvement in survival and neural differentiation. Significantly, improvement in both BMS scores (6.2 +/- 1.30 vs. 4 +/- 0) and thermal hyperalgesia latency (7.74 +/- 2.36 s vs. 4.52 +/- 0.39 s) was seen compared with the SCI naive treatment at 4 weeks post-transplantation. Our study demonstrates that CREB1 is crucial in generating induced GABAergic neuron cells (iGNs) originating from hMSCs. Transplanting iGNs to injured spinal cord provides a promising strategy for alleviating neuropathic pain and locomotion recovery after SCI.