OBJECTIVE Hormonal contraceptives may adversely affect bone mineral density . However, racial differences and the reversibility of these changes are poorly understood. This study measured bone mineral density changes during hormonal contraceptive use and after discontinuation in a triethnic population. METHODS Bone mineral density was measured every 6 months for up to 3 years in 703 white, black, and Hispanic women using oral contraceptives (OCPs), depot medroxyprogesterone acetate (DMPA), or nonhormonal contraception, and in 68 DMPA discontinuers for up to 2 additional years. Mixed-model regression analyses were used to estimate the percentage change in bone mineral density for each contraceptive method. RESULTS Over 3 years, DMPA and OCP users lost more bone mineral density than nonhormonal contraception users (−3.7% and −0.5% vs. +1.9% at lumbar spine, and −5.2% and −1.3% vs. +0.6% at femoral neck, respectively). No differences were observed by race in bone mineral density changes that resulted from DMPA or OCP use. However, DMPA users aged 16–24 years lost more bone mineral density at the spine (4.2% vs. 3.2%, P=.006) and femoral neck (6.0% vs. 4.2%, P=.001) than those aged 25–33 years. After DMPA discontinuation, women who selected nonhormonal contraception gained bone mineral density (+4.9% at spine; +3.2% at femoral neck) while those who selected OCP recovered spinal (+2.3%), but not femoral neck bone mineral density (−0.7%). CONCLUSIONS Use of very low-dose OCP may result in a small amount of bone loss. DMPA use results in greater bone loss, but this is largely reversible at the spine. Use of very low-dose OCPs after DMPA discontinuation may slow bone recovery.

Parathyroid hormone-related protein (PTHrP) plays a major role in prostate carcinoma progression and bone metastasis. Once prostate cancers become androgen-independent, treatment options become limited. Vitamin D analogues represent a potentially valuable class of agents in this clinical context. Using the prostate cancer cell line C4-2 as a model, we studied the effects of PTHrP and the noncalcemic vitamin D analogue EB1089 on markers of prostate cancer cell progression in vitro and in vivo. C4-2 is a second-generation androgen-independent LNCaP subline that metastasizes to the lymph nodes and bone when injected into nude mice and produces mixed lytic/blastic lesions, mimicking the in vivo situation. We report that PTHrP increases cell migration and invasion, and that a pathway via which EB1089 inhibits these processes is through down-regulation of PTHrP expression. PTHrP also increases anchorage-independent cell growth in vitro and xenograft growth in vivo; EB1089 reverses these effects. The in vivo PTHrP effects are accompanied by increased tumor cell proliferation and survival. Treatment with EB1089 reverses the proliferative but not the antiapoptotic effects of PTHrP. PTHrP also increases intratumor vessel density and vascular endothelial growth factor expression; EB1089 reverses these effects. Intracardially injected C4-2 cells produce predominantly osteoblastic lesions; PTHrP overexpression decreases the latency, increases the severity and alters the bone lesion profile to predominantly osteolytic. EB1089 largely reverses these PTHrP effects. A direct correlation between PTHrP immunoreactivity and increasing tumor grade is observed in human prostate cancer specimens. Thus, decreasing PTHrP production by treatment with vitamin D analogues may prove therapeutically beneficial for prostate cancer.

To investigate the role of bone morphogenetic protein (BMP-2) in ossifying rat bone marrow stromal cell cultures, we determined the population of fibroblast-like stromal cells that expressed BMP-2 immunocytochemically (anti-rhBMP-2 monoclonal antibody), and compared that to alkaline phosphatase (AP) and collagen synthesis formed in culture over a 4-week period in control and dexamethasone-supplemented mineralizing media. In control media, the percentage of BMP-2-positive stromal cells (BMP-2(+)) increased from 12 to 25% within the first 4 days of culture. In mineralizing media, the level of BMP-2(+) cells was significantly increased (43-44%). The intensity of immunostaining gradually increased with time. The levels of AP were undetectable at 1 week in both control and mineralizing media, but increased gradually over the next 2 weeks and peaked at 3 weeks. ALP levels were significantly greater in cultures grown in mineralizing medium (P < 0.05 at 3 weeks, P < 0.01 at 4 weeks). Collagen synthesis peaked and was significantly greater at 3 weeks (P < 0.05) in cultures grown in mineralizing medium. The levels of AP and collagen synthesis most closely reflected the changes in the percentage of BMP-2(+) cells from 7 to 28 days. Though these changes may reflect a primary action of BMP-2 on marrow osteoprogenitor-like stromal cells, they do not exclude a mechanism that involves the induction of other members of the BMP family known to stimulate AP and collagen synthesis. We conclude that BMP-2 expression in cultures of fibroblast-like marrow stromal cells is enhanced when those cells are induced to become osteoblasts by exposure to dexamethasone.

No abstract

Electron microscopic techniques have been used to profile the morphologies of marrow sacs in different laboratory species. These structures all comprise a condensed layer of overlapping fibroblast-like stromal cells and apparently confine the medullary and endosteal osteoblast/lining cells to separate histiotypic compartments. There were some variations in the morphology of the sac cells in the different species. In rats, cats, and sheep, scanning electron microscopy (SEM) showed a seamless arrangement of marrow sac cells which resembled a thin, flat simple squamous epithelium; they displayed few intercellular cytoplasmic processes. In the rabbit and pigeon, the sac comprised a more woven, multilayered fabric of broadly elongate flat fibroblast-like cells which displayed numerous intercellular processes. Transmission electron microscopy (TEM) showed that all marrow sac cells were attenuated with elongated nuclei, a few small round mitochondria, and a sparse rough endoplasmic reticulum. In the majority of animals, the sac was one to two cell layers thick. The rabbit and pigeon sacs were multilayered, and never less than three to four cells deep. The cell layers were not closely apposed. Tight or gap junctions were absent at the points of intercellular contact. These morphological results suggest that marrow sacs are common elements of the vertebrate skeleton with species specific morphologies.