Introduction:Dysregulation of spinal cord development can lead to serious neuronal damage and dysfunction, causing significant health problems in newborns. MiRNA-138 appears to be crucial for proliferation, differentiation, and apoptosis of cells. However, the regulation of miRNA-138 and downstream molecules in embryonic spinal cord development remains elusive. The aim of this experiment is to determine whether overexpression of miRNA-138 or RNA interference (RNAi) can regulate the development of spinal cord in fetal rats. Methods:Two plasmid vectors including pLenti-III-mico-GFP (miRNA-138 open reading frame (ORF)) and pLenti-III-miR-Off (miRNA-138 short hairpin) were constructed and injected into the tail vein of rats on the 14th day of pregnancy. Hematoxylin-eosin staining (HE) staining was used to observe the cell morphology. QRT-PCR, western blot, and immunostaining confirmed the regulatory relationship between miRNA-138 and downstream molecules sonic hedgehog (Shh).Results:Overexpression of miRNA-138 increased neuron regeneration significantly and decreased neuronal apoptosis when compared with the control. Silencing of miRNA-138 increased neuronal apoptosis and spinal cord atrophy significantly. Furthermore, miRNA-138 ORF treatment effectively increased the expression level of miRNA-138 and also up-regulated the level of Shh. Comparatively, knockdown of miRNA-138 down-regulated Shh levels in myelodysplastic regions. Conclusion:These findings indicated that miRNA-138 overexpression could protect the spinal cord development of fetal rats, and the underlying mechanisms were associated with Shh expression. The present study provides a novel strategy to promote the molecular mechanism of embryonic spinal cord development.