TY - JOUR
T1 - Expression of estrogen receptors and enzymes involved in sex steroid metabolism in the rat tibia during sexual maturation
AU - van der Eerden, B. C.J.
AU - Löwik, C. W.G.M.
AU - Wit, J. M.
AU - Karperien, M.
PY - 2004/3
Y1 - 2004/3
N2 - Estrogens are essential for bone mass accrual but their role before sexual maturation has remained elusive. Using in situ hybridization and immunohistochemistry, we investigated the expression of both estrogen receptor (ER) α and β mRNA and protein as well as several mRNAs coding for enzymes involved in sex steroid metabolism (aromatase, type I and II 17β-hydroxysteroid dehydrogenase (17β -HSD), steroid sulfatase (STS) and type I 5α-reductase) on sections of tibial metaphyses before (1- and 4-week-old), during (7-week-old) and after (16-week-old) sexual maturation in female and male rats. ERα and ERβ mRNA and protein were detected in metaphyseal bone in lining cells, osteoblasts, osteoclasts and some osteocytes with no apparent differences in expression during development or between the sexes. In contrast, aromatase, type I and II 17β-HSD and type I 5α-reductase mRNAs were first detected in osteoblasts, osteoclasts and occasionally in osteocytes from sexual maturation (7-week-old rat) and onwards. Only STS was present before sexual maturation. To study the significance of ERα and β expression in bone before sexual maturation when circulating sex steroid levels are low, 26-day-old female and male rats underwent gonadectomy or 17β-estradiol (E2) supplementation (0.5 mg/21 days) during 3 weeks. Following gonadectomy, trabecular bone volume (TBV) was lower in males (P = 0.03) and there was a trend towards reduction in females (P = 0.057). E2 supplementation increased tibial TBV compared with controls in both genders as assessed by Masson-Goldner staining. These data suggest that the presence of ERs in bone cells before sex maturation might be of significance for bone mass accrual. Furthermore, based on the mRNA expression of the crucial enzymes aromatase and type I 17β-HSD, we suggest that bone cells in the tibial metaphysis acquire the intrinsic capacity to metabolize sex steroids from sexual maturation onwards. This process may contribute to the beneficial effects of estrogen on bone mass accrual, possibly by intracrinology.
AB - Estrogens are essential for bone mass accrual but their role before sexual maturation has remained elusive. Using in situ hybridization and immunohistochemistry, we investigated the expression of both estrogen receptor (ER) α and β mRNA and protein as well as several mRNAs coding for enzymes involved in sex steroid metabolism (aromatase, type I and II 17β-hydroxysteroid dehydrogenase (17β -HSD), steroid sulfatase (STS) and type I 5α-reductase) on sections of tibial metaphyses before (1- and 4-week-old), during (7-week-old) and after (16-week-old) sexual maturation in female and male rats. ERα and ERβ mRNA and protein were detected in metaphyseal bone in lining cells, osteoblasts, osteoclasts and some osteocytes with no apparent differences in expression during development or between the sexes. In contrast, aromatase, type I and II 17β-HSD and type I 5α-reductase mRNAs were first detected in osteoblasts, osteoclasts and occasionally in osteocytes from sexual maturation (7-week-old rat) and onwards. Only STS was present before sexual maturation. To study the significance of ERα and β expression in bone before sexual maturation when circulating sex steroid levels are low, 26-day-old female and male rats underwent gonadectomy or 17β-estradiol (E2) supplementation (0.5 mg/21 days) during 3 weeks. Following gonadectomy, trabecular bone volume (TBV) was lower in males (P = 0.03) and there was a trend towards reduction in females (P = 0.057). E2 supplementation increased tibial TBV compared with controls in both genders as assessed by Masson-Goldner staining. These data suggest that the presence of ERs in bone cells before sex maturation might be of significance for bone mass accrual. Furthermore, based on the mRNA expression of the crucial enzymes aromatase and type I 17β-HSD, we suggest that bone cells in the tibial metaphysis acquire the intrinsic capacity to metabolize sex steroids from sexual maturation onwards. This process may contribute to the beneficial effects of estrogen on bone mass accrual, possibly by intracrinology.
UR - http://www.scopus.com/inward/record.url?scp=1842582910&partnerID=8YFLogxK
U2 - 10.1677/joe.0.1800457
DO - 10.1677/joe.0.1800457
M3 - Article
C2 - 15012600
AN - SCOPUS:1842582910
VL - 180
SP - 457
EP - 467
JO - Journal of Endocrinology
JF - Journal of Endocrinology
SN - 0022-0795
IS - 3
ER -
