Dysregulation Of Ghrelin In Adolescent Idiopathic Scoliosis Osteopenia

Background:Adolescent idiopathic scoliosis(AIS)is the most common pediatric spinal deformity,affecting approximately 4% of the adolescent population worldwide.It is characterized by adolescence-onset,progressive lateral curvature of the spine in the coronal plane with sagittal decompensation and vertebral rotation in the axial plane.However,its pathogenesis remains largely unknown,which is a considerable obstacle for the early prevention and treatment of AIS patients.Osteopenia has been well documented in AIS,and ghrelin has been shown to have a positive effect on bone metabolism.But the circulating level of ghrelin is increased in AIS osteopenia.It is suggested that some differences exist in the process of bone metabolism in which ghrelin participates between AIS osteopenia and controls.The aim of the study is to clarify the relationship between AIS low bone mass and ghrelin,as well as explore the possible etiology and pathogenesis in the perspective of abnormal bone metabolism,which may contribute to a further understanding of AIS.Method:1.The plasma levels of ghrelin were measured by ELISA in the AIS osteopenia and age-matched controls.2.DNA was collected from AIS osteopenia,AIS normal bone mass and age-matched controls.Four single nucleotide polymorphism which may affect the plasma level of ghrelin were determined.3.The cancellous bone from facet joints were collected from AIS osteopenia and age-matched control.The expression of osteoblast-and osteoclast-related factors were tested by q PCR,Western blotting and immunohistochemistry.4.The primary osteoblasts were extracted from facet joint from AIS osteopenia and age-matched controls.The cells were exposed by the ghrelin and observed the changes.5.The primary bone marrow stem cells(BMSCs)were extracted from intramedullary blood from AIS osteopenia and age-matched controls.During osteogenesis induction,the cells were exposed by the ghrelin and observed the changes.6.RNA sequencing was conducted to explore the lnc RNA expression profiles in peripheral blood from AIS patients and controls.Comprehensive bioinformatics analyses were then used to enrich datasets for gene ontology and pathways.Results:1.The plasma level of adiponectin in AIS low bone mass(27.33?6.57pg/ml)were significantly higher than that in control group(15.81?3.82pg/ml).2.There were no significant differences in the selected SNPs between the AIS and control groups.3.The expression levels of osteoclast-related factors TRAP,RANKL and RANKL/OPG in AIS cancellous bone were significantly higher than those in control group.The expression levels of osteoblast-related factors OCN and Runx2 in AIS cancellous bone were significantly lower than those in control group.4.ghrelin increased OPG expression and decreased RANKL expression with increasing ghrelin concentration.In contrast,AIS osteopenia primary osteoblasts showed no significant variation in OPG or RANKL expression with increasing ghrelin.Moreover,compared with the control group,OPG expression was lower in the AIS osteopenia group than in the control group at a higher concentration of ghrelin,and expression of RANKL was higher in the AIS osteopenia group.5.The expression levels of Col1 a,Runx2,BMP2 and OPG in both the AIS and control groups increased in time-dependent and dose-dependent manners when exposed to different concentrations of ghrelin.With the variation in the concentration of ghrelin,the expression levels of OPG and RANKL in the control group changed more significantly than did those in the AIS osteopenia group when treated for the same number of days.6.The results suggested that a number of lnc RNAs were differentially expressed in peripheral blood from AIS patients.The most meaningful pathways were the hedgehog signaling pathway,c AMP signaling pathway,insulin pathway,thyroid hormone signaling pathway and adipocytokine signaling pathway.Conclusion:In conclusion,our findings provide new insight into AIS osteopenia.We found that dysregulation of the ghrelin/RANKL/OPG pathway leads to decreased osteogenic ability of osteoblasts and BMSCs,which may be related to lower bone mass in AIS osteopenia.These results suggest that ghrelin may play an important role in AIS osteopenia.These differentially expressed lnc RNAs and molecular pathways might play a significant role in the initiation and development of AIS.Further studies are required to clarify the mechanism underlying AIS pathogenesis.