Androgens regulate bone resorption activity of isolated osteoclasts in vitro

For many years, sex steroids have been known to influence bone metabolism, with estrogen primarily linked to reduced bone resorption. However, the role of androgens in modulating bone resorption has remained less clear. Prior research has shown that androgens may promote bone deposition, but direct effects on osteoclast activity have not been fully established. This gap motivated investigations into whether androgens can directly affect osteoclasts, which are key cells responsible for bone resorption. No prior work had resolved how androgens might interact with these cells. The current paper addresses this uncertainty by examining androgen responsiveness in osteoclasts from different species. Understanding these interactions could clarify the role of androgens in bone health. The study builds on existing knowledge of androgen receptor signaling in other tissues. It also addresses the lack of direct evidence linking androgens to osteoclast function. By exploring this, the research aims to expand the understanding of hormonal regulation of bone turnover.

The aim of this study was to determine whether androgens can directly modulate the resorption activity of osteoclasts in vitro. The researchers sought to investigate if androgens could act as direct regulators of bone resorption by testing their effects on osteoclasts from avian, human, and mouse sources. The motivation for this work stems from the lack of direct evidence linking androgens to osteoclast function. The study focused on whether androgens could influence resorption activity and whether this effect was mediated through androgen receptors. The researchers also aimed to assess the functional activity of androgen receptors in these cells. By examining the response to specific androgen ligands and antagonists, they sought to confirm the presence of functional receptors. The study aimed to explore the downstream effects of androgen treatment on osteoclast activity. This work contributes to understanding the hormonal regulation of bone metabolism.

The study used isolated osteoclasts from avian, human, and mouse sources to assess androgen responsiveness. Researchers tested the effects of various androgens, including alpha-DHT, beta-DHT, testosterone, and RU1881, on bone resorption activity. They measured resorption activity as a function of androgen concentration. The researchers also used hydroxyflutamide to block androgen effects and determine receptor involvement. Nuclear binding of tritiated RU1881 was assessed in avian osteoclasts to confirm receptor presence. A reporter plasmid system was employed to evaluate androgen response element activation. Secretion levels of cathepsin B and tartrate-resistant acid phosphatase were measured after androgen treatment. Transforming growth factor beta production was also analyzed to assess androgen-induced responses.

Treatment with alpha-DHT, beta-DHT, testosterone, or RU1881 led to a dose-dependent decrease in osteoclast resorption activity. This effect was blocked by hydroxyflutamide, indicating androgen receptor involvement. Avian osteoclasts showed specific and saturable nuclear binding of RU1881. Alpha-DHT increased androgen response element activity in a reporter assay. Androgen treatment elevated transforming growth factor beta production in avian osteoclasts. After 24 hours of treatment, both alpha-DHT and beta-DHT reduced cathepsin B and acid phosphatase secretion. Beta-DHT, an inactive isomer in other systems, still affected osteoclasts, suggesting unique receptor properties. These findings confirm functional androgen receptors in osteoclasts and their responsiveness to androgens.

The study confirms that osteoclasts can respond directly to androgens in vitro. Functional androgen receptors are present in these cells, as evidenced by ligand binding and response element activation. Androgen treatment reduces resorption activity, suggesting a regulatory role in bone metabolism. The observed decrease in cathepsin B and acid phosphatase secretion supports this conclusion. The response to beta-DHT implies unique receptor characteristics in osteoclasts. These findings suggest that osteoclasts are potential androgen target cells in vivo. The results support the hypothesis that androgens modulate bone resorption through direct effects on osteoclasts. This work provides evidence for a direct hormonal regulation of bone resorption.