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2-Methoxyestradiol inhibits longitudinal bone growth in normal female rats
1Departments of Orthopedics and Biochemistry and Molecular Biology, 3-69 Medical Science Bldg, Mayo Clinic, Rochester, Minnesota 55905, USA.
Abstract:
2-Methoxyestradiol (2-MeO-E(2)), a major metabolite of 17beta-estradiol, may function as a physiological tumor suppressor and is being investigated for clinical applications. It has been reported to target rapidly dividing cells. We investigated the effects of 2-MeO-E(2) on the growth plate of young rats because normal longitudinal bone growth requires rapid proliferation of cartilage and endothelial cells. Sexually mature (3-month-old) normal female rats were treated with 2-MeO-E(2) (100 mg/kg/day) for 13 days and it was found to have no effect on uterine weight but reduced serum cholesterol. The estrogen metabolite had no effect on either cortical or cancellous bone. In contrast, 2-MeO-E(2) dramatically reduced longitudinal bone growth rate at the proximal tibia from 55 +/- 2 to 20 +/- 2 microm/day (P < 0.001) and growth plate thickness from 153 +/- 14 to 70 +/- 6 microm (P < 0.001). The latter decrease was due to significant reductions in the height of both the proliferative (P < 0.001) and the hypertrophic (P < 0.001) zones. These results in normal female rats demonstrate that 2-MeO-E(2) inhibited longitudinal bone growth but had no effect on either radial bone growth or cancellous bone turnover. 2-MeO-E(2) was shown by these studies to have the ability to discriminate between bone and cartilage, as well as between reproductive and nonreproductive estrogen-target tissues. Thus, 2-MeO-E(2) is a naturally produced estrogen metabolite that demonstrates unique tissue selectivity.
Insights
2-Methoxyestradiol (2-MeO-E(2)), an estrogen metabolite, significantly inhibits longitudinal bone growth in rats by reducing growth plate thickness. It shows unique tissue selectivity, impacting cartilage but not bone or reproductive tissues.
Area of Science:
- Endocrinology
- Bone Biology
- Pharmacology
Background:
- 2-Methoxyestradiol (2-MeO-E(2)) is a metabolite of 17beta-estradiol with potential tumor suppressor activity.
- It targets rapidly dividing cells, making its effect on growth plates, which require cell proliferation, an area of interest.
Purpose of the Study:
- To investigate the effects of 2-MeO-E(2) on longitudinal bone growth in young rats.
- To determine the tissue selectivity of 2-MeO-E(2) in bone and cartilage.
Main Methods:
- Adult female rats were treated with 2-MeO-E(2) (100 mg/kg/day) for 13 days.
- Measurements included uterine weight, serum cholesterol, bone parameters (cortical, cancellous), longitudinal bone growth rate, and growth plate thickness.
Main Results:
- 2-MeO-E(2) did not affect uterine weight or bone turnover but reduced serum cholesterol.
- A significant reduction in longitudinal bone growth rate (from 55±2 to 20±2 µm/day) and growth plate thickness (from 153±14 to 70±6 µm) was observed.
- The reduction in growth plate thickness was due to decreased proliferative and hypertrophic zones.
Conclusions:
- 2-Methoxyestradiol (2-MeO-E(2)) inhibits longitudinal bone growth by affecting the growth plate cartilage.
- 2-MeO-E(2) demonstrates significant tissue selectivity, impacting cartilage proliferation without affecting bone or reproductive tissues.