Ski Regulates Astrocyte Proliferation Through The MAPK/ERK1/2 Pathway

Objective: Ski,a primitive oncogene,is expressed in almost all tissues.Mitogenactivated protein kinase（MAPK）signaling is a major pathway regulating cell proliferation,differentiation,apoptosis and inflammation.ERK1/2 is a member of MAPK,which is also involved in cell proliferation and differentiation.Spinal cord injury（SCI）causes astrocyte proliferation,which is an important process of glial scar formation and affects the recovery of neurological function after SCI.Our group has demonstrated that Ski gene expression is upregulated in astrocytes after spinal cord injury and is associated with astrocyte proliferation.This study focuses on the regulation of downstream signaling molecules MAPK/ERK1/2 by Ski,which in turn regulates astrocyte proliferation.Methods: Rat astrocytes were extracted,purified and cultured,and an astrocyte activation model was established using LPS stimulation of rat astrocytes.（1）The astrocytes were randomly divided into: control group and LPS activation group.The expression changes of Ski protein,astrocyte-specific protein GFAP and astrocyte proliferation（expression changes of PCNA,CDK4,Cyclin D1）were detected in each group.（2）The expression changes of ERK1/2 pathway proteins in control and LPS activation groups were examined,and the relationship between MAPK/ERK1/2pathway and astrocyte proliferation was verified by interfering with astrocytes using U0126,an ERK1/2 pathway-specific inhibitor.（3）Knockdown of Ski gene using lentivirus to verify the relationship between Ski gene and astrocyte proliferation.（4）To detect the change of MAPK/ERK1/2 pathway protein expression after lentiviral knockdown of Ski gene and verify the relationship between Ski and this pathway.Results: RT-PCR and Western Blotting experiments revealed upregulation of Ski and GFAP RNA and protein expression,upregulation of PCNA,CDK4,Cyclin D1 protein and RNA expression,increased astrocyte proliferation and MAPK/ERK1/2pathway activation after LPS stimulation in rat astrocytes;the use of ERK1/2 inhibitor U0126 intervention in astrocytes resulted in inhibition of astrocyte proliferation,indicating that ERK1/2 affects astrocyte proliferation.After knockdown of Ski gene using lentivirus,Ski protein expression was reduced and astrocyte proliferation was inhibited,indicating that Ski regulates astrocyte proliferation;At the same time,ERK1/2phosphorylation was inhibited,suggesting that Ski could play a role in proliferation regulation through ERK1/2 pathway.Conclusion: This study confirmed that Ski regulates astrocyte proliferation and affects glial scar formation through MAPK/ERK1/2 signaling pathway.It is expected to be a new idea in the treatment of spinal cord injury.