Effect of Calcitonin Gene-Related Peptide on the Neurogenesis of Rat Adipose-Derived Stem Cells In Vitro

Calcitonin gene-related peptide (CGRP) promotes neuron recruitment and neurogenic activity. However, no evidence suggests that CGRP affects the ability of stem cells to differentiate toward neurogenesis. In this study, we genetically modified rat adipose-derived stem cells (ADSCs) with the CGRP gene (CGRP-ADSCs) and subsequently cultured in complete neural-induced medium. The formation of neurospheres, cellular morphology, and proliferative capacity of ADSCs were observed. In addition, the expression of the anti-apoptotic protein Bcl-2 and special markers of neural cells, such as Nestin, MAP2, RIP and GFAP, were evaluated using Western blot and immunocytochemistry analysis. The CGRP-ADSCs displayed a greater proliferation than un-transduced (ADSCs) and Vector-transduced (Vector-ADSCs) ADSCs (p<0.05), and lower rates of apoptosis, associated with the incremental expression of Bcl-2, were also observed for CGRP-ADSCs. Moreover, upon neural induction, CGRP-ADSCs formed markedly more and larger neurospheres and showed round cell bodies with more branching extensions contacted with neighboring cells widely. Furthermore, the expression levels of Nestin, MAP2, and RIP in CGRP-ADSCs were markedly increased, resulting in higher levels than the other groups (p<0.05); however, GFAP was distinctly undetectable until day 7, when slight GFAP expression was detected among all groups. Wnt signals, primarily Wnt 3a, Wnt 5a and β-catenin, regulate the neural differentiation of ADSCs, and CGRP gene expression apparently depends on canonical Wnt signals to promote the neurogenesis of ADSCs. Consequently, ADSCs genetically modified with CGRP exhibit stronger potential for differentiation and neurogenesis in vitro, potentially reflecting the usefulness of ADSCs as seed cells in therapeutic strategies for spinal cord injury.