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BRITISH SCOLIOSIS RESEARCH FOUNDATION
The Role of Estrogens and Estrogen Receptors in the Pathogenesis of
Adolescent Idiopathic Scoliosis (AIS)
F. Moldovan PhD.1,2 , K. Letel ier B.Sc. 1 , F. B. Azeddine M.Sc. 1, G. Lacroix 1, DS Wang PhD. 1 , I.
Turgeon B.Sc. 1 , G. Grimard M.D. 3, H. Label e M.D. 3, A Moreau Ph.D. 1, 4
1 Bone Molecular Genetics Laboratory & Musculoskeletal Malformations, Research Centre,
Hôpital Sainte-Justine, Montréal, QC, CANADA
2 Faculty of Dentistry, Université de Montréal
3 Orthopedic Division, Hôpital Sainte-Justine, Université de Montréal, Montréal
4 Stomatology and Biochemistry Department, Université de Montréal
Adolescent idiopathic scoliosis (AIS) is the most common form of scoliosis, which appears to be
caused by a melatonin signal ing dysfunction proved recently in osteoblasts. This pathology occurs
and progresses during the time of pre-puberty and puberty growth. This period is known to be under
the hormonal control and coincides with many biological changes related to the secretion of
estrogens, of which estradiol (E2) is the most active. The female prevalence of AIS disease is clearly
evident. Indeed, in Quebec the spine deformities considered clinical y significant (at least 11° of
deformity) are found in a girl:boy ratio of approximately 2:1 for reduced scoliosis, and this ratio
increases to 10:1 for scoliosis of more than 30o of deformation. However, the reason for this female
prevalence as wel as the role of estrogens and estrogen receptors in AIS is not clear despite the fact
that these hormones are known for their impact on bone and bone growth, including the spine.
The purpose of the present study was to investigate the role of E2 on the responsiveness of the AIScel s to the melatonin, to determine the expression of estrogens receptors (ER_ and ER_) in AIS tissues and to clarify the impact of estrogen receptor gene polymorphisms in the pathogenesis of AIS.
The effects of estrogen on the AIS osteoblasts (n=10) response to the melatonin was determined by
measuring the reduction of forskolin-induced cAMP accumulation. The forskolin treated osteoblasts
were incubated in the presence of increasing amounts of melatonin (10-11 to 10-5 M) with or without
physiological concentrations (10-10 M) of 17-β-estradiol for 16 hours, and the intracel ular cAMP
measured by radioimmunoassay using Biotrak Kit. Using RT-PCR, we determined ER_ and
ER_ mRNA expression in osteoblasts from AIS patients (n=14). Polymorphisms of the first intron of
the ER_ gene, which contains the XbaI and PvuII polymorphisms, were investigated by PCR
fol owing digestion with restriction enzyme and using the genomic DNA from lymphocytes isolated
from scoliotic patients (n=33). Using the restriction enzymes XbaI and PvuII, the al elic variants XX,
Xx, xx, PP, Pp, and pp were identified in 33 AIS patients (uppercase letters represent absence, and
lowercase letters represent presence of restriction sites).
The intracel ular level of cAMP was significantly increased (p< 0.01) in the presence of a
physiological concentration of 17-β-estradiol when compared to the level observed in the presence of
melatonin alone (melatonin + estradiol: 109.46 ± 20.07; melatonin 76.09 ± 12.32 (mean ± SD)). As
previously described by Dr Moreau’s team, the same pattern (three type of response to melatonin)
takes place in the presence of 17-β-estradiol. We observed the loss of ER_ gene expression in 8/ 14
AIS patients contrasting with ER_ gene expression that was found in al AIS patients. The XbaI and 1
PvuII polymorphisms were found in 70% (23/33) and 80% (26/33) of the cases respectively. Of the 33 cases, 21 presented both digestion sites, 24 presented PvuII digestion site (6 homozygote,18 heterozygote) and 23 (8 homozygote, 15 heterozygote) presented XbaI digestion site. The al elicvariants were found as fol ows: XX: n=8, Xx: n=15, xx: n=8, PP: n=6, Pp: n=18 and pp: n=6. Classified by their location in the spine, 7 right thoracic, 1 left thoracic, 1 right thoracolumbar, 3 leftthoracolumbar and 9 right thoracic-left lumbar were found among the patients presenting PvuII positive polymorphism. Among the patients with XbaI positive polymorphism, 6 right thoracic, 1 leftthoracic, 1 right thoracolumbar, 3 left thoracolumbar and 8 right thoracic left lumbar were found.
These results show the antagonistic effects of the 17-β-estradiol on AIS osteoblasts response to the
melatonin. Thus estrogens interference with melatonin signal ing activity would act as a triggering or
aggravating factor in the pathogenesis of AIS. At the molecular level, it is possible that estrogens
attenuate the response of AIS cel s to melatonin through the desensitization of melatonin receptors.
The loss of ER_ expression in a significant number of AIS patients appears to be important for the
change of the ER_/ER_ receptors ratio that consequently may perhaps alter estrogens signal ing
pathways. The XbaI and PvuII polymorphisms are present in a significant number of AIS patients but
this was not dependant of the curve pattern. These results clearly support the interplays and
crosstalk between estrogens and melatonin signal ing pathways in AIS etiopathogenesis.
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