Female estrogen receptor beta-/- mice are partially protected against age-related trabecular bone loss.

• Recently, it has been shown that inactivation of estrogen receptor beta (ER-beta) by gene targeting results in increased cortical bone formation in adolescent female mice. To study the possible involvement of ER-beta in the regulation of the mature skeleton, we have extended the analyses to include 1-year-old ER-beta knockout mice (ER-beta-/-). Male ER-beta-/- mice did not express any significant bone phenotypic alterations at this developmental stage. However, the increase in cortical bone parameters seen already in the adolescent female ER-beta-/- mice was maintained in the older females. The aged female ER-beta-/- mice further exhibited a significantly higher trabecular bone mineral density (BMD) as well as increased bone volume/total volume (BV/TV) compared with wild-type (wt) mice. This was caused by a less pronounced loss of trabecular bone during adulthood in female ER-beta-/- mice. The growth plate width was unaltered in the female ER-beta-/- mice. Judged by the expression of the osteoclast marker tartrate-resistant acid phosphatase (TRAP) and cathepsin K (cat K; reverse-transcription-polymerase chain reaction [RT-PCR]) as well as the serum levels of C-terminal type I collagen cross-linked peptide, bone resorption appeared unaffected. However, an increase in the messenger RNA (mRNA) expression levels of the osteoblast marker core-binding factor alpha1 (Cbfa1) suggested an anabolic effect in bones of old female ER-beta-/- mice. In addition, the mRNA expression of ER-alpha was augmented, indicating a role for ER-alpha in the development of this phenotype. Taken together, the results show that ER-beta is involved in the regulation of trabecular bone during adulthood in female mice and suggest that ER-beta acts in a repressive manner, possibly by counteracting the stimulatory action of ER-alpha on bone formation.

Keyword

Animals

Body Weight

Bone Density

Collagen

blood

Collagen Type I

Cross-Linking Reagents

Disease Models

Animal

Estradiol

blood

Estrogen Receptor alpha

Estrogen Receptor beta

Female

Femur

metabolism

pathology

Gene Expression

Insulin-Like Growth Factor I

analysis

Male

Mice

Mice

Knockout

Osteoblasts

metabolism

Osteocalcin

blood

Osteoclasts

metabolism

Osteoporosis

metabolism

pathology

prevention & control

Peptides

blood

RNA

Messenger

metabolism

Receptors

Estrogen

genetics

physiology

Publication and Content Type

ref (subject category)

art (subject category)