Potential role of COMP as a biomarker for adolescent idiopathic scoliosis

Microarray expression profiling identifies genes with altered expression in Adolescent Idiopathic Scoliosis

PURPOSE

Adolescent Idiopathic Scoliosis (AIS) is considered a complex genetic disease, in which malfunctioning or dysregulation of one or more genes has been proposed to be responsible for the expressed phenotype. However, to date, no disease causing genes has been identified and the pathogenesis of AIS remains unknown. The aim of this study is, therefore, to identify specific molecules with differing expression patterns in AIS compared to healthy individuals.

METHODS

Microarray analysis and quantitative RT-PCR have examined differences in the gene transcription profile between primary osteoblasts derived from spinal vertebrae of AIS patients and those of healthy individuals.

RESULTS

There are 145 genes differentially expressed in AIS osteoblasts. A drastic and significant change has been noted particularly in the expression levels of Homeobox genes (HOXB8, HOXB7, HOXA13, HOXA10), ZIC2, FAM101A, COMP and PITX1 in AIS compared to controls. Clustering analysis revealed the interaction of these genes in biological pathways crucial for bone development, in particular in the differentiation of skeletal elements and structural integrity of the vertebrae.

CONCLUSIONS

This study reports on the expression of molecules that have not been described previously in AIS. We also provide for the first time gene interaction pathways in AIS pathogenesis. These genes are involved in various bone regulatory and developmental pathways and many of them can be grouped into clusters to participate in a particular biological pathway. Further studies can be built on our findings to further elucidate the association between different biological pathways and the pathogenesis of AIS.

Adolescent idiopathic scoliosis (AIS), environment, exposome and epigenetics: a molecular perspective of postnatal normal spinal growth and the etiopathogenesis of AIS with consideration of a network approach and possible implications for medical therapy

Genetic factors are believed to play an important role in the etiology of adolescent idiopathic scoliosis (AIS). Discordant findings for monozygotic (MZ) twins with AIS show that environmental factors including different intrauterine environments are important in etiology, but what these environmental factors may be is unknown. Recent evidence for common chronic non-communicable diseases suggests epigenetic differences may underlie MZ twin discordance, and be the link between environmental factors and phenotypic differences. DNA methylation is one important epigenetic mechanism operating at the interface between genome and environment to regulate phenotypic plasticity with a complex regulation across the genome during the first decade of life. The word exposome refers to the totality of environmental exposures from conception onwards, comprising factors in external and internal environments. The word exposome is used here also in relation to physiologic and etiopathogenetic factors that affect normal spinal growth and may induce the deformity of AIS. In normal postnatal spinal growth we propose a new term and concept, physiologic growth-plate exposome for the normal processes particularly of the internal environments that may have epigenetic effects on growth plates of vertebrae. In AIS, we propose a new term and concept pathophysiologic scoliogenic exposome for the abnormal processes in molecular pathways particularly of the internal environment currently expressed as etiopathogenetic hypotheses; these are suggested to have deforming effects on the growth plates of vertebrae at cell, tissue, structure and/or organ levels that are considered to be epigenetic. New research is required for chromatin modifications including DNA methylation in AIS subjects and vertebral growth plates excised at surgery. In addition, consideration is needed for a possible network approach to etiopathogenesis by constructing AIS diseasomes. These approaches may lead through screening, genetic, epigenetic, biochemical, metabolic phenotypes and pharmacogenomic research to identify susceptible individuals at risk and modulate abnormal molecular pathways of AIS. The potential of epigenetic-based medical therapy for AIS cannot be assessed at present, and must await new research derived from the evaluation of epigenetic concepts of spinal growth in health and deformity. The tenets outlined here for AIS are applicable to other musculoskeletal growth disorders including infantile and juvenile idiopathic scoliosis.